Image forming apparatus

Abstract

To achieve both the electrostatic properties of the photoreceptor and the wear resistance of the electrostatic roller in an image forming apparatus. [Solution] The image forming apparatus includes a photoreceptor and a volume resistivity of 1 × 10 8 Ω cm or more 1×10 14 The image forming apparatus comprises a charging roller having a surface layer of Ω·cm or less for charging the photoreceptor, and a power supply for applying a DC voltage to the charging roller. In the image forming apparatus, the current flowing into the photoreceptor when the photoreceptor is charged by the charging roller is 0.40 mC / m 2 1.0mC / m or more 2 The following applies:

Description

[Technical Field]

[0001] This technology relates to an electrophotographic image forming apparatus. [Background technology]

[0002] In an electrophotographic image forming apparatus, a drum-type photoreceptor is used as the image carrier. After uniformly charging the surface of the photoreceptor with a charging device, light is irradiated onto the surface of the photoreceptor with an exposure device, thereby forming an electrostatic latent image on the surface of the photoreceptor where the charge in the light-irradiated area is attenuated. The electrostatic latent image is then developed into a toner image with a developing device, and the toner image is directly transferred onto the recording medium by applying a transfer voltage with the opposite polarity to the toner with a transfer device, or it is first transferred to an intermediate transfer medium and then secondarily transferred onto the recording medium, and the toner image is thermally fixed onto the recording medium with a fixing device. Patent Document 1 discloses a technology that can improve the charge stability of the photoreceptor and suppress transfer memory. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-181418 [Overview of the project] [Problems that the invention aims to solve]

[0004] Image forming apparatuses are equipped with charging rollers for charging a photoreceptor. In order to form high-quality images, image forming apparatuses require good charging properties that allow the charging rollers to uniformly charge the photoreceptor at a sufficiently high potential. Furthermore, the charging rollers must also have high wear resistance to withstand long-term use. In this regard, the image forming apparatus described in Patent Document 1 does not achieve both good charging properties for the photoreceptor and wear resistance for the charging rollers.

[0005] In view of the above circumstances, the object of the present invention is to achieve both the electrostatic properties of the photoreceptor and the wear resistance of the electrostatic roller in an image forming apparatus. [Means for solving the problem]

[0006] An image forming apparatus according to one embodiment of the present invention comprises a photoreceptor and a photoreceptor with a volume resistivity of 1 × 10⁻⁶ 8 Ω cm or more 1×10 14 The device comprises a charging roller having a surface layer of Ω·cm or less for charging the photoreceptor, and a power supply for applying a DC voltage to the charging roller. The current flowing into the photoreceptor when the photoreceptor is charged by the charging roller described above is 0.40 mC / m 2 1.0mC / m or more 2 The following applies:

[0007] Preferably, the surface layer has a structure in which conductive particles are dispersed in nylon resin.

[0008] Preferably, the conductive particles include at least one of carbon black and tin oxide.

[0009] The above-mentioned photoreceptor is preferably a single-layer photoreceptor. [Effects of the Invention]

[0010] In this invention, it is possible to achieve both the electrostatic properties of the photoreceptor and the wear resistance of the electrostatic roller in an image forming apparatus. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of an image forming apparatus according to one embodiment of the present invention. [Figure 2] This is a schematic diagram of the image forming unit included in the image forming apparatus described above. [Figure 3] This is a schematic diagram of the photoreceptor included in the image forming apparatus described above. [Figure 4] This is a schematic diagram of the electrostatic roller included in the image forming apparatus described above.

Embodiments for Carrying out the Invention

[0012] Embodiments of the present invention will be described.

[0013] [Overall Configuration of Image Forming Apparatus] An image forming apparatus 100 according to an embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing the configuration of the image forming apparatus 100. The image forming apparatus 100 is, for example, a tandem type color printer.

[0014] As shown in FIG. 1, the image forming apparatus 100 includes a control unit 10, an operation unit 20, a paper feeding unit 30, a conveyance unit 40, a toner replenishment unit 50, an image forming unit 60, a transfer device 70, a fixing device 80, and a discharge unit 90.

[0015] The control unit 10 controls the operations of each part included in the image forming apparatus 100. The control unit 10 includes an arithmetic processing unit and a storage unit not shown. The arithmetic processing unit is, for example, a CPU (Central Processing Unit), and the storage unit is, for example, a semiconductor memory or an HDD (Hard Disk Drive). The arithmetic processing unit controls the operation of the image forming apparatus 100 by executing a control program. The storage unit stores the control program.

[0016] The operation unit 20 receives instructions from the user. When the operation unit 20 receives an instruction from the user, it transmits a signal indicating the instruction from the user to the control unit 10. Thereby, the image forming operation by the image forming apparatus 100 is started.

[0017] The paper feeding unit 30 has a paper feeding cassette 31 and a paper feeding roller group 32. The paper feeding cassette 31 can accommodate a plurality of recording media P. The recording media P is, for example, printing paper. The paper feeding roller group 32 feeds the recording media P accommodated in the paper feeding cassette 31 to the conveyance unit 40 one by one.

[0018] The transport unit 40 is equipped with rollers and guide members. The transport unit 40 extends from the paper feeding unit 30 to the discharge unit 90. The transport unit 40 transports the recording medium P from the paper feeding unit 30 to the discharge unit 90 so that it passes through the image forming unit 60 and the fixing device 80.

[0019] The toner supply unit 50 supplies toner to the image forming unit 60. The toner supply unit 50 comprises a first mounting unit 51Y, a second mounting unit 51C, a third mounting unit 51M, and a fourth mounting unit 51K. The first mounting unit 51Y is fitted with a first toner container 52Y. The second mounting unit 51C is fitted with a second toner container 52C, the third mounting unit 51M is fitted with a third toner container 52M, and the fourth mounting unit 51K is fitted with a fourth toner container 52K.

[0020] The first toner container 52Y contains yellow toner, the second toner container 52C contains cyan toner, the third toner container 52M contains magenta toner, and the fourth toner container 52K contains black toner. Note that the colors of each toner are not limited to those shown here; other colors may be used. The number of colors may also be one or more.

[0021] The image forming unit 60 comprises an exposure apparatus 61, a first image forming unit 62Y, a second image forming unit 62C, a third image forming unit 62M, and a fourth image forming unit 62K. Figure 2 is a schematic diagram of the image forming unit 62. The first image forming unit 62Y, the second image forming unit 62C, the third image forming unit 62M, and the fourth image forming unit 62K have the configuration of the image forming unit 62 shown in Figure 2. The image forming unit 62 includes a charging device 63, a developing device 64, a photoreceptor 65, a cleaning device 66, and a static elimination device 67. The charging device 63, the developing device 64, the cleaning device 66, and the static elimination device 67 are arranged along the surface 65a of the photoreceptor 65.

[0022] The exposure apparatus 61 (see Figure 1) irradiates light (dashed line in the figure) onto the surface 65a of the photoreceptor 65 of each image forming unit 62, thereby exposing the surface 65a. Based on the supplied image data, the exposure apparatus 61 irradiates each image forming unit 62 with light for each color, performing exposure. The exposure apparatus 61 can perform exposure using laser light.

[0023] The photoreceptor 65 forms an electrostatic latent image when exposed by the exposure device 61. The surface 65a of the photoreceptor 65 is pre-charged positively or negatively. When this surface 65a is exposed by the exposure device 61, the charge attenuates in the irradiated area, and an electrostatic latent image is formed. For example, an OPC (Organic Photo Conductor) can be used for the photoreceptor 65. The detailed configuration of the photoreceptor 65 will be described later. The photoreceptor 65 rotates in the direction indicated by the arrow in Figure 2 (clockwise).

[0024] The charging device 63 positively or negatively charges the surface 65a. The charging device 63 comprises a charging roller 631, a charging voltage power supply 632, and a cleaning brush 633. The charging roller 631 contacts the surface 65a to uniformly charge the surface 65a. The detailed configuration of the charging roller 631 will be described later. The charging voltage power supply 632 applies a charging voltage to the charging roller. A DC voltage is preferred for this charging voltage. The cleaning brush 633 contacts the charging roller 631 to clean it.

[0025] The developing device 64 supplies toner supplied from the toner supply unit 50 to the surface 65a. As shown in Figure 2, the developing device 64 is equipped with a developing roller 641. The toner supplied from the toner container is mixed with a magnetic carrier to form a two-component developer. At this time, the toner becomes charged with the same polarity as the surface 65a due to friction with the carrier.

[0026] The two-component developer is attracted to the developing roller 641 by magnetic force and transported to a position opposite the photoreceptor 65. A voltage is applied between the developing roller 641 and the photoreceptor 65, causing the toner in the two-component developer to adhere to the electrostatic latent image on the surface 65a. This forms a toner image on the surface 65a that matches the electrostatic latent image.

[0027] The developing device 64 of the first image forming unit 62Y is connected to the first toner container 52Y, and yellow toner is supplied. As a result, a yellow toner image is formed on the surface of the photoreceptor 65 of the first image forming unit 62Y. Similarly, the developing device 64 of the second image forming unit 62C is connected to the second toner container 52C, and a cyan toner image is formed on the surface of the photoreceptor 65 of the second image forming unit 62C.

[0028] Furthermore, the developing device 64 of the third image forming unit 62M is connected to the third toner container 52M, and a magenta toner image is formed on the surface of the photoreceptor 65 of the third image forming unit 62M. The developing device 64 of the fourth image forming unit 62K is connected to the fourth toner container 52K, and a black toner image is formed on the surface of the photoreceptor 65 of the fourth image forming unit 62K.

[0029] The cleaning device 66 recovers the toner adhering to the surface 65a after the transfer by the primary transfer roller 71, which will be described later. Specifically, the cleaning device 66 recovers the toner adhering to the surface 65a by pressing the cleaning blade 661 against the surface 65a. The static elimination device 67 removes static electricity from the surface 65a by irradiating it with static elimination light.

[0030] The transfer device 70 (see Figure 1) transfers the toner image from the photoreceptor 65 to the recording medium P, which is the object to be transferred. Specifically, the transfer device 70 transfers the toner images of each color formed on the surface 65a of the photoreceptor 65 of each image forming unit 62 onto the recording medium P. The transfer device 70 can transfer each toner image onto the recording medium P by a secondary transfer method (intermediate transfer method). For the secondary transfer method, the transfer device 70 has four primary transfer rollers 71, an intermediate transfer belt 72, a drive roller 73, a driven roller 74, and a secondary transfer roller 75.

[0031] The intermediate transfer belt 72 is an endless belt stretched over four primary transfer rollers 71, a drive roller 73, and a driven roller 74. The intermediate transfer belt 72 is driven in accordance with the rotation of the drive roller 73. In Figure 1, the intermediate transfer belt 72 rotates in the direction indicated by the arrow in Figure 1 (counterclockwise). The driven roller 74 is rotationally driven in accordance with the driving of the intermediate transfer belt 72.

[0032] Each image forming unit 62 faces the lower surface of the intermediate transfer belt 72 and is arranged in the order of the first image forming unit 62Y to the fourth image forming unit 62K, from the upstream side to the downstream side in the driving direction of the lower surface of the intermediate transfer belt 72.

[0033] Each primary transfer roller 71 is positioned opposite each photoreceptor 65 via an intermediate transfer belt 72 and is pressed toward each photoreceptor 65. As a result, the toner image formed on the surface 65a of each photoreceptor 65 is sequentially transferred to the intermediate transfer belt 72 by each primary transfer roller 71. In the configuration shown in Figure 1, the yellow toner image, cyan toner image, magenta toner image, and black toner image are transferred to the intermediate transfer belt 72 in this order, but the order of the toner images is not limited to this. Hereinafter, the toner image formed by stacking the yellow toner image, cyan toner image, magenta toner image, and black toner image will be referred to as a "stacked toner image".

[0034] The secondary transfer roller 75 is positioned opposite the drive roller 73 via the intermediate transfer belt 72. The secondary transfer roller 75 is pressed toward the drive roller 73. This forms a transfer nip (contact area) between the secondary transfer roller 75 and the drive roller 73, and as the recording medium P passes through the transfer nip, the secondary transfer roller 75 transfers the layered toner image on the intermediate transfer belt 72 to the recording medium P. The layering order of the layered toner image on the recording medium P is the opposite of the layering order of the layered toner image on the intermediate transfer belt 72. The recording medium P on which the layered toner image has been transferred is transported toward the fuser 80 by the transport unit 40.

[0035] The fuser unit 80 fixes the stacked toner image onto the recording medium P. The fuser unit 80 includes a heating member 81 and a pressurizing member 82. The heating member 81 and the pressurizing member 82 are arranged facing each other to form a fuser nip. The recording medium P, transported from the image forming unit 60, is heated and pressurized at a predetermined fixing temperature as it passes through the fuser nip, and the stacked toner image is fixed onto the recording medium P. The recording medium P is transported from the fuser unit 80 to the discharge unit 90 by the transport unit 40.

[0036] The discharge unit 90 discharges the recording medium P on which the stacked toner image has been fixed. The discharge unit 90 has a pair of discharge rollers 91, a discharge port 92, and a discharge tray 93. The pair of discharge rollers 91 transports the recording medium P to the discharge tray 93 via the discharge port 92.

[0037] The image forming method using the image forming apparatus 100 will now be described. When the control unit 10 acquires image data and the operation unit 20 receives an instruction from the user to start the image forming operation, the photoreceptor 65 in each image forming unit 62 is rotated, and the charging roller 631 uniformly charges the surface 65a.

[0038] Next, the exposure device 61 exposes the surface 65a of each image forming unit 62 according to the image data, forming an electrostatic latent image for each color on the surface 65a. The developing device 64 of each image forming unit supplies toner of each color to the surface 65a, which then electrostatically adheres to the electrostatic latent image for each color. As a result, a toner image of each color is formed on the surface 65a of each photoreceptor 65. If the amount of toner filled in each developing device 64 falls below a specified value due to the formation of the toner image, toner is replenished to each developing device 64 from the first toner container 52Y to the fourth toner container 52K.

[0039] An electric field is applied between the primary transfer roller 71 and the photoreceptor 65 at a predetermined transfer voltage by the primary transfer roller 71. As a result, the toner images of each color on the surface 65a are primary transferred onto the intermediate transfer belt 72. The toner images of each color are stacked, and a stacked toner image is formed on the intermediate transfer belt 72. Subsequently, in preparation for the formation of a new electrostatic latent image, any toner remaining on the surface 65a after the primary transfer is removed by the cleaning device 66.

[0040] As the intermediate transfer belt 72 rotates counterclockwise in conjunction with the rotation of the drive roller 73, the transport unit 40 transports the recording medium P to the transfer nip between the secondary transfer roller 75 and the drive roller 73 at a predetermined timing, and the laminated toner image on the intermediate transfer belt 72 is secondarily transferred onto the recording medium P. The recording medium P on which the laminated toner image has been secondarily transferred is then transported by the transport unit 40 to the fuser 80.

[0041] The recording medium P, transported to the fixing device 80, is heated and pressurized by the heating element 81 and the pressurizing element 82, causing the laminated toner image to fix to the surface of the recording medium P, and a color image is formed on the recording medium P. The recording medium P on which the color image has been formed is discharged to the discharge tray 93 in the discharge unit 90.

[0042] The image forming apparatus 100 has the configuration described above. The configuration of the image forming apparatus according to the present invention is not limited to that described above, and may include a photoreceptor 65 and a charging roller 631 having the configuration described later. For example, although the image forming apparatus 100 is an image forming apparatus capable of forming color images, the image forming apparatus according to the present invention may be an image forming apparatus capable of forming monochrome images. In this case, the image forming apparatus may include only one image forming unit.

[0043] Furthermore, although the image forming apparatus 100 is a tandem type image forming apparatus, the image forming apparatus according to the present invention may be a rotary type image forming apparatus. In addition, although the image forming apparatus 100 is a touchdown development type image forming apparatus, the image forming apparatus according to the present invention may be an image forming apparatus with a development method other than the touchdown development method.

[0044] Furthermore, although the image forming apparatus 100 is an intermediate transfer type image forming apparatus, the image forming apparatus according to the present invention may be a direct transfer type image forming apparatus. In this case, the toner image is directly transferred from the photoreceptor 65 to the recording medium P while the photoreceptor 65 is in contact with the recording medium P. In addition, although each image forming unit 62 is equipped with a static elimination device 67, each image forming unit 62 may not be equipped with a static elimination device 67.

[0045] [Composition of the photoreceptor] The structure of the photoreceptor 65 described above will now be explained. Figure 3 is a cross-sectional view of the surface of the photoreceptor 65. As shown in the figure, the photoreceptor 65 comprises a conductive substrate 651 and a photosensitive layer 652. The conductive substrate 651 is made of a conductive material such as aluminum and has a cylindrical shape. The photosensitive layer 652 is made of an organic photosensitive material and is formed as a thin film on the conductive substrate 651. Generally, there are "single-layer photoreceptors" in which the photosensitive layer is a single layer and "multilayer photoreceptors" in which the photosensitive layer is a multiple layer, but a single-layer photoreceptor is preferred for the photoreceptor 65. An undercoat layer may be provided between the conductive substrate 651 and the photosensitive layer 652.

[0046] In the photoreceptor 65, it is preferable that the thickness of the photosensitive layer 652 is between 20 μm and 40 μm. By making the thickness of the photosensitive layer 652 of the photoreceptor 65 20 μm or more, the current flowing into the photoreceptor 65 when the charging roller 631 charges the photoreceptor 65 is less likely to be excessive. Also, by making the thickness of the photosensitive layer 652 of the photoreceptor 65 40 μm or less, it is easier to ensure that a sufficient current flows into the photoreceptor 65 when the charging roller 631 charges the photoreceptor 65.

[0047] [Structure of the electrostatic roller] The configuration of the electrostatic roller 631 described above will now be explained. Figure 4 is a cross-sectional view of the electrostatic roller 631. As shown in the figure, the electrostatic roller 631 comprises a conductive shaft 634, an elastic layer 635, and a surface layer 636.

[0048] The conductive shaft 634 is a rod-shaped component made of a conductive material. Examples of conductive materials include metals such as iron, aluminum, titanium, copper, and nickel, alloys such as stainless steel, duralumin, brass, and bronze, and composite materials made by solidifying carbon black or carbon fibers with plastic. The conductive shaft 634 may be cylindrical or cylindrical in shape.

[0049] The elastic layer 635 is conductive and elastic and is provided around the conductive shaft 634. As the material for the elastic layer 635, a mixture of an elastic material and a conductive material can be used. Examples of elastic materials include hydrin rubber, polyurethane elastomer, hydrin rubber, styrene-butadiene rubber (SBR), polynorbornene rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (H-NBR), butadiene rubber (BR), isoprene rubber (IR), natural rubber (NR), and silicone rubber. Hydrin rubber is more preferred as the elastic material, and specifically epichlorohydrin rubber is preferred.

[0050] The conductive material mixed with the above-mentioned elastic material is at least one of an electronic conductive material and an ionic conductive material. Examples of electronic conductive materials include carbon black, graphite, potassium titanate, iron oxide, titanium oxide, zinc oxide, and tin oxide. Tin oxide and carbon black are more preferred as electronic conductive materials. The content ratio of the electronic conductive material in the elastic layer 635 is preferably 5 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the elastic material.

[0051] Examples of ionic conductive materials include organic salts (e.g., sodium trifluoroacetate), inorganic salts (e.g., quaternary ammonium salts), metal complexes, and ionic liquids. Sodium trifluoroacetate is more preferred as the ionic conductive material. The preferred content of the ionic conductive material in the elastic layer 635 is 0.1 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the elastic material.

[0052] The elastic layer 635 may further contain one or more additives such as plasticizers, fillers, vulcanizing agents, vulcanization accelerators, antioxidants, scorch inhibitors, dispersants, and release agents.

[0053] The surface layer 636 preferably has a structure in which conductive particles are dispersed in a binder resin. A polyamide resin can be used as the binder resin, and a nylon resin is more preferable. Specifically, the copolymer nylon resin "PA100-AS" (manufactured by T&K TOKA Co., Ltd.) can be used as the nylon resin. The binder resin content in the surface layer 636 is preferably 25% by mass or more and 60% by mass or less, and more preferably 35% by mass or more and 45% by mass or less. By setting the content to 25% by mass or more, sufficient strength of the surface layer 636 can be ensured, and by setting it to 60% by mass or less, it becomes easier to ensure the amount of resin particles and conductive particles in the surface layer 636.

[0054] The conductive particles impart appropriate conductivity to the surface layer. Examples of the conductive particles include carbon black, graphite, and metal oxide particles. Examples of the metal oxide include potassium titanate, iron oxide, titanium oxide, zinc oxide, tin oxide, antimony-doped tin oxide, and phosphorus-doped tin oxide. The conductive particles preferably contain at least one of carbon black and tin oxide.

[0055] The surface layer 636 may further have a configuration in which resin particles are dispersed in the binder resin. The resin particles impart appropriate surface roughness to the surface layer 636. Examples of the resin forming the resin particles include (meth)acrylic resin, urethane resin, silicone resin, polyester resin, polystyrene resin, styrene-(meth)acrylic resin, and polyolefin resin. Acrylic resin is more preferable as the resin, and specifically, "MZ-5HN" (crosslinked acrylic dispersed particles, manufactured by Soken Chemical & Engineering Co., Ltd.) made of crosslinked polymethyl methacrylate can be used.

[0056] In the charging roller 631, the volume resistivity of the surface layer 636 is preferably 1×10 8 Ω·cm or more and 1×10 14 Ω·cm or less. In the charging roller 631, by setting the volume resistivity of the surface layer 636 to 1×10 8 Ω·cm or more, it becomes easier to uniformly charge the photoreceptor 65 without unevenness. Further, in the charging roller 631, by setting the volume resistivity of the surface layer 636 to 1×10 14 Ω·cm or less, it becomes easier to secure a sufficient charging potential for forming an image in the charging roller 631.

[0057] The volume resistivity of the surface layer 636 can be adjusted by the content of the conductive particles in the surface layer 636. Specifically, when using carbon black and tin oxide particles as the conductive particles, with the content of carbon black being 5 phr and the content of tin oxide particles being 40 phr or more and 100 phr or less, the volume resistivity of the surface layer 636 is 1×10 8 Ω·cm or more and 1×10 14The density can be Ω·cm or less. Note that "phr" represents parts by mass of carbon black or tin oxide particles per 100 parts by mass of elastic material.

[0058] In the image forming apparatus 100, the photoreceptor 65 and the charging roller 631 have a current flowing into the photoreceptor 65 when the charging roller 631 charges the photoreceptor 65, which is 0.40 mC / m 2 1.0mC / m or more 2 The configuration is as follows: The charging roller 631 has a current flowing into the photoreceptor 65 of 0.40 mC / m 2 By doing so, it becomes easier to charge the photoreceptor 65 evenly and uniformly. In addition, the charging roller 631 sets the current flowing into the photoreceptor 65 to 1.0 mC / m 2 The following measures make it easier to achieve high wear resistance.

[0059] The current flowing into the photoreceptor 65 when the charging roller 631 charges the photoreceptor 65 can be adjusted, for example, by the thickness of the photosensitive layer 652 of the photoreceptor 65 and the volume resistivity of the surface layer 636 of the charging roller 631.

[0060] [Method for manufacturing an electrostatic roller] A method for manufacturing the electrostatic roller 631 will now be described. The electrostatic roller 631 can be manufactured by forming an elastic layer 635 on a conductive shaft 634 and then forming a surface layer 636 on the elastic layer 635. The elastic layer 635 can be formed by preparing a composition by mixing the elastic material and conductive material described above, heating this composition and injecting it into a mold in which the conductive shaft 634 is set, and then demolding after cooling. The mixing of the elastic material and conductive material can be done using a stirrer.

[0061] The surface layer 636 can be formed on the elastic layer 635 by preparing a coating solution by mixing a solvent with the aforementioned binder resin, conductive particles, and resin particles, applying this coating solution to the elastic layer 635, and then removing the solvent. The materials can be mixed using a wet disperser such as a ball mill, bead mill, or roll mill.

[0062] The coating solution can be applied using a method that allows for uniform application, and one of the following methods can be used: dip coating, spray coating, spin coating, bar coating, or blade coating. The solvent can be removed by heating, reduced pressure, or a combination of heating and reduced pressure, specifically using a high-temperature dryer or a vacuum dryer. [Examples]

[0063] As examples and comparative examples of the present invention, a photoreceptor and a charging roller were fabricated and evaluated. Note that the following examples merely illustrate one aspect of the present invention, and the present invention is not limited to the configurations described below.

[0064] [Fabrication of the photoreceptor] The photoreceptor was prepared as follows. First, a coating solution was prepared by dispersing the following materials in a solvent using a rod-shaped acoustic oscillator. The dispersion time was 20 minutes. The materials consisted of 3 parts by mass of Y-type titanyl phthalocyanine shown in formula (1) as a charge generating material, 60 parts by mass of the substance shown in formula (2) as a hole transport material, 50 parts by mass of the substance shown in formula (3) as an electron transport material, and 100 parts by mass of polyalate resin as a binder resin, with 500 parts by mass of tetrahydrofuran as the solvent. The polyalate resin contained 40 parts by mass of repeating units shown in formula (4), 10 parts by mass of repeating units shown in formula (5), 25 parts by mass of repeating terminals shown in formula (6), and 25 parts by mass of repeating units shown in formula (7). The solvent was 500 parts by mass of tetrahydrofuran.

[0065] [ka]

[0066] [ka]

[0067] [ka]

[0068] [ka]

[0069] [ka]

[0070] [ka]

[0071] [ka]

[0072] Next, the prepared coating solution was filtered through a 5 μm mesh filter. The coating solution was then applied to the surface of the conductive substrate using a dip-coating method to form a coating film. The coating film was dried at 120°C for 50 minutes to remove the solvent and form a photosensitive layer. The thickness of the photosensitive layer differed between the examples and comparative examples. The photoreceptor was prepared as described above.

[0073] [Manufacturing of an electrostatic roller] The electrostatic roller was manufactured as follows. First, the following materials were stirred and mixed using a stirrer to prepare the composition. The materials were: 100 parts by mass of epichlorohydrin rubber ("Epichromer CG-102" (manufactured by Osaka Soda Co., Ltd.)), 5 parts by mass of vulcanization aid (zinc oxide, "Zinc Oxide Type 2" (manufactured by Mitsui Mining & Smelting Co., Ltd.)), 1.5 parts by mass of vulcanization accelerator (MBT (2-Mercaptobenzothiazole), "Noxellar MP" (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)), 1 part by mass of sulfur ("Sulfax PS" (manufactured by Tsurumi Chemical Industry Co., Ltd.)), 50 parts by mass of filler (calcium carbonate, "Hakuenka CC" (manufactured by Shiraishi Kogyo Co., Ltd.)), 20 parts by mass of electronically conductive material (carbon black, "Asahi #50" (manufactured by Asahi Carbon Co., Ltd.)), and 0.5 parts by mass of ionic conductive material (sodium trifluoroacetate).

[0074] A conductive shaft (6 mm in diameter) was placed in a mold, the above composition was injected into the mold, heated at 160°C for 20 minutes, then cooled and demolded to form an elastic layer with a thickness of 1.8 mm on the outer circumference of the conductive shaft.

[0075] Next, a coating solution was prepared by dispersing the following materials in a solvent using a ball mill. The materials consisted of 100 parts by mass of copolymerized nylon resin ("PA100-AS" (manufactured by T&K TOKA)) as a binder resin, 50 parts by mass of crosslinked acrylic dispersed particles ("MZ-5HN" (manufactured by Soken Chemical Co., Ltd.)) as resin particles, and 5 parts by mass of tin oxide particles ("SP2" (manufactured by Mitsubishi Materials Corporation)) and carbon black (manufactured by Tokai Carbon Co., Ltd.) as conductive particles. The content of tin oxide particles differed between the examples and comparative examples. 1-butanol was used as the solvent.

[0076] Next, the prepared coating solution was applied to the outer circumference of the elastic layer described above to a thickness of 10 μm by blade coating to form a coating film. Furthermore, the coating film was dried in an electric furnace at 120°C for 40 minutes to remove the solvent and form a surface layer. The electrostatic roller was manufactured in this manner.

[0077] [Measurement and Evaluation] In the examples and comparative examples, the current flowing into the photoreceptor was measured, and the volume resistivity of the surface layer of the charging roller was measured. In addition, the photoreceptor and charging roller were evaluated for their chargeability, image uniformity, and abrasion resistance.

[0078] • Method for measuring incoming current Using an evaluation machine for image forming apparatus (Kyocera Document Solutions' "TASKalfa MA4500ci"), the current flowing into the photoreceptor was measured when the photoreceptor was charged to V0 (initial surface potential): 470V. The current was measured using a microampere meter "MA-100N" (Narika).

[0079] • Method for measuring the volume resistivity of the surface layer A thin film sample for volume resistivity measurement was prepared by applying the coating liquid of a charging roller onto an aluminum sheet. Using a high resistivity meter (Mitsubishi Chemical Analytec "High Resta-UX MCP-HT800"), the electrode probe was pressed against the coated thin film sample, and a voltage of 100V was applied for 10 seconds to measure the volume resistivity.

[0080] • Method for evaluating electrostatic properties The photoreceptor and charging roller were set in an evaluation machine (Kyocera Document Solutions' "TASKalfa MA4500ci"), and the applied voltage was set to 1100V, 1200V, 1300V, 1400V, and 1500V at room temperature. The charging potential was measured at each applied voltage. The charging potential was used as the evaluation value for chargeability. The evaluation value was assessed according to the following A and B criteria. For chargeability, the photoreceptor and charging roller with an evaluation of A were considered to pass, and the photoreceptor and charging roller with an evaluation of B were considered to fail. A: More than 50V B: 50V or less

[0081] Image unevenness The photoreceptor and charging roller were set in an evaluation machine (Kyocera Document Solutions' "TASKalfa MA4500ci"), and under conditions of 23.2°C and 52% RH, the applied voltage was set to 1100V, 1200V, 1300V, 1400V, and 1500V. 25% half-images were formed at each applied voltage. The 25% half-images were visually observed and evaluated according to the following A and B criteria. Regarding image uniformity, the photoreceptor and charging roller with an evaluation of A were considered acceptable, and the photoreceptor and charging roller with an evaluation of B were considered unacceptable. A: No image inconsistencies are visible. B: Some image inconsistencies are visible. C: Image inconsistencies are visible throughout.

[0082] • Abrasion resistance The photoreceptor and charging roller were set in an evaluation machine (Kyocera Document Solutions' "TASKalfa MA4500ci"), and image formation was performed under conditions of 23.2°C and 52% RH. The print pattern was a 5% density character image, the printing method was continuous printing, the number of printed sheets was 50,000, and the evaluation paper was "Askul Multipaper Super Economy+". The charging polarity of the charging roller was positive, the applied voltage to the charging roller was DC voltage, and the transfer method was intermediate transfer. The film thickness T1 of the surface layer of the charging roller before 50,000 prints and the film thickness T2 of the surface layer of the charging roller after 50,000 prints were measured using an eddy current film thickness meter (Kett Scientific Research Institute Co., Ltd.'s "LH-373"), and the amount of wear per 1,000 prints was determined. Wear amount (μm / 1000 sheets) = (1000 / 50000)(T1-T2) The wear resistance of the surface layer of the electrostatic roller was evaluated using the amount of wear as the evaluation value. The evaluation value was performed according to the following A and B criteria. For the wear resistance of the surface layer of the electrostatic roller, the photoreceptor and electrostatic roller that received an evaluation of A were deemed to pass, and the photoreceptor and electrostatic roller that received an evaluation of B were deemed to fail. A: 0.12μm / less than 1000 sheets B:0.12μm / 1000 sheets or more

[0083] [Examples 1-9] In Examples 1-9, the film thickness of the photosensitive layer of the photoreceptor and the amount of tin oxide on the surface of the charging roller were varied. Table 1 shows the film thickness of the photosensitive layer of the photoreceptor, the incoming current, the amount of tin oxide on the surface of the charging roller, and the volume resistivity for Examples 1-9. Note that the volume resistivity is shown on a logarithmic scale. As shown in Table 1, in Examples 1-9, the incoming current was 0.40 mC / m 2 1.0mC / m or more 2 The volume resistivity of the surface layer of the electrostatic roller is within the following range, and is 1 × 10⁻⁶. 8 Ω cm or more 1×10 14 It is within the range of Ω·cm or less.

[0084] [Table 1]

[0085] Table 2 shows the evaluation results for the electrostatic properties of the photoreceptors and charging rollers in Examples 1 to 9. All of the photoreceptors and charging rollers in Examples 1 to 9 passed the electrostatic property test.

[0086] [Table 2]

[0087] Table 3 shows the evaluation results for image uniformity for the photoreceptors and charging rollers of Examples 1 to 9. All of the photoreceptors and charging rollers of Examples 1 to 9 passed the evaluation for image uniformity.

[0088] [Table 3]

[0089] Table 4 shows the evaluation results of the wear resistance of the surface layer of the electrostatic rollers for Examples 1 to 9. In all of Examples 1 to 9, the wear resistance of the surface layer of the electrostatic rollers passed the evaluation.

[0090] [Table 4]

[0091] [Comparative Examples 1-5] In Comparative Examples 1 to 5, the film thickness of the photosensitive layer of the photoreceptor and the amount of tin oxide on the surface of the charging roller were varied. Table 5 shows the film thickness of the photosensitive layer of the photoreceptor, the inflow current, the amount of tin oxide on the surface of the charging roller, and the volume resistivity for Comparative Examples 1 to 5. Note that the volume resistivity is shown on a logarithmic scale. Comparative Example 1 had an inflow current of 1.0 mC / m 2 Comparative Example 2 differs from the above embodiment in that it is greater than [a certain value]. Comparative Example 2 has a photoreceptor current of 0.40 mC / m 2 It differs from the above embodiment in that it is less than 10. Comparative Example 3 has a volume resistivity of 1 × 10⁻⁶ of the surface layer of the electrostatic roller.8 It differs from the above examples in that it is less than Ω·cm. Comparative Examples 4 and 5 have a volume resistivity of 1 × 10⁻⁶ of the surface layer of the electrostatic roller. 14 This differs from the above embodiment in that it is greater than Ω·cm.

[0092] [Table 5]

[0093] Table 6 shows the evaluation results for the electrostatic properties of the photoreceptors and charging rollers related to Comparative Examples 1 to 5. The photoreceptors and charging rollers related to Comparative Examples 4 and 5 failed the electrostatic property evaluation. This is thought to be because the volume resistivity of the surface layer of the charging rollers in Comparative Examples 4 and 5 was too high.

[0094] [Table 6]

[0095] Table 7 shows the evaluation results for image uniformity for the photoreceptors and charging rollers of Comparative Examples 1 to 5. The photoreceptors and charging rollers of Comparative Examples 2 and 3 failed to pass the image uniformity evaluation at applied voltages of 1200V, 1300V, 1400V, and 1500V. This is thought to be because the current flowing into the photoreceptor was too low in Comparative Example 2, and the volume resistivity of the surface layer of the charging roller was too low in Comparative Example 3. Furthermore, the photoreceptors and charging rollers of Comparative Examples 4 and 5 were unable to form a 25% half image, and therefore image uniformity could not be evaluated. This is thought to be because the volume resistivity of the surface layer of the charging roller was too high in Comparative Examples 4 and 5.

[0096] [Table 7]

[0097] Table 8 shows the evaluation results for the abrasion resistance of the surface layer of the charging rollers for Comparative Examples 1 to 5. Comparative Example 1 failed to meet the abrasion resistance standards for the surface layer of the charging roller. This is thought to be because the current flowing into the photoreceptor was too high in Comparative Example 1. Furthermore, in Comparative Examples 4 and 5, it was not possible to form an image with the photoreceptor and charging roller, and therefore the abrasion resistance of the surface layer of the charging roller could not be evaluated. This is thought to be because the volume resistivity of the surface layer of the charging roller was too high in Comparative Examples 4 and 5.

[0098] [Table 8] [Explanation of Symbols]

[0099] 100…Image forming apparatus 65...Photoreceptor 631... Electrostatic roller 635...Elastic layer 636…Surface layer

Claims

1. Photoreceptor and Volume resistivity is 1 × 10⁻⁶ ８ Ω・cm or more 1×10 １４ A charging roller having a surface layer of Ω·cm or less, which charges the photoreceptor, The system comprises a power supply for applying a DC voltage to the aforementioned charging roller, The current flowing into the photoreceptor when the photoreceptor is charged by the charging roller is 0.40 mC / m ２ 1.0 mC / m or more ２ The following is Image forming apparatus.

2. An image forming apparatus according to claim 1, The surface layer has a structure in which conductive particles are dispersed in nylon resin. Image forming apparatus.

3. An image forming apparatus according to claim 2, The conductive particles include at least one of carbon black and tin oxide. Image forming apparatus.

4. An image forming apparatus according to any one of claims 1 to 3, The photoreceptor is a single-layer photoreceptor. Image forming apparatus.

Images