Developing roller, process cartridge, and electrophotographic image forming apparatus

Abstract

The invention relates to a developing roller, a process cartridge, and an electrophotographic image forming apparatus. The developing roller includes a base including a conductive surface and a conductive layer on the surface of the base, an outer surface of the developing roller is configured from at least a first region and a second region having a higher conductivity than the first region, the first region and the second region are disposed adjacent to each other, the first region contains at least one polycarbonate, and the second region contains at least one polycarbonate. And the at least one polycarbonate has a specific structure having a substituent in the aromatic ring of the main chain.

Description

Technical Field

[0001] The present disclosure relates to a developing roller, a process cartridge, and an electrophotographic image forming apparatus. Background Art

[0002] In recent years, there has been an increasing trend toward higher speeds, higher durability, and greater energy savings in electrophotographic image forming apparatuses (electrophotographic devices). This trend has also led to a demand for reduced drive torque when driving these devices. A significant portion of the drive torque in electrophotographic devices is generated by the developing device, with the majority of this torque occurring between the toner supply roller and the developing roller. Therefore, energy savings can be achieved by reducing the drive torque between the toner supply roller and the developing roller.

[0003] To reduce the driving torque, for example, the contact area of ​​the toner supply roller relative to the developer roller is reduced, or the peripheral speed difference between the developer roller and the toner supply roller is reduced. However, if the contact area of ​​the toner supply roller is reduced or the peripheral speed difference is reduced as described above, the amount of toner supplied from the toner supply roller to the developer roller may become insufficient.

[0004] Japanese Patent Application Publication No. 2020-020958 discloses a developing roller that can attract a sufficient amount of toner even when driving torque is reduced by having an insulating portion and a conductive portion exist together in a small area near the surface.

[0005] The developing roller disclosed in Japanese Patent Application Publication No. 2020-020958 has an insulating portion and a conductive portion present together in a small area near the surface. This allows sufficient toner to be attracted even when the driving torque is reduced, for example, by slowing the rotation speed of the toner supply roller and reducing the peripheral speed difference of the developing roller. The invention discloses an embodiment in which a highly durable polycarbonate is used in the insulating portion. Summary of the Invention

[0006] However, in the case of using the developing roller disclosed in Japanese Patent Application Laid-Open No. 2020-020958 and further increasing the process speed, the image density may deteriorate.

[0007] Therefore, the present disclosure provides a developing roller that can suppress a decrease in the density of an electrophotographic image for a long period of time even when the driving torque between the toner supply roller and the developing roller is reduced and the process speed is increased. Furthermore, the present disclosure provides a process cartridge and an electrophotographic image forming apparatus that can stably form high-quality electrophotographic images.

[0008] The present disclosure relates to a developing roller comprising:

[0009] a substrate comprising a surface having electrical conductivity; and

[0010] a conductive layer on the surface of the substrate,

[0011] The outer surface of the developing roller is composed of at least a first region and a second region having a higher conductivity than the first region.

[0012] The first region and the second region are arranged adjacent to each other,

[0013] The first region comprises at least one polycarbonate, and

[0014] The at least one polycarbonate comprises a structure represented by formula (1A):

[0015]

[0016] In formula (1A),

[0017] R1 to R8 each independently represent a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, or an aryl group having 6 to 10 carbon atoms,

[0018] R9 and R 10 each independently represents a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, or an aryl group having 6 to 10 carbon atoms, or

[0019] R9 and R 10 It is R9 and R 10 The atomic groups necessary to bond with each other to form an alicyclic structure having 6 to 12 carbon atoms,

[0020] Wherein (1A) satisfies at least one condition selected from the group consisting of the following conditions 1 and 2:

[0021] -Condition 1

[0022] At least one selected from the group consisting of R1 to R8 is an alkyl group having 1 to 9 carbon atoms or an aryl group having 6 to 10 carbon atoms,

[0023] -Condition 2

[0024] Choose between R9 and R 10 At least one of the group consisting of the above is a linear or branched alkyl group having 2 or more carbon atoms or an aryl group having 6 to 10 carbon atoms.

[0025] Furthermore, the present disclosure relates to a process cartridge configured to be detachably mounted to a main body of an electrophotographic image forming apparatus,

[0026] The process box at least includes: a developing device,

[0027] Wherein, the developing device includes the aforementioned developing roller.

[0028] Furthermore, the present disclosure relates to an electrophotographic image forming apparatus comprising:

[0029] developing device,

[0030] Wherein, the developing device is the aforementioned developing roller.

[0031] According to the present disclosure, a developing roller can be obtained that can suppress a decrease in the density of an electrophotographic image for a long period of time even when the driving torque between the toner supply roller and the developing roller is reduced and the process speed is further increased. In addition, according to the present disclosure, a process cartridge and an electrophotographic image forming apparatus can be obtained that can stably form high-quality electrophotographic images.

[0032] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1A and Figure 1B is a schematic cross-sectional view illustrating an example of a developing roller.

[0034] Figure 2 is a schematic configuration diagram of an example of a process cartridge.

[0035] Figure 3 is a schematic cross-sectional view of an example of an electrophotographic apparatus. DETAILED DESCRIPTION

[0036] In the present disclosure, unless otherwise specified, the phrase "XX or more and YY or "XX to YY" when expressing a numerical range means that the numerical range includes both the lower limit and the upper limit as endpoints. When describing a numerical range in stages, the upper and lower limits of each numerical range can be combined as needed. In addition, in the present disclosure, for example, a phrase such as "at least one selected from the group consisting of XX, YY, and ZZ" means any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ.

[0037] In a typical non-magnetic, single-component development method, a sufficient amount of toner is first supplied from a developing device to a developing roller via a toner supply roller. Next, the toner supplied to the developing roller is regulated by a toner regulating member, such as a developing blade. In this way, the developing roller is coated with an appropriate amount of toner.

[0038] The developing roller according to Japanese Patent Application Publication No. 2020-020958 is a developing roller comprising: a substrate having a conductive surface and a conductive layer on the substrate surface, wherein the outer surface of the developing roller is composed of at least an insulating portion and a conductive portion, and the insulating portion and the conductive portion are arranged adjacent to each other. By driving such a developing roller in a developing device, the insulating portion on the surface of the developing roller is charged by sliding relative to an abutting member such as a developing blade or the toner at a position where the insulating portion abuts against the abutting member such as a developing blade. In this way, a local potential difference is generated between the charged surface of the insulating portion and the uncharged surface of the conductive portion.

[0039] When a local potential difference exists on the surface of the developer roller, an electric field gradient is generated due to the potential difference. If an object is present in the electric field gradient, it is polarized by the electric field gradient, generating a gradient force in the direction of the developer roller's surface. In other words, when toner is present near the developer roller, which has such a local potential difference on its surface, the developer roller can attract the toner to its own surface. Therefore, even if the amount of toner supplied from the toner supply roller to the developer roller decreases due to the reduction in the contact area between the toner supply roller and the developer roller, the developer roller itself attracts the toner, allowing image formation without a decrease in density.

[0040] However, when the developing roller disclosed in Japanese Patent Application Publication No. 2020-020958 increases its processing speed, the time the insulating portion slides against the abutment member and toner as it passes the abutment position is shortened, and the amount of charge on the insulating portion decreases. As a result, it is believed that the local potential difference generated between the surface of the insulating portion and the conductive portion decreases, reducing the gradient force, and thus reducing the amount of toner attracted to the developing roller, resulting in a lower concentration.

[0041] Furthermore, with prolonged use of the developing roller, defects such as wear and cracks may develop on the surface of the insulating portion. This can lead to, for example, a decrease in the area of ​​the insulating portion, a decrease in the amount of charge on the insulating portion, and a decrease in the gradient force. As a result, it is believed that the amount of toner attracted decreases, leading to a lower concentration.

[0042] Therefore, the present inventors have continued their research to obtain a developing roller capable of suppressing a decrease in image density even when the processing speed is increased and the developing roller is used for a long time, focusing on the dielectric properties of the insulating portion and its durability against wear, cracks, etc. As a result, the present inventors have discovered that a developing roller having the following configuration suppresses a decrease in density even when the processing speed is further increased and the developing roller is used for a long time.

[0043] The present disclosure relates to a developing roller comprising:

[0044] a substrate comprising a surface having electrical conductivity; and

[0045] The conductive layer on the substrate surface,

[0046] The outer surface of the developing roller is composed of at least a first region and a second region having a higher conductivity than the first region.

[0047] The first region and the second region are arranged adjacent to each other,

[0048] The first region comprises at least one polycarbonate, and

[0049] The at least one polycarbonate comprises a structure represented by formula (1A).

[0050]

[0051] In formula (1A),

[0052] R1 to R8 each independently represent a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, or an aryl group having 6 to 10 carbon atoms,

[0053] R9 and R 10 each independently represents a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, or an aryl group having 6 to 10 carbon atoms, or

[0054] R9 and R 10 It is R9 and R 10 The atomic groups necessary to bond with each other to form an alicyclic structure having 6 to 12 carbon atoms,

[0055] Wherein (1A) satisfies at least one condition selected from the group consisting of the following conditions 1 and 2:

[0056] -Condition 1

[0057] At least one selected from the group consisting of R1 to R8 is an alkyl group having 1 to 9 carbon atoms or an aryl group having 6 to 10 carbon atoms,

[0058] -Condition 2

[0059] Choose between R9 and R 10 At least one of the group consisting of the above is a linear or branched alkyl group having 2 or more carbon atoms or an aryl group having 6 to 10 carbon atoms.

[0060] The reason why the first region (insulating portion) including the polycarbonate having such a structure exhibits the effects of suppressing a decrease in image density and achieving durability is presumably as follows.

[0061] First, the polycarbonate having the structure of formula (1A) contained in the first region has a benzene ring in the main chain and therefore has high durability and is excellent in durability against wear, cracks, etc. even when the developing roller is used for a long time.

[0062] In addition, the polycarbonate having the structure of formula (1A) has steric hindrance in the aromatic ring of the main chain and has lower molecular orientation and higher molecular mobility than conventional polycarbonates. Therefore, it is believed that by using the polycarbonate of formula (1A), even when the processing speed is further increased, the decrease in concentration can be suppressed.

[0063] The insulating portion is charged at the point of contact with an abutting member such as a developer blade. The width of the abutment point is less than 1 mm, and a high electric field is applied to it by the blade bias or the charge of the toner. If the processing speed is further increased, the insulating portion passes the abutment point in a short time, so the sliding time of the insulating portion relative to the abutment member and the toner may be further shortened, and the charging may become insufficient. Therefore, if the processing speed is further increased, the insulating portion needs to be charged in a short time, and it is believed that it is necessary to reach a state with a high dielectric constant and a high probability of charge exchange within a short time.

[0064] On the other hand, in order to generate a strong gradient force for attracting the desired toner, it is necessary to generate a large electric field due to the received charge, and the dielectric constant of the insulating portion is preferably low. Since an electric field does not act on the developing roller from the outside when the toner in the developing container is attracted, it is believed that a low dielectric constant is necessary when no external electric field acts on the developing roller.

[0065] Here, the dielectric constant of a resin is strongly affected by molecular orientation. When the molecular orientation is high, the dielectric constant is high, while when the molecular orientation is low, the dielectric constant is low. Based on this situation, the present inventors estimated the dielectric constant based on the molecular orientation in the structure of polycarbonate.

[0066] It is speculated that the polycarbonate used in the present disclosure plays a role in relaxing the adhesive force of the aromatic ring relative to conventional polycarbonate by providing steric hindrance around the aromatic ring, and compared with conventional polycarbonate, the polycarbonate used in the present disclosure has low crystallinity and relatively uneven molecular orientation. Therefore, when a high electric field is applied thereto for a short time, due to the steric hindrance around the aromatic ring, etc., there is a portion with high molecular mobility, and microscopic molecular orientation is generated in a portion of this portion, so the dielectric constant is higher than that of conventional polycarbonate. On the other hand, in the absence of the influence of an external electric field, the polycarbonate used in the present disclosure has a lower molecular orientation than conventional polycarbonate, and therefore it is believed that its dielectric constant is lower than that of conventional polycarbonate.

[0067] Based on the above inference, by using the polycarbonate of formula (1A), when the processing speed is further increased, the dielectric constant immediately after passing the abutment position is higher than before, thereby making it more likely that charge will be exchanged between the abutment member and the toner, and the insulating portion will be sufficiently charged. Furthermore, since the dielectric constant is lower than before when the external electric field is not applied after passing the abutment position, it is believed that the gradient force can be increased, and a sufficient amount of toner can be attracted.

[0068] In other words, the present disclosure provides steric hindrance around the aromatic ring of the polycarbonate structure. In this way, a developing roller can be obtained that can suppress a decrease in image density even when the developing roller is applied to an electrophotographic apparatus with a reduced drive torque and a further increased process speed and used for a long time.

[0069] Hereinafter, the developing roller according to the present aspect will be described in detail.

[0070] developing roller

[0071] For the developing roller, for example, Figure 1A and Figure 1B As shown in FIG, a schematic cross-sectional view of the developing roller when it is cut in a direction perpendicular to the longitudinal direction (axial direction) of the developing roller is illustrated as an example. Figure 1A As shown, the developing roller 1 includes a conductive substrate 2 and a conductive layer 3 on the substrate. In addition, the configuration of the developing roller 1 is exemplified in which a first region 4 (insulating portion) exposed from the outer surface (the surface opposite to the substrate side) of the conductive layer 3 and a second region 5 (conductive portion) having a higher conductivity than the first region are present. Figure 1A As shown, for example, the first region 4 may protrude from the outer surface of the developer roller.

[0072] In addition, if Figure 1B As shown, the developer roller can be configured such that the first region 4 is present within the conductive layer 3, and the first region 4 and the second region 5 are exposed from the outer surface. For example, the first region 4 and the second region 5 can form a substantially flat outer surface. In other words, the developer roller only requires that the second region 5 be disposed on a portion of the surface (outer surface) of the conductive layer 3, and the outer surface of the developer roller at least include the first region 4 and the second region 5 adjacent to each other. Note that the conductive layer 3 can be a single layer or include multiple layers.

[0073] matrix

[0074] The substrate has electrical conductivity and functions to support the conductive layer provided thereon. Examples of the substrate material include metals such as iron, copper, aluminum, and nickel; and alloys containing these metals such as stainless steel, duralumin, brass, and bronze. One of these metals may be used, or two or more may be used in combination. For the purpose of imparting scratch resistance, the surface of the substrate may be plated without impairing conductivity. Alternatively, a substrate obtained by coating the surface of a resin substrate with metal to impart conductivity, or a substrate made from a conductive resin composition, may be used.

[0075] Conductive layer

[0076] In the developer roller, the conductive layer is disposed on a substrate and may have a single-layer structure or a stacked structure of two or more layers. In non-magnetic single-component contact development systems, a developer roller having two conductive layers is particularly preferred. Note that when the developer roller includes multiple conductive layers, unless otherwise specified, the following conditions are preferably met for each conductive layer.

[0077] Conductive layer can include elastic material, such as resin and rubber.The specific example of resin and rubber includes polyurethane resin, polyamide, urea resin, polyimide, melamine resin, fluororesin, phenolic resin, alkyd resin, silicone resin, polyester, ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), fluororubber, silicone rubber, epichlorohydrin rubber, hydrogenated NBR and polyurethane rubber etc.Can use one of these resins and rubber alone, or can use two or more thereof in combination as needed.

[0078] The second region 5 preferably contains at least one selected from the group consisting of resin and rubber. Note that the materials of the resin and rubber can be identified by measuring the conductive layer included in the developing roller using a Fourier transform infrared visible spectrometer.

[0079] Among the above materials, when the conductive layer has a stacked structure, the layer (lower layer) disposed closest to the substrate in the conductive layer preferably contains silicone rubber.

[0080] Examples of the silicone rubber include polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polyphenylvinylsiloxane, and copolymers of these siloxanes.

[0081] Furthermore, the layer disposed on the outermost surface of the conductive layer (outermost layer) preferably comprises a polyurethane resin. Polyurethane resins are preferably used because they have excellent triboelectric charging properties against toners and excellent flexibility, thus easily coming into contact with toners and exhibiting wear resistance. The conductive layer preferably has a two-layer structure, wherein the layer disposed on the substrate side (lower layer) comprises silicone rubber, and the layer disposed on the outer surface side of the conductive layer (outermost layer) comprises a polyurethane resin.

[0082] Examples of the polyurethane resin include ether polyurethane resins, ester polyurethane resins, acrylic polyurethane resins, and carbonate polyurethane resins. These polyurethane resins can be obtained by reacting a known polyol with an isocyanate compound.

[0083] Specific examples of the polyol include polyether polyols such as polyethylene glycol, polypropylene glycol and polytetramethylene ether glycol, polyester polyols such as polyethylene succinate diol, polybutylene succinate diol, polyethylene adipate diol and polybutylene adipate diol, and polycarbonate polyols such as polyethylene carbonate diol and polybutylene carbonate diol.

[0084] Although the isocyanate component to be reacted with these polyol components is not particularly limited, examples thereof include aliphatic polyisocyanates such as ethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), etc., alicyclic polyisocyanates such as isophorone diisocyanate (IPDI), cyclohexane 1,3-diisocyanate, cyclohexane 1,4-diisocyanate, etc., aromatic isocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), polymeric diphenylmethane diisocyanate, xylylenediisocyanate, naphthalene diisocyanate, etc., as well as copolymers, isocyanurates, TMP adducts, biuret bodies, and block bodies thereof. Among them, aromatic isocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and polymeric diphenylmethane diisocyanate are more preferably used.

[0085] The conductive layer preferably contains a conductive agent to obtain conductivity. Examples of the conductive agent include ion conductive agents and electronic conductive agents such as carbon black. Carbon black is preferably used because the conductivity of the conductive layer and the charging performance of the conductive layer relative to the toner can be controlled. Typically, the volume resistivity of the conductive layer is preferably 1.0×10 3 Ω·cm to 1.0×10 11 The volume resistivity of the conductive layer can be measured using a method similar to the volume resistivity of the first region described below.

[0086] Specific examples of carbon black include conductive carbon black such as "Ketjen Black" (product name; manufactured by Lion Corporation) or acetylene black; and rubber carbon black such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT. In addition, as the carbon black, oxidation-treated color ink carbon black or thermally decomposed carbon black can be used.

[0087] The amount of carbon black added is preferably 5 to 50 parts by mass relative to 100 parts by mass of the total of the resin and rubber in the conductive layer. The carbon black content in the conductive layer can be measured using a thermogravimetric analyzer (TGA).

[0088] In addition to the carbon black mentioned above, other conductive agents that can be used in the conductive layer include graphite, such as natural graphite and artificial graphite; metal powders, such as copper, nickel, iron, and aluminum; metal oxide powders, such as titanium oxide, zinc oxide, and tin oxide; and conductive polymers, such as polyaniline, polypyrrole, and polyacetylene. Any of these can be used alone, or two or more can be combined as needed. Furthermore, the amount of these conductive agents added can be appropriately adjusted.

[0089] The conductive layer may further contain a charge control agent, a lubricant, a filler, an antioxidant, an anti-aging agent, etc., without interfering with the functions of the resin, rubber, and conductive agent described above. The amount of these additives added may be appropriately set.

[0090] The thickness of the conductive layer (total thickness in the case of a stacked structure) is preferably 1 μm to 5 mm. The thickness of the conductive layer can be obtained by observing with an optical microscope and measuring the cross section of the conductive layer when the conductive layer is cut in a direction perpendicular to the axial direction of the developing roller. In the case where the conductive layer has a two-layer structure, the thickness of the lower layer is preferably 0.1 mm to 50.0 mm, more preferably 0.5 mm to 10.0 mm. The thickness of the outermost layer is preferably 4 μm to 100 μm, more preferably 6 μm to 30 μm.

[0091] If the developer roller requires a certain surface roughness, the conductive layer may contain particles for controlling the roughness. In this case, the volume average particle size of the particles for controlling the roughness is preferably 3 to 20 μm. The amount of these particles in the conductive layer is preferably 1 to 50 parts by mass per 100 parts by mass of the resin and rubber in the conductive layer. The content of these particles in the conductive layer can be measured using analytical techniques such as thermogravimetric analysis.

[0092] Examples of particles that can be used for controlling roughness include fine particles of polyurethane resins, polyester resins, polyether resins, polyamide resins, acrylic resins, and polycarbonates.

[0093] First Area

[0094] The first region (hereinafter also referred to as the insulating portion) is disposed on the outermost layer of the conductive layer and is exposed from the outermost layer of the conductive layer. The first region preferably covers a portion of the outermost layer and constitutes a portion of the outer surface of the developer roller. The first region may be present on the outer surface of the developer roller, for example, in a dotted pattern. The first region may be connected to the extent that the conductive layer (second region) of the developer roller is exposed.

[0095] Material constituting the first region (insulating portion)

[0096] The material constituting the insulating portion (insulating material) includes polycarbonate represented by the following formula (1A). Therefore, even when the driving torque between the toner supply roller and the developing roller is reduced and the process speed is further increased, the decrease in density of the electrophotographic image can be suppressed for a long time.

[0097]

[0098] In formula (1A),

[0099] R1 to R8 each independently represent a hydrogen atom, an alkyl group having 1 to 9 carbon atoms (preferably 1 to 4, or more preferably 1 to 3), or an aryl group having 6 to 10 carbon atoms (preferably 6 to 8, or more preferably 6).

[0100] R9 and R 10 each independently represents a hydrogen atom, an alkyl group having 1 to 9 carbon atoms (preferably 1 to 4, or more preferably 1 to 3), an aryl group having 6 to 10 carbon atoms (preferably 6 to 8, or more preferably 6), or

[0101] R9 and R 10 It is R9 and R 10 Atom groups necessary to bond with each other to form an alicyclic structure having 6 to 12 carbon atoms.

[0102] However, (1A) satisfies at least one condition selected from the group consisting of the following Condition 1 and Condition 2.

[0103] -Condition 1

[0104] At least one member selected from the group consisting of R1 to R8 (preferably 1 to 4 members, more preferably 1 to 3 members, or even more preferably 2 members) is an alkyl group having 1 to 9 carbon atoms (preferably 1 to 4 members, or even more preferably 1 to 3 members), or an aryl group having 6 to 10 carbon atoms (preferably 6 to 8 members, or even more preferably 6 members). Preferably, the remaining R1 to R8 members are hydrogen atoms.

[0105] -Condition 2

[0106] Choose between R9 and R 10At least one of the group consisting of is a linear or branched alkyl group having 2 or more carbon atoms (preferably 2 to 10, or more preferably 3 to 6), or an aryl group having 6 to 10 carbon atoms (preferably 6 to 8, or more preferably 6). 10 One of them preferably satisfies the above conditions, and the other is preferably an alkyl group having 1 to 3 (preferably 1) carbon atoms.

[0107] Hereinafter, preferred polycarbonates will be described. Examples of polycarbonates include polycarbonates of formula (1A), wherein at least one of R1 and R3 is an alkyl group or aryl group as described above, and at least one of R6 and R8 is an alkyl group or aryl group as described above. In this case, the remaining R1 to R8 are hydrogen atoms.

[0108] In addition, the polycarbonate of formula (1A) is exemplified, wherein R9 and R 10 At least one of them is a linear or branched alkyl group or an unsubstituted phenyl group having 1 to 9 (preferably 1 to 4) carbon atoms. 10 Specifically, the polycarbonate preferably contains at least one selected from the group consisting of the following structural formulas (1) to (3).

[0109]

[0110] The polycarbonate containing the above-mentioned structural formulas (1) to (3) can achieve not only excellent durability but also improved micromolecular orientation. As a result, a developing roller can be obtained that can further suppress a decrease in image density even when the developing roller is applied to an electrophotographic image forming apparatus having a reduced drive torque and a further increased process speed and used for a long period of time.

[0111] Furthermore, the polycarbonate preferably has at least one structure selected from the group consisting of the structure represented by structural formula (2) and the structure represented by structural formula (3). Therefore, the adhesion between aromatic rings in the main chain can be relaxed, and microscopic molecular orientation can be improved. As a result, a developing roller can be obtained that can further suppress a decrease in density in an electrophotographic image even when the developing roller is applied to an electrophotographic image forming apparatus with a further increased process speed.

[0112] Furthermore, the at least one polycarbonate preferably includes a first polycarbonate and a second polycarbonate having mutually different structures. Furthermore, the first polycarbonate preferably has a structure represented by structural formula (1), and the second polycarbonate preferably includes a polycarbonate having at least one structure selected from the group consisting of a structure represented by structural formula (2) and a structure represented by structural formula (3).

[0113] With this configuration, the adhesion of the aromatic rings can be further relaxed and the microscopic molecular orientation can be improved. As a result, a developing roller can be obtained that can further suppress a decrease in density in an electrophotographic image even when the developing roller is applied to an electrophotographic image forming apparatus with a further increased process speed.

[0114] Furthermore, it is preferred that the first polycarbonate further have a structure represented by the structural formula (4). Furthermore, it is preferred that the second polycarbonate further have a structure represented by the structural formula (4).

[0115]

[0116] In addition to relaxing the microscopic adhesive force by structural formulas (1) to (3), a developing roller having further excellent durability can be obtained by having structural formula (4).

[0117] Note that, from the viewpoint of durability, polycarbonate is preferably a copolymer.

[0118] Hereinafter, methods for synthesizing polycarbonate in this case will be described. For example, two methods will be described below. The first method is a method in which a bisphenol compound is directly reacted with phosgene (phosgene method). The second method is a method in which a bisphenol compound is subjected to an ester exchange reaction with a diaryl carbonate such as diphenyl carbonate, di-p-tolyl carbonate, phenyl-p-tolyl carbonate, di-p-chlorophenyl carbonate, or dinaphthyl carbonate (ester exchange method).

[0119] In the phosgene process, a bisphenol compound is usually reacted with phosgene in the presence of an acid binder and a solvent. Examples of the acid binder used at this time include pyridine and alkali metal hydroxides such as potassium hydroxide and sodium hydroxide. In addition, examples of solvents include dichloromethane and chloroform. In addition, a catalyst or a molecular weight regulator can be added to promote the polycondensation reaction. Examples of catalysts include tertiary amines such as triethylamine or quaternary ammonium salts. Examples of molecular weight regulators include monofunctional compounds such as phenol, p-cumylphenol, tert-butylphenol and long-chain alkyl-substituted phenols.

[0120] Furthermore, when synthesizing polycarbonates, antioxidants such as sodium sulfite or bisulfite, and branching agents such as phloroglucinol or isatin bisphenol may be used. Furthermore, the reaction temperature during the synthesis of polycarbonates is preferably 0°C to 150°C, or more preferably 5°C to 40°C. The reaction time depends on the reaction temperature, but is generally preferably 0.5 minutes to 10 hours, more preferably 1 minute to 2 hours. Furthermore, during the reaction, the pH of the reaction system is preferably set to 10 or higher.

[0121] As a material constituting the insulating portion, polycarbonate having a structure represented by Formula (1A) is preferably used. Note that the chemical structure of the material constituting the insulating portion can be determined by NMR analysis.

[0122] In this case, the weight average molecular weight (Mw) of the polycarbonate is preferably 1,000 to 800,000, more preferably 10,000 to 100,000, and even more preferably 50,000 to 75,000. Generally, as the number average molecular weight of the polycarbonate decreases, the insulating portion is more likely to aggregate when formed on the elastic layer, and thus the insulating portion is more likely to have a relatively tall bowl shape. Furthermore, as the number average molecular weight of the polycarbonate increases, the polycarbonate is more likely to spread over the elastic layer and more likely to have a branched shape with a low height. Therefore, by setting the number average molecular weight of the polycarbonate within the above range, it is easier to form an insulating portion that covers a portion of the elastic layer, which is preferred.

[0123] The weight average molecular weight of the resin can be measured as follows.

[0124] -GPC

[0125] The molecular weight distribution of polycarbonate is measured by gel permeation chromatography (GPC) as follows.

[0126] First, the sample was dissolved in tetrahydrofuran (THF) at room temperature for 24 hours. The resulting solution was then filtered through a solvent-resistant membrane filter "Mysyori Disc" (manufactured by Tosoh Corporation) having a pore size of 0.5 μm to obtain a sample solution. Note that the sample solution was prepared to have a concentration of 0.5% by mass. The sample solution was measured under the following conditions:

[0127] - Equipment: HLC-8320GPC (detector: RI) (manufactured by Tosoh Corporation)

[0128] - Column: Shodex LF-404, LF-404 tandem (manufactured by Showa Denko KK)

[0129] -Eluent: Tetrahydrofuran (THF)

[0130] -Flow rate: 0.4ml / min

[0131] - Oven temperature: 40.0℃

[0132] -Sample injection volume: 0.10ml

[0133] In order to calculate the molecular weight of the sample, a molecular weight calibration curve created using a standard polystyrene resin (for example, product name "EasiVial PS-H polystyrene", manufactured by Agilent Technology) is used.

[0134] The content of the structure represented by formula (1A) in at least one polycarbonate is preferably 20 to 100 mol% based on the total structural units in the polycarbonate. Furthermore, the content of the structure represented by formula (1A) is preferably 30 to 100 mol% based on the total resin in the first region. By setting the content within this range, steric hindrance near the aromatic ring can relax microscopic adhesion, achieving a desired dielectric constant, and attracting a sufficient amount of toner. Note that the polycarbonate structural unit is assumed to be -OR-OCO- (R is an arbitrary group) in the calculation of mol%.

[0135] The content of the structure represented by formula (1A) in at least one polycarbonate is preferably 20 to 100% by mass, more preferably 40 to 100% by mass, and further preferably 50 to 90% by mass, based on the mass of the polycarbonate. Furthermore, the content of the structure represented by formula (1A) is preferably 5 to 100% by mass, more preferably 5 to 25% by mass, based on the total resin in the first region.

[0136] The content of the structure represented by structural formula (1) in the polycarbonate is preferably 10 to 100% by mass, more preferably 20 to 70% by mass.

[0137] The content of the structure represented by structural formula (2) in the polycarbonate is preferably 10 to 100% by mass, more preferably 20 to 70% by mass.

[0138] The content of the structure represented by structural formula (3) in the polycarbonate is preferably 10 to 100% by mass, more preferably 20 to 70% by mass.

[0139] The polycarbonate preferably contains 0 to 80% by mass of the structure represented by the structural formula (4), and more preferably contains 15 to 50% by mass of the structure represented by the structural formula (4).

[0140] The content of each structure in polycarbonate can be analyzed by infrared absorption spectroscopy and NMR.

[0141] -IR analysis of polycarbonate

[0142] ATR-IR analysis using polycarbonate was performed by the following method.

[0143] In the IR analysis, a Fourier transform infrared spectrometer (Spectrum One: manufactured by PerkinElmer, Inc.) equipped with a universal ATR sampling accessory was used. Other conditions were as follows.

[0144] The incident angle of infrared light (λ=5 μm) was set to 45°. As the ATR crystal, a Ge ATR crystal (refractive index=4.0) was used. Other conditions are as follows.

[0145] -scope

[0146] Starting: 4000cm -1

[0147] End: 650cm -1 (Ge ATR crystal)

[0148] - Duration

[0149] Number of scans: 16

[0150] Resolution: 4.00cm -1

[0151] -Advanced: with CO2 / H2O correction

[0152] (1) Install the Ge ATR crystal (refractive index = 4.0) on the device.

[0153] (2) Set the scan type to background, the unit to EGY, and measure the background.

[0154] (3) Set the scan type to sample and the unit to A.

[0155] (4) Weigh 0.01 g of sample onto the ATR crystal.

[0156] (5) Use the pressure arm to pressurize the sample (the dynamometer is 90).

[0157] (6) Measure the sample.

[0158] -NMR analysis of polycarbonate

[0159] NMR analysis using polycarbonate was performed by the following method.

[0160] 1 g of deuterated chloroform (99.8 atomic % D chloroform-d containing 0.05% (v / v) TMS, manufactured by Sigma-Aldrich Japan) was added to 20 mg of the sample and then completely dissolved. The solution was transferred to a glass NMR sample tube with an outer diameter of 5 mm (ST500-7, manufactured by Norell, Inc.) and proton NMR measurement was performed. The NMR instrument used was an AVANCE 500 from Bruker. Other conditions are as follows.

[0161] -The cumulative number of times is 32 times.

[0162] -The rotation speed is 20Hz.

[0163] Automatic measurement was performed by ICON-NMR except for various settings. In the obtained spectrum, the chemical shift value of the peak of the methyl group of tetramethylsilane was corrected to 0 ppm.

[0164] Note that, in order to confirm the polycarbonate structure of the insulating portion formed on the outer surface of the developing roller, the insulating portion of the developing roller was collected by using a micromanipulator (product name: Axis-Pro; manufactured by Micro Support Co., Ltd.), and the above analysis was performed to confirm the polycarbonate structure.

[0165] The first region (insulating portion) may comprise polycarbonate alone, or may comprise the second resin listed below. Specific examples of the second resin include at least one selected from the group consisting of acrylic resins, polyolefin resins, epoxy resins, and polyester resins. Preferably, the first region further comprises a (meth) acrylic resin, and more preferably, the first region further comprises an acrylic resin. The present inventors speculate that the use of the second resin leads to a more satisfactory effect for the following reasons.

[0166] Polycarbonate has steric hindrance in the aromatic ring of the main chain, and has lower molecular orientation and higher molecular mobility than general polycarbonate. However, the microscopic adhesion of the main chain of polycarbonate is strong. In order to further improve the molecular mobility, it is necessary to relax the above-mentioned microscopic adhesion. Here, in particular, a monomer with two or more functional groups is used, and the second resin forms a three-dimensional structure. When the second resin is used, the second resin enters the main chain and helps to relax the microscopic adhesion. In addition, the molecular orientation of the polycarbonate becomes uneven. Therefore, when a high electric field is applied instantaneously, in addition to the steric hindrance around the aromatic ring, a part with high molecular mobility of the main chain itself is formed and a microscopic molecular orientation is generated in a part thereof, so the dielectric constant is further increased.

[0167] Based on the foregoing, it is speculated that by using a second resin in addition to the polycarbonate of formula (1A), the instantaneous dielectric constant upon passing the abutment position is further increased when the processing speed is further increased, making charge exchange with the abutment member and the toner more likely to occur, and further fully charging the insulating portion. Furthermore, since the dielectric constant is low when no external electric field is applied after passing the abutment position, it is believed that the gradient force can be increased, thereby attracting a sufficient amount of toner.

[0168] Specific examples of the acrylic resin include at least one polymer selected from the group consisting of methyl methacrylate, 4-tert-butylcyclohexanol acrylate, stearyl acrylate, lauryl acrylate, 2-phenoxyethyl acrylate, isodecyl acrylate, isooctyl acrylate, isobornyl acrylate, 4-ethoxylated nonylphenol acrylate, isobornyl acrylate, ethoxylated bisphenol A diacrylate, and polymers and copolymers of PO-modified neopentyl glycol diacrylate.

[0169] The content of the polycarbonate in the first region is preferably 20 to 90% by mass, more preferably 40 to 70% by mass, based on the entire resin in the first region.

[0170] For example, the first region may contain 10 to 80% by mass of the second resin, and more preferably 30 to 60% by mass of the second resin, based on the entire resin in the first region.

[0171] Note that, when the first region contains the second resin, the presence of the second resin can be confirmed by analysis of infrared absorption spectra.

[0172] Volume resistivity of the first region

[0173] The volume resistivity of the first region is preferably 1.0×10 13 to 1.0×10 18 Ω·cm, more preferably 1.0×10 14 to 1.0×10 17 If the volume resistivity of the first region is within the above range, the first region can be easily and quickly charged.

[0174] The volume resistivity of the first region can be controlled by the amount and crystallinity of the polar groups in the polycarbonate used and the second resin such as an acrylic resin used as needed.

[0175] - Confirmation of the first and second areas

[0176] First, the presence of two or more regions on the outer surface of the electrophotographic member is confirmed using an optical microscope or a scanning electron microscope, so that the first region and the second region can be distinguished.

[0177] The first region and the second region can be considered to be a difference in reflectivity intensity due to the difference in surface morphology and the exposed portion surface. In addition, due to the difference in resistivity, the first region and the second region can be more clearly distinguished by combining with an electrostatic force microscope (EFM). For example, as an optical microscope, a digital microscope VHX-5000 (product name, manufactured by Keyence Corporation) can be used, as an electron microscope, a JSM-7800FPRIME (product name, manufactured by JEOL Ltd.) can be used, and as an electrostatic force microscope, a MODEL 1100TN (product name, manufactured by Trek Japan) can be used.

[0178] -Measure the volume resistivity in the first region

[0179] The sample was cut from the developing roller and a thin slice sample with a plane size of 50 μm square and a thickness t of 100 nm was prepared by a microtome. Next, the thin slice sample was placed on a metal plate with an area S of 100 μm. 2 The sheet sample was pressed from above using a metal terminal on the pressing surface. In this state, a voltage of 1 V was applied between the metal terminal and the metal flat plate using an electrometer (product name: 6517B, manufactured by KEITHLEY) to obtain resistance R. The volume resistivity pv was calculated from resistance R using the following expression (1).

[0180] Expression (1)

[0181] pv=R×S / t

[0182] The area occupied by the first area

[0183] When a square observation area having a side length of 900 μm is provided on the outer surface of the developing roller so that the axial direction of the developing roller and one side of the observation area are parallel to each other, the ratio of the total area of ​​the first region to the area of ​​the square area (hereinafter also referred to as “occupancy rate RE”) is preferably 10 to 60 area%. The occupancy rate RE is more preferably 20 to 50 area%, and further preferably 20 to 40 area%. By setting the occupancy rate RE within the above range, a more satisfactory toner transport force of the developing roller can be achieved.

[0184] The occupancy ratio RE can be controlled by the wettability of the constituent material solution in the first region, the viscosity of the solution, the drying speed, the surface roughness of the conductive layer, the solid content of the solution, and the like.

[0185] On the other hand, the ratio of the total area of ​​the second region to the area of ​​the square region is preferably 40 to 90 area %, more preferably 50 to 80 area %, and further preferably 60 to 80 area %.

[0186] -Measure the occupancy rate RE of the first area

[0187] The occupancy rate RE of the first region is measured as follows.

[0188] A laser microscope (product name: VK-X100, manufactured by Keyence Corporation) was equipped with an objective lens having a magnification of 20. The surface of the developing roller was then photographed at a total of nine areas, namely, two locations 10 mm inward from both ends in the longitudinal direction, one location in the center, and three locations in the circumferential direction (at intervals of 120°). The photographed images were connected so that the length of one side was 900 μm.

[0189] Next, the tilt correction of the obtained observation image is performed in a quadratic curve correction mode. In the center of the correction image, the area occupied by the first region in a square area with a side length of 900 μm is measured. Image processing software such as ImageJ is used for measurement. The value obtained by dividing the area occupied by the first region by the square area with a side length of 900 μm is defined as the occupancy rate RE in the area. The arithmetic mean value is obtained from the occupancy rates RE obtained in the 9 areas and is regarded as the occupancy rate RE of the developing roller 1.

[0190] Note that the first region and the second region were distinguished on the surface of the developing roller through the aforementioned process using an electron microscope and an electrostatic force microscope.

[0191] Height of the first area

[0192] The average height HD of each of the plurality of first regions from the portion thereof in contact with the second region is preferably 0.1 to 15.0 μm, more preferably 0.5 to 7.0 μm. Setting the average height HD to 0.1 μm or greater maintains durability against wear and cracking while further attracting toner. Setting the average HD to 15.0 μm or less increases the likelihood of friction between the insulating portion and the toner even at increased processing speeds, making the insulating portion more susceptible to charging.

[0193] -Height measurement of the first area

[0194] The height of the first region was measured by attaching a 20x objective lens to a laser microscope (product name: VK-8700; manufactured by Keyence Corporation) and observing the surface of the developing roller. The resulting observed image was then tilt-corrected. Tilt correction was performed in quadratic curve correction mode. The corrected image was used to measure the first region captured in the image. Using the resulting three-dimensional observed image, the difference "H2 - H1" between the highest point H2 of the first region and the height H1 of the conductive elastic layer (the contact portion between the first and second regions) was calculated.

[0195] Note that the first region and the second region were distinguished by the aforementioned process using an electron microscope and an electrostatic force microscope.

[0196] Observation is performed at 10 points on the developing roller (at each position in each of the 10 regions obtained by equally dividing the developing roller into 10 pieces in the longitudinal direction), and the arithmetic mean of the obtained "H2 - H1" is defined as the average value HD of the height of the first region. At this time, all first regions completely included in a square region with a side length of 300 μm are defined as measurement objects, and first regions not completely included therein are not defined as measurement objects.

[0197] Second area

[0198] The second region is a partial region of the outer surface of the developing roller, is a region adjacent to the insulating portion, and serves as a conductive portion having a higher conductivity than the insulating portion. Figure 1A and Figure 1B In the illustrated aspect, a portion of the conductive layer constituting the outer surface of the developing roller corresponds to the second region.

[0199] Note that the second region only needs to be present at a portion of the outer surface of the developing roller (exposed from a portion of the outer surface of the developing roller), and a plurality of conductive portions may be present separately on the outer surface of the developing roller, or a plurality of conductive portions may be present in a connected manner (for example, as a series of conductive portions). However, from the viewpoint of uniformly conveying toner, it is preferable to arrange (a series of) the second region on the outer surface of the developing roller so that the second region surrounds a plurality of first regions arranged at equal intervals on the outer surface of the developing roller.

[0200] The volume resistivity of the second region is preferably 1.0×10 5 to 1.0×10 11 Ω·cm, more preferably 1.0×10 5 to 1.0×10 8Ω·cm. If the volume resistivity of the second region is within the above range, the charge can be sufficiently removed. Note that in the above-mentioned measurement of the volume resistivity of the first region, by selecting the second region, the volume resistivity of the second region can be similarly measured.

[0201] The volume resistivity of the second region can be controlled by, for example, the content or dispersion state of the conductive agent.

[0202] Confirmation of the first and second areas

[0203] The presence of the first region and the second region in the developing roller can be first confirmed by observing the presence of two or more regions on the outer surface of the developing roller using an optical microscope or a scanning electron microscope.

[0204] Furthermore, by charging the outer surface of the developing roller including the first and second regions and then measuring the residual potential distribution, it is possible to confirm that the first region has electrical insulation and that the second region has higher conductivity than the first region.

[0205] The residual potential distribution can be confirmed by sufficiently charging the outer surface of the developing roller using a charging device such as a corona discharge device, and then measuring the residual potential distribution on the charged outer surface of the developing roller using, for example, an electrostatic force microscope (EFM) or a surface potential microscope (KFM).

[0206] In addition to volume resistivity, the electrical insulation of the electrically insulating portion constituting the first region and the electrical conductivity of the conductive layer constituting the second region can also be evaluated using the residual potential time constant. The residual potential time constant is the time required for the residual potential to decay to 1 / e of its initial value and is an indicator of how easily the charged potential can be maintained. Here, e is the base of the natural logarithm.

[0207] The potential decay time constant, defined as the time required for the potential on the surface of the first region to decay to V0×(1 / e)(V) when the surface of the first region is charged to a potential of V0 (V), is preferably 60.0 seconds or longer, and more preferably 2000 to 5000 seconds. The time constant of the first region is preferably 60.0 seconds or longer because the first region is quickly charged and the potential caused by the charge is easily maintained.

[0208] Furthermore, the potential decay time constant, defined as the time required for the potential on the surface of the second region to decay to V0 × (1 / e) (V) when the surface of the second region is charged to V0 (V), is preferably less than 6.0 seconds, and more preferably less than the lower limit of measurement. The time constant of the second region is preferably 6.0 seconds or less because charging of the second region is suppressed, a potential difference is easily generated between the second region and the charged first region, and a gradient force is more easily exerted.

[0209] Note that in the measurement of the time constant, when the residual potential at the measurement start point is approximately 0 V, that is, when the potential has completely decayed before the measurement start point, the time constant at the measurement point is considered to be less than 6.0 seconds by the following measurement method. The time constant of the residual potential can be obtained by sufficiently charging the outer surface of the developing roller using a charging device such as a corona discharge device, and then measuring the temporal transition of the residual potential in the first and second regions on the charged outer surface of the developing roller using, for example, an electrostatic force microscope (EFM).

[0210] -Observation of the outer surface of the developing roller

[0211] As for observation of the outer surface of the developing roller, observation was performed using an optical microscope (VHX5000 (product name), manufactured by Keyence Corporation), and the presence of two or more regions on the outer surface was confirmed.

[0212] -Measurement of residual potential distribution

[0213] For measurement of the residual potential distribution, the outer surface of the developing roller on the thin sheet to be described later was corona charged by a corona discharge device, and the residual potential of the outer surface was measured by an electrostatic force microscope (MODEL 1100TN; manufactured by Trek Japan) while scanning the thin sheet to obtain the residual potential distribution.

[0214] To prepare the slices, a cryostat (UC-6, manufactured by Leica Microsystems) was used to cut a slice from the developer roller, including the outer surface of the developer roller. The slices were cut at -150°C, such that the outer surface of the developer roller had a size of 100 μm x 100 μm, a thickness of 1 μm relative to the outer surface of the conductive layer, and included two or more regions on the outer surface of the developer roller. The slices were placed on a smooth silicon wafer with the surface including the outer surface of the developer roller facing upward and placed in an environment at 23°C and 50% relative humidity for 24 hours.

[0215] In the same environment, a silicon wafer with a thin film placed on it was mounted on a high-precision XY stage included in an electrostatic force microscope. A corona discharge device was used with an 8mm distance between the wire and the gate electrode. The corona discharge device was positioned at a distance of 2mm between the gate electrode and the silicon wafer surface. The silicon wafer was then grounded, and an external power supply was used to apply a voltage of -5kV to the wire and -0.5kV to the gate electrode. After the application began, the high-precision XY stage was used to scan parallel to the silicon wafer surface at a speed of 20mm / second, so that the thin film passed directly under the corona discharge device, thereby corona charging the outer surface of the developer roller on the thin film.

[0216] The sheet was then moved to a position directly below the cantilever of the electrostatic force microscope using a high-precision XY stage. Next, the residual potential distribution was measured by scanning the corona-charged outer surface of the developer roller using the high-precision XY stage. The measurement conditions are shown below.

[0217] -Measurement environment: temperature 23℃, relative humidity 50%

[0218] - Time from the measurement position passing directly under the corona discharge device to the start of measurement: 60 seconds

[0219] -Cantilever: Cantilever for Model 1100TN (Model: Model 1100TNC-N; manufactured by Trek Japan)

[0220] - Gap between the measuring surface and the cantilever tip: 10 μm

[0221] -Measuring range: 99μm×99μm

[0222] -Measurement interval: 3μm×3μm

[0223] By confirming the presence of residual potentials in two or more regions on the sheet from the residual potential distribution obtained through measurement, it is determined whether each region corresponds to an electrically insulating first region or a second region having higher conductivity than the first region. Specifically, among the two or more regions, the region including a location where the absolute value of the residual potential is less than 1V is considered the second region, and the region including a location where the absolute value of the residual potential is greater than the absolute value of the residual potential of the second region by 1V or more is considered the first region, and its presence is confirmed.

[0224] Note that the measurement method of the residual potential distribution is an example and can be changed to equipment and conditions suitable for confirming the presence or absence of residual potential in two or more regions according to the size, interval, and time constant of the first and second regions.

[0225] -Measurement of the time constant of the residual potential

[0226] The time constant of the residual potential was obtained by corona charging the outer surface of the developer roller using a corona discharge device, measuring the time-dependent change in the residual potential in the first or second region of the outer surface using an electrostatic force microscope (MODEL 1100TN, Trek Japan), and fitting the results to the following expression (1). Here, the point where the absolute value of the residual potential in the first region, as determined by the residual potential distribution measurement, is the largest is defined as the measurement point in the first region. Furthermore, the point where the residual potential in the second region, as determined by the residual potential measurement, is approximately 0 V is defined as the measurement point in the second region.

[0227] First, a sheet for measuring residual potential distribution was placed on a smooth silicon wafer with the surface including the outer surface of the developing roller facing upward, and placed in an environment at room temperature of 23° C. and relative humidity of 50% for 24 hours.

[0228] Subsequently, in the same environment, the silicon wafer with the thin slice placed on it was mounted on a high-precision XY stage included in the electrostatic force microscope. A corona discharge device with an 8mm distance between the wire and the gate electrode was used. The corona discharge device was configured at a distance of 2mm between the gate electrode and the surface of the silicon wafer. The silicon wafer was then grounded, and an external power supply was used to apply a voltage of -5kV to the wire and -0.5kV to the gate electrode. After the application began, the high-precision XY stage was used to scan parallel to the surface of the silicon wafer at a speed of 20mm / second, so that the thin slice passed directly under the corona discharge device, thereby corona charging the thin slice.

[0229] Subsequently, using a high-precision XY stage, the measurement point in the first or second region was moved to a position directly below the cantilever of an electrostatic force microscope, and the change in residual potential over time was measured. An electrostatic force microscope was used for the measurement. The measurement conditions are as follows.

[0230] -Measurement environment: temperature 23℃, relative humidity 50%

[0231] - Time from the measurement position passing directly under the corona discharge device to the start of measurement: 15 seconds

[0232] -Cantilever: Cantilever for Model 1100TN (Model: Model 1100TNC-N; manufactured by Trek Japan)

[0233] - Gap between the measuring surface and the cantilever tip: 10 μm

[0234] -Measurement frequency: 6.25Hz

[0235] - Measurement time: 1000 seconds

[0236] From the temporal change in the residual potential obtained by the measurement, the time constant τ is obtained by fitting to the following expression (1) by the least square method.

[0237] V0=V(t)×exp(-t / τ)...(1)

[0238] t: Time (seconds) after the measuring part passes directly under the corona discharge device

[0239] V0: Initial potential (potential at t = 0 seconds) (V)

[0240] V(t): Residual potential (V) t seconds after the measurement part passes directly under the corona discharge device

[0241] τ: Time constant of residual potential (seconds)

[0242] The time constant τ of the residual potential was measured at a total of nine points (i.e., three points in the longitudinal direction and three points in the circumferential direction) on the outer surface of the developer roller. The average value was defined as the time constant of the residual potential of the first or second region according to the present invention. Note that in the measurement of the second region, when the residual potential reaches approximately 0 V at the start of measurement (i.e., 15 seconds after corona charging), the time constant was defined as being smaller than the average value of the time constants at the remaining measurement points. Furthermore, when the potential at the start of measurement is approximately 0 V at all measurement points, the time constant is defined as being smaller than the lower limit of the measurement.

[0243] Method for forming the first region and the second region

[0244] In the case where a conductive layer on a conductive substrate has a stacked structure, for example, on a layer (lower layer) arranged on the side closest to the substrate in the conductive layer, a conductive layer (outermost layer) arranged on the outermost surface side including the first region and the second region can be produced by the following method.

[0245] First, a material other than the first region resin is used on the conductive lower layer to form the outermost layer (conductive layer formation step). Then, an insulating portion made of the first region resin is formed on the surface of the conductive layer, and a conductive layer containing the first region resin and the second region resin is formed (insulating portion formation step).

[0246] -Conductive layer formation process

[0247] The lower layer having conductivity can be formed by a known method depending on the material to be used.

[0248] The formation of the outermost layer will be described by taking polyurethane resin as an example. Examples of a method of forming the outermost layer on the conductive lower layer include a method of coating a substrate with a coating liquid obtained by mixing and dispersing polyurethane resin, carbon black, a solvent, etc. with additives.

[0249] The solvent used in the coating solution can be appropriately selected under conditions that dissolve (or disperse) the polyurethane resin. Specific examples of the solvent include ketones such as methyl ethyl ketone and methyl isobutyl ketone; hydrocarbons such as hexane and toluene; alcohols such as methanol and isopropyl alcohol; esters; and water. Methyl ethyl ketone or methyl isobutyl ketone is particularly preferred from the perspective of resin solubility and boiling point.

[0250] -First region forming step

[0251] While the method for forming the first region to function as the insulating portion is not particularly limited, the following method can be used, for example. Specifically, examples include methods in which a material (insulating material) such as polycarbonate constituting the first region (before curing) is applied to the conductive layer in a dotted pattern by screen printing or a jet dispenser, and then cured (polymerized) by heating or irradiation with ultraviolet light, as needed. Examples also include methods in which an insulating material is applied to the conductive layer by dipping, spraying, or roller coating, intentionally causing the conductive layer to repel the insulating material, and then cured by heating or irradiation with ultraviolet light, as needed.

[0252] In order to make the conductive layer repel the material forming the first region, for example, it is only necessary to coat the conductive layer with a solution of the constituent material of the first region (by spraying or dipping, etc.), and control the wettability of the constituent material solutions of the first region and the second region, the viscosity and drying speed of the solutions, and the surface roughness of the conductive layer.

[0253] When a second resin is used in addition to polycarbonate, a method can be used in which an insulating material (before curing) containing a monomer of the second resin and polycarbonate is dissolved in a solvent, the solution is applied to the elastic layer by spraying, dipping, or roller coating, and the solution is cured by heating and / or irradiation with ultraviolet light, as needed. Note that drying can be performed as needed after forming the insulating portion.

[0254] Note that the insulating material may include the material constituting the first region (polycarbonate having the structure represented by Formula (1A) and the second resin, etc.), a solvent to be described later, and additives such as a polymerization initiator as needed.

[0255] Note that from the viewpoint of forming the first region on the conductive layer and also exposing the second region from the surface, the solid content concentration (dilution concentration) of the insulating material is preferably 0.1 to 50 mass %, more preferably 0.5 to 5 mass %.

[0256] A known polymerization initiator can be appropriately used, and specifically, the following polymerization initiators can be used.

[0257] In the case of conducting heating and polymerization, examples of the polymerization initiator include peroxides such as 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate, α-cumyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-butyl peroxypivalate, t-amyl peroxy-n-octanoate, t-butyl peroxy-2-ethylhexyl carbonate, dicumyl peroxide, di-t-butyl peroxide, di-t-amyl peroxide, 1,1-di(t-butylperoxy)cyclohexane, n-butyl-4,4-di(t-butylperoxy)valerate; and azo compounds such as 2,2-azobis(isobutyronitrile), 2,2- Azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2-azobis(2,4-dimethylvaleronitrile), 2,2-azobis(2-methylbutyronitrile), 1,1-azobis(cyclohexane-1-carbonitrile), 2,2-azobis[2-(2-imidazolin-2-yl)propane], 2,2-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2-azobis(N-butyl-2-methoxypropionamide), 2,2-azobis(dimethylisobutyrate).

[0258] In the case of conducting irradiation with ultraviolet light and polymerization, examples of the polymerization initiator include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenylketone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2- Methylpropane-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butane-1-one, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butane-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0259] Among these, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methylpropane-1-one having high surface hardening property is preferably used as an initiator because surface curing is more likely to proceed and the crosslinking density of the second resin is increased, thereby further improving durability.

[0260] Note that one of these polymerization initiators may be used alone, or two or more polymerization initiators may be used together. When the total amount of the compound (e.g., the compound having a (meth)acryloyl group) used to form the second resin is defined as 100 parts by mass, the amount of the polymerization initiator to be used is preferably 0.5 to 20 parts by mass from the viewpoint of efficient reaction.

[0261] Note that known heating equipment and ultraviolet irradiation equipment can be used appropriately. Examples of usable light sources for ultraviolet irradiation include LED lamps, high-pressure mercury lamps, metal halide lamps, xenon lamps, and low-pressure mercury lamps. The cumulative light amount required for polymerization can be appropriately adjusted according to the type and amount of the compound and polymerization initiator to be used. The solvent used for the coating solution can be appropriately selected under conditions that dissolve acrylic resins or methacrylic resins.

[0262] Specific examples of the solvent include ketones such as methyl ethyl ketone and methyl isobutyl ketone; hydrocarbons such as hexane and toluene; alcohols such as methanol and isopropyl alcohol; esters; and water. A particularly preferred solvent is a low-boiling-point solvent such as methyl ethyl ketone, which is preferably used because sufficient drying is required when subsequently curing with ultraviolet light.

[0263] As a method of controlling the wettability of the surface of the conductive layer, for example, a method of adding a surface conditioner can be used.

[0264] The developing roller according to the present aspect can also be applied to a non-contact type developing device and a contact type developing device using a magnetic single-component developer or a non-magnetic single-component developer.

[0265] Processing box

[0266] The process cartridge according to the present aspect includes at least a developing device, and the developing device is characterized by including the developing roller according to the present aspect. Figure 2 1 is a schematic cross-sectional view of an example of a process cartridge according to one aspect of the present disclosure. The process cartridge is configured to be detachably mounted to a main body of an electrophotographic image forming apparatus and includes at least a developing device.

[0267] Figure 2The illustrated process cartridge 100 is configured to be removably attached to the main body of an electrophotographic apparatus. The process cartridge 100 includes a developing chamber 102 as a developing device, which includes an opening in the portion facing the electrophotographic photoreceptor 101. A toner container 104 containing toner 103 is disposed on the back side of the developing chamber 102. A conveying member 107 for conveying toner 103 to the developing chamber 102 is disposed in the toner container 104 as needed. The opening establishing communication between the developing chamber 102 and the toner container 104 is separated by a sealing member 105, which is removed when the process cartridge 100 is first used. Furthermore, the developing chamber 102 is provided with a developing roller 106, a toner supply roller 108, a developing blade 109, and a toner splash prevention sheet 110. The aforementioned developing roller can be used as the developing roller 106.

[0268] The toner 103 is applied to the developing roller 106 by the toner supply roller 108. The developing roller 106 rotates in the direction indicated by the arrow in the figure, and the toner 103 carried on the developing roller 106 is adjusted to a predetermined layer thickness by the developing blade 109 and then sent to the developing area facing the electrophotographic photoreceptor 101.

[0269] In addition to the above-described configuration, the process cartridge 100 includes a charging roller 111 , a cleaning blade 112 , and a waste toner container 119 .

[0270] Electrophotographic image forming equipment

[0271] An electrophotographic image forming apparatus (electrophotographic apparatus) according to the present aspect includes a developing device, and the developing device is characterized by including the developing roller according to the present aspect. Figure 3 is a schematic cross-sectional view of an example of an electrophotographic apparatus. Figure 2 The process cartridge 100 shown is used for an electrophotographic apparatus. The developing device is the developing chamber 102 described above.

[0272] The following describes the printing operation of the electrophotographic apparatus. Electrophotographic photoreceptor 101 is uniformly charged by charging roller 111 connected to a bias power source (not shown). Next, an electrostatic latent image is formed on the surface of electrophotographic photoreceptor 101 using exposure light 113 for writing the electrostatic latent image. Exposure light 113 can be either LED light or laser light.

[0273] Next, a toner charged to a negative polarity is applied (developed) to the electrostatic latent image by a developing roller 106 included in a process cartridge 100 configured to be detachably attached to the main body of the electrophotographic apparatus. A toner image is then formed on the electrophotographic photoreceptor 101, converting the electrostatic latent image into a visible image. At this time, a bias power supply (not shown) applies a voltage to the developing roller 106.

[0274] The toner image developed on the electrophotographic photoreceptor 101 is primarily transferred to the intermediate transfer belt 114. The primary transfer member 115 abuts on the back surface of the intermediate transfer belt 114, and by applying a voltage to the primary transfer member 115, the toner image having a negative polarity is primarily transferred from the electrophotographic photoreceptor 101 to the intermediate transfer belt 114. The primary transfer member 115 may have a roller shape or may have a blade shape.

[0275] exist Figure 3 In the illustrated electrophotographic apparatus, a total of four process cartridges 100 are installed, each containing a toner of yellow, cyan, magenta, and black. The process cartridges 100 are detachably mounted on the apparatus's main body. The charging, exposure, development, and primary transfer processes are sequentially performed with predetermined time differences, resulting in a state where toner images of four colors representing a full-color image are superimposed on an intermediate transfer belt 114.

[0276] As intermediate transfer belt 114 rotates, the toner image on intermediate transfer belt 114 is conveyed to a position facing secondary transfer member 116. Until then, recording paper, serving as a transfer material, has been conveyed along recording paper conveyance path 117 between intermediate transfer belt 114 and secondary transfer member 116 at a predetermined timing. Then, a secondary transfer bias is applied to secondary transfer member 116, thereby transferring the toner image on intermediate transfer belt 114 to the recording paper.

[0277] The recording paper onto which the toner image has been transferred by the secondary transfer member 116 is conveyed to the fixing device 118, where the toner image on the recording paper is melted and fixed to the recording paper. The recording paper is then discharged to the outside of the electrophotographic apparatus, and the printing operation is completed. Note that the toner image remaining on the electrophotographic photoreceptor 101, which has not been transferred from the electrophotographic photoreceptor 101 to the intermediate transfer belt 114, is scraped off by the cleaning blade 112 and then stored in the waste toner storage container 119.

[0278] Example

[0279] Although Examples and Comparative Examples of the present disclosure will be described below, the present disclosure is not limited thereto.

[0280] Synthesis of polycarbonate

[0281] Polycarbonate was synthesized as follows.

[0282] Synthesis Example 1 of Polycarbonate

[0283] In 1100 ml of a 5% by mass sodium hydroxide aqueous solution, 42.5 g of 2,2-bis(4-hydroxyphenyl)propane (manufactured by Tokyo Chemical Industry Co., Ltd., product code B0494), 37.5 g of 2,2-bis(3-methyl-4-hydroxyphenyl)propane (manufactured by Tokyo Chemical Industry Co., Ltd., product code B1567), and 0.1 g of hydrogen sulfite were dissolved. 500 mL of dichloromethane was added to the mixture and stirred, and then 60 g of phosgene was blown into the mixture over 60 minutes while the mixture was maintained at 15° C.

[0284] After the phosgene blowing was completed, 1.3 g of p-tert-butylphenol (hereinafter abbreviated as "PTBP"; manufactured by Tokyo Chemical Industry Co., Ltd., product code: B0383) was added as a molecular weight modifier and stirred to emulsify the reaction solution. After emulsification, 0.4 ml of triethylamine was added, and the mixture was stirred at 23°C for 1 hour to induce polymerization.

[0285] After the polymerization was completed, the reaction solution was separated into an aqueous phase and an organic phase. The organic phase was neutralized with phosphoric acid and repeatedly washed with water until the conductivity of the washing solution (aqueous phase) became less than 10 μS / cm. The resulting polymer solution was added dropwise to warm water maintained at 45°C, and the solvent was evaporated to obtain a white powdery precipitate. The obtained precipitate was filtered and dried at 110°C for 24 hours to obtain polycarbonate (PC-1). The molecular weight Mw of this polycarbonate measured by GPC was 56,000. The measurement method using GPC is as described above.

[0286] Then, the obtained polycarbonate was analyzed by IR and NMR to confirm that the structure of the polycarbonate consisted of structural formulas (1) and (4). Note that IR and NMR analyses were performed as described above.

[0287]

[0288] Synthesis Examples 2 to 17 of Polycarbonate

[0289] PC-2 to PC-17 in Table 2 were obtained similarly to Synthesis Example 1 of Polycarbonate, except that the materials and compounding ratios shown in Table 1 below were used.

[0290] Note that the materials 1 to 5 described in Table 1 are as follows:

[0291] Material 1: 2,2-bis(4-hydroxyphenyl)propane (corresponding to structural formula (4)) (Product name: manufactured by Tokyo Chemical Industry Co., Ltd., product code B0494)

[0292] Material 2: 2,2-bis(3-methyl-4-hydroxyphenyl)propane (corresponding to structural formula (1))

[0293] (Product name: manufactured by Tokyo Chemical Industry Co., Ltd., product code B1567)

[0294] Material 3: 1,1-bis(4-hydroxyphenyl)-1-phenylethane (corresponding to structural formula (3))

[0295] (Product name: manufactured by Tokyo Chemical Industry Co., Ltd., product code M1098)

[0296] Material 4: 2,2-bis(4-hydroxyphenyl)-4-methylpentane (corresponding to structural formula (2))

[0297] (Product name: manufactured by Tokyo Chemical Industry Co., Ltd., product code D3267)

[0298] Material 5: 4,4'-dihydroxybiphenyl (corresponding to structural formula (5))

[0299] (Product name: manufactured by Tokyo Chemical Industry Co., Ltd., product code B0464) Table 1

[0300] Material name PC-1 PC-2 PC-3 PC-4 PC-5 PC-6 PC-7 PC-8 PC-9 Material 1 42.5 - - - - - 31.8 21.1 62.5 Material 2 37.5 - 37.3 50.9 - 16.3 24.3 19.8 17.5 Material 3 - 45.8 - - 32.0 40.3 23.9 22.4 - Material 4 - 34.2 42.7 - - 23.4 - 16.7 - Material 5 - - - 29.1 48.0 - - - -

[0301] Material name PC-10 PC-11 PC-12 PC-13 PC-14 PC-15 PC-16 PC-17 Material 1 60.7 61.7 32.4 41.4 - - - 72.0 Material 2 - - 24.8 - 80.8 - - - Material 3 19.3 - - - - 91.5 - - Material 4 - 18.3 22.7 38.6 - - 85.2 - Material 5 - - - - - - - -

[0302] The unit of the numerical value of each material is g.

[0303]

[0304] Table 2

[0305]

[0306] The numerical values ​​in Table 2 each show the molar ratio of each structural formula.

[0307] Example 1

[0308] Formation of the first conductive layer

[0309] The conductive substrate was prepared by coating a mandrel made of stainless steel (SUS304) and having a diameter of 6 mm with a primer (product name "DY39-012" manufactured by Dow Corning Toray Co., Ltd.) to a thickness of 10 μm, placing the resulting object in a hot air vulcanization oven at 150°C for 15 minutes, and baking the resulting object. The mandrel was placed in a mold, and an addition-type silicone rubber composition obtained by mixing the materials shown in Table 3 below was injected into the cavity formed in the mold.

[0310] Table 3

[0311]

[0312] Subsequently, the mold was heated to vulcanize and cure the addition-type silicone rubber composition at 130°C for 5 minutes, and the addition-type silicone rubber composition was removed from the mold. Thereafter, the addition-type silicone rubber was further heated at 180°C for 1 hour to complete the curing reaction of the silicone rubber layer, thereby manufacturing an elastic roller including a first conductive layer having a thickness of 3 mm on the outer periphery of the base.

[0313] Formation of the second conductive layer

[0314] Next, the materials shown in Table 4 below were mixed, methyl ethyl ketone was added thereto so that the total solid content ratio became 30% by mass, and the mixture was mixed using a sand mill. Then, the viscosity was adjusted to 10 to 12 cps (mPa·s) with methyl ethyl ketone to prepare a coating liquid.

[0315] Table 4

[0316]

[0317] This coating liquid was applied to an elastic roller by dipping to a thickness of 10 μm. In the dipping method, the elastic roller was dipped into the coating liquid while holding the upper end of the substrate with the longitudinal direction of the developing roller perpendicular. The resulting coating was dried at room temperature (23°C) for 30 minutes and then cured in an oven at 150°C for 2 hours, thereby producing a polyurethane roller having a second conductive layer on the outer peripheral surface of the first conductive layer. A second region may be formed on the surface of the polyurethane roller.

[0318] Formation of the first region

[0319] Polycarbonate (PC-1) was dispersed in MEK and applied to the outer peripheral surface of a polyurethane roller, thereby forming a first region on the outer peripheral surface.

[0320] Specifically, 20 parts by mass of polycarbonate (PC-1) were weighed, MEK was added to the mixture so that the concentration of the insulating resin compound forming the first region became 2% by mass, and the fully dissolved mixture was placed in an overflow-type circulation coating apparatus. A polyurethane roller was immersed in the coating apparatus and pulled up, followed by air drying for 40 minutes. The polyurethane roller was then heated at 90°C for 1 hour to produce a developing roller 1. Note that the first region was applied while being repelled from the conductive layer.

[0321] Confirmation of the first and second areas

[0322] As described above, it was confirmed that the first region and the second region existed on the outer surface of the developing roller 1. The first region and the second region accounted for 30% and 70% of the outer surface area of ​​the developing roller, respectively.

[0323] Analysis of insulation

[0324] The chemical structure of the insulating portion was confirmed by performing IR and NMR analysis as described above, and it was confirmed that the polycarbonate consisted of structural formulas (1) and (4).

[0325] Insulation resistance measurement

[0326] The volume resistivity was confirmed as described above and was 2.8×10 14 Ω·cm.

[0327] Conductive resistance measurement

[0328] The volume resistivity was confirmed as described above and was 7.2×10 6 Ω·cm.

[0329] Time constant of the first region (insulating portion)

[0330] The time constant was confirmed as described above and was 2958.0 seconds.

[0331] Time constant of the second region (conductive portion)

[0332] The time constant was confirmed as described above and was below the measurement lower limit.

[0333] Height of the first region (insulating portion)

[0334] The height of the first region (insulating portion) was confirmed as described above and was found to be 5.5 μm.

[0335] Image evaluation

[0336] First, for the purpose of reducing the torque of the produced developing roller, the gear of the toner supply roller was removed from a commercially available toner cartridge 318 (cyan) for a process cartridge (manufactured by Canon Inc.) By removing the gear, the torque of the toner supply roller was reduced relative to the developing roller, and the amount of toner scraped off the developing roller was reduced.

[0337] Next, the produced developing roller 1 was assembled with a process cartridge, and the process cartridge was installed in a commercially available laser printer, LBP-7600C (manufactured by Canon Inc.) The laser beam printer was left in an environment of 23° C. and 50% relative humidity for 24 hours.

[0338] Next, in the same environment, one full-surface solid image is output, and then 20,000 images are output at a print rate of 0.2% and one full-surface solid image is output, which is repeated 25 times (normally).

[0339] In addition, the above-mentioned electronic photographic image forming device is modified so that it can output at a speed of 50 A4 sheets / min, output a full solid image under the same environment, and then output 20,000 images at a printing rate of 0.2% and output a full solid image repeatedly 25 times (50 sheets / min).

[0340] Afterwards, the image density of a total of 26 full-surface solid images was measured under various conditions (normal) and (50 sheets / min) using a spectrophotometer X-Rite504 (product name, SDG KK). Note that the average value obtained by measuring at 15 points for each full-surface solid image is regarded as the density of each image. The image density is compared according to the number of output sheets, and evaluation is performed based on the following evaluation criteria 1 and 2. Note that evaluation criteria 1 is used to evaluate images output under normal conditions. The results are shown in Tables 6-1 and 6-2. Hereinafter, the image density of the first solid image output will be referred to as the "image density of the first sheet of paper," and the image density of the solid image output in the Xth processing will be referred to as the "image density of the Xth sheet of paper."

[0341] Evaluation Criteria 1

[0342] S: The difference between the image density of the first sheet and the image density of the twentieth sheet is less than 0.1, and the difference between the image density of the first sheet and the image density of the twenty-sixth sheet is less than 0.1.

[0343] A: The difference between the image density of the first sheet and the image density of the twentieth sheet is less than 0.1, and the difference between the image density of the first sheet and the image density of the twenty-sixth sheet is 0.1 or more.

[0344] B: The difference between the image density of the first sheet and the image density of the twentieth sheet is 0.1 or more and less than 0.2, and the difference between the image density of the first sheet and the image density of the twenty-sixth sheet is less than 0.2.

[0345] C: The difference between the image density of the first sheet and the image density of the twentieth sheet is 0.1 or more and less than 0.2, and the difference between the image density of the first sheet and the image density of the twenty-sixth sheet is 0.2 or more.

[0346] D: The difference between the image density of the first sheet and the image density of the twentieth sheet is 0.2 or more and less than 0.3.

[0347] E: The difference between the image density of the first sheet and the image density of the twentieth sheet is 0.3 or more.

[0348] Evaluation Criteria 2

[0349] S: The difference between the image density of the twentieth sheet of paper under normal conditions and the image density of the twentieth sheet of paper when output at a speed of 50 sheets / min is less than 0.1, and the difference between the image density of the twenty-sixth sheet of paper under normal conditions and the image density of the twenty-sixth sheet of paper when output at a speed of 50 sheets / min is less than 0.1.

[0350] A: The difference between the image density of the 20th sheet of paper under normal conditions and the image density of the 20th sheet of paper when output at a speed of 50 sheets / min is less than 0.1, and the difference between the image density of the 26th sheet of paper under normal conditions and the image density of the 26th sheet of paper when output at a speed of 50 sheets / min is greater than 0.1.

[0351] B: The difference between the image density of the twentieth sheet of paper under normal conditions and the image density of the twentieth sheet of paper when output at a speed of 50 sheets / min is greater than 0.1 and less than 0.2, and the difference between the image density of the twenty-sixth sheet of paper under normal conditions and the image density of the twenty-sixth sheet of paper when output at a speed of 50 sheets / min is less than 0.2.

[0352] C: The difference between the image density of the twentieth sheet of paper under normal conditions and the image density of the twentieth sheet of paper when output at a speed of 50 sheets / min is greater than 0.1 and less than 0.2, and the difference between the image density of the twenty-sixth sheet of paper under normal conditions and the image density of the twenty-sixth sheet of paper when output at a speed of 50 sheets / min is greater than 0.2.

[0353] D: The difference between the image density of the twentieth sheet in normal state and the image density of the twentieth sheet when output at a speed of 50 sheets / min is 0.2 or more and less than 0.3.

[0354] E: The difference between the image density of the twentieth sheet in normal state and the image density of the twentieth sheet when output at a speed of 50 sheets / min is 0.3 or more.

[0355] Examples 2 to 33 and Comparative Examples 1 and 2

[0356] Developing rollers 2 to 35 in Examples 2 to 33 and Comparative Examples 1 and 2 were produced similarly to Example 1, except that the materials and amounts of the insulating resin-forming compounds used to form the first region were changed as shown in Table 5 below. The resulting developing rollers 2 to 35 were evaluated similarly to Example 1. The results are shown in Tables 6-1 and 6-2.

[0357] However, in the following examples, the molecular weight regulator PTBP was added as follows: In Example 30, 1.0 g of the molecular weight regulator PTBP was added. In Example 31, 1.2 g of the molecular weight regulator PTBP was added.

[0358] In addition, in Examples 5 to 8, 11, 12, 14, 16, 19, 21, 23, 25, and 29 and Comparative Example 1, the insulating portion was formed as follows.

[0359] Specifically, the materials shown in Table 5 (parts by mass) were weighed, MEK was added to the mixture to a concentration of 2% by mass for the insulating resin compound forming the first region, and the fully dissolved mixture was placed in an overflow-type circulation coating apparatus. A polyurethane roller was immersed in the coating apparatus and then pulled up. Air drying was performed for 40 minutes, followed by heating at 90°C for 1 hour. Note that at this point, the components forming the first region had already been applied to the conductive layer in a scattered state.

[0360] Thereafter, the outer surface of the polyurethane roller on which the mixture was attached was irradiated with ultraviolet light so that the accumulated light amount became 2000 mJ / cm 2 , so that the component forming the first region is cured, thereby forming the first region. Thus, the developing roller according to these embodiments was produced. Note that a high-pressure mercury lamp (product name: handheld UV curing device, manufactured by Marionetwork) was used as the ultraviolet irradiation device.

[0361] Note that in Examples 1 to 33, the first region and the second region are arranged adjacent to each other, and the first region exists in a dot-like pattern.

[0362] Comparative Examples 1 and 2 are Examples that do not include the structure represented by formula (1A).

[0363] Table 5

[0364]

[0365] Table 5 (continued)

[0366]

[0367] The acrylic compound and polymerization initiator used were as follows.

[0368] Acrylic compounds:

[0369] PO modified neopentyl glycol diacrylate

[0370] (Product name: EBECRYL 145, manufactured by Daicel-Allnex Ltd.)

[0371] Polymerization initiator:

[0372] 1-Hydroxycyclohexylphenyl ketone

[0373] (Product name: IRAGACURE 184, manufactured by BASF Corporation) Table 6-1

[0374]

[0375] Table 6-1 (continued)

[0376]

[0377] X: less than the lower limit of measurement

[0378] Table 6-2

[0379]

[0380] X: less than the lower limit of measurement

[0381] In the table, the insulating portion represents the first region, and the conductive portion represents the second region.

[0382] The occupancy rate of the insulating portion represents the ratio (occupancy rate RE) of the total area of ​​the first region to the area of ​​the square observation area with a side length of 900 μm when the square observation area with a side length of 900 μm is set on the outer surface of the developing roller so that the axial direction of the developing roller is parallel to one side of the observation area.

[0383] The height of the insulating portion indicates an average value HD of the heights of the first regions from the portions in contact with the second region.

[0384] As shown in Tables 6-1 and 6-2, it was found that by using the developing rollers of Examples 1 to 33, even when the driving torque between the toner supply roller and the developing roller was reduced and the process speed was further increased, the decrease in the density of the electrophotographic image could be suppressed for a long period of time. On the other hand, Comparative Examples 1 and 2 resulted in large changes in image density.

[0385] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A developing roller comprising: a substrate comprising a surface having electrical conductivity; and a conductive layer on the surface of the substrate, The outer surface of the developing roller is composed of at least a first region and a second region having a higher conductivity than the first region. The first region and the second region are arranged adjacent to each other, The first region comprises at least one polycarbonate, and The at least one polycarbonate comprises a structure represented by formula (1A): In formula (1A), R1 to R8 each independently represent a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, or an aryl group having 6 to 10 carbon atoms, R9 and R 10 each independently represents a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, or an aryl group having 6 to 10 carbon atoms, or R9 and R 10 It is R9 and R 10 The atomic groups necessary to bond with each other to form an alicyclic structure having 6 to 12 carbon atoms, Wherein (1A) satisfies at least one condition selected from the group consisting of the following conditions 1 and 2: -Condition 1 At least one selected from the group consisting of R1 to R8 is an alkyl group having 1 to 9 carbon atoms or an aryl group having 6 to 10 carbon atoms, -Condition 2 Choose between R9 and R 10 At least one of the group consisting of the above is a linear or branched alkyl group having 2 or more carbon atoms or an aryl group having 6 to 10 carbon atoms.

2. The developing roller according to claim 1, wherein in formula (1A), at least one of R1 and R3 is an alkyl group having 1 to 9 carbon atoms or an aryl group having 6 to 10 carbon atoms, at least one of R6 and R8 is an alkyl group having 1 to 9 carbon atoms or an aryl group having 6 to 10 carbon atoms, and the rest are hydrogen atoms.

3. The developing roller according to claim 1 or 2, wherein the at least one polycarbonate comprises at least one structure selected from the group consisting of a structure represented by the following structural formula (2) and a structure represented by the following structural formula (3):

4. The developing roller according to claim 1, wherein the at least one polycarbonate comprises a first polycarbonate and a second polycarbonate having mutually different structures, The first polycarbonate comprises a structure represented by the following structural formula (1), and The second polycarbonate includes at least one structure selected from the group consisting of a structure represented by the following structural formula (2) and a structure represented by the following structural formula (3):

5. The developing roller according to claim 4, wherein the first polycarbonate further comprises a structure represented by the following structural formula (4):

6. The developing roller according to claim 4 or 5, wherein the second polycarbonate further comprises a structure represented by the following structural formula (4):

7. The developing roller according to claim 1 or 2, wherein the content of the structure represented by formula (1A) in the at least one polycarbonate is 20 to 100 mol% relative to all structural units in the polycarbonate. 8 . The developing roller according to claim 1 , wherein the content of the structure represented by formula (1A) is 30 to 100 mol % relative to the entire resin in the first region.

9. The developing roller according to claim 1 or 2, wherein the volume resistivity in the second region is 1.0×10 5 to 1.0×10 11 Ω·cm.

10. The developing roller according to claim 1 or 2, wherein the volume resistivity in the first region is 1.0×10 13 to 1.0×10 18 Ω·cm.

11. A developing roller according to claim 1 or 2, wherein the potential decay time constant is greater than 60.0 seconds, and the potential decay time constant is defined as the time required for the potential of the surface in the first region to decay to V0×(1 / e) when the potential of the surface is charged to V0, and the unit of V0 is V.

12. A developing roller according to claim 1 or 2, wherein the potential decay time constant is less than 6.0 seconds, and the potential decay time constant is defined as the time required for the potential of the surface in the second region to decay to V0×(1 / e) when the potential of the surface is charged to V0, and the unit of V0 is V.

13. A developing roller according to claim 1 or 2, wherein when a square observation area with a side length of 900 μm is arranged on the outer surface of the developing roller so that the axial direction of the developing roller and one side of the observation area are parallel to each other, the proportion of the area of ​​the square area in the total area of ​​the first area is 10 to 60 area%.

14. The developing roller according to claim 1 or 2, wherein the first region further comprises an acrylic resin.

15. A process cartridge configured to be detachably mounted to a main body of an electrophotographic image forming apparatus, The process box at least includes: developing device, Wherein, the developing device includes the developing roller according to any one of claims 1 to 14.

16. An electrophotographic image forming apparatus comprising: developing device, Wherein, the developing device includes the developing roller according to any one of claims 1 to 14.

Images