Developing device, process cartridge and image forming apparatus

Abstract

To prevent the occurrence of uneven coating, while improving the electrification characteristics of a developer coat layer formed on a developer carrier.SOLUTION: A developer used in a developing device including a metal blade has a toner base particle and an external additive. The external additive includes silica fine particles having a particle diameter of 5 nm or more and 25 nm or less, and inorganic spacer particles having a particle diameter of 50 nm or more and 150 nm or less. On the surface of the toner base particles, the area occupation rate of the silica fine particles is 40% or more.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, a developing device and a process cartridge used in the image forming apparatus, and more particularly to an electrophotographic image forming apparatus that employs an electrophotographic system, and a developing device and a process cartridge used in the electrophotographic image forming apparatus. [Background technology]

[0002] Conventionally, a widely known configuration is one in which the free end of a metal developing blade contacts (abuts) the surface of a developing roller, and as the developing roller rotates, the toner layer deposited (coated) on the developing roller is regulated and a charge is imparted to the toner by frictional charging.

[0003] On the other hand, Patent Document 1 proposes adding inorganic fine particles of a predetermined particle size to toner in order to improve the fluidity (chargeability) of the toner in a configuration using a metallic developing blade.

[0004] Specifically, the configuration of Patent Document 1 uses a toner to which multiple inorganic fine particles with different average diameters are added. The small inorganic fine particles contained in the toner contribute to the toner's chargeability, while the large inorganic fine particles inhibit the small inorganic fine particles from being embedded in the toner base particles. By using fine particles with different diameters in combination, the fluidity (chargeability) of the toner is improved. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4370422 Summary of the Invention [Problem to be solved by the invention]

[0006] However, with the configuration of Patent Document 1, as the image formation operation progresses (durability), there is a possibility that large inorganic fine particles may become embedded in the toner base particles. The large inorganic fine particles that have become integrated with the toner base particles through embedding will have a stronger abrasive action on the tip (contact portion) of the metal developing blade, and wear will change the contact state of the metal blade with the developing roller or the state of toner uptake into the contact portion, making it more likely to cause regulation defects such as "uneven coating."

[0007] In view of the above problems, the present invention aims to provide a developing device, a process cartridge, and an image forming apparatus that can improve the charging property of the developer coating layer formed on the developer carrier while suppressing the occurrence of coating unevenness. [Means for solving the problem]

[0008] The developing device of the present invention has a developing frame that accommodates a developer, and a regulating member that is rotatably supported by the developing frame and includes a developer carrier that carries the developer and a metal blade, and the metal blade has one end fixed to the developing frame and the other end arranged to contact the developer carrier, and regulates the thickness of the developer carried on the developer carrier, wherein the developer has toner base particles and an external additive, and the external additive includes silica fine particles having a particle diameter of 5 nm or more and 25 nm or less and inorganic spacer particles having a particle diameter of 50 nm or more and 150 nm or less, and the developer has, on the surface of the toner base particles, Adhered to the surface of the toner particles The area occupancy of the silica fine particles is characterized by being 40% or more.

[0009] Another developing device of the present invention is a developing frame that accommodates a developer; a developer carrier rotatably supported by the developing frame and carrying a developer; a developing device including a metal blade, one end of the metal blade being fixed to the developing frame and the other end being arranged to contact the developer carrier, and a regulating member for regulating a thickness of a developer carried on the developer carrier, the developer comprises toner base particles having an organic silica-containing surface layer made of an organic silicon compound, and an external additive; the external additive contains inorganic spacer particles having a particle size of 50 nm or more and 150 nm or less, The toner is characterized in that the area occupancy of the organosilicon compound on the surface of the toner base particle is 40% or more. [Effects of the Invention]

[0010] According to the present invention, it is possible to improve the charging property of the developer coating layer formed on the developer carrier, while suppressing the occurrence of coating unevenness. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional conceptual diagram of an image forming apparatus according to a first embodiment of the present invention; [Figure 2] 1 is a cross-sectional conceptual diagram of a developing device used in an image forming apparatus according to a first embodiment of the present invention; [Figure 3] Cross-sectional conceptual diagram of the developer used in Examples 1 to 5 of the present invention [Figure 4] (a) and (b) Schematic diagram showing the contact state between silica particles and spacer particles on the surface of a toner base particle [Figure 5] (a) and (b) Schematic diagram showing the positional relationship between silica particles and spacer particles on the surface of a toner base particle [Figure 6] Table showing the relationship between the particle size n of silica particles on the surface of a toner base particle, the area occupancy H of silica particles, and the outer diameter MR of a virtual circle [Figure 7] 1 is a cross-sectional conceptual diagram showing the relative positions of the developing blade and developing roller used in Example 1 of the present invention; [Figure 8] 1 is a cross-sectional conceptual diagram showing the relative positions of a developing blade and a developing roller used in a second embodiment of the present invention; [Figure 9] (a) and (b) Schematic diagram showing the mechanism by which spacer particles cause wear at the tip (contact) of the developing blade. [Figure 10] Cross-sectional conceptual diagram of a developer used in Example 6 of the present invention DETAILED DESCRIPTION OF THE INVENTION

[0012] Example 1 <Configuration of image forming device> The overall configuration of an electrophotographic image forming apparatus (hereinafter referred to as an image forming apparatus) according to the present invention will be described below. Fig. 1 is a cross-sectional conceptual diagram of an image forming apparatus 100 according to this embodiment.

[0013] The image forming apparatus 100 of this embodiment is a full-color laser printer that employs an in-line system and an intermediate transfer system.

[0014] The image forming apparatus 100 can form a full-color image on a recording material P (e.g., recording paper, plastic sheet) in accordance with image information. The image information is input to the image forming apparatus 100 from an image reading device or a host device such as a personal computer communicatively connected to the image forming apparatus 100.

[0015] The image forming apparatus 100 has a plurality of image forming units, including first, second, third, and fourth process cartridges Sa, Sb, Sc, and Sd for forming images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. In this embodiment, the first to fourth process cartridges Sa, Sb, Sc, and Sd are arranged in a row in a direction intersecting the vertical direction. In this embodiment, the configurations and operations of the first to fourth process cartridges Sa, Sb, Sc, and Sd are essentially the same except for the colors of the images they form. Therefore, hereinafter, unless a distinction is required, the suffixes a, b, c, and d, which are added to reference numerals to indicate that the element is provided for one of the colors, will be omitted and the description will be generalized.

[0016] In this embodiment, the image forming apparatus 100 has, as its multiple image carriers, four drum-shaped electrophotographic photosensitive members, i.e., photosensitive drums 1 (1a, 1b, 1c, 1d), arranged side by side in a direction intersecting the vertical direction. The photosensitive drums 1 are driven to rotate by a driving means (drive source) (not shown). Around the photosensitive drum 1, there are arranged charging rollers 2 (2a, 2b, 2c, 2d), scanner units (exposure devices) 3 (3a, 3b, 3c, 3d), and developing units (developing devices) 4 (4a, 4b, 4c, 4d). The charging rollers 2 are charging means for uniformly charging the surface of the photosensitive drums 1.

[0017] The scanner unit 3 is an exposure means that irradiates a laser to form an electrostatic image (electrostatic latent image) on the photosensitive drum 1 based on the output calculated by a CPU (not shown) from image information input from a host device such as a personal computer. The development unit 4 is a development means that develops the electrostatic image into a developer (hereinafter, toner) image. The photosensitive drum 1, the charging roller 2 as a process means acting on the photosensitive drum 1, and the development unit 4 are integrated to form a process cartridge S.

[0018] The process cartridge S is detachably mountable to the image forming apparatus 100 via mounting means such as a mounting guide and a positioning member provided in the image forming apparatus 100 .

[0019] In addition, an intermediate transfer belt 10 is disposed opposite the four photosensitive drums 1 as an intermediate transfer member for transferring the toner images on the photosensitive drums 1 to a recording material P. The intermediate transfer belt 10, which is formed as an endless belt, contacts all the photosensitive drums 1 and moves (rotates) in a circular motion in the direction of arrow R3 in the drawing. The intermediate transfer belt 10 is stretched over a secondary transfer opposing roller 13, a drive roller 11, and a tension roller 12, which serve as multiple support members.

[0020] Four primary transfer rollers 14 (14a, 14b, 14c, 14d) serving as primary transfer means are arranged side by side on the inner peripheral surface of the intermediate transfer belt 10 so as to face each photosensitive drum 1. The primary transfer rollers 14 press the intermediate transfer belt 10 toward the photosensitive drums 1, forming a primary transfer section where the intermediate transfer belt 10 and the photosensitive drums 1 come into contact with each other.

[0021] Furthermore, a secondary transfer roller 20 serving as a secondary transfer means is disposed at a position facing the secondary transfer opposing roller 13 on the outer peripheral surface side of the intermediate transfer belt 10. The secondary transfer roller 20 is pressed against the secondary transfer opposing roller 13 via the intermediate transfer belt 10, forming a secondary transfer section where the intermediate transfer belt 10 and the secondary transfer roller 13 come into contact.

[0022] The recording material P onto which the toner image has been transferred is conveyed to a fixing device 30 serving as a fixing means. The fixing device 30 applies heat and pressure to the recording material P, thereby fixing the toner image to the recording material P.

[0023] In addition, the image forming apparatus 100 is also capable of forming a monochromatic or multicolor image using only one desired image forming unit or using only some (but not all) of the image forming units.

[0024] In this embodiment, the image forming apparatus 100 is a printer with a process speed of 148.2 mm / sec and compatible with A4 size paper.

[0025] <Image formation process> When forming an image, first, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2 .

[0026] Next, the surface of the charged photosensitive drum 1 is scanned and exposed to laser light emitted from the scanner unit 3 based on the output calculated by the CPU from the image information input from the host device, and an electrostatic image according to the image information is formed on the photosensitive drum 1.

[0027] Next, the electrostatic image formed on the photosensitive drum 1 is developed into a toner image by the developing unit 4.

[0028] A voltage of a polarity opposite to the normal charging polarity of the toner is applied to the primary transfer roller 14 (transfer member) from a primary transfer voltage power supply 15 (high voltage power supply) as a primary transfer voltage application means.

[0029] As a result, the toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 10. When a full-color image is formed, the above-described process is carried out sequentially in the first to fourth process cartridges Sa, Sb, Sc, and Sd, and the toner images of each color are sequentially superimposed and primarily transferred onto the intermediate transfer belt 10.

[0030] Thereafter, the recording material P is conveyed to the secondary transfer roller 20 in synchronization with the movement of the intermediate transfer belt 10. Then, a voltage of a polarity opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 20 from a secondary transfer voltage power supply 21 (high voltage power supply) serving as a secondary transfer voltage application means. As a result, the four-color toner image on the intermediate transfer belt 10 is secondarily transferred all at once onto the recording material P conveyed by the feeding means by the action of the secondary transfer roller 20 which is in contact with the intermediate transfer belt 10 via the recording material P.

[0031] The recording material P onto which the toner image has been transferred is conveyed to a fixing device 30 serving as a fixing means. In the fixing device 30, heat and pressure are applied to the recording material P to fix the transferred toner image, and the recording material P is then discharged from the image forming apparatus 100.

[0032] In order to control the amount of toner developed, the developing unit 4 performs reversal development by bringing a developing roller 22 (described later) as a developer carrier into contact with the photosensitive drum 1 at a speed difference. That is, the developing unit 4 develops an electrostatic image by attaching toner charged with the same polarity (negative polarity in this embodiment) as the charging polarity of the photosensitive drum 1 to portions of the photosensitive drum 1 where the charge has decayed due to exposure (image portions, exposed portions). In this embodiment, the developing roller 22 moves at a speed ratio 1.4 times that of the photosensitive drum 1.

[0033] Furthermore, residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer process is collected and reused by the developing roller 22, which will be described later. The residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer process is charged to the normal charging polarity when it passes through the charging roller 2. Thereafter, the residual toner is collected by the developing roller 22 and reused due to an electric field caused by the difference between the potential of the photosensitive drum 1 formed by the charging roller 2 and the potential of the developing roller 22 formed by applying a DC voltage to the developing roller 22.

[0034] <Process cartridge configuration> Next, the overall configuration of the process cartridge S to be mounted in the image forming apparatus 100 of this embodiment will be described (see FIG. 1). The developing unit 4 that constitutes a part of the process cartridge will be described with reference to FIG. 2. FIG. 2 is a cross-sectional conceptual diagram of the developing unit (developing device).

[0035] The process cartridges S for each color have the same shape except for an identification portion (not shown), and the developing unit 4 of the process cartridge S for each color contains toner of each color: yellow (Y), magenta (M), cyan (C), and black (K). The developing unit 4 uses non-magnetic single-component toner as the developer.

[0036] The process cartridge S is configured by integrating a photosensitive unit including a photosensitive drum 1 and a rotatable charging roller 2, and a developing unit (developing device) 4 including a rotatable developing roller 22 and the like.

[0037] The photosensitive drum 1 is rotatably supported via a bearing (not shown). The photosensitive drum 1 is configured to be rotated in the direction of arrow R1 in accordance with the image forming operation by transmitting the driving force of a driving means (drive source) (not shown) to the photosensitive unit. The charging roller 2 is configured such that its conductive rubber roller portion is in pressure contact with the photosensitive drum 1 and is rotated by the photosensitive drum 1.

[0038] On the other hand, the developing unit 4 (developing device) has a developing roller 22 that carries toner, a developing blade 23 (metal blade) that constitutes a regulating member, a supply member 26 that is arranged to come into contact with the developing roller, and a developing frame body 24 that fixes these.

[0039] One end of the developing blade 23 is fixed to a support member 23b fixed to the developing frame 24, and the other end of the developing blade 23 is brought into contact with the developing roller 22, enabling the regulation of the toner coat amount on the developing roller 22 and the application of electric charge. The developing roller 22 is disposed in the developing opening and is capable of coming into contact with the photosensitive drum 1. The developing roller 22 is disposed so as to be driven to rotate in the direction of the arrow R4 in the figure.

[0040] In this embodiment, the developing roller 22 and the photosensitive drum 1 are rotated so that their surfaces move in the same direction (in this embodiment, from above to below in the direction of gravity) at the opposing portion. A predetermined DC voltage is applied to the developing roller 22 as a developing bias, and the toner, negatively charged by friction, comes into contact with the photosensitive drum 1 at the developing portion, where the electrostatic latent image is visualized to form a toner image.

[0041] <Regulating member> Next, the developing blade 23 (regulating member) will be described.

[0042] As shown in FIG. 2, the developing blade 23 is in contact with the developing roller 22 so as to face in the counter direction, and regulates the toner coating amount and applies electric charge.

[0043] In this embodiment, the developing blade 23 is made of a 50-120 μm thick metal SUS plate 23a (metal blade) in the shape of a leaf spring, and a support member (23b). The spring elasticity of the metal SUS plate 23a is utilized to bring the surface of the developing blade into contact with the developing roller 22. The developing blade has a developing blade formed at one end in the short direction, and the other end is fixed to and supported by the developing frame 24. The developing blade 23 is not limited to the above embodiment, and a thin metal plate, such as phosphor bronze or aluminum, may also be used as the support member. Meanwhile, metals such as SUS, phosphor bronze, and aluminum may be used for the developing blade from the viewpoint of charging the toner. In this embodiment, SUS is used. Furthermore, to stabilize the charging performance of the toner, the same DC voltage is applied to the developing blade 23 and the developing roller 22.

[0044] The supply member 26 is composed of a φ4 (mm) conductive core metal and a soft, open-cell urethane sponge layer formed around it. The outer diameter of the supply member 26 is φ11 (mm). The open-cell urethane sponge used for the supply member 26 allows toner to be stored inside the sponge. During development, the supply member 26 contacts the developing roller 22 and is supported by the developing frame 24 so that it can rotate in the direction of arrow R5.

[0045] The developing roller 22, which is a developer carrier, is made up of a metal core, a base layer, and a surface layer made of urethane laminated in this order. A developing bias is applied to the surface layer and the base layer via the metal core.

[0046] Carbon black is preferred because it can control the conductivity of the conductive elastic layer and the charging performance of the conductive elastic layer against toner. The volume resistivity of the conductive elastic layer is preferably in the range of 1×10^3 Ω·cm or more and 1×10^11 Ω·cm or less. In this embodiment, 1×10^6 Ω·cm was used.

[0047] Next, the attachment of the developing blade 23 will be described in detail with reference to FIG.

[0048] 7 is a cross-sectional conceptual diagram showing the attached state (posture) of the developing blade before the developing roller is attached. For reference, in FIG. 7, the imaginary outer circumference (outer peripheral surface) of the developing roller is shown by a dotted line.

[0049] 7, one end 23a1 in the lateral direction of the metal blade (metal SUS plate 23a) is fixed by a support member 23b to the developing frame 24. The other end 23a2 in the lateral direction of the metal blade is a free end.

[0050] Next, let us assume that the developing roller 22 is not yet assembled in the developing frame 24, but the developing roller is assembled in the developing frame. When viewed from the direction X1 of the rotation axis of the developing roller, an intersection 23a23 where the tip surface 23a21 of the other end 23a2 (free end) of the developing blade 23 intersects with the contact surface 23a22 that comes into contact with the developing roller is located inside the imaginary outer circumference MC1 of the developing roller 22. At the same time, the intersection 23a23 is located in a first imaginary region TD1 on one side where the developing blade exists, when a first imaginary plane SF1 that passes through the rotation center X0 of the developing roller and is parallel to the contact surface 23a22 is used as a reference.

[0051] In particular, in this embodiment, when a first imaginary plane SF1 and a second imaginary plane SF2 perpendicular to the first imaginary plane are used as references, the intersection is located in a range TD1d of the first imaginary region that is downstream of the second imaginary plane and upstream of the first imaginary plane in the rotation direction R4 of the developing roller. In other words, as shown in Figure 7, the developing blade 23 is positioned so that the edge (intersection 23a23) of the other end 23a2 (free end) abuts against the surface of the developing roller 22.

[0052] By setting the developing blade in this range, the free end of the developing blade contacts the developing roller, making it possible to reduce the size of the regulating portion intake opening and obtain a high regulating force. Toner with a particularly high charge has a high electrostatic adhesion force, which increases the adhesion force to the developing roller and between toner particles. However, the configuration of the present invention allows for stable toner regulation and the formation of a toner coat layer.

[0053] <Developer> Next, the toner (developer T) used in this embodiment will be described with reference to Fig. 3. Fig. 3 shows a cross-sectional view of the toner (developer T).

[0054] The toner particles (including the toner base particles TM and the small-diameter silica fine particles S1) have an average diameter (average particle size) of 7 μm. Specifically, the toner particles have small-diameter silica fine particles S1 ("adhered silica" described below) externally added to the surface of the toner base particles TM in an amount of 1.0 part by mass per 100 parts by mass of the toner base particles, and are adhered to the surface of the toner base particles TM.

[0055] Next, 0.6 parts of silica particles S2 having a primary particle diameter (r1) of 100 nm as spacer particles SP were externally added to 100 parts of the toner particles using a Henschel mixer (FM10C type manufactured by Nippon Coke and Engineering Co., Ltd.).

[0056] The silica fine particles S1 and spacer particles SP (silica particles S2) of this example constitute the external additive of the present invention.

[0057] The particle size (n) of the primary particles of the silica fine particles S1 (adhered silica) is 5 nm or more and 25 nm or less, and preferably 5 nm or more and 15 nm or less.

[0058] If the particle size n of the primary particles of the silica fine particles S1 (adhered silica) is less than 5 nm, the silica fine particles S1 will be significantly embedded in the toner particles, making it difficult to adequately adjust the chargeability and fluidity throughout the test, which is undesirable. Furthermore, if the particle size n of the primary particles of the silica fine particles S1 is greater than 25 nm, uneven coating will become apparent. In this embodiment, silica fine particles S1 (adhered silica) with a particle size of 20 nm were used.

[0059] <Spacer particles> The inorganic particles constituting the spacer particles SP may be, for example, silica, alumina, titanium oxide, boron nitride, etc. In this example, inorganic silica was used.

[0060] In this embodiment, the particle size (r1) of the primary particles of the spacer particles SP is 50 nm or more and 150 nm or less.

[0061] If the particle size r1 of the primary particles of the spacer particles SP is less than 50 nm, the spacer function is weak, the silica particles are less likely to be embedded in the toner matrix, and the toner fluidity changes significantly.On the other hand, if the particle size r1 of the primary particles of the spacer particles SP exceeds 150 nm, the scraping action against the contact area of ​​the metal blade becomes stronger, as described below, and "coating unevenness" becomes more likely to occur.

[0062] If the particle size r1 of the spacer particles SP exceeds 150 nm, the spacer particles may further adhere to the surface of the developing blade, which may cause low-charge toner (fogging) because it becomes difficult for the developing blade to transfer charge to the toner.

[0063] In this embodiment, the primary particle diameter r1 of the spacer particles SP is 100 nm.

[0064] <Area occupancy rate of silica fine particles S1> The process of observing the fine silica particles S1 and spacer particles SP adhering to the surface of the toner base particle TM and the method of calculating the area occupancy rate of the fine silica particles S1 will be described.

[0065] (Water washing process) Weigh out 20 g of a 30% by weight aqueous solution of "Contaminon N" (a neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, with a pH of 7) into a 50 mL vial and mix it with 1 g of toner.

[0066] The mixture is placed in a KM Shaker (model: V.SX) manufactured by Iwaki Sangyo Co., Ltd., and shaken at a speed of 50 for 120 seconds. This causes the silica fine particles, which tend to detach from the toner surface, to migrate from the toner base particles or the toner particle surface to the dispersion liquid. The toner is then separated from the external additives, such as silica fine particles, that have migrated to the supernatant liquid using a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) (16.67 S-1 for 5 minutes). The precipitated toner is dried in a vacuum at 40°C for 24 hours, and is then washed with water to obtain the toner.

[0067] The toner is photographed using a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation).

[0068] The measurement target is identified by elemental analysis using energy dispersive X-ray analysis (EDS). A magnification of 5,000,000 times is used as the analysis size to reflect the toner surface. The occupancy rate (area occupancy rate) of silica particles S1, where silica atoms exist, in the analysis area is calculated.

[0069] The above calculation was carried out for 10 toner particles, and the average value was taken as the area occupancy H of the silica fine particles S1.

[0070] The occupancy rate H of the silica fine particles S1 in this example was 60%.

[0071] As will be described later, if the occupancy rate H of the silica fine particles S1 is 40% or more, adhesion of the spacer particles to the toner base particles can be effectively suppressed.Furthermore, if the occupancy rate H of the silica fine particles S1 is 40% or more, a sufficient charge amount can be imparted to the toner.

[0072] On the other hand, the occupancy rate H of the silica fine particles S1 is preferably 75% or less for the following reasons: If it exceeds 75%, the toner becomes difficult to melt when heated (for example, at 100°C or higher), which may result in poor fixing.

[0073] <Particle size of spacer particles SP> Next, the relationship between the particle size (r1) of the spacer particles SP and the occupancy rate (H) of the silica fine particles S1 in the present invention will be explained with reference to Fig. 4. Fig. 4(a) and (b) are conceptual diagrams showing the "contact state" between the silica fine particles S1 and the spacer particles SP.

[0074] The main role of the spacer particles in the present invention is to interpose between toner base particles (base) and prevent contact between the toner base particles. This prevents the silica fine particles S1 from being embedded in the toner base particles TM and makes the toner particles more mobile. In other words, the toner fluidity (and therefore the chargeability) is improved.

[0075] To improve the fluidity of the toner, it is necessary to prevent the spacer particles from coming into direct contact with the toner base particles, as shown in Figure 4(a). Specifically, as shown in Figure 4(a), by increasing the area occupancy of the silica fine particles on the surface of the toner base particles, the possibility of the spacer particles coming into direct contact with the toner base particles is reduced. In other words, the adhesion of the spacer particles to the toner base particles is achieved through the silica fine particles S1, which reduces the adhesive strength (adhesion force F1) of the spacer particles to the toner base particles and maintains the fluidity of the toner.

[0076] On the other hand, in the state shown in Figure 4(b), the toner base particles are rich in resin components (the proportion of resin on the surface of the toner base particles is high), and the surface area occupied by the silica fine particles S1 is relatively low. In this case, the spacer particles SP and the resin components are more likely to come into contact with each other, and the adhesion (adhesion force F2) of the spacer particles to the toner base particles TM increases. As a result, the movement of the spacer particles on the toner surface is restricted, and the toner fluidity also decreases.

[0077] In particular, when an external force is applied to the toner base particles TM and the spacer particles SP in direct contact with each other (for example, when the toner coating layer on the developing roller passes through an area where the toner coat layer abuts against another member), the spacer particles adhere to or become embedded in the toner base particles. In this case, the function of the spacer particles SP is reduced, and the fluidity of the spacer particles themselves is reduced. As a result, it becomes difficult to ensure stable toner fluidity over time.

[0078] Thus, it is necessary to create a state in which the spacer particles SP are less likely to come into contact with the surface of the base particles. In the present invention, the conditions (factors) under which the spacer particles SP are less likely to come into contact with the resin component of the toner base particles TM were investigated in detail. These conditions (factors) will be explained using FIG. 5.

[0079] 5(a) and (b) are conceptual diagrams showing the "positional relationship" between the silica fine particles S1 and the spacer particles SP.

[0080] 5(a) and (b) show enlarged conceptual diagrams of the surface condition of the toner base particle. The area occupancy of the "adhered silica" consisting of silica fine particles S1 is indicated as "H", and the particle size of the silica fine particles S1 that make up the adhering silica is indicated as "n".

[0081] 5(b) shows a state in which the adhered silica (silica fine particles S1) are closest packed (arranged) (i.e., a state in which the occupancy rate H is approximately 1). In this case, the distance L between the centers C1 of two adjacent silica fine particles S1 is equal to n.

[0082] On the other hand, when the occupancy rate is expressed as H, the distance increases by 1 / √H, so the distance L between the centers C1 of two adjacent silica particles S1 becomes L = n / √H.

[0083] Next, the outer diameter MR of an imaginary circle MC2 that passes through the centers C1 of three adjacent silica particles S1 is 2L / √3. If the particle size (r1) of the spacer particle SP is larger than the outer diameter MR of the imaginary circle MC2 (r1>MR), it is thought that contact between the spacer particle and the surface of the toner base particle is suppressed.

[0084] The table in Fig. 6 shows the relationship between the particle size (n) and area occupancy (H) of the silica microparticles and the outer diameter (MR) of the imaginary circle MC2 based on the above MR (= 2L / √3) and L (= n / √H). That is, Fig. 6 shows the value of the outer diameter MR when the particle size (n) of the silica microparticles S1 that make up the fixed silica and the area occupancy (H) of the silica microparticles are changed.

[0085] As mentioned above, the particle size n of the silica fine particles S1 that constitute the adhered silica is preferably 5 to 25 nm from the viewpoint of suppressing adhesion. That is, if the particle size n is less than 5 nm, the silica fine particles become significantly embedded in the toner base particles. On the other hand, if the particle size exceeds 25 nm, uneven coating of the silica fine particles on the surface of the toner base particles becomes apparent.

[0086] As mentioned above, the particle size of the spacer particles is preferably 50 nm or more. That is, if the particle size is less than 50 nm, the effect as a spacer is small, and the change in toner fluidity is small.

[0087] After extensive research, the inventors of the present invention found that if the outer diameter MR of the imaginary circle MC2 of the fixed silica consisting of silica microparticles on the surface of the toner base particle is smaller than the lower limit of the particle size of the spacer particle (50 nm), it becomes difficult for the spacer particle to approach the toner base particle due to volumetric reasons.

[0088] That is, we succeeded in identifying an appropriate range for the occupancy rate (H) of the silica fine particles when the conditions of "particle size (n = 5 to 25 nm) of the silica fine particles S1 constituting the adhered silica" and the outer diameter (MR < 50 nm) of the imaginary circle MC2 shown in the table of Fig. 6 are satisfied. In other words, if the occupancy rate of the silica fine particles S1 is set to H > 0.4, it is possible to maintain an appropriate toner charge amount (i.e., when the occupancy rate H is less than 0.40, the toner charge amount is likely to decrease), and also to reliably reduce the adhesion of the spacer particles SP to the toner base particles TM.

[0089] Furthermore, if the occupancy rate of the silica fine particles S1 exceeds 0.75, it is thought that poor fixing is likely to occur, so the silica (area) occupancy rate H is preferably in the range of 0.40 to 0.75.

[0090] With the above-described configuration, the charge amount (chargeability) of the toner is maintained at a normal level, and blade abrasion (wear) is reduced due to the adhesion of the spacer particles to the toner base particles, thereby suppressing coating unevenness.

[0091] To ensure toner fluidity more effectively, it is preferable that the particle size of the spacer particles be approximately twice the outer diameter MR of the imaginary circle MC2 or more. In this case, the occupancy rate H of the silica particles can be 0.45 or more, and the particle size of the spacer particles can be 80 nm or more.

[0092] Furthermore, if the particle size (n) of the silica particles S1 that make up the adhered silica is less than 5 nm, silica aggregation may occur significantly, and the distance between the silica particles S1 may become large, making it easier for the spacer particles SP to adhere to the toner base particles TM during endurance testing.

[0093] [Prior art (reference example)] This reference example (prior art) is similar to Example 1, but differs in the following respects.

[0094] The toner used had the silica fine particles S1 externally added in an amount of 0.3 parts by mass per 100 parts by mass of the toner particles, and the occupancy rate H of the silica fine particles S1 was 35%.

[0095] Comparative Example 1 Comparative Example 1 is similar to Example 1, but differs from Example 1 in the following respects.

[0096] Toner was used to which 0.3 parts by mass of the silica fine particles S1 per 100 parts by mass of toner particles had been externally added. Next, 0.6 parts by mass of silica particles S2 with a primary particle diameter of 100 nm were externally added as spacer particles SP using a Henschel mixer per 100 parts by mass of toner particles. The area occupancy H of the silica fine particles S1 at this time was 32%.

[0097] Example 2 The second embodiment is similar to the first embodiment, but differs from the first embodiment in the following respects.

[0098] In the first embodiment, the other end 23a2 (free end) of the developing blade is disposed so as to abut against the surface of the developing roller 22 at the edge (intersection 23a23) (see FIG. 7). That is, the intersection 23a23 exists within the range of TD1d in the first imaginary region TD1.

[0099] On the other hand, in the second embodiment, as shown in FIG. 8, the intersection 23a23 is set to exist within the range of TD1u in the first virtual region TD1.

[0100] Specifically, when a first imaginary plane SF1 and a second imaginary plane SF2 perpendicular to the first imaginary plane are used as references, the intersection is located in a range TD1u of the first imaginary region TD1 that is upstream of the second imaginary plane and downstream of the first imaginary plane in the rotation direction R4 of the developing roller. In other words, as shown in Figure 8, the developing blade 23 is disposed so that the flat portion (opposing surface 23a22) of the other end 23a2 (free end) abuts against the surface of the developing roller 22.

[0101] 7, the restricting portion intake opening is larger when the free end tip of the developing blade shown in FIG. 8 comes into contact with the developing roller.

[0102] Example 3 The third embodiment is similar to the first embodiment, but differs from the first embodiment in the following respects.

[0103] Alumina particles were used as the spacer particles SP.

[0104] Example 4 The fourth embodiment is similar to the first embodiment, but differs from the first embodiment in the following respects.

[0105] A bias of -300 V was applied to the developing roller, and a bias of -400 V was applied to the developing blade. A voltage difference of 100 V was created between the developing roller and the developing blade for toner whose normal charging polarity is negative, and a negative charge was imparted from the developing blade to the toner, resulting in a highly negatively charged toner.

[0106] Example 5 The fifth embodiment is similar to the first embodiment, but differs from the first embodiment in the following respects.

[0107] A bias of −300 V was applied to the developing roller, and a bias of −400 V was applied to the developing blade. Alumina particles were used as the spacer particles SP.

[0108] Example 6 The sixth embodiment is similar to the fourth embodiment, but differs from the fourth embodiment in the following respects.

[0109] Toner particles TM having a surface layer OS of an organosilicon polymer were formed as follows.

[0110] Into a reaction vessel equipped with a stirrer, a thermometer, and a reflux tube, 650.0 parts of ion-exchanged water and 14.0 parts of sodium phosphate (Rasa Kogyo Co., Ltd., 12-hydrate) were added, and the mixture was kept at 65°C for 1.0 hour while purging with nitrogen.

[0111] Aqueous medium containing a dispersion stabilizer was prepared by adding an aqueous calcium chloride solution prepared by dissolving 9.2 parts of calcium chloride (dihydrate) in 10.0 parts of ion-exchanged water all at once while stirring at 15,000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) Further, 10% by mass of hydrochloric acid was added to the aqueous medium to adjust the pH to 5.0, thereby obtaining aqueous medium 1.

[0112] (Preparation of Polymerizable Monomer Composition) Styrene: 60.0 parts CI Pigment Blue 15:3: 6.5 parts The material was placed in an attritor (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) and further dispersed using zirconia particles having a diameter of 1.7 mm at 220 rpm for 5.0 hours, after which the zirconia particles were removed to prepare a colorant dispersion.

[0113] on the other hand, Styrene: 20.0 parts n-Butyl acrylate: 20.0 parts Crosslinking agent (divinylbenzene): 0.3 parts Saturated polyester resin: 5.0 parts (Polycondensation product of propylene oxide-modified bisphenol A (2-mol adduct) and terephthalic acid (molar ratio 10:12), glass transition temperature (Tg) 68°C, weight average molecular weight (Mw) 10,000, molecular weight distribution (Mw / Mn) 5.12) Fischer-Tropsch wax (melting point 78°C): 7.0 parts The material was added to the colorant dispersion and heated to 65° C., and then uniformly dissolved and dispersed at 500 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a polymerizable monomer composition.

[0114] (granulation process) The temperature of the aqueous medium 1 was adjusted to 70°C, and the polymerizable monomer composition was charged into the aqueous medium 1 while maintaining the rotation speed of the TK homomixer at 15,000 rpm, and 10.0 parts of t-butyl peroxypivalate as a polymerization initiator was added. Granulation was continued for 10 minutes while maintaining the rotation speed at 15,000 rpm with the stirring device.

[0115] (Polymerization process and distillation process) After the granulation step, the agitator was replaced with a propeller agitator blade, and polymerization was carried out for 5.0 hours while stirring at 150 rpm and maintaining the temperature at 70°C, and then further heated to 85°C and maintained at that temperature for 2.0 hours.

[0116] Thereafter, the reflux tube of the reaction vessel was replaced with a cooling tube, and the obtained slurry was heated to 100°C to carry out distillation for 6 hours, thereby distilling off the unreacted polymerizable monomer and obtaining a resin particle dispersion liquid.

[0117] (Organosilicon Polymer Formation Process) 60.0 parts of ion-exchanged water was weighed into a reaction vessel equipped with a stirrer and a thermometer, and the pH was adjusted to 4.0 using 10% by mass of hydrochloric acid. This was heated with stirring until the temperature reached 40°C. 40.0 parts of methyltriethoxysilane, an organosilicon compound (OS), was then added, and the mixture was stirred for 2 hours or more to carry out hydrolysis.

[0118] The end point of the hydrolysis was confirmed by visual inspection when the oil and water no longer separated and became a single layer, and the mixture was cooled to obtain a hydrolyzed liquid of the organosilicon compound.

[0119] The temperature of the resin particle dispersion obtained above was adjusted to 55°C, and 25.0 parts of the organosilicon compound hydrolyzate (10.0 parts of the organosilicon compound) was added to initiate polymerization of the organosilicon compound (OS). After maintaining the mixture for 0.25 hours, the pH was adjusted to 5.5 with a 3.0% aqueous solution of sodium bicarbonate. The mixture was maintained at 55°C for 1.0 hour (condensation reaction 1), and then the pH was adjusted to 9.5 with a 3.0% aqueous solution of sodium bicarbonate. This was maintained for a further 4.0 hours (condensation reaction 2), yielding a toner particle dispersion.

[0120] (Washing process and drying process) After the organosilicon polymer formation process was completed, the toner particle dispersion was cooled, and hydrochloric acid was added to the toner particle dispersion to adjust the pH to 1.5 or less, and the dispersion was left to stand with stirring for 1.0 hour.

[0121] Thereafter, solid-liquid separation was carried out using a pressure filter to obtain a toner cake.

[0122] The obtained toner cake was reslurried in ion-exchanged water to prepare a dispersion again, and then subjected to solid-liquid separation using the above-mentioned filter to obtain a toner cake.

[0123] The obtained toner cake was transferred to a thermostatic chamber at 40°C, and dried and classified for 72 hours to obtain toner particles. The organic silica (organosilicon compound OS) occupancy rate of the organic silica-containing surface PSL was 58%.

[0124] Next, 0.6 parts of silica fine particles having a primary particle size of 100 nm were externally added as spacer particles SP to 100 parts of the toner particles using a Henschel mixer (FM10C type manufactured by Nippon Coke and Engineering Co., Ltd.).

[0125] (Measurement of organic silica-containing surface PSL) Weigh out 20 g of a 30% by weight aqueous solution of "Contaminon N" (a neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, with a pH of 7) into a 50 mL vial and mix it with 1 g of toner.

[0126] The mixture is placed in a KM Shaker (model: V.SX) manufactured by Iwaki Sangyo Co., Ltd., and shaken at a speed of 50 for 120 seconds. This causes the silica fine particles, which tend to detach from the toner surface, to migrate from the toner base particles or the toner particle surface to the dispersion liquid. The toner is then separated from the external additives, such as silica fine particles, that have migrated to the supernatant liquid using a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) (16.67 S-1 for 5 minutes). The precipitated toner is dried in a vacuum at 40°C for 24 hours, and is then washed with water to obtain the toner.

[0127] Next, the toner obtained through the above washing step (washed toner) is photographed using a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation).

[0128] The measurement target is identified by elemental analysis using energy dispersive X-ray analysis (EDS). A magnification of 5,000,000 times is used as the analysis size to reflect the toner surface. The occupancy rate (area occupancy rate) of organic silica (OS), where silica atoms exist, in the analysis area is calculated.

[0129] The above calculation was performed for 10 toner particles, and the average value was taken as the area occupancy H of the organic silica (OS).

[0130] The occupancy rate H of the organosilica (OS) in this example was 58%.

[0131] If the occupancy rate H of the organic silica (OS) is 40% or more, adhesion of the spacer particles to the toner base particles can be effectively suppressed.Furthermore, if the occupancy rate H of the organic silica (OS) is 40% or more, a sufficient charge amount can be imparted to the toner.

[0132] On the other hand, the occupancy rate H of organic silica (OS) is preferably 75% or less for the following reason: If it exceeds 75%, it becomes difficult to dissolve when heated (for example, at 100°C or higher), which may result in poor fixing.

[0133] The toner particles obtained by the manufacturing process described in Example 6 have an organic silica-containing surface layer PSL made of an organic silicon compound OS. Furthermore, the occupancy rate H of the organic silicon compound OS in the organic silica-containing surface layer PSL is 40% or more relative to the inorganic spacer particles SP having a particle size of 50 nm to 150 nm. In Example 6, similar to Example 1, from the viewpoint of "fixing," the occupancy rate H of the organic silica-containing surface layer made of the organic silicon image material OS is preferably 75% or less. That is, in Example 6 as well, the (area) occupancy rate of the organic silicon compound OS is preferably in the range of 0.40 to 0.75. FIG. 10 is a cross-sectional conceptual diagram of the developer of Example 6.

[0134] Table 1 below shows the main configuration of each of the developing devices of Examples 1 to 6, Reference Example, and Comparative Example 1 described above.

[0135] The "regulating portion intake port" in Table 1 refers to the toner inlet located upstream in the rotation direction of the developing roller at the contact (nip) portion where the developing blade contacts the developing roller. For example, compared to the case where the "edge portion (intersecting portion 23a23)" of the tip of the developing blade contacts the developing roller as shown in Figure 7, the "regulating portion intake port" is larger when the "flat portion (opposing surface 23a22)" of the tip of the developing blade contacts the developing roller as shown in Figure 8.

[0136] [Table 1]

[0137] (Evaluation method) Each of the Examples (1 to 6), Reference Example, and Comparative Example 1 shown in Table 1 was evaluated for the following items 1 to 5. The evaluation results are shown in Table 2.

[0138] The evaluation method will be described in detail below.

[0139] (1.) Fog evaluation under high humidity conditions Fog is an image defect that appears like background smearing due to a small amount of toner being developed in a white area (unexposed area) where no image is supposed to be printed. The amount of fog was evaluated as follows.

[0140] The image forming apparatus is stopped while printing a solid white image. After development and before transfer, the toner on the photosensitive drum is temporarily transferred to transparent tape, and the toner-covered tape is attached to a recording paper or the like. A tape without toner is also attached to the same recording paper. The optical reflectance of the tape attached to the recording paper is measured using a green filter with an optical reflectance measuring device (TC-6DS manufactured by Tokyo Denshoku Co., Ltd.). This is subtracted from the reflectance of the tape without toner to determine the amount of fog and evaluate it as the amount of fog. The amount of fog was measured at three or more points on the tape and the average value was calculated. A: The amount of fogging is less than 1.0%. B: The amount of fogging is 1.0 to less than 3.0%. C: The amount of fogging is 3.0 to less than 5.0%. D: The fog level is 5.0 or more (image defects are evident).

[0141] The fog evaluation was performed in a test environment of 30°C and 80% RH after printing 3,000 sheets and leaving the sheet for 24 hours. The printing test was performed by continuously printing horizontal line images with an image ratio of 5%. Specifically, the horizontal line image with an image ratio of 5% was an image in which 1 dot line was printed followed by 19 dot lines not being printed.

[0142] (2.) Evaluation of development streaks in low humidity environments The evaluation of development streaks under a low humidity environment was carried out by outputting a solid black image and a halftone image and visually judging them based on the following criteria. A: No vertical streaks of uneven density were observed in solid black images and halftone images. B: No vertical stripes of uneven density are observed in a solid black image, but vertical stripes of uneven density are observed in a halftone image. C: Vertical stripes of uneven density are visible in solid black images and halftone images.

[0143] Evaluation of development streaks in a low-humidity environment was performed in a test environment of 15°C and 10% RH after printing 3,000 sheets and leaving the sheet for 24 hours. The printing test was performed by continuously printing horizontal line images with an image ratio of 5%. Specifically, the horizontal line image with an image ratio of 5% was an image in which 1 dot line was printed followed by 19 dot lines not being printed.

[0144] This evaluation is aimed at evaluating the image damage caused by uneven longitudinal abrasion near the inlet of the developing blade. In areas with large abrasion amounts, the inlet becomes larger, increasing the amount of toner carried in the longitudinal portion of the toner coating layer on the developing roller, resulting in the appearance of high-density vertical streaks on a uniform image.

[0145] (3.) Dot reproducibility evaluation under high humidity conditions Dot reproducibility in a high-humidity environment was evaluated by visually inspecting a two-dot image based on the following criteria. Specifically, a two-dot image is created by printing two dots, followed by an 80-dot line without printing. Next, 80 dots are left unprinted in the main scanning direction. This process is repeated to create an image. Evaluations were made in a test environment of 30°C and 80% RH, after printing the 100th and 3,000th sheets, and after leaving the sheet for 24 hours. A: Dots in the dot image are visible on both the 100th and 3000th sheets. B: The dot image on the 100th sheet is visible, but the dot image on the 3000th sheet is not visible. C: The dot image on both the 100th and 3000th sheets cannot be recognized.

[0146] (4.) Evaluation of development streaks under high humidity conditions The uniformity of a solid black image was determined by outputting a solid black image and a halftone image and visually observing the image based on the following criteria. A: No vertical streaks of uneven density were observed in solid black images and halftone images. B: No vertical stripes of uneven density are observed in a solid black image, but vertical stripes of uneven density are observed in a halftone image. C: Vertical stripes of uneven density are visible in solid black images and halftone images.

[0147] Evaluation of development streaks in a high humidity environment was carried out in a test environment of 30° C., 80% RH, after printing 100 sheets, and after leaving the image for 24 hours.

[0148] *This evaluation is intended to evaluate image defects when spacer particles adhere to a portion of the longitudinal side of the developing blade.

[0149] When spacer particles or other deposits are formed near the development blade inlet, the toner intake is reduced in the deposit-forming area, resulting in a smaller amount of toner coating than in the non-deposited area, resulting in the generation of thin vertical streaks in the image.

[0150] (5.) Evaluation of edge coating defects at low temperature and low humidity Toner that has become more likely to aggregate due to toner deterioration becomes more difficult to control with the developing blade, and the amount of toner carried by the toner coating layer increases (particularly noticeable at the edges), resulting in edge coating defects.

[0151] To evaluate the longitudinal uniformity of the toner coating layer, evaluation was carried out using halftone images and solid white images. Immediately after printing 3,000 sheets at 15.0°C and 10% RH, solid white images and halftone images were continuously printed. The printing test was carried out by continuously printing horizontal line images with an image ratio of 5%. Evaluation was carried out according to the following criteria. A: In all images, no vertical bands of uneven shading can be recognized on either side of the image. B: In halftone images, vertical bands of uneven density are visible on both sides of the image. C: In a solid white image, vertical bands of uneven density are recognized on both sides of the image.

[0152] In this evaluation, a halftone image is a microscopic striped pattern in which one line is printed in the main scanning direction, followed by four lines that are not printed, and which overall expresses halftone density.

[0153] (Evaluation results) Table 2 shows the evaluation results of Examples 1 to 6, the prior art (reference example), and Comparative Example 1.

[0154] [Table 2]

[0155] The advantages of the present invention over the prior art (reference example) will be explained by comparing Example 1 with the reference example.

[0156] The spacer particles SP in the first embodiment are present between the toner particles, thereby preventing the surfaces of the toner base particles TM from coming into contact with each other, thereby creating a state in which the toner can move easily.

[0157] In addition, Example 1 achieves a high occupancy rate H of the silica fine particles S1 on the toner base particle surface. This reduces contact between the spacer particles SP and the surface of the toner base particle TM, ensuring releasability between the toner and the spacer particles and preventing the spacer particles from adhering to the toner base particle due to stress applied to the toner. As a result, the fluidity of the toner is maintained from the initial stage (at the start of use) through to the endurance stage (over time), allowing stable images to be obtained.

[0158] On the other hand, in the prior art (reference example), the occupancy rate of the silica fine particles S1 on the surface of the toner base particles TM is low (low coverage), and the toner base particles TM do not have spacer particles SP. Because of the absence of spacer particles, contact between the surfaces of the toner base particles increases, and the unevenness caused by the silica fine particles S1 on the surface is reduced due to stress on the toner. As a result, the toner fluidity decreases, and when the toner passes between the developing roller and the developing blade (contact area), the opportunity for frictional charging between the developing blade and the toner decreases. This reduces the amount of charge retained by the toner, making it more likely to develop fog after endurance testing.

[0159] Compared to the Reference Example, Example 1 exhibits good durability against fog throughout the durability test. Because the surface area occupancy of the fine silica particles S1 on the surface of the toner base particles TM is high and the spacer particles SP are present, the toner surface irregularities change little throughout the durability test. Additionally, because the spacer particles SP are present between toner particles and between the toner and other components, the toner surface is less likely to come into direct contact, which prevents the silica particles S1 from reducing the surface irregularities. As a result, the toner fluidity is maintained well throughout the durability test, effectively preventing an increase in fog.

[0160] Next, the effects of the present invention will be explained by comparing Comparative Example 1 with Example 1.

[0161] Comparative Example 1 has spacer particles SP, but the occupancy rate of silica fine particles S1 on the surface of the toner base particles TM is low. Because it contains spacer particles SP, changes in toner fluidity due to toner deterioration can be suppressed, and the increase in fog amount after durability testing is minimal. However, vertical stripes in solid images become noticeable. The reason for this is explained below.

[0162] Although Comparative Example 1 has spacer particles SP, the occupancy rate of the silica fine particles S1 on the surface of the toner base particle is low, so the toner base particle TM and the spacer particle SP come into contact with each other frequently. When the contact frequency between the toner base particle TM and the spacer particle SP increases, the spacer particle SP adheres to the toner base particle TM due to stress on the toner, etc.

[0163] FIG. 9(b) shows a conceptual diagram of when toner having spacer particles fixed to the toner base particles enters the developing blade while being held on the developing roller.

[0164] The spacer particles SP are fixed to the surface of the toner base particles TM and cannot move on the toner surface, so they scrape the tip of the metal developing blade (the scraping area "K1" is shown in Figure 9(b)).

[0165] The toner with the spacer particles SP adhering to it is generated in parts of the longitudinal direction, causing uneven wear of the regulating blade along the longitudinal direction. The uneven wear of the tip of the developing blade along the longitudinal direction causes uneven regulating force along the longitudinal direction, which causes unevenness in the amount of toner coated on the developing roller along the longitudinal direction. This results in vertical streaks in the solid image.

[0166] On the other hand, in this embodiment 1, the spacer particles SP adhere to the toner base particles TM that have a high surface occupancy H of the fine silica particles S1, and therefore, it is possible to suppress the adhesion of the spacer particles to the toner base particles due to stress applied to the toner, etc. In other words, the toner and the spacer particles can maintain high releasability.

[0167] As shown in Figure 9(a), the spacer particles SP in Example 1 are easily moved away from the toner base particles TM. Therefore, when the toner on the developing roller passes through the restricting section, the spacer particles on the surface of the toner base particles are able to move away from the surface of the toner base particles, even if they are subjected to high stress from the restricting section, thereby reducing the stress on the spacer particles. As a result, it is possible to avoid a local increase in pressure between the spacer particles and the metal blade, and it is possible to suppress uneven scraping in the longitudinal direction at the tip of the developing blade.

[0168] In this way, the configuration of Example 1 can effectively suppress unevenness in the longitudinal abrasion of the tip of the developing blade, unevenness in the longitudinal regulating force, and unevenness in the longitudinal toner coat amount on the developing roller, thereby suppressing vertical streaks in solid images. Note that, since the amount of abrasion at the tip of the developing blade increases when the size of the spacer particles is large, in order to suppress abrasion at the tip of the developing blade, it is preferable that the particle size of the spacer particles is 150 nm or less, and more preferably 120 nm or less.

[0169] Next, Examples 2 and 3, which are modifications of Example 1, will be described.

[0170] First, the configuration of the second embodiment will be described.

[0171] In Example 2, the intake opening of the developing blade is set larger than in Example 1. Therefore, in the configuration of Example 2, the amount of toner passing through the developing blade is larger than in Example 1. Therefore, compared to Example 1, in Example 2, the amount of toner that cannot contact the developing blade increases slightly, and the amount of toner that does not have a high charge also increases slightly.

[0172] As a result, compared to Example 1, in Example 2, dot reproducibility is relatively lower and durable fog is relatively slightly increased, but a high regulating force can be achieved at the regulating position, as in Example 1. This makes it possible to effectively suppress dot reproducibility and durable fog in a high-humidity environment.

[0173] Next, the configuration of the third embodiment will be described.

[0174] In Example 3, alumina (particles) were used as the spacer particles SP. Alumina has a polarity opposite to the charge polarity of the toner. Therefore, compared to Example 1, the spacer particles made of alumina in Example 3 and the silica fine particles S1 on the top surface of the toner base particles TM are more likely to electrically adhere to each other, and although the releasability between the spacer particles and the toner base particles is relatively reduced, almost the same effects as in Example 1 can be obtained.

[0175] Next, the configurations of fourth and fifth embodiments of the present invention will be described.

[0176] In both Examples 4 and 5, a voltage having the same polarity as the normal charging polarity of the toner is applied to the developing blade relative to the potential of the developing roller in order to promote the imparting of charge to the toner. Note that the spacer particles SP used in Example 4 are silica particles S2, and the spacer particles SP used in Example 5 are alumina (particles).

[0177] Specifically, in the above-described first embodiment, the voltage between the developing roller and the developing blade is 0 V, whereas in the fourth and fifth embodiments, a voltage is applied to the developing blade with a potential difference of −100 V relative to the developing roller.

[0178] In Examples 4 and 5, the toner is more easily charged, and better results are obtained in dot reproducibility and durability against fog than in Example 1.

[0179] On the other hand, Example 4 is better than Example 5 in terms of H / H (high temperature and high humidity) streak-like fog.

[0180] Specifically, the spacer particles SP in Example 5 are alumina (particles), which have a triboelectric charge polarity opposite to that of the toner.

[0181] Therefore, in Example 5, the toner has a "negative" charge, and the alumina of the spacer particles SP has a "positive" charge, and passes between the developing blade and the developing roller. In Example 5, the developing blade has a potential difference of -100 V with respect to the developing roller, and the "negative" charge acts as an electric force toward the developing roller, and the "positive" charge acts as an electric force toward the developing blade. Therefore, the alumina of the spacer particles are easily attached to the developing blade because a force acts toward the developing blade.

[0182] Furthermore, if alumina adheres to a portion of the longitudinal tip of the developing blade, the toner intake opening at the adhered portion becomes smaller, reducing the amount of toner in the toner coating layer at the adhered portion. This can result in streaky density differences on a uniform image. The inventors of this application observed the developing blade in the portion where the streaky images occurred and confirmed that there was a relatively large amount of alumina adhering to the blade and that the streaky images were reduced after the adhering material was removed.

[0183] On the other hand, in Example 4, a voltage of -100 V is applied to the developing blade with respect to the developing roller, and silica particles S2 are used as the spacer particles SP. Therefore, both the toner and the spacer particles SP have negative polarity, which can suppress contamination of the developing blade. In other words, compared to Example 5, Example 4 can improve image quality through high chargeability, while more effectively suppressing deterioration of toner fluidity due to durability and contamination of the developing blade.

[0184] Next, a sixth embodiment of the present invention will be described.

[0185] Example 6 differs from Example 4 in that the surface layer of the toner particles is formed of organic silica (organosilicon polymer).

[0186] Compared to inorganic silica (Example 4), organic silica is heated to a lower temperature during the manufacturing process, resulting in a lower hardness. Therefore, the organic silica-containing surface layer can better suppress abrasion that occurs when it comes into contact with the tip of the developing blade. Therefore, compared to Example 4, Example 6 can maintain a high developing blade regulating force throughout durability, increase the amount of toner carried by the toner coating layer, and better suppress poor regulating performance in low-humidity environments.

[0187] In Example 4, the silica fine particles S1 on the surface of the toner base particles TM are inorganic particles with high hardness. Therefore, when the developing blade comes into contact with the silica fine particles, slight abrasion of the tip of the developing blade may occur, resulting in a slight decrease in the regulating force of the developing blade. Therefore, compared to Example 4, Example 6 is more advantageous in terms of the stability of the toner coating layer amount and maintaining regulating performance in a low-humidity environment.

[0188] <Relationship between the occupancy rate H of silica fine particles S1 on the surface of toner base particles and inorganic spacer particles SP> Next, the relationship between the occupancy rate H of the fine silica particles S1 on the surface of the toner base particle TM and the inorganic spacer particles SP will be described.

[0189] Table 3 below shows the configurations and evaluation results of Examples 7 to 10 and Comparative Examples 2 to 6. Table 3 also lists the configurations (see Table 1) and evaluation results (see Table 2) of the aforementioned "Example 1" and "Comparative Example 1."

[0190] Examples 7 to 10 basically conform to the configuration of Example 1, but differ from Example 1 in the following points.

[0191] Specifically, in Examples 7, 8, 9, and 10, the (area) occupancy of the fine silica particles S1 on the surface of the toner base particles is 42%, 42%, 74%, and 74%, respectively.

[0192] The area occupancy of the silica fine particles S1 was adjusted appropriately by adjusting the amount of the fixed silica added.

[0193] In Examples 7, 8, 9, and 10, the particle sizes of the inorganic spacer particles SP were 50 nm, 150 nm, 50 nm, and 150 nm, respectively.

[0194] On the other hand, Comparative Examples 2 to 5 basically conform to the configuration of Example 1, but differ from Example 1 in the following points.

[0195] Specifically, in Comparative Examples 2, 3, 4, and 5, the (area) occupancy of the silica fine particles S1 on the toner base particle surface is 38%, 80%, 60%, and 74%, respectively.

[0196] The area occupancy of the silica fine particles S1 was adjusted appropriately by adjusting the amount of the fixed silica added.

[0197] In Examples 7, 8, 9, and 10, the particle sizes of the inorganic spacer particles SP were 200 nm, 100 nm, 30 nm, and 200 nm, respectively.

[0198] The above-mentioned (1.) high-humidity fogging, (2.) low-humidity development streaks, and (4.) high-humidity development streaks were further evaluated using Examples 7 to 10 and Comparative Examples 2 to 5. The evaluation results are shown in Table 3.

[0199] [Table 3]

[0200] As shown in Table 3, Examples 1 and 7 to 10 are good and have no image defects.

[0201] On the other hand, in Comparative Examples 1 and 2, the (area) occupancy rate H of the silica fine particles S1 on the toner base particle surface was too low (less than 40%), so as the number of printed sheets (durability) increased, stress was applied to the toner, and the inorganic spacer particles adhered to the toner base particles. When the inorganic spacer particles adhered to the toner base particles, as mentioned above, partial abrasion occurred at the tip of the developing blade, resulting in low-humidity development streaks.

[0202] In Comparative Examples 2, 3, and 5, the inorganic spacer particles are too large (over 150 nm), which means that they have high releasability from the toner and tend to adhere to the tip of the developing blade, causing streaks during high-humidity development.

[0203] In Comparative Example 4, the inorganic spacer particles were too small (less than 40 nm), so when stress was applied to the toner as the number of printed sheets (durability) increased, the toner particles came closer to each other, reducing the toner fluidity. As a result, it became difficult to obtain charge from the developing blade, resulting in significant high-humidity fogging.

[0204] In this embodiment, by setting the occupancy rate H of the silica particles on the toner base particle surface to 40% or more and the particle size of the inorganic spacer particles SP to 50 to 150 nm, it is possible to effectively suppress abrasion of the tip of the metal developing blade while maintaining high charging properties. As a result, stable, good images can be obtained even after long-term use.

[0205] The configuration of the present invention can be summarized as follows.

[0206] (1) The developing device (4) of the present invention comprises a developing frame (24) that contains a developer (T), a developer carrier (22) that is rotatably supported by the developing frame and carries a developer; The developing device has a metal blade (23a), one end (23a1) of which is fixed to the developing frame, and the other end (23a2) of which is arranged to contact the developer carrier, and a regulating member (23) that regulates the thickness of the developer carried on the developer carrier.

[0207] The developer (T) contains toner base particles TM and external additives (S1, SP).

[0208] The external additive contains silica fine particles (S1) having a particle size (n) of 5 nm or more and 25 nm or less, and inorganic spacer particles (SP) having a particle size (r1) of 50 nm or more and 150 nm or less.

[0209] The surface area occupancy (H) of the silica fine particles (S1) on the surface of the toner base particle is 40% or more.

[0210] (2) The developing device (4) of the present invention comprises a developing frame (24) that accommodates the developer (T); a developer carrier (22) that is rotatably supported by the developing frame and carries a developer; The developing device has a metal blade (23a), one end (23a1) of which is fixed to the developing frame, and the other end (23a2) of which is arranged to contact the developer carrier, and a regulating member (23) that regulates the thickness of the developer carried on the developer carrier.

[0211] The developer contains toner base particles (TM) having an organosilicon-containing surface layer (PSL) made of an organosilicon compound (OS), and an external additive (SP).

[0212] The external additive contains inorganic spacer particles (SP) having a particle size (r1) of 50 nm or more and 150 nm or less.

[0213] The area occupancy (H) of the organosilicon compound (OS) on the surface of the toner base particle is 40% or more.

[0214] (3) In the developing device of the present invention, the other end (23a2) of the metal blade may be disposed so as to extend upstream in the rotation direction (R4) of the developer carrier.

[0215] (4) In the developing device of the present invention, when the developer carrier (22) is not incorporated into the developing frame (24), and a developer carrier is incorporated into the developing frame, as viewed from the direction of the rotation axis (X1) of the developer carrier, The tip end surface (23a21) of the other end of the metal blade and the contact surface (23a22) that contacts the developer carrier intersect at an intersection (23a23) inside the virtual outer circumference (MC1) of the developer carrier, It may be configured so that, when a first imaginary plane (SF1) that passes through the rotation center (X0) of the developer carrier and is parallel to the contact surface (23a22) is used as a reference, it is located in a first imaginary region (TD1) on one side where the metal blade is located.

[0216] (5) In the developing device of the present invention, when a first imaginary plane (SF1) and a second imaginary plane (SF2) perpendicular to the first imaginary plane are used as references, The intersection (23a23) may be configured to be located in a range (TD1d) of the first imaginary region (TD1) downstream of the second imaginary surface in the rotation direction of the developer carrier and upstream of the first imaginary surface.

[0217] (6) In the developing device of the present invention, when a first imaginary plane (SF1) and a second imaginary plane (SF2) perpendicular to the first imaginary plane are used as references, The intersection (23a23) may be configured to be located in a range (TD1u) of the first imaginary region (TD1) that is upstream of the second imaginary surface in the rotation direction of the developer carrier and downstream of the first imaginary surface.

[0218] (7) In the developing device of the present invention, the metal blade (23a) may be configured so that a bias of the same polarity as the normal charging polarity of the developer (T) is applied to the developer carrier (22).

[0219] (8) In the developing device of the present invention, the charge polarity of the inorganic spacer particles (SP) may be the same as the normal charge polarity of the developer.

[0220] (9) In the developing device of the present invention, the silica fine particles (S1) may be fixed to the toner base particles (TM).

[0221] (10) In the developing device of the present invention, the inorganic spacer particles (SP) may be silica particles (S2).

[0222] (11) In the developing device of the present invention, the particle diameter (r1) of the inorganic spacer particles is 80 nm or more and 150 nm or less, The surface area (H) of the silica fine particles (S1) on the surface of the toner base particle (TM) is preferably 45% or more.

[0223] (12) In the developing device of the present invention, the surface area occupancy (H) of the silica fine particles (S1) on the surface of the toner base particle (TM) is preferably 75% or less.

[0224] (13) The process cartridge (S) of the present invention comprises a developing device (4) and an image carrier (1) that carries a developer image (T), and is detachably mountable to an image forming apparatus.

[0225] (14) The image forming apparatus (100) of the present invention includes a developing device (4) or a process cartridge (S) and a transfer member (14). [Explanation of symbols]

[0226] 4. Development unit (developing device) 22 Developing roller (developer carrier) 23 Developing blade (regulating member) 23a Metal SUS plate (metal blade) 23a1 (of a metal blade) 23a2 (the other end of the metal blade) 24 Developing frame H (Silica fine particle) area occupancy n particle size (of silica particles) r1 (inorganic spacer particle) particle size S1 Silica fine particles (external additive) SP inorganic spacer particles (external additive) T Toner (developer) TM toner base particles

Claims

1. a developing frame that accommodates a developer; a developer carrier rotatably supported by the developing frame and carrying a developer; a developing device including a metal blade, one end of the metal blade being fixed to the developing frame and the other end being arranged to contact the developer carrier, and a regulating member for regulating a thickness of a developer carried on the developer carrier, the developer contains toner base particles and an external additive; the external additive includes silica fine particles having a particle size of 5 nm or more and 25 nm or less, and inorganic spacer particles having a particle size of 50 nm or more and 150 nm or less, a developing device comprising: a toner base particle surface area occupied by the silica fine particles fixed to the toner base particle surface;

2. the other end of the metal blade is disposed so as to extend upstream in the rotation direction of the developer carrier; 2. The developing device according to claim 1.

3. In a state where the developer carrier is not incorporated into the developing frame, Assuming that the developer carrier is incorporated in the developing frame, when viewed from the direction of the rotation axis of the developer carrier, an intersection where the tip surface of the other end of the metal blade and a contact surface that contacts the developer carrier intersect, Inside the virtual outer circumference of the developer carrier, and the developer bearing member is positioned in a first imaginary region on one side where the metal blade is present, when a first imaginary plane that passes through the rotation center of the developer bearing member and is parallel to the contact surface is used as a reference; 3. The developing device according to claim 2.

4. When the first imaginary plane and a second imaginary plane that passes through the rotation center of the developer carrier and is perpendicular to the first imaginary plane are used as references, the intersecting portion is located in a range of the first imaginary area that is downstream of the second imaginary surface and upstream of the first imaginary surface in the rotation direction of the developer carrier.

4. The developing device according to claim 3.

5. When the first imaginary plane and a second imaginary plane perpendicular to the first imaginary plane are used as references, the intersecting portion is located in a range of the first imaginary area that is upstream of the second imaginary surface and downstream of the first imaginary surface in the rotation direction of the developer carrier.

4. The developing device according to claim 3.

6. a bias having the same polarity as the normal charging polarity of the developer is applied to the metal blade with respect to the developer carrier; 6. The developing device according to claim 1, wherein the developing device is a developing unit.

7. The charge polarity of the inorganic spacer particles is the same as the normal charge polarity of the developer.

7. The developing device according to claim 1, wherein the developing device is a developing unit.

8. The surface area occupancy of the silica fine particles in the developer in which the silica fine particles are fixed to the surfaces of the toner base particles is obtained by weighing 20 g of a 30 mass % aqueous solution of a neutral detergent for cleaning precision measuring instruments containing Contaminon N and having a pH of 7 into a 50 mL vial, mixing the solution with 1 g of the developer, setting the vial in a KM Shaker (model: V.SX) manufactured by Iwaki Sangyo Co., Ltd., shaking the mixture for 120 seconds at a speed of 50, separating the mixture in a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) (at 16.67 S-1 for 5 minutes), and vacuum-drying the precipitated developer (at 40°C for 24 hours) to dryness, and then photographing the washed developer using a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation).

2. The developing device according to claim 1.

9. 9. The developing device according to claim 1, wherein the inorganic spacer particles are silica particles.

10. the inorganic spacer particles have a particle size of 80 nm or more and 150 nm or less; 2. The developing device according to claim 1, wherein the surface area of ​​the silica fine particles is 45% or more of the surface of the toner base particles.

11. 11. The developing device according to claim 10, wherein the area occupancy of the silica fine particles on the surface of the toner base particle is 75% or less.

12. The developing device according to any one of claims 1 to 11, A process cartridge comprising: an image carrier that carries a developer image; and a developer image carrier that is detachably mountable to an image forming apparatus.

13. The developing device according to any one of claims 1 to 11 or the process cartridge according to claim 12; a transfer member.

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