Developing device, processing cartridge, and image forming apparatus

Abstract

A developer used in a developing device equipped with a metal blade, the developer including toner base particles and an external additive, the external additive including 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 an area occupancy rate of the silica fine particles on the surface of the toner base particles being 40% or more.

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus, a developing device, and a processing cartridge each for use in the image forming apparatus. More specifically, the present disclosure relates to an electrophotographic image forming apparatus using electrophotography and to a developing device and a processing cartridge each for use in the electrophotographic image forming apparatus. Background Art

[0002] Heretofore, a technique has been widely known in which the free end of a metal developing blade is brought into contact with (abutted against) the surface of a developing roller, and then a toner layer coated on the developing roller is adjusted and charges are applied to the toner by triboelectrification due to the rotation of the developing roller.

[0003] Meanwhile, Japanese Patent No. 4370422 proposes a technique in which, in the case of using a metal developing blade, inorganic fine particles having a predetermined particle diameter are added to the toner to improve the fluidity (chargeability) of the toner.

[0004] More specifically, the technique proposed in Japanese Patent No. 4370422 uses a toner to which a plurality of types of inorganic fine particles having different average diameters are added. The small-diameter inorganic fine particles included in the toner contribute to improving the chargeability of the toner, and the large-diameter inorganic fine particles contribute to suppressing the small-diameter inorganic fine particles from being buried in the toner base particles. The fluidity (chargeability) of the toner is improved by using the fine particles having different diameters in combination.

[0005] However, the technique proposed in Japanese Patent No. 4370422 has a possibility that, as the number of image forming operations increases (i.e., as the cumulative use time increases), the large-diameter inorganic fine particles may be buried in the toner base particles. The large-diameter inorganic fine particles buried in the toner base particles and combined with the toner base particles enhance the wear action on the leading edge portion (abutting portion) of the metal developing blade, and thus change the contact state between the metal blade and the developing roller or the situation where the toner is brought into the abutting portion due to wear. Therefore, adjustment failures such as "coating change" are more likely to occur. Summary of the Invention

[0006] In view of the above-described drawbacks, the present disclosure provides a developing device, a processing cartridge, and an image forming apparatus each capable of suppressing the occurrence of coating change while improving the chargeability of a developer coating formed on a developer carrier member.

[0007] A developing device according to one aspect of the present disclosure includes: a developing frame configured to store a developer; a developer carrier member rotatably supported by the developing frame and configured to carry the developer; and an adjusting member including a metal blade, one end of the metal blade being fixed to the developing frame and the other end being disposed to contact the developer carrier member, the adjusting member adjusting the thickness of the developer carried on the developer carrier member, wherein the developer includes toner base particles and an external additive, the external additive includes silica 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 area occupancy rate of the silica particles on the surface of the toner base particles is 40% or more.

[0008] A developing device according to another aspect of the present disclosure includes: a developing frame configured to store a developer; a developer carrier member rotatably supported by the developing frame and configured to carry the developer; and an adjusting member including a metal blade, one end of the metal blade being fixed to the developing frame and the other end being disposed to contact the developer carrier member, the adjusting member adjusting the thickness of the developer carried on the developer carrier member, wherein the developer includes toner base particles and an external additive, the toner base particles have a surface layer containing organosilica made of an organosilicon compound, the external additive includes inorganic spacer particles having a particle diameter of 50 nm or more and 150 nm or less, and the area occupancy rate of the organosilicon compound on the surface of the toner base particles is 40% or more.

[0009] Other features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a conceptual cross-sectional view of an image forming apparatus according to Embodiment 1 of the present disclosure.

[0011] Figure 2 is a conceptual cross-sectional view of a developing device used in the image forming apparatus according to Embodiment 1 of the present disclosure.

[0012] Figure 3 is a conceptual cross-sectional view of a developer used in Embodiments 1 to 5 of the present disclosure.

[0013] Figure 4A and 4B are each a conceptual view showing the contact state between spacer particles and silica fine particles on the surface of toner base particles.

[0014] Figure 5A and 5BEach is a conceptual view showing the positional relationship between the spacer particles and the silica fine particles on the surface of the toner base particles.

[0015] Figure 6 It is a table showing the relationship between the particle diameter (n) of the silica fine particles on the surface of the toner base particles, the area occupancy H of the silica fine particles thereon, and the outer diameter MR of the imaginary circle.

[0016] Figure 7 It is a conceptual cross-sectional view showing the relative positions of both the developing blade and the developing roller used in Example 1 of the present disclosure.

[0017] Figure 8 It is a conceptual cross-sectional view showing the relative positions of both the developing blade and the developing roller used in Example 2 of the present disclosure.

[0018] Figure 9A and 9B Each is a conceptual view showing the wear generation mechanism caused by the spacer particles at the leading edge (abutting) portion of the developing blade.

[0019] Figure 10 It is a conceptual cross-sectional view of the developer used in Example 6 of the present disclosure. Detailed Description

[0020] Example 1

[0021] Configuration of the Image Forming Apparatus

[0022] The overall configuration of an electrophotographic image forming apparatus (hereinafter referred to as "image forming apparatus") according to the present disclosure will be described below. Figure 1 It is a conceptual cross-sectional view of the image forming apparatus 100 according to this embodiment.

[0023] The image forming apparatus 100 according to this embodiment is a full-color laser printer using an on-line system and an intermediate transfer system.

[0024] The image forming apparatus 100 is capable of forming a full-color image on a recording material P (for example, recording paper or plastic sheet) according to image information. The image information is input into the image forming apparatus 100 from an image reading device or a host device, such as a personal computer connected so as to be able to communicate with the image forming apparatus 100.

[0025] The image forming apparatus 100 includes first, second, third, and fourth processing cartridges Sa, Sb, Sc, and Sd as a plurality of image forming units, which are respectively configured to form images of yellow (Y), magenta (M), cyan (C), and black (K). In this embodiment, the first to fourth processing cartridges Sa, Sb, Sc, and Sd are arranged in a row in a direction intersecting the vertical direction. In this embodiment, except that the colors of the images to be formed are different from each other, the configurations and operations of the first to fourth processing cartridges Sa, Sb, Sc, and Sd are substantially the same. Therefore, hereinafter, unless it is particularly necessary to distinguish each processing cartridge, the suffixes a, b, c, and d indicating which of the four colors the processing cartridge corresponds to are omitted, and the term "processing cartridge" is used in a collective sense.

[0026] In this embodiment, the image forming apparatus 100 includes four drum-type electrophotographic photoreceptors, namely, photosensitive drums 1 (1a, 1b, 1c, and 1d), which are arranged side by side as a plurality of image bearing members in a direction intersecting the vertical direction. Each of the photosensitive drums 1 is driven and rotated by a driving unit (driving source) (not shown). Around each photosensitive drum 1, a charging roller 2 (2a, 2b, 2c, or 2d), a scanner unit (exposure device) 3 (3a, 3b, 3c, or 3d), and a developing unit (developing device) 4 (4a, 4b, 4c, or 4d) are provided. The charging roller 2 is a charging unit configured to uniformly charge the surface of the photosensitive drum 1.

[0027] The scanner unit 3 is an exposure unit configured to emit a laser beam and form an electrostatic image (electrostatic latent image) on the photosensitive drum 1 based on a calculation output obtained from image information input from a host device (such as a personal computer) by a CPU (not shown). The developing unit 4 is a developing unit configured to develop the electrostatic latent image into a developer (hereinafter referred to as "toner") image. The photosensitive drum 1 is integrated with the charging roller 2 and the developing unit 4, and they each act as a processing unit that acts on the photosensitive drum 1, thereby forming a processing cartridge S.

[0028] The processing cartridge S is detachably mounted to the image forming apparatus 100 through a mounting unit (such as mounting rails and positioning members) provided in the image forming apparatus 100.

[0029] An intermediate transfer belt 10 that acts as an intermediate transfer member for transferring the toner image on the photosensitive drum 1 to the recording material P is disposed opposite to the four photosensitive drums 1. The intermediate transfer belt 10 in the form of an endless belt is in contact with all the photosensitive drums 1 and circulates (rotates) in the direction shown by the arrow R3 in the figure. The intermediate transfer belt 10 is wound around a plurality of support members, namely, an opposed roller 13 for secondary transfer, a driving roller 11, and a tension roller 12.

[0030] Four primary transfer rollers 14 (14a, 14b, 14c, and 14d) serving as a primary transfer unit are arranged in a row on the inner peripheral surface side of the intermediate transfer belt 10 so as to face the photosensitive drum 1 in a one-to-one relationship. Each primary transfer roller 14 presses the intermediate transfer belt 10 against the photosensitive drum 1 and forms a primary transfer area where the intermediate transfer belt 10 and the photosensitive drum 1 are in contact with each other.

[0031] The secondary transfer roller 20 serving as a secondary transfer unit is provided on the outer peripheral surface side of the intermediate transfer belt 10 at a position opposite to the counter roller 13 for secondary transfer. The secondary transfer roller 20 is kept in pressure contact with the counter roller 13 for secondary transfer (with the intermediate transfer belt 10 interposed therebetween), and forms a secondary transfer area where the intermediate transfer belt 10 and the secondary transfer roller 20 are in contact with each other.

[0032] The recording paper P on which the toner image has been transferred is conveyed to the fixing device 30 serving as a fixing unit. By applying heat and pressure to the recording paper P in the fixing device 30, the toner image is fixed to the recording paper P.

[0033] The image forming apparatus 100 is configured to be able to form a monochromatic or multicolor image by using only a desired one or some (but not all) of the image forming units.

[0034] In this embodiment, the image forming apparatus 100 is a printer applicable to a processing speed of 148.2 mm / second and A4-size paper.

[0035] Image forming process

[0036] In the image forming period, first, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2.

[0037] Then, according to the calculation output obtained from the image information input from the host device by the CPU, scanning exposure is performed on the surface of the photosensitive drum 1 that has been charged by the laser beam emitted from the scanner unit 3, and an electrostatic image according to the image information is formed on the photosensitive drum 1.

[0038] Then, the electrostatic image formed on the photosensitive drum 1 is developed into a toner image by the developing unit 4.

[0039] Then, a voltage having a polarity opposite to the normal charging polarity of the toner is applied from the primary transfer voltage supply source 15 (high-voltage power supply) serving as a primary transfer voltage applying unit to the primary transfer roller 14 (transfer member).

[0040] As a result, the toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 10 at once. When forming a full-color image, the above-described processes are sequentially performed in the first to fourth process cartridges Sa, Sb, Sc, and Sd, and the toner images of respective colors are sequentially transferred onto the intermediate transfer belt 10 at once in a superimposed relationship.

[0041] Thereafter, the recording material P is conveyed to the secondary conveyance area in synchronization with the movement of the intermediate conveyor belt 10. Then, a voltage having a polarity opposite to the normal charging polarity of the toner is applied from a secondary transfer voltage supply source 21 (high-voltage power supply), which serves as a secondary transfer voltage application unit, to the secondary transfer roller 20. As a result, the four-color toner image on the intermediate transfer belt 10 is secondarily transferred onto the recording paper P together by the action of the secondary transfer roller 20 that is in contact with the intermediate transfer belt 10 with the recording paper P interposed therebetween, and the recording paper has been conveyed to the secondary transfer area by the supply unit.

[0042] The recording material P onto which the toner image has been transferred is conveyed to a fixing device 30 that serves as a fixing unit. In the fixing device 30, the transferred toner image is fixed onto the recording material P by applying heat and pressure. The recording material P is then discharged from the image forming apparatus 100.

[0043] To control the amount of developed toner, the developing unit 4 is configured to perform reverse development in such a manner that a developing roller 22 (described later), which serves as a developer carrier member, contacts the photosensitive drum 1 while providing a speed difference therebetween. More specifically, the developing unit 4 used here is configured to develop an electrostatic image by attaching toner having the same charging polarity as the charging polarity of the photosensitive drum 1 (negative polarity in this embodiment) to an area where the charge on the photosensitive drum 1 decays with exposure (image area or exposure area). In this embodiment, the developing roller 22 moves at a speed ratio of 1.4 times that of the photosensitive drum 1.

[0044] The transfer residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer step is collected by the developing roller 22 (described later) and reused. The transfer residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer step is charged to the normal charging polarity when passing through the charging roller 2. Thereafter, the transfer residual toner is collected by the developing roller 22 for reuse under an electric field formed 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.

[0045] Configuration of the Process Cartridge

[0046] The overall configuration of the process cartridge S installed in the image forming apparatus 100 according to this embodiment will be described below (refer to Figure 1 ). Refer to Figure 2To describe the developing unit 4 that forms part of the processing cartridge S. Figure 2 It is a conceptual cross-sectional view of the developing unit (device).

[0047] Except for identification parts etc. (not shown), the processing cartridges S for the respective colors have the same shape. Toners of various colors, yellow (Y), magenta (M), cyan (C), and black (K), are stored in the developing unit 4 of the processing cartridge S in a one-to-one relationship. In the developing unit 4, a non-magnetic one-component toner is used as the developer.

[0048] The processing cartridge S is constituted by integrating a photosensitive unit including a photosensitive drum 1 and a rotatable charging roller 2 and a developing unit (device) 4 including a rotatable developing roller 22 etc.

[0049] The photosensitive drum 1 is rotatably supported by a bearing (not shown). The driving force from a driving unit (driving source) not shown is transmitted to the photosensitive drum 1, so that the photosensitive drum 1 is driven according to the image forming operation and rotates in the direction shown by the arrow R1 in the figure. The charging roller 2 has a roller portion made of conductive rubber and is held in pressure contact with the photosensitive drum 1 to rotate by friction.

[0050] On the other hand, the developing unit (device) 4 includes a developing roller 22 that carries toner, a developing blade 23 (metal blade) that constitutes an adjusting member, a supply member 26 provided in contact with the developing roller, and a developing frame 24 that fixedly supports the above members.

[0051] One end of the developing blade 23 is fixed to a support member 23b, the support member 23b is fixed to the developing frame 24, and the other end of the developing blade 23 is held in contact with the developing roller 22 so as to be able to adjust the amount of toner coated on the developing roller 22 and apply charge to the developing roller 22. The developing roller 22 is provided in a developing opening so as to be able to abut against the photosensitive drum 1. The developing roller 22 is driven and rotates in the direction indicated by the arrow R4 in the figure.

[0052] In this embodiment, the developing roller 22 and the photosensitive drum 1 rotate such that the surfaces of the developing roller 22 and the photosensitive drum 1 move in the same direction in the relative area (in this embodiment, from top to bottom in the gravity direction). A predetermined direct current is applied to the developing roller 22 as a developing bias, and the electrostatic latent image is visualized with the triboelectrically negatively charged toner, thereby forming a toner image in the developing area where the developing roller 22 contacts the photosensitive drum 1.

[0053] Adjusting member

[0054] The developing blade 23 (adjusting member) will be described below.

[0055] As Figure 2As shown, the developing blade 23 is held in contact with the developing roller 22 so as to be oriented in the opposite direction, and has the function of adjusting the toner coating amount and applying charge.

[0056] In this embodiment, a metal SUS plate 23a (metal blade) in the form of a leaf spring with a thickness of 50 to 120 μm and a support member 23b are used as the developing blade 23, and the surface of the developing blade is held in contact with the developing roller 22 by the spring elasticity of the metal SUS plate 23a. The developing blade 23 portion on the other end side in the width direction is formed as a metal blade, and one end thereof is fixed to and supported by the developing frame 24. The developing blade 23 is not limited to the example mentioned above. The support member may be made of a SUS plate or a thin metal plate such as phosphor bronze or aluminum. From the perspective of applying charge to the toner, a metal such as SUS, phosphor bronze, or aluminum can be used for the metal blade. In this embodiment, SUS is used. The voltages applied to the developing blade 23 and the developing roller 22 (as a predetermined DC voltage) are set to the same value to stabilize the performance of providing charge to the toner.

[0057] The supply member 26 is composed of a conductive core metal with an outer diameter of 4 (mm) and a polyurethane sponge layer made of a soft continuous foam and formed around the core metal. The outer diameter of the supply member 26 is 11 (mm). Since a polyurethane sponge layer made of a soft continuous foam is used, the supply member 26 can hold the toner in the sponge. The supply member 26 is supported by the developing frame 24 so as to be in contact with the developing roller 22 and is rotationally driven in the direction shown by the arrow R5 in the figure during the developing operation.

[0058] The developing roller 22 serving as a developer carrier member is formed by continuously laminating a base layer and a surface layer made of polyurethane around a metal core. The developing bias is applied to the surface layer and the base layer through the core metal.

[0059] It is preferable to use carbon black because the conductivity of the conductive elastic layer and the charging characteristics of the conductive elastic layer for the toner can be controlled by using carbon black. The volume resistivity of the conductive elastic layer is preferably in the range of 1×10 3 Ω·cm or more to 1×10 11 Ω·cm or less. In this embodiment, 1×10 6 Ω·cm is used.

[0060] The installation of the developing blade 23 will be described in detail below with reference to Figure 7 FIG.

[0061] Figure 7 is a conceptual cross-sectional view showing the installation state (posture) of the developing blade before connecting the developing roller. For reference, the imaginary outer diameter circumference (outer peripheral surface) MC1 of the developing roller is indicated by a dotted line in Figure 7 FIG.

[0062] As shown Figure 7 in the figure, one end 23a1 in the width direction of the metal blade (metal SUS plate 23a) is fixed to the developing frame 24 through the support member 23b. The other end 23a2 in the width direction of the metal blade is a free end.

[0063] In a state where the developing roller 22 is not assembled in the developing frame 24, it is assumed here that the developing roller 22 is hypothetically assembled into the developing frame 24. When observed in the rotational axis direction X1 of the developing roller in such a hypothetical assembled state, the intersection point 23a23 where the leading edge surface 23a21 at the other end 23a2 (free end) of the developing blade 23 intersects with its abutting surface 23a22 against the developing roller is located inside the hypothetical outer diameter circumference MC1 of the developing roller 22. Further, assuming a first hypothetical plane SF1 passing through the rotation center X0 of the developing roller 22 and parallel to the abutting surface 23a22 as a reference, the intersection point 23a23 is located in the first hypothetical region TD1 on the side of the first hypothetical plane SF1 where the developing blade exists.

[0064] Particularly, in this embodiment, assuming the first hypothetical plane SFl and a second hypothetical plane SF2 passing through the rotation center X0 of the developing roller and perpendicular to the first hypothetical plane as references, in the rotational direction R4 of the developing roller, the intersection point 23a23 is located in the region TD1d within the first hypothetical region (TD1) on the downstream side of the second hypothetical plane and the upstream side of the first hypothetical plane. In other words, as Figure 7 shown in the figure, the developing blade 23 is arranged to abut against the surface of the developing roller at the edge (intersection point 23a23) of the other end 23a2 (free end).

[0065] With the above arrangement, since the free end edge of the developing blade abuts against the developing roller, the size of the toner intake defined by the adjusting member can be reduced, and a higher adjusting force can be obtained. Particularly, the highly charged toner has a high electrostatic adhesion force, thereby increasing the adhesion force between the toner and the developing roller and the adhesion force between the toners. However, the toner adjustment and the formation of the toner coating can be stably performed according to the configuration of the present disclosure.

[0066] Developer

[0067] Next, the toner (developer T) used in this embodiment will be described with reference to Figure 3 the figure. Figure 3 is a conceptual cross-sectional view of the toner (developer T).

[0068] The average diameter (average particle diameter) of the toner particles (including the toner base particles TM and the small-diameter silica fine particles S1) is 7 μm. More specifically, in the toner particles, the small-diameter silica fine particles S1 ("fixed silica described later") are externally added to the surface of the toner base particles TM at a content of 1.0 part by mass per 100 parts by mass of the toner base particles TM, so that the small-diameter silica fine particles Si adhere to the surface of the toner base particles TM.

[0069] Then, 0.6 part of silica particles S2 is externally added to 100 parts of the toner particles as the spacer particles SP by using a Henschel mixer (model FM10C, manufactured by NIPPON COKE&ENGINEERING, CO., LTD), and the silica particles S2 have a particle diameter (rl) of 100 nm in terms of primary particles.

[0070] The silica fine particles S1 and the spacer particles SP (silica particles S2) in this example are external additives in the present disclosure.

[0071] The particle diameter (n) of the silica fine particles S1 (fixed silica) in terms of primary particles is 5 nm or more and 25 nm or less, and preferably 5 nm or more and 15 nm or less.

[0072] If the particle diameter (n) of the silica fine particles S1 (fixed silica) in terms of primary particles is less than 5 nm, the silica fine particles S1 are significantly buried in the toner particles, resulting in the adverse effect that the chargeability and fluidity can no longer be sufficiently adjusted during long-term use. On the other hand, if the particle diameter (n) of the silica fine particles S1 in terms of primary particles is greater than 25 nm, the coating change becomes obvious. Silica fine particles S1 (fixed silica) with a particle diameter of 20 nm are used in this example.

[0073] Spacer particles

[0074] The inorganic particles constituting the spacer particles SP can be made of, for example, silica, alumina, titanium oxide, or boron nitride. Inorganic silica is used in this example.

[0075] In this example, the particle diameter (r1) of the spacer particles SP in terms of primary particles is 50 nm or more and 150 nm or less.

[0076] If the particle diameter (r1) of the spacer particles SP in terms of primary particles is less than 50 nm, the effect as a spacer is small, the adjustment for embedding the silica fine particles into the toner base particles is weak, and the fluidity of the toner can no longer be sufficiently adjusted. On the other hand, if the particle diameter (r1) of the spacer particles SP in terms of primary particles is greater than 150 nm, the wear effect on the abutting portion of the metal wiper is enhanced and "coating change" is more likely to occur, as described below.

[0077] If the particle diameter (r1) of the spacer particles SP is greater than 150 nm, in some cases, the adhesion of the spacer particles to the surface of, for example, the developing blade may develop. In such cases, it is difficult for the charge to be transferred from the developing blade to the toner, which may result in low-charge toner (i.e., fogging).

[0078] In this embodiment, the particle diameter (r1) of the spacer particles SP in terms of primary particles is 100 nm.

[0079] Area occupancy of the silica fine particles S1

[0080] The steps of observing the adhesion of both the silica fine particles S1 and the spacer particles SP to the surface of the toner base particles TM and the method of calculating the area occupancy of the silica fine particles S1 will be described below.

[0081] Water washing step

[0082] Weigh 20 g of an aqueous solution containing 30 mass% of a precision machine-washing neutral detergent with a pH of 7, put it into a small bottle with a capacity of 50 mL, and mix it with 1 g of toner. The detergent is composed of "Contaminon N" (nonionic surfactant), an anionic surfactant, and an organic co-builder.

[0083] Put the prepared mixture into a "KM Shaker" (model: V.SX) manufactured by IWAKI INDUSTRY CO., LTD. And vibrate it for 120 seconds with the "speed" set to 50. With the vibration, the silica fine particles that are easily detached from the toner surface are transferred from the surface of the toner base particles or toner particles to the dispersion liquid side. Subsequently, the toner is separated from the external additives (such as the silica fine particles that have been transferred to the supernatant) by centrifugation (5 minutes, at 16.67 S-1) using a centrifugal separator (H-9R: manufactured by KOKUSAN Co., Ltd.). The precipitated toner is dried and solidified by vacuum drying (40 °C / 24 hours), and the toner after water washing is obtained.

[0084] The image of the toner was taken by a Hitachi ultra-high-resolution field emission electron scanning microscope S-4800 (manufactured by Hitachi High-Technologies Corporation).

[0085] Elemental analysis was performed using an energy-dispersive X-ray spectrometer (EDS) to identify the measurement target. A magnification of 50 million times was used as the analysis size that can reflect the toner surface. The occupancy rate (area occupancy rate) H of the fine silica particles S1 was calculated, which is represented by the percentage of the area occupied by silicon atoms in the analysis region.

[0086] The above calculations were performed on 10 types of toners, and the average value of the 10 calculated values was used as the area occupancy rate H of the fine silica particles Sl.

[0087] The area occupancy rate H of the fine silica particles S1 in this example was 60%.

[0088] As described below, when the area occupancy rate H of the fine silica particles S1 is 40% or more, it is possible to effectively suppress the fixed attachment of spacer particles to the toner base particles. In addition, when the area occupancy rate H of the fine silica particles S1 is 40% or more, sufficient charge can be provided to the toner.

[0089] On the other hand, for the following reasons, the area occupancy rate H of the fine silica particles S1 is ideally 75% or less. If the area occupancy rate H exceeds 75%, the toner becomes difficult to melt during heating (for example, 100 °C or higher), leading to the possibility of fixing failure.

[0090] The particle diameter of the spacer particle SP

[0091] Below will refer to Figure 4A and 4B Describe the relationship between the particle diameter (r1) of the spacer particle SP and the area occupancy rate H of the fine silica particles S1 in the present disclosure. Figure 4A and 4B Each is a conceptual diagram showing the "contact state" between the fine silica particles S1 and the spacer particle SP.

[0092] The main role of the spacer particles in the present disclosure is that the spacer particles are interposed between the toner base particles (base material) and suppress the contact between the toner base particles. As a result, it is suppressed that the fine silica particles S1 are buried in the toner base particle TM, and the toner particles become more mobile. In other words, the toner fluidity (and thus the chargeability) is improved.

[0093] To improve the toner fluidity, as Figure 4A shown, it is necessary to suppress the direct contact between the spacer particles and the toner base particles. More specifically, asFigure 4A As shown, the possibility of direct contact between the spacer particles and the toner base particles is reduced by increasing the area occupancy of the silica fine particles on the surface of the toner base particles. In other words, at a high area occupancy, since the spacer particles adhere to the toner base particles in a state where the silica fine particles S1 are interposed between the spacer particles and the toner base particles, the adhesion of the spacer particles to the toner base particles (adhesive force F1) is weakened, and the toner fluidity is maintained.

[0094] On the other hand, in Figure 4B the state shown, the resin component of the toner base particles is relatively rich (i.e., the percentage of resin on the surface of the toner base particles is relatively high), and the area occupancy of the silica fine particles S1 on the surface of the toner base particles is relatively low. In this case, the spacer particles SP are more likely to contact the resin component, and the adhesion (adhesive force F2) between the spacer particles and the toner base particles TM is enhanced. As a result, the movement of the spacer particles on the toner surface is restricted, and the toner fluidity decreases as the movement of the spacer particles is restricted.

[0095] In particular, when an external force is applied in a state where the toner base particles TM and the spacer particles SP are in direct contact with each other (for example, when the toner coating on the developing roller passes through the abutting area between the developing roller and another member), the spacer particles are fixedly attached to or buried 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. Therefore, it is difficult to ensure stable toner fluidity over time.

[0096] Therefore, it is necessary to form a state in which the spacer particles are less likely to contact the surface of the toner base particles. In the present disclosure, the conditions (factors) under which the spacer particles SP are less likely to contact the resin component of the toner base particles TM are studied in detail. Refer to Figure 5A and 5B for a description of this condition (factor).

[0097] Figure 5A and 5B are conceptual diagrams showing the "positional relationship" between the silica fine particles S1 and the spacer particles SP, respectively.

[0098] More specifically, Figure 5A and 5B are enlarged conceptual diagrams schematically showing the surface conditions of the toner base particles. In this figure, "H" represents the area occupancy of the "fixed silica" formed by the silica fine particles S1, and "n" represents the particle diameter of the silica fine particles S1 forming the fixed silica.

[0099] Figure 5BIt shows the state where the fixed silica (fine silica particles S1) is closely packed (arranged), that is, the state where the area occupancy H≈1. In this state, the distance between the centers C1 of two adjacent fine silica particles S1 is given by L=n.

[0100] On the other hand, considering the area occupancy H represented, the distance L increases by 1 / √H. Therefore, the distance between the centers C1 of two adjacent fine silica particles S1 is given by L=n / √H.

[0101] The outer diameter (diameter) MR of the imaginary circle MC2 passing through the centers C1 of three adjacent fine silica particles S1 is given by 2L / √3. It is considered that if the particle diameter (r1) of the spacer particle SP is larger than the outer diameter MR of the imaginary circle MC2 (r1>MR), the contact between the spacer particle and the surface of the toner base particle can be suppressed.

[0102] Figure 6 The table shows the relationship between the particle diameter (n) of the fine silica particles, the area occupancy H of the fine silica particles, and the outer diameter MR of the imaginary circle MC2 under the above assumptions MR(=2L / √3) and L(=n / √H). In other words, Figure 6 It shows the value of the outer diameter MR when the particle diameter (n) of the fine silica particles S1 forming the fixed silica and the area occupancy H of the fine silica particles change.

[0103] As described above, from the perspective of restricting the fixed attachment of the spacer particles, the particle diameter (n) of the fine silica particles S1 forming the fixed silica is appropriately maintained in the range of 5 to 25 nm. More specifically, if the particle diameter (n) is less than 5 nm, the fine silica particles are significantly buried in the toner base particles. On the other hand, if the particle diameter (n) is greater than 25 nm, the coating change in the fine silica particles on the surface of the toner base particles becomes obvious.

[0104] In addition, as described above, the particle diameter of the spacer particles is appropriately 50 nm or more. If the particle diameter of the spacer particles is less than 50 nm, the function of the spacer particles as spacers is small, and thus the fluidity of the toner can no longer be sufficiently adjusted.

[0105] As a result of in-depth research, the inventors of the present application found that when the outer diameter MR of the imaginary circle MC2 of the fixed silica formed based on the fine silica particles on the surface of the toner base particle is less than the lower limit of the particle diameter of the spacer particle (50 nm), it is difficult for the spacer particle to approach the toner base particle due to the volume relationship between the two types of particles.

[0106] In other words, the inventors have successfully specified an appropriate range of the area occupancy ratio H of the fine silica particles, which range satisfies the following conditions: the particle diameter of the fine silica particles S1 that form the fixed silica is (n = 5 to 25 nm) and the outer diameter MR of the imaginary circle MC2 is (MR < 50 nm), as shown in the table of Figure 6 When the area occupancy ratio H of the fine silica particles S1 is set to H > 0.40, the charge amount of the toner can be maintained at an appropriate value (if the area occupancy ratio H is less than 0.40, the toner charge amount tends to decrease), and the fixed attachment of the spacer particles SP to the toner base particles TM can be reliably suppressed.

[0107] If the area occupancy ratio H of the fine silica particles S1 is greater than 0.75, it is considered that fixing failure is more likely to occur. Therefore, the silica area occupancy ratio H is preferably maintained in the range of 0.40 to 0.75.

[0108] With the above configuration, the charge amount (chargeability) of the toner can be maintained at a normal level to reduce the wear (abrasion) of the blade due to the fixed attachment of the spacer particles to the toner base particles and to reduce the coating change.

[0109] In order to more effectively ensure the fluidity of the toner, the particle diameter of the spacer particles is more preferably set to be not less than about twice the outer diameter MR of the imaginary circle MC2. In this case, the area occupancy ratio H of the fine silica particles can be set to 0.45 or more, and the particle diameter of the spacer particles can be set to 80 nm or more.

[0110] If the particle diameter (n) of the fine silica particles S1 that form the fixed silica is less than 5 nm, in some cases, due to the significant aggregation of silica, the distance between the fine silica particles S1 increases, and during long-term use, the spacer particles SP are more likely to be fixedly attached to the toner base particles TM.

[0111] Related art (reference example)

[0112] This reference example (related art) is consistent with Example 1, but is different in the following points.

[0113] A toner prepared by externally adding fine silica particles S1 at a content of 0.3 parts by mass per 100 parts by mass of toner particles was used. The area occupancy ratio H of the fine silica particles S1 was 35%.

[0114] Comparative Example 1

[0115] Comparative Example 1 is consistent with Example 1, but is different from Example 1 in the following points.

[0116] A toner prepared by externally adding silica fine particles S1 at a content of 0.3 parts by mass per 100 parts by mass of toner particles was used. Then, 0.6 parts of silica particles S2 having a primary particle diameter of 100 nm as spacer particles SP were externally added to 100 parts of toner particles using a Henschel mixer. In this case, the area occupancy H of the silica fine particles S1 was 32%.

[0117] Example 2

[0118] Example 2 is the same as Example 1, but is different from Example 1 in the following points.

[0119] In Example 1, the other end 23a2 (free end) of the developing blade was arranged to abut against the surface of the developing roller 22 at the edge (intersection point 23a23) (see Figure 7 ). In other words, the intersection point 23a23 exists in the region TD1d within the first imaginary region TD1.

[0120] In Example 2, as Figure 8 shown, the intersection point 23a23 was arranged to be located in the region TD1u within the first imaginary region TD1.

[0121] More specifically, assuming a first imaginary plane SF1 and a second imaginary plane SF2 perpendicular to the first imaginary plane as references, in the developing roller rotation direction R4, the intersection point 23a23 is located in the region TD1u within the first imaginary region TD1 on the upstream side of the second imaginary plane and the downstream side of the first imaginary plane. In other words, as Figure 8 shown, the developing blade 23 was arranged to abut against the surface of the developing roller 22 at the flat portion (opposite surface 23a22) of the other end 23a2 (free end).

[0122] Compared with the configuration shown in Figure 7 , when the edge of the free end of the developing blade shown in Figure 8 abuts against the developing roller, the size of the toner inlet defined by the adjusting member is larger.

[0123] Example 3

[0124] Example 3 is the same as Example 1, but is different from Example 1 in the following points.

[0125] Aluminum oxide particles were used as the spacer particles SP.

[0126] Example 4

[0127] Example 4 is the same as Example 1, but is different from Example 1 in the following points.

[0128] A bias voltage of -300 V is applied to the developing roller, and a bias voltage of -400 V is applied to the developing blade. For a toner with a conventional charging polarity of negative, a voltage difference of 100 V is formed between the developing roller and the developing blade. Since negative charges are applied to the toner from the developing blade, a highly negatively charged toner is obtained.

[0129] Example 5

[0130] Example 5 is the same as Example 1, but is different from Example 1 in the following points.

[0131] A bias voltage of -300 V is applied to the developing roller, and a bias voltage of -400 V is applied to the developing blade. Alumina particles are used as the spacer particles SP.

[0132] Example 6

[0133] Example 6 is the same as Example 4, but is different from Example 4 in the following points.

[0134] Toner particles TM including a surface layer OS made of a silicone polymer are formed as follows.

[0135] 650.0 parts of ion-exchanged water and 14.0 parts of sodium phosphate (manufactured by RASA Industries, LTD., dodecahydrate) are put into a reaction vessel equipped with a stirrer, a thermometer, and a reflux tube, and maintained at 65 °C for 1.0 hour under a nitrogen purge.

[0136] An aqueous medium containing a dispersion stabilizer is prepared by charging an aqueous calcium chloride solution into the reaction vessel at once. The aqueous solution contains 9.2 parts of calcium chloride (dihydrate) dissolved in 10.0 parts of ion-exchanged water, and is stirred at 15000 rpm using a T.K. homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). Then, an aqueous medium 1 is obtained by adding 10 mass% hydrochloric acid to the above aqueous medium and adjusting the pH to 5.0.

[0137] Preparation of polymerizable monomer composition

[0138] Prepare the following materials:

[0139] · 60.0 parts of styrene

[0140] · 6.5 parts of C.I. Pigment Blue 15:3

[0141] A colorant dispersion is prepared as follows: The materials listed above are put into a grinder (manufactured by MitsuiMiike Kakoki Co., Ltd.), and these materials are dispersed at 220 rpm for 5.0 hours while using 1.7 mm diameter zirconia particles, and then the zirconia particles are removed.

[0142] On the other hand, prepare the following materials:

[0143]

[0144]

[0145] (Polycondensation product of propylene oxide-modified bisphenol A (2-mole 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)

[0146] · Fischer-Tropsch wax (melting point 78 °C): 7.0 parts

[0147] Prepare the polymerizable monomer composition by adding the substances listed above to the above-mentioned colorant dispersion, heating the mixture to 65 °C, and then uniformly dissolving and dispersing the mixture using a T.K. homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) at 500 rpm.

[0148] Granulation step

[0149] After adjusting the temperature of the aqueous medium to 1 to 70 °C, while maintaining the rotation speed of the T.K. homomixer at 15,000 rpm, add the polymerizable monomer composition to aqueous medium 1 and add 10.0 parts of tert-butyl peroxyneodecanoate used as a polymerization initiator. While the stirrer is maintained at 15,000 rpm, perform granulation as it is for 10 minutes.

[0150] Polymerization step and distillation step

[0151] After the granulation step, perform polymerization as follows: Replace the stirrer with a propeller stirring blade and continue polymerization with stirring at 150 rpm while maintaining the temperature at 70 °C for 5.0 hours, and after raising the temperature to 85 °C, maintain this state for 2.0 hours.

[0152] Then, obtain the resin particle dispersion by replacing the reflux pipe of the reaction vessel with a cooling pipe, heating the resulting slurry to 100 °C to distill the slurry for 6 hours, and removing the unreacted polymerizable monomer by distillation.

[0153] Step of forming an organosilicon polymer

[0154] Weigh 60.0 parts of ion-exchanged water, put it into a reaction vessel equipped with a stirrer and a thermometer, and adjust the pH value to 4.0 with 10 mass% hydrochloric acid. Heat the ion-exchanged water to 40 °C with stirring. Thereafter, add 40.0 parts of methyltriethoxysilane as an organosilicon compound (OS), and carry out hydrolysis for 2 hours or longer with stirring.

[0155] Confirm the end of hydrolysis by visually checking that oil and water form a single layer without separation, and obtain a hydrolyzate of the organosilicon compound after cooling.

[0156] After adjusting the temperature of the resin particle dispersion obtained as described above to 55 °C, add 25.0 parts of the hydrolyzate of the organosilicon compound (the addition amount of the organosilicon compound is 10.0 parts) to the resin particle dispersion to initiate the polymerization of the organosilicon compound (OS). After continuing the polymerization as it is for 0.25 hours, adjust the pH value to 5.5 with a 3.0% aqueous sodium bicarbonate solution. Obtain a toner particle dispersion by maintaining the obtained organosilicon polymer for 1.0 hour (condensation reaction 1) while continuing stirring at 55 °C, then adjusting the pH value to 9.5 with a 3.0% aqueous sodium bicarbonate solution, and further maintaining the organosilicon polymer under the said conditions for 4.0 hours (condensation reaction 2).

[0157] Washing step and drying step

[0158] After the step of forming the organosilicon polymer is completed, cool the toner particle dispersion, add hydrochloric acid to the toner particle dispersion to adjust the pH value to below 1.5, and let the toner particle dispersion stand for 1.0 hour with stirring.

[0159] Thereafter, carry out solid-liquid separation of the toner particle dispersion using a pressure filter to obtain a toner cake.

[0160] Use ion-exchanged water to convert the obtained toner cake into a dispersion again by re-slurrying, and obtain a toner cake by solid-liquid operation using the above pressure filter.

[0161] Transfer the toner cake obtained above to a constant-temperature oven at 40 °C, and dry and classify the toner particles for 72 hours to obtain toner particles. In the surface PSL containing organosilica, the area occupancy rate of organosilica (organosilicon compound OS) is 58%.

[0162] Then, 0.6 parts of silica particles were externally added to 100 parts of toner particles by using a Henschel mixer (model FM10C, manufactured by NIPPON COKE & ENGINEERING, CO., LTD.). The silica particles served as spacer particles SP and had a particle diameter of 100 nm in terms of primary particles.

[0163] Measurement of the silicone-containing surface layer PSL

[0164] Weighed out 20 g of an aqueous solution containing 30 mass% of a precision machine-washed neutral detergent with a pH of 7 and placed it in a vial with a capacity of 50 mL. Then it was mixed with 1 g of toner. The detergent consisted of "Contaminon N" (nonionic surfactant), an anionic surfactant, and an organic builder.

[0165] The prepared mixture was placed in a "KM Shaker" (model: V.SX) manufactured by IWAKI INDUSTRY CO., LTD. and vibrated for 120 seconds with the "speed" set to 50. With the vibration, fine silica particles that were easily detached from the toner surface were transferred from the surface of the toner base particles or toner particles to the dispersion liquid side. Subsequently, the toner was separated from the external additives (such as the fine silica particles that had been transferred to the supernatant) by centrifugation using a centrifugal separator (H-9R: manufactured by KOKUSAN Co., Ltd.) (for 5 minutes, at 16.67 S-1). The precipitated toner was dried and solidified by vacuum drying (40 °C / 24 hours), and the toner was obtained after washing with water.

[0166] Then, an image of the toner (after washing with water) was taken by a Hitachi ultra-high resolution field emission electron scanning microscope S-4800 (manufactured by Hitachi High Technologies Corporation).

[0167] Identification of the measurement target was carried out by elemental analysis using an energy dispersive X-ray spectrometer (EDS). A magnification of 50,000 times was used as the analysis size that could reflect the toner surface. The occupancy rate (area occupancy rate) H of organosilica (OS) was measured and expressed as the percentage of the area occupied by silicon atoms in the analysis region.

[0168] The above calculations were performed on 10 kinds of toners, and the average value of the 10 calculated values was taken as the area occupancy rate H of organosilica (OS).

[0169] The area occupancy rate H of organosilica (OS) in this example was 58%.

[0170] When the area occupancy ratio H of the organosilica (OS) is 40% or more, the fixed adhesion of the spacer particles to the toner base particles can be effectively suppressed. In addition, when the area occupancy ratio H of the organosilica (OS) is 40% or more, sufficient charge amount can be provided to the toner.

[0171] On the other hand, for the following reasons, the area occupancy ratio H of the organosilica (OS) is preferably 75% or less. If the area occupancy ratio H exceeds 75%, the toner becomes difficult to melt during heating (for example, 100 °C or higher), leading to the possibility of fixing failure.

[0172] The toner particles obtained by the manufacturing method described in Example 6 have a surface layer PSL containing organosilica made of an organosilicon compound OS. In addition, with respect to the inorganic spacer particles SP having a particle diameter of 50 nm to 150 nm, the area occupancy ratio H of the organosilicon compound OS in the surface layer PSL containing organosilica is 40% or more. In addition, in Example 6, from the perspective of "fixing", it is desirable that the area occupancy ratio H of the organosilicon compound OS in the surface layer PSL containing organosilica is 75% or less, as in Example 1. Therefore, also in Example 6, the area occupancy ratio H of the organosilicon compound OS is preferably in the range of 0.40 to 0.75. Figure 10 is a conceptual cross-sectional view of the developer used in Example 6.

[0173] Table 1 given below shows the main specification data of the developing devices according to the above Examples 1 to 6, Reference Example, and Comparative Example 1.

[0174] The item "toner inlet defined by the regulating member" in Table 1 indicates the toner inlet in the abutting area (clamping portion) between the developing blade located on the upstream side in the rotation direction of the developing roller and the developing roller. For example, compared with Figure 7 the case where the "edge (intersection point 23a23)" at the front end of the developing blade abuts against the developing roller as shown, in Figure 8 the case where the "flat portion (opposite surface 23a22)" at the front end of the developing blade abuts against the surface of the developing roller, the size of the toner inlet defined by the regulating member is larger.

[0175] Table 1

[0176]

[0177] Evaluation method

[0178] The developing devices of the above Examples 1 to 6, Reference Example, and Comparative Example 1 listed in Table 1 are evaluated according to the following items. The evaluation results are shown in Table 2.

[0179] The evaluation method will be described in detail below.

[0180] (1) Evaluation of fogging in high humidity environments

[0181] The term "fogging" refers to an image defect in which toner development is blurred and looks like scumming in a white area (unexposed area) where no image is printed. The method for evaluating the amount of fogging is as follows.

[0182] The operation of the image forming apparatus is stopped during the printing of a pure white image. For example, the toner on the photosensitive drum at the moment after development and before transfer is transferred to a transparent strip, and the strip including the toner attached thereto is pasted to, for example, recording paper. At the same time, a strip not including the attached toner is also pasted to the same recording paper. The light reflectivity of each strip pasted to the recording paper is measured from above the strip using a green filter by an optical reflectometer (TC-6DS, manufactured by Tokyo Denshoku KK), and the amount of fogging is evaluated by subtracting the measured reflectivity of the strip to which the toner is pasted from the measured reflectivity of the strip to which the toner is not pasted. The amount of fogging is determined by measuring the reflectivity at three or more points on each strip and calculating the average of the measured values.

[0183] A: The amount of fogging is less than 1.0%.

[0184] B: The amount of fogging is 1.0% or more and less than 3.0%.

[0185] C: The amount of fogging is 3.0% or more and less than 5.0%.

[0186] D: The amount of fogging is 5.0% or more (image defects clearly occur).

[0187] After the printing of 3000 sheets was completed, the tape was left in a test environment at 30°C and 80% relative humidity for 24 hours, and then fogging evaluation was performed. The printing test was performed by continuously passing through a horizontal line image with an image percentage of 5%. More specifically, an image obtained by repeating a cycle of printing 1 dot line and then not printing 19 dot lines was used as a horizontal line image with an image percentage of 5%.

[0188] (2) Evaluation of development streaks under low humidity conditions

[0189] Evaluation of development streaks under a low-humidity environment was performed by outputting a solid black image and a halftone image and visually observing the images according to the following criteria.

[0190] A: Density variation in the form of vertical streaks does not appear in either the pure black image or the halftone image.

[0191] B: There is no density change in the form of vertical stripes in the pure black image, but it is visually recognized in the halftone image.

[0192] C: Density changes in the form of vertical stripes are visually recognized in both the pure black image and the halftone image.

[0193] After printing 3000 sheets, the image is placed in a test environment of 15°C and 10% relative humidity for 24 hours, and then the developing stripes in the low-humidity environment are evaluated. The printing test is carried out through a horizontal line image with a continuous percentage of 5% across the image. More specifically, an image obtained by repeating the cycle of printing 1 dot line and then not printing 19 dot lines is used as the horizontal line image with a percentage of 5% of the image.

[0194] This evaluation aims to evaluate the adverse effects on the image when longitudinal wear changes occur in the developing roller near the toner inlet defined by the developing blade. In the area with a large amount of wear, due to the increase in the size of the toner inlet, the load-bearing capacity in a part of the toner coating on the developing roller increases longitudinally, and vertical stripes with a higher density are generated on the uniform image.

[0195] (3) Evaluation of dot reproducibility in high-humidity environment

[0196] The dot reproducibility in the high-humidity environment is evaluated by outputting a 2-dot image and visually inspecting the output image according to the following criteria. More specifically, the 2-dot image is obtained as follows. After printing 2 dots, 80 dot lines are not printed. Then, 80 dots are not printed in the main scanning direction. The image formed by repeating the above cycle is used. After printing 100 sheets and 3000 sheets, the image is placed in a test environment of 30°C and 80% relative humidity for 24 hours and then evaluated.

[0197] A: In both cases after printing 100 sheets and 3000 sheets, the dots in the dot image can be visually recognized.

[0198] B: In the case after printing 100 sheets, the dots in the dot image can be visually recognized, but in the case after printing 3000 sheets, they cannot be visually recognized.

[0199] C: In both cases after printing 100 sheets and 3000 sheets, the dots in the dot image cannot be visually recognized.

[0200] (4) Evaluation of developing stripes in high-humidity environment

[0201] The uniformity evaluation of the pure black image is carried out by outputting the pure black image and the halftone image and visually inspecting the output image according to the following criteria.

[0202] A: No density change in the form of vertical stripes appears in either the pure black image or the halftone image.

[0203] B: No density change in the form of vertical stripes appears in the pure black image, but is visually identified in the halftone image.

[0204] C: Density changes in the form of vertical stripes are visually identified in both the pure black image and the halftone image.

[0205] After 100 prints are completed, the image is left standing for 24 hours in a test environment of 30 °C and 80% relative humidity, and then the evaluation of developing stripes in a high humidity environment is carried out.

[0206] This evaluation aims to evaluate image defects in the case where spaced particles adhere longitudinally to a part of the developing blade.

[0207] For example, when an attachment made of spaced particles is formed near the toner inlet defined by the developing blade, in the area where the adhesion is formed, the amount of inhaled toner is reduced. Therefore, in this area, the load-bearing capacity of the toner coating is reduced compared to the area where no attachment is formed. As a result, an image with faint vertical stripes is produced.

[0208] (5) Evaluation of end coating defects in a low temperature and low humidity environment

[0209] Toner that is prone to aggregation as the toner deteriorates is difficult to adjust by the developing blade, and the load-bearing capacity in the toner coating increases (this phenomenon is particularly significant at the ends). Therefore, end coating defects are caused.

[0210] To evaluate the longitudinal uniformity of the toner coating, halftone images and pure white images are used for evaluation. After 3000 prints are completed, the halftone image and the pure white image are continuously passed through immediately in an environment of 15.0 °C and 10% relative humidity. In the print test, a horizontal line image with a continuous passing image percentage of 5% is used. The evaluation is carried out according to the following criteria.

[0211] A: In each image, no shade change in the form of vertical stripes can be identified at both ends of the image.

[0212] B: In the halftone image, shade changes in the form of vertical stripes are identified at the ends of the image.

[0213] C: In the pure white image, shade changes in the form of vertical stripes are identified at the ends of the image.

[0214] In this evaluation, the halftone image includes a stripe pattern formed microscopically by repeating the cycle of recording 1 row in the main scanning direction and then not recording 4 rows. Overall, the halftone image presents a halftone density.

[0215] Evaluation result

[0216] Table 2 shows the evaluation results of Examples 1 to 6, the related art (reference example), and Comparative Example 1.

[0217] Table 2

[0218]

[0219] The superiority of the present disclosure over the related art (reference example) will be described below by comparing Example 1 and the reference example.

[0220] Since the spacer particles SP in Example 1 are interposed between the toner particles, contact between the surfaces of the toner base particles TM can be prevented. As a result, the toner can be kept in a state where it is easy to move.

[0221] In addition, in Example 1, the toner forms a state in which the area occupancy ratio H of the silica fine particles S1 on the surface of the toner base particles is high. Therefore, contact between the spacer particles SP and the surface of the toner base particles TM is suppressed, so that the detachability between the toner and the spacer particles can be ensured, and fixed adhesion of the spacer particles to the toner base particles due to, for example, stress applied to the toner can be suppressed. As a result, the fluidity of the toner can be maintained, and a stable image can be obtained during long-term use (cumulative use time) from the start (beginning of use).

[0222] On the other hand, in the related art (reference example), the area occupancy ratio H of the silica fine particles S1 on the surface of the toner base particles TM is low (low coating), and spacer particles SP are not used. Since the spacer particles are not used, contact between the surfaces of the toner base particles increases, and the unevenness formed by the silica fine particles S1 on the toner surface decreases due to, for example, stress applied to the toner. As a result, the fluidity of the toner decreases, and when the toner passes through the nip (contact area) between the developing roller and the developing blade, the chance of triboelectrification between the developing blade and the toner decreases. Therefore, the charge retention amount of the toner decreases, and fogging tends to increase during long-term use.

[0223] In Example 1, during long-term use, better results than in the reference example were obtained for fogging. Since the area occupancy ratio H of the silica fine particles S1 on the surface of the toner base particles TM is high and spacer particles SP are used, during long-term use, the unevenness change on the toner surface is small. In addition, since the spacer particles SP are present between the toners and between the toner and other members, it is more difficult for the toner surfaces to come into direct contact with each other, so that a decrease in surface unevenness due to the presence of the silica fine particles S1 can be suppressed. As a result, good toner fluidity can be maintained, and an increase in the amount of fogging can be effectively suppressed during long-term use.

[0224] The beneficial effects of the present disclosure will be described below by comparing Comparative Example 1 and Example 1.

[0225] In Comparative Example 1, although spacer particles SP were used, the area occupancy ratio H of the silica fine particles S1 on the surface of the toner base particles TM was low. Since the spacer particles SP were used, a decrease in toner fluidity due to toner deterioration could be suppressed, and the increase in the amount of fogging during long-term use was small. However, vertical stripes in the solid color image became significant. The reasons are as follows.

[0226] In Comparative Example 1, although spacer particles SP were used, since the area occupancy ratio H of the silica fine particles S1 on the surface of the toner base particles TM was low, the contact frequency between the toner base particles TM and the spacer particles SP increased. As the contact frequency between the toner base particles TM and the spacer particles SP increased, the spacer particles SP tended to be fixedly attached to the toner base particles TM due to, for example, the stress applied to the toner.

[0227] Figure 9B It is a conceptual diagram showing a case where a toner including spacer particles SP fixedly attached to toner base particles abuts against a developing blade and at the same time the toner is held on a developing roller.

[0228] Since the spacer particles SP are fixedly attached to the surface of the toner base particles TM and cannot move above the toner surface, the spacer particles wear the leading edge of the metal developing blade (the worn area “K1” is shown in Figure 9B ).

[0229] The toner to which the spacer particles SP have been fixedly attached is partially generated in the longitudinal direction, so that wear changes of the regulating member (blade) occur in the longitudinal direction. The wear change in the leading edge of the developing blade causes a change in the regulating force in the longitudinal direction and causes a change in the toner coating amount on the developing roller in the longitudinal direction. As a result, vertical stripes are generated in the solid color image.

[0230] On the other hand, in Example 1, since the spacer particles SP are attached to the toner base particles, a state is formed in which the area occupancy rate H of the silica fine particles Sl on the surface of the toner base particles TM is high. Therefore, it is possible to suppress the fixed attachment of the spacer particles to the toner base particles due to, for example, the stress applied to the toner. Therefore, high detachment performance can be maintained between the toner and the spacer particles.

[0231] As Figure 9A shown, the spacer particles SP in Example 1 are liable to move from the toner base particles TM. Therefore, even when the spacer particles on the surface of the toner base particles are subjected to high stress from the regulating member when the toner on the developing roller passes through the regulating member, the spacer particles can move from the surface of the toner base particles, and the stress applied to the spacer particles can be reduced. Therefore, an increase in local pressure between the spacer particles and the metal wiper can be avoided, and wear variations at the leading edge of the developing wiper in the longitudinal direction can be suppressed.

[0232] As described above, the configuration of Example 1 can effectively suppress wear variations at the leading edge of the developing wiper in the longitudinal direction, variations in the regulating force, variations in the longitudinal coating amount of the toner on the developing roller, and the generation of vertical stripes in a solid color image. If the spacer particles have a large size, the amount of wear at the leading edge of the developing wiper increases. In order to suppress the wear at the leading edge of the developing wiper, the particle diameter of the spacer particles is preferably 150 nm or less, more preferably 120 nm or less.

[0233] Next, Examples 2 and 3, which are modified examples of Example 1, will be described.

[0234] First, the configuration of Example 2 will be described.

[0235] In Example 2, the size of the toner inlet defined by the developing wiper is set to be larger than the toner inlet size in Example 1. Therefore, in the configuration of Example 2, the amount of toner passing through the developing wiper 23 is larger than that in Example 1. Therefore, compared with those in Example 1, the amount of toner that cannot contact the developing wiper in Example 2 slightly increases, and the amount of toner having a low charge amount also slightly increases.

[0236] Therefore, compared with Example 1, the dot reproducibility in Example 2 is relatively reduced, and fogging during long-term use slightly increases. However, as in Example 1, a high regulating force can be formed at the regulating position. As a result, it is possible to effectively suppress dot reproducibility and fogging during long-term use in a high-humidity environment.

[0237] Next, the configuration of Example 3 will be described.

[0238] In Example 3, alumina (particles) is used as the spacer particle SP. The polarity of alumina is opposite to the charging polarity of the toner. Therefore, compared with Example 1, the spacer particles made of alumina in Example 3 are more likely to be electrically attached to the silica fine particles S1 on the surface of the toner base particle TM. Therefore, although the detachment performance between the spacer particles and the toner base particles is relatively reduced, favorable effects substantially similar to those in Example 1 can be obtained.

[0239] Configurations of Examples 4 and 5 of the present disclosure will be described below.

[0240] In Examples 4 and 5, in order to promote charging of the toner, a voltage having the same polarity as the conventional charging polarity of the toner is applied to the developing blade with respect to the potential of the developing roller. The spacer particle SP used in Example 4 is the silica particle S2, and the spacer particle SP used in Example 5 is alumina (particles).

[0241] More specifically, although the voltage between the developing roller and the developing blade was 0 V in Example 1 above, in Examples 4 and 5, a voltage is applied to the developing blade with a potential difference of -100 V with respect to the developing roller.

[0242] Compared with Example 1, the chargeability of the toner is improved in Examples 4 and 5, and more satisfactory results are obtained in terms of dot reproducibility and fogging during long-term use.

[0243] On the other hand, regarding streaky fogging in an H / H (high temperature and high humidity) environment, the results obtained in Example 4 are better than those in Example 5.

[0244] More specifically, the spacer particle SP in Example 5 is made of alumina (particles). Alumina has a triboelectric charging polarity opposite to that of the toner.

[0245] Therefore, in Example 5, in a state where the toner has a "negative" charge and the alumina of the spacer particle SP has a "positive" charge, the toner passes between the developing blade and the developing roller. In Example 5, since the developing blade has a potential difference of -100 V with respect to the developing roller, the "negative charge" is subjected to an electric force acting toward the developing roller side, and the "positive charge" is subjected to an electric force acting toward the developing blade side. Therefore, the alumina of the spacer particles is subjected to an electric force acting toward the developing blade side and is more likely to adhere to the developing blade.

[0246] When alumina adheres to a part of the leading edge of the developing blade in the longitudinal direction, the size of the toner inlet in the alumina adhesion area decreases, and the amount of toner in the toner coating in the alumina adhesion area also decreases. This can lead to the possibility of causing streaky density differences on the uniform image. By observing the part of the developing blade corresponding to the area on the image where streaks have occurred, the inventors of the present application have confirmed that the alumina content in the adherent is relatively large, and the streaks on the image decrease after removing the adherent.

[0247] On the other hand, in Example 4, a voltage is applied to the developing blade with a potential difference of -100 V relative to the developing roller, and silica particles S2 are used as spacer particles SP. Therefore, both the toner and the spacer particles SP have a negative polarity, so that contamination of the developing blade can be suppressed. Therefore, compared with Example 5, in Example 4, it is possible to more effectively adjust the decrease in toner fluidity and the contamination of the developing blade caused by changes during long-term use, and the image quality is improved due to higher chargeability.

[0248] Next, Example 6 of the present disclosure will be described.

[0249] Example 6 is different from Example 4 in that the surface layer of the toner particles is made of organosilica (organosilicon polymer).

[0250] Due to heating at a relatively low temperature during the production process, the hardness of organosilica is lower than that of inorganic silica (Example 4). Therefore, the surface layer containing organosilica can further suppress the wear of the leading edge of the developing blade when it comes into contact with the leading edge. As a result, compared with Example 4, Example 6 can maintain a higher developing blade regulating force during long-term use, can increase the loading capacity of the toner coating, and can further suppress the regulation failure in a low-humidity environment.

[0251] The silica fine particles S1 on the surface of the toner base particles TM in Example 4 are inorganic particles and have high hardness. Therefore, when the developing blade and the silica fine particles come into contact with each other, there is a possibility that the leading edge of the developing blade may be slightly worn and the regulating force of the developing blade may be slightly reduced. Therefore, it can be said that Example 6 is more advantageous than Example 4 in terms of the stability of the loading capacity of the toner coating and the maintenance of the regulating performance in a low-humidity environment.

[0252] Next, the relationship between the area occupancy H of the silica fine particles S1 on the surface of the toner base particles TM and the inorganic spacer particles SP will be described.

[0253] Table 3 given below shows the configurations and evaluation results of Examples 7 to 10 and Comparative Examples 2 to 6. Table 3 further shows the configurations (refer to Table 1) and evaluation results (refer to Table 2) of the above-mentioned "Example 1" and "Comparative Example 1".

[0254] Examples 7 to 10 are substantially the same as Example 1, but are different from Example 1 in the following points.

[0255] More specifically, in Examples 7, 8, 9, and 10, the area occupancy ratios of the silica fine particles S1 on the surface of the toner base particles are 42%, 42%, 74%, and 74%, respectively.

[0256] By adjusting the amount of the fixed silica to be added, the area occupancy ratio of the above-mentioned silica fine particles S1 is appropriately set.

[0257] In addition, in Examples 7, 8, 9, and 10, the particle diameters of the inorganic spacer particles SP are 50 nm, 150 nm, 50 nm, and 150 nm, respectively.

[0258] Comparative Examples 2 to 5 are substantially the same as Example 1, but are different from Example 1 in the following points.

[0259] More specifically, in Comparative Examples 2, 3, 4, and 5, the area occupancy ratios of the silica fine particles S1 on the surface of the toner base particles are 38%, 80%, 60%, and 74%, respectively.

[0260] By adjusting the amount of the fixed silica to be added, the area occupancy ratio of the above-mentioned silica fine particles S1 is appropriately set.

[0261] In addition, in Comparative Examples 2, 3, 4, and 5, the particle diameters of the inorganic spacer particles SP are 200 nm, 100 nm, 30 nm, and 200 nm, respectively.

[0262] The above evaluations were also carried out on Examples 7 to 10 and Comparative Examples 2 to 5: (1) fogging at high humidity, (2) developing streaks at low humidity, and (4) developing streaks at high humidity. The evaluation results are listed in Table 3.

[0263] Table 3

[0264]

[0265] As shown in Table 3, in Example 1 and Examples 7 to 10, there are no image defects, and good results are obtained.

[0266] On the other hand, in Comparative Examples 1 and 2, the area occupancy rate H of the fine silica particles S1 on the surface of the toner base particles was too low (less than 40%). Therefore, when the number of printed sheets (cumulative use time) increased, stress was applied to the toner, and the inorganic spacer particles were fixedly attached to the toner base particles. As described above, if the inorganic spacer particles are fixedly attached to the toner base particles, partial wear occurs at the leading edge of the developing blade, and developing streaks are generated at low humidity.

[0267] In Comparative Examples 2, 3, and 5, since the inorganic spacer particles were too large (greater than 150 nm), the detachment performance with respect to the toner was high, and the inorganic spacer particles tended to adhere to the leading edge of the developing blade. Therefore, developing streaks were generated at high humidity.

[0268] In Comparative Example 4, the inorganic spacer particles were too small (less than 40 nm). Therefore, when the number of printed sheets (cumulative use time) increased and stress was applied to the toner, adjacent toners approached each other and the toner fluidity decreased. As a result, it became difficult for the toner to receive charge from the developing blade, and fogging became significant in a high-humidity environment.

[0269] Therefore, in the above-described embodiments, by setting the area occupancy rate H of the fine silica particles on the surface of the toner base particles to 40% or more and setting the particle diameter of the inorganic spacer particles SP to 50 to 150 nm, it is possible to effectively suppress wear of the leading edge of the metal developing blade while maintaining high chargeability. As a result, stable good images can be obtained during long-term use (even when the cumulative use time increases).

[0270] The features of the present invention can be summarized as follows.

[0271] (1) The developing device (4) according to the present disclosure includes: a developing frame (24) configured to store a developer (T); a developer carrier member (22) rotatably supported by the developing frame (24) and configured to carry the developer; and an adjusting member (23) including a metal blade (23a), one end (23a1) of the metal blade being fixed to the developing frame and the other end (23a2) being set to contact the developer carrier member, the adjusting member adjusting the thickness of the developer carried on the developer carrier member.

[0272] The developer (T) includes toner base particles (TM) and external additives (S1, SP).

[0273] The external additives include silica particles (S1) having a particle diameter (n) of 5 nm or more and 25 nm or less, and inorganic spacer particles (SP) having a particle diameter (r1) of 50 nm or more and 150 nm or less.

[0274] The area occupancy (H) of the silicon oxide particles (S1) on the surface of the toner base particles is 40% or more.

[0275] (2) According to the present disclosure, the developing device (4) includes: a developing frame (24) configured to store a developer (T); a developer carrying member (22) rotatably supported by the developing frame (24) and configured to carry the developer; and a regulating member (23) including a metal scraper (23a), one end (23a1) of the metal scraper being fixed to the developing frame and the other end (23a2) being arranged to contact the developer carrying member, the regulating member regulating the thickness of the developer carried on the developer carrying member.

[0276] The developer includes toner base particles (TM) having an organic silicon oxide-containing surface layer (PSL) made of an organic silicon compound (OS) and an external additive (SP).

[0277] The external additive includes inorganic spacer particles (SP) having a particle diameter (r1) of 50 nm or more and 150 nm or less.

[0278] The area occupancy (H) of the organic silicon compound (OS) on the surface of the toner base particles is 40% or more.

[0279] (3) In the developing device according to the present invention, the other end (23a2) of the metal blade may be arranged to extend toward the upstream side in the rotation direction (R4) of the developer carrying member.

[0280] (4) In the developing device according to the present disclosure, when observed along the rotation axis direction (X1) of the developer carrying member, and when the developer carrying member (22) is hypothetically assembled into the developing frame (24), in a state in which the developer carrying member is not assembled in the developing frame and the regulating member is assembled, the intersection (23a23) of the leading edge surface (23a21) of the other end of the metal scraper and its abutting surface (23a22) abutting against the developer carrying member may be located within the hypothetical outer diameter circumference (MC1) of the developer carrying member, and when a first hypothetical plane (SF1) passing through the rotation center (X0) of the developer carrying member and parallel to the abutting surface (23a22) is used as a reference, the intersection (23a23) may be located in a first hypothetical area (TD1) on one side of the first hypothetical plane (SF1) where the metal scraper exists.

[0281] (5) In the developing device according to the present disclosure, when the first imaginary plane (SF1) and the second imaginary plane (SF2) perpendicular to the first imaginary plane are used as references, the intersection point (23a23) may be located on the downstream side of the second imaginary plane and on the upstream side of the first imaginary plane in the rotational direction of the developer carrier member, within the first imaginary region.

[0282] (6) In the developing device according to the present disclosure, when the first imaginary plane (SFl) and the second imaginary plane (SF2) perpendicular to the first imaginary plane are used as references, the intersection point (23a23) may be located on the upstream side of the second imaginary plane and on the downstream side of the first imaginary plane in the rotational direction of the developer carrier member, within the first imaginary region.

[0283] (7) In the developing device according to the present disclosure, a bias voltage may be applied to the metal blade (23a), and the bias voltage has the same polarity as the normal charging polarity of the developer (T) with respect to the developer carrier member (22).

[0284] (8) In the developing device according to the present disclosure, the charging polarity of the inorganic spacer particles (SP) may be the same as the normal charging polarity of the developer.

[0285] (9) In the developing device according to the present disclosure, the silica particles (S1) may be fixed to the toner base particles (TM).

[0286] (10) In the developing device according to the present disclosure, the inorganic spacer particles (SP) may be another type of silica particles (S2).

[0287] (11) In the developing device according to the present disclosure, the particle diameter (r1) of the inorganic spacer particles is preferably 80 nm or more and 150 nm or less, and the area occupancy rate (H) of the silica particles (S1) on the surface of the toner base particles (TM) is preferably 45% or more.

[0288] (12) In the developing device according to the present disclosure, the area occupancy rate (H) of the silica particles (S1) on the surface of the toner base particles (TM) is preferably 75% or less.

[0289] (13) The processing cartridge (S) according to the present disclosure includes a developing device (4) and an image carrier member (1) configured to carry a developer image (T), and the processing cartridge is detachably attached to the image forming device.

[0290] (14) The image forming device (100) according to the present disclosure includes a developing device (4) or a processing cartridge (S), and a transfer member (14).

[0291] According to the present disclosure, the occurrence of coating variations can be suppressed while improving the chargeability of a developer coating formed on a developer carrier member.

[0292] Although the present disclosure has been described with reference to exemplary embodiments, it should be understood that the present disclosure is not limited to the disclosed exemplary embodiments. The scope of the appended claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A developing device, comprising: a developing frame configured to store a developing agent; a developer carrying member rotatably supported by the developing frame and configured to carry a developer; and a regulating member including a metal blade having one end fixed to the developing frame and the other end disposed in contact with the developer carrying member, the regulating member regulating the thickness of the developer carried on the developer carrying member, wherein the developer comprises toner base particles and external additives, The external additive includes silicon oxide 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, the inorganic spacer particles being externally added to the developer after the silicon oxide particles, and The area occupancy of the silicon oxide particles fixed on the surface of the toner base particles is 40% or more.

2. A developing device, comprising: a developing frame configured to store a developing agent; a developer carrying member rotatably supported by the developing frame and configured to carry a developer; and a regulating member including a metal blade having one end fixed to the developing frame and the other end disposed in contact with the developer carrying member, the regulating member regulating the thickness of the developer carried on the developer carrying member, wherein the developer comprises toner base particles and an external additive, the toner base particles having a surface layer containing organic silicon oxide made of an organic silicon compound, The external additive includes inorganic spacer particles having a particle diameter of 50 nm or more and 150 nm or less, the inorganic spacer particles being externally added to the developer after the surface layer containing organic silicon oxide is formed on the toner base particles, and The organosilicon compound has an area occupancy rate of 40% or more in the surface layer including the organosilicon oxide. 3 . The developing device according to claim 1 , wherein the other end of the metal blade is arranged to extend toward an upstream side in a rotation direction of the developer carrying member.

4. The developing device according to claim 2, wherein in a state where the developer carrying member is not assembled and the regulating member is assembled in the developing frame, When viewed along the rotational axis direction of the developer carrying member, and when the developer carrying member is virtually assembled into the developing frame, an intersection point where the leading edge surface of the other end of the metal blade intersects with its abutting surface abutting against the developer carrying member, is located within the circumference of the imaginary outer diameter of the developer carrying member, and When a first imaginary plane passing through the rotation center of the developer carrying member and parallel to the abutting surface is taken as a reference, the intersection point is located in a first imaginary area on one side of the first imaginary plane where the metal blade exists.

5. The developing device according to claim 4, wherein when a first imaginary plane and a second imaginary plane perpendicular to the first imaginary plane are used as references, In the rotational direction of the developer carrier member, the intersection point is located on the downstream side of the second imaginary plane and on the upstream side of the first imaginary plane, within the first imaginary region.

6. The developing device according to claim 4, wherein when the first imaginary plane and the second imaginary plane perpendicular to the first imaginary plane are used as references, In the rotational direction of the developer carrier member, the intersection point is located on the upstream side of the second imaginary plane and on the downstream side of the first imaginary plane, within the first imaginary region.

7. The developing device according to claim 1 or 2, wherein a bias voltage is applied to the metal wiper, and the bias voltage has the same polarity as the normal charging polarity of the developer with respect to the developer carrier member.

8. The developing device according to claim 1 or 2, wherein the charging polarity of the inorganic spacer particles is the same as the normal charging polarity of the developer.

9. The developing device according to claim 1 or 2, wherein the inorganic spacer particles are another type of silica particles.

10. The developing device according to claim 1, wherein the particle diameter of the inorganic spacer particles is 80 nm or more and 150 nm or less, and the area occupancy rate of the silica particles on the surface of the toner base particles is 45% or more.

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

12. A process cartridge, comprising: The developing device according to claim 1; and An image carrier member configured to carry a developer image, the process cartridge being detachably attached to an image forming apparatus.

13. An image forming apparatus, comprising: The developing device according to claim 1; and A transfer member.

14. A process cartridge, comprising: The developing device according to claim 2; and An image carrier member configured to carry a developer image, the process cartridge being detachably attached to an image forming apparatus.

15. An image forming apparatus, comprising: The developing device according to claim 2; and A transfer member.

16. An image forming apparatus, comprising: The process cartridge according to claim 12; and A transfer member.

Images