Developing device, process cartridge, and electrophotographic image forming apparatus

Abstract

The present invention relates to a developing device, a process cartridge, and an electrophotographic image forming apparatus. A developing device includes a developer; a developing member configured to carry the developer on a surface, the developing member including an electrically conductive base and a single-layered elastic layer serving as a surface layer on the base, the surface layer containing a binder resin, and the binder resin containing a crosslinked polyurethane resin and a crosslinked acrylic resin, the crosslinked polyurethane resin and the crosslinked acrylic resin forming an interpenetrating polymer network structure in a first region from an outer surface of the surface layer to a position 0.1 μm deep from the outer surface, wherein the developer contains developer particles each containing at least the binder resin and a magnetic substance.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a developing device introduced to an apparatus employing an electrophotographic system. The present disclosure also relates to an electrophotographic process cartridge and an electrophotographic image forming apparatus each including the developing device. BACKGROUND

[0002] In an electrophotographic image forming apparatus (also referred to as an "electrophotographic apparatus"), a developing device includes a developing roller for carrying a developer on a surface, and functions to supply the developer on the developing roller to an electrostatic latent image on an electrophotographic photosensitive member to form a developer image.

[0003] In Japanese Patent Application Laid-Open No. 2014-197064, an electrophotographic member for an electrophotographic apparatus including a rubber elastic body having rubber elasticity and a surface treatment layer containing a cured product of a photocurable composition impregnated from a surface of the rubber elastic body as a material of a portion including the surface is disclosed. As the photocurable composition, a modified rubber elastic body containing a photopolymerizable polymer including a (meth)acrylic monomer, an organic silicon group and / or a fluorine-containing group in a molecule, and a (meth)acryl group, and a photopolymerization initiator has been used. In addition, in Japanese Patent Application Laid-Open No. 2014-197064, it is described that according to such an electrophotographic member, both developer releasability and low frictionality are achieved.

[0004] When the electrophotographic member described in Japanese Patent Application Laid-Open No. 2014-197064 is used together with a developer containing a magnetic substance to perform image output in a high-temperature high-humidity environment, in some cases, so-called fogging occurs in which toner is transferred to a region of an electrophotographic image where toner is not originally transferred. SUMMARY

[0005] At least one aspect of the present disclosure aims to provide a developing device that can suppress the occurrence of fogging of an electrophotographic image even when an electrophotographic image is formed with a developer containing a magnetic substance in a high-temperature high-humidity environment.

[0006] Another aspect of the present disclosure aims to provide an electrophotographic process cartridge that is advantageous for stable formation of a high-quality electrophotographic image. Still another aspect of the present disclosure aims to provide an electrophotographic image forming apparatus that can stably form a high-quality electrophotographic image.

[0007] According to one aspect of the present disclosure, there is provided a developing device including: a developer; and a developing member configured to carry the developer on a surface, the developing member including an electrically conductive base and a single-layered elastic layer serving as a surface layer on the base, the surface layer containing a binder resin, and the binder resin containing a crosslinked polyurethane resin and a crosslinked acrylic resin, the crosslinked polyurethane resin and the crosslinked acrylic resin forming an interpenetrating polymer network structure in a first region from an outer surface of the surface layer to a position 0.1 μm in depth from the outer surface of the surface layer, wherein the developer contains developer particles each containing at least the binder resin and a magnetic substance.

[0008] Further, according to another aspect of the present disclosure, there is provided a developing device including: a developer; and a developing member configured to carry the developer on a surface, wherein the developing member includes an electrically conductive base and a single-layered elastic layer serving as a surface layer on the base, the surface layer containing a binder resin, and the binder resin containing a crosslinked polyurethane resin and a crosslinked acrylic resin, wherein a first region from an outer surface of the surface layer to a position 0.1 μm in depth from the outer surface of the surface layer contains both the crosslinked polyurethane resin and the crosslinked acrylic resin, wherein when a first sample is sampled from the first region and a peak top temperature of a thermogram originating from the crosslinked acrylic resin in the first sample is defined as Al (°C), and when a second sample is obtained by decomposing the crosslinked polyurethane resin in the first sample, and a peak top temperature of a thermogram originating from the crosslinked acrylic resin in the second sample is defined as A2 (°C), Al and A2 satisfy a relationship represented by the following formula (1): Formula (1) Al > A2, wherein the developer contains developer particles each containing at least the binder resin and a magnetic substance.

[0009] Further, according to another aspect of the present disclosure, there is provided a process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, the process cartridge including the above-described developing device.

[0010] Further, according to another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including: an image bearing member for bearing an electrostatic latent image; a charging device for primarily charging the image bearing member; an exposure device for forming the electrostatic latent image on the primarily charged image bearing member; a developing member for developing the electrostatic latent image with a developer to form a developer image; and a transfer device for transferring the developer image to a transfer material, wherein the developing device including the developing member is the above-described developing device.

[0011] Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1A and Figure 1B Each is a schematic view of a developing roller for illustrating an aspect according to the present disclosure.

[0013] Figure 2 is a schematic view of a developing device according to an aspect of the present disclosure.

[0014] Figure 3 is a schematic view of an electrophotographic image forming apparatus according to an aspect of the present disclosure.

[0015] Figure 4 is a cross-sectional view of a surface layer of a developing roller according to an aspect of the present disclosure.

[0016] Figure 5 is an explanatory view of a presumed mechanism of action of a developing member according to the present disclosure. DETAILED DESCRIPTION

[0017] The inventors of the present disclosure conducted research, and as a result, found that when an electrophotographic image is formed using a developer containing a binder resin and a magnetic substance (hereinafter also referred to as “magnetic developer”), a high-quality electrophotographic image in which fogging is reduced can be formed even under a high-temperature high-humidity environment when a developing member having a specific structure is used.

[0018] That is, a developing device according to an aspect of the present disclosure includes a developer; and a developing member configured to carry the developer on a surface. The developing member includes an electrically conductive base and a single-layer elastic layer serving as a surface layer on the base. The surface layer has a binder resin, and the binder resin contains a crosslinked polyurethane resin and a crosslinked acrylic resin. The crosslinked polyurethane resin and the crosslinked acrylic resin form an interpenetrating polymer network structure in a first region from an outer surface of the surface layer to a position 0.1 pm in depth from the outer surface of the surface layer. In addition, the developer contains developer particles each containing at least a binder resin and a magnetic substance.

[0019] A developing device according to another aspect of the present disclosure includes a developer; and a developing member configured to carry the developer on a surface. The developing member includes an electrically conductive base and a single-layered elastic layer serving as a surface layer on the base. The surface layer contains a binder resin, and the binder resin contains a crosslinked polyurethane resin and a crosslinked acrylic resin. A first region between an outer surface of the surface layer and a position 0.1 pm in depth from the outer surface of the surface layer contains the crosslinked polyurethane resin and the crosslinked acrylic resin. A peak top temperature of a thermogram originating from the crosslinked acrylic resin, measured from a first sample taken from the first region, is defined as Al (°C). In addition, a peak top temperature of a thermogram originating from the crosslinked acrylic resin, measured from a second sample obtained by decomposing the crosslinked polyurethane resin in the first sample, is defined as A2 (°C). In addition, Al and A2 satisfy a relationship represented by the following formula (1).

[0020] Formula (1) Al > A2

[0021] In addition, the developer contains developer particles each containing at least a binder resin and a magnetic substance.

[0022] The inventors of the present disclosure speculate that the reason why a high-quality electrophotographic image can be formed even in a high-temperature high-humidity environment using the developing device having the configuration as described above is as follows. The following will describe the mechanism of action of the developing device according to one aspect of the present disclosure as only one possible speculation, and the present disclosure is not limited thereto. In addition, the following describes an example in which a developing member having a roll shape (hereinafter also referred to as a "developing roll") is used as the developing member, but the developing member according to the present disclosure is not limited to the developing roll.

[0023] An interpenetrating polymer network structure is formed in a first region from a toner carrying surface (hereinafter also referred to as an "outer surface") of the developing roll according to one aspect of the present disclosure to a depth of 0.1 pm. The interpenetrating polymer network structure is also referred to as an "IPN structure" hereinafter. The IPN structure is defined as a structure in which network structures of two or more high molecular compounds are intertwined with each other without being combined with each other by covalent bonds. The IPN structure does not loosen unless the molecular chains of the high molecular compounds used to form the network thereof are cleaved. In the IPN structure in the surface layer according to the present disclosure, as Figure 5 As schematically shown, the crosslinked acrylic resin 503 is intertwined with the network of the three-dimensional crosslinked structure of the crosslinked polyurethane resin 501.

[0024] In this IPN structure, an electron cloud (not shown) of a highest occupied molecular orbital (also referred to as "HOMO") present on a nitrogen atom in a urethane bond of the crosslinked polyurethane resin serves to impart a charge to the developer particles 505.

[0025] Meanwhile, the nitrogen atom in the urethane bond (hereinafter also referred to as "urethane nitrogen") is bonded to a hydrogen atom (hereinafter also referred to as "urethane hydrogen"). The bonding electron of the hydrogen atom bonded to the nitrogen atom having a high electronegativity is attracted toward the nitrogen atom. In this case, the nitrogen atom attracting the bonding electron has a slight negative charge (δ-), while the hydrogen atom whose bonding electron is attracted has a slight positive charge (δ+). Such a hydrogen atom is also referred to as "active hydrogen".

[0026] Here, in the IPN structure according to the present disclosure, the urethane bond in the crosslinked polyurethane resin 501 and the carbonyl bond in the crosslinked acrylic resin 503 can exist at a position very close to each other.

[0027] In addition, when a molecule having a carbonyl bond exists in the vicinity of the urethane hydrogen having a slight positive charge, the urethane hydrogen forms an intermolecular hydrogen bond (507) with the oxygen atom in the carbonyl bond (also referred to as "carbonyl oxygen"). In this case, the urethane hydrogen is attracted to the carbonyl oxygen, and thus the urethane nitrogen bonded to the urethane hydrogen can further attract the bonding electron to itself. It is likely that due to the above reason, the electron density of the electron cloud on the nitrogen atom increases, thereby greatly improving its ability to impart a charge to the developer.

[0028] Further, the magnetic developer according to the present disclosure contains a magnetic substance. The magnetic substance contains a metal atom therein. Examples of the magnetic material suitable for use in the developer include the following materials: iron-based metal oxides such as magnetite, maghemite, and ferrite; and magnetic metals such as Fe, Co, and Ni.

[0029] Each of these magnetic materials also functions as a Lewis acid, and is capable of accepting an electron in its lowest unoccupied molecular orbital (also referred to as "LUMO"). When a Lewis base having an electron-donating ability approaches a Lewis acid, charge exchange can smoothly proceed through Lewis acid-base interaction.

[0030] In the present disclosure, the electron density of the urethane nitrogen functioning as a Lewis base increases due to the above reason, and thus, it is possible to more effectively impart a charge to the magnetic metal atom in the developer (see reference numeral 509 in Figure 5 Therefore, even in a high-temperature high-humidity environment in which the developer is hardly rubbed to be charged, the developer is imparted with sufficient charge. It is likely that due to the above reason, the occurrence of fogging of the electrophotographic image in a high-temperature high-humidity environment can be effectively prevented.

[0031] Further, preventing the leakage of the charge obtained from the developer to the developing member by increasing the volume resistivity of the surface layer is effective in mitigating fogging. That is, the charge leakage from the developer in contact with the outer surface of the developing member is caused by the escape of the charge from the surface layer of the developing roller toward the elastic layer and the base. In order to suppress such charge leakage, the volume resistivity of the binder resin in the surface layer of the developing member is preferably within the following range in which the resin exhibits insulating properties: the volume resistivity is preferably 1.0 x 10 10 Ω·cm or more and 1.0 x 10 18 Ω·cm or less, more preferably 1.0 x 10 13 Ω·cm or more and 1.0 x 10 16 Ω·cm or less. Thus, the charge of the developer can be more reliably maintained in the developer by the surface layer having the IPN structure. Examples of the crosslinked polyurethane resin that provides such volume resistivity include a polyether-modified polyurethane resin, a polyester-modified polyurethane resin, and a polycarbonate-modified polyurethane resin. Among them, the polycarbonate-modified polyurethane resin can be suitably used because the resin can have a higher volume resistivity. An example of the polycarbonate-modified polyurethane resin can be a polyurethane resin including a chemical structure represented by the following structural formula (1) between two adjacent urethane bonds.

[0032]

[0033] Further, it is preferable to use a polyurethane resin having an alkyl group such as a methyl group as a side chain in the soft segment. That is, the side chain suppresses the crystallization of the soft segment portion, and thus, the increase in the conductivity of the surface layer due to the development of the crystal structure can be suppressed. Thus, the resin can be used as a binder resin that is advantageous to the formation of a surface layer having a higher volume resistivity. A polyurethane resin having a structure containing a side chain methyl group represented by the following structural formula (2) between two adjacent urethane bonds in the soft segment portion can be cited as an example.

[0034]

[0035] <<Developing roller>>

[0036] Hereinafter, a developing roller according to one aspect of the present disclosure will be described in detail with reference to the accompanying drawings.

[0037] As shown in Figure 1A and Figure 1B , a developing roller according to one aspect of the present disclosure includes an electrically conductive base 2 and a single-layer elastic layer serving as a surface layer 1 on the base. As shown in Figure 1A , the surface layer 1 can be directly provided on the electrically conductive base, or a primer layer 3 such as Figure 1BA developing roller shown in the drawing is further provided with one or more intermediate layers 3 as needed between the base 2 and the surface layer 1.

[0038] <Surface layer>

[0039] To achieve this aspect of the present disclosure, the following needs to be done: disposing a crosslinked polyurethane resin and a crosslinked acrylic resin on the outermost surface of the developing roller; and creating a spatial environment in which the resins influence each other. To this end, it is effective to form an interpenetrating polymer network (IPN) structure of the crosslinked polyurethane resin and the crosslinked acrylic resin in a first region from the outer surface of the surface layer to a position at a depth of 0.1 μm from the outer surface of the surface layer.

[0040] [Method of identifying IPN structure]

[0041] The presence of the IPN structure in the surface layer (elastic layer) can be identified by, for example, a shift in the glass transition temperature (Tg) of the polymer used to form the IPN structure.

[0042] That is, the peak top temperature in the thermogram corresponding to the thermal decomposition temperature of the crosslinked acrylic resin moves to the higher temperature side compared to the case where the resin alone exists in the IPN structure.

[0043] Therefore, the formation of the IPN structure by both the crosslinked polyurethane resin and the crosslinked acrylic resin can be identified by the fact that, when the peak top temperatures of the thermograms of the crosslinked acrylic resin before and after the decomposition of the crosslinked polyurethane resin in the surface layer are compared with each other, the peak top temperature after the decomposition is lower than the peak top temperature before the decomposition. Here, the thermogram is a mass spectrum that can be obtained by a micro-sampling thermal decomposition mass spectrometry.

[0044] The outline of the micro-sampling thermal decomposition mass spectrometry is described below.

[0045] First, the region of the electrophotographic member to be measured is sliced into a thin sheet with a microtome to prepare a sample. In this regard, as Figure 4 As shown, the sample is prepared from three regions called a first region 41, a second region 42, and a third region 43. The first region 41 is a region from the outer surface of a surface layer 44 to a depth of 0.1 μm, the second region 42 is a region of a thickness of 0.1 μm from the back surface (the surface facing the conductive base 45) of the surface layer 44 toward the outer surface, and the third region 43 is a region corresponding to a depth of 1.0 μm or more and 1.1 μm or less from the outer surface.

[0046] A 100-μm square thin piece having a thickness of 0.1 μm was prepared from each region of the surface layer. For example, an ion trap type mass spectrometer attached to a gas chromatograph mass spectrometer ("Polaris Q" (product name, manufactured by Thermo Electron Corporation) was used in the measurement. The sample was fixed to a filament at the front end of the probe of the ion trap type mass spectrometer, and was directly inserted into the ionization chamber of the gas chromatograph mass spectrometer. Thereafter, the sample was rapidly heated from room temperature to 1,000°C at a constant heating rate. The sample vaporized by heating was ionized by irradiation with an electron beam, and was detected with the mass spectrometer. At this time, under the condition that the heating rate is constant, a thermogram similar to a thermogravimetry-mass spectrometry (TG-MS) method was obtained as a mass spectrum called a total ion chromatogram (TIC). In addition, a thermogram of a fragment having a predetermined mass can also be obtained, and thus a peak temperature of the thermogram corresponding to the decomposition temperature of a desired molecular structure can be obtained. The peak temperature of the thermogram is related to the crosslinked structure in the resin structure, and thus, as the crosslinking of the crosslinked structure becomes denser, the peak temperature moves to a higher temperature.

[0047] The fact that the crosslinked acrylic resin and the crosslinked polyurethane resin form an IPN structure can be identified as described below. That is, only the difference between the peak temperature of the thermogram of the fragment derived from the crosslinked acrylic resin before and after the decomposition and removal of the crosslinked polyurethane resin in the composition of the electrophotographic member needs to be identified.

[0048] Here, the peak top temperature of the thermogram of the fragment derived from the crosslinked acrylic resin measured from the first sample sampled from the first region is represented by Al (°C). In addition, the peak top temperature of the thermogram of the fragment derived from the crosslinked acrylic resin measured from the second sample obtained by decomposing the crosslinked polyurethane resin in the first sample is represented by A2 (°C). When the IPN structure is formed, Al and A2 satisfy the relationship represented by the following formula (1):

[0049] Formula (1) Al > A2.

[0050] Examples of the method of forming the IPN structure include the following method (i) and method (ii):

[0051] (i) a method including the following: a network structure of a polymer of a first component is formed in advance, and then the polymer of the first component is swelled with a monomer of a second component and a polymerization initiator, and a network structure of a polymer of the second component is formed after the swelling (this method is also referred to as "sequential network formation method"); and

[0052] (ii) a method including the following: a monomer of a first component and a monomer of a second component having mutually different reaction mechanisms, and a polymerization initiator of each monomer are mixed to simultaneously form a network structure (this method is also referred to as "simultaneous network formation method").

[0053] A method of manufacturing the surface layer (elastic layer) having an IPN structure in the first region according to this aspect is described later.

[0054] [Crosslinked polyurethane resin]

[0055] The crosslinked polyurethane resin is obtained by allowing a polyol having a hydroxyl group and an isocyanate compound to react with each other to form a urethane group. The term "crosslinking" used herein means that each of one compound or both compounds selected from the group consisting of a polyol and an isocyanate compound as raw materials of the polyurethane resin has three or more reactive functional groups, and thus the crosslinked polyurethane resin has a three-dimensional network structure. Such a crosslinked polyurethane resin has excellent softness and high strength.

[0056] The polyurethane resin can be obtained from a polyol and an isocyanate compound, and a chain extender as necessary. Examples of the polyol as a raw material of the polyurethane resin include polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, acrylic polyols, and mixtures thereof. Among them, a polyol that can provide a chemical structure represented by Structural Formula (1) or (2) is preferably used. For example, a polyether polyol having a side chain methyl group or a polycarbonate polyol having a side chain methyl group can be appropriately used.

[0057] Examples of the isocyanate compound as a raw material of the polyurethane resin include the following isocyanate compounds: toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), phenylene diisocyanate (PPDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), cyclohexane diisocyanate, and mixtures thereof.

[0058] Examples of the chain extender as an optional component include: difunctional low molecular weight diols such as ethylene glycol, 1,4-butanediol, and 3-methylpentanediol; trifunctional low molecular weight triols such as trimethylolpropane; and mixtures thereof. In addition, a prepolymer type isocyanate compound having an isocyanate group at the terminal can be used, which is obtained by previously allowing the above-described various isocyanate compounds to react with various polyols in an excess state of isocyanate groups with respect to hydroxyl groups. In addition, as these isocyanate compounds, a material obtained by capping an isocyanate group with various capping agents such as methyl ethyl ketone (MEK) oxime can be used.

[0059] Regardless of the material used, a polyurethane resin can be obtained by reacting a polyol and an isocyanate compound with each other with the aid of heating. When one or both of the polyol and the isocyanate compound preferably has a branched structure and three or more functional groups, the polyurethane resin obtained becomes a crosslinked polyurethane resin.

[0060] [Crosslinked acrylic resin]

[0061] The crosslinked acrylic resin forms an IPN structure together with the crosslinked polyurethane resin, thereby bringing about a significant improvement effect on the ability of the surface layer of the developing member to impart a magnetic developer electric charge through the above-described mechanism of action.

[0062] The crosslinked acrylic resin is formed by polymerization of an acrylic monomer. The term "acrylic monomer" as used herein refers not only to an acrylic monomer but also to a methacrylic monomer. That is, the crosslinked acrylic resin is formed by polymerization of one or both of an acrylic monomer and a methacrylic monomer.

[0063] As described above, the IPN structure of the crosslinked acrylic resin and the crosslinked polyurethane resin is formed by impregnating a liquid acrylic monomer in a resin layer containing the crosslinked polyurethane resin and curing the impregnated product. The kind of the acrylic monomer used here includes a multifunctional monomer having a plurality of acryloyl groups or methacryloyl groups as functional groups for forming a crosslinked structure. Meanwhile, when the number of functional groups is four or more, the viscosity of the acrylic monomer becomes significantly high. Therefore, the monomer is difficult to impregnate in the surface of the resin layer formed of the crosslinked polyurethane resin, and as a result, it is difficult to form an IPN structure. Therefore, as the acrylic monomer, a monomer having a total number of acryloyl groups and methacryloyl groups present in the molecule of 2 or 3 is preferred, and a difunctional acrylic monomer having 2 such groups is more preferred as an example thereof.

[0064] The molecular weight of the acrylic monomer is preferably in the range of 200 or more and 750 or less. When an acrylic monomer having a molecular weight in this range is used, the network structure of the crosslinked polyurethane resin easily forms an IPN structure, and thus the strength of the surface layer can be effectively improved.

[0065] As described above, the acrylic monomer is impregnated in a resin layer containing the crosslinked polyurethane resin. For this reason, the monomer needs to have an appropriate viscosity. That is, when the viscosity of the monomer is high, the monomer is difficult to impregnate, and when the viscosity of the monomer is low, the impregnated state thereof is difficult to control. Therefore, the viscosity of the acrylic monomer is preferably 5.0 mPa-s or more and 140 mPa-s or less at 25°C.

[0066] That is, the IPN structure of the crosslinked polyurethane resin and the crosslinked acrylic resin can be formed by selecting one or more than two kinds of acrylic monomers each satisfying the above-mentioned molecular weight range and viscosity range, impregnating the selected monomers in the resin layer, and polymerizing the monomers.

[0067] The polymerization method of the acrylic monomers is not particularly limited, and a publicly known method can be used. Specific examples thereof include thermal polymerization based on heating and photopolymerization based on UV irradiation.

[0068] A known radical polymerization initiator or ionic polymerization initiator can be used for each polymerization method.

[0069] The thermal polymerization initiator when thermal polymerization is performed is, for example, a peroxide such as 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate, α-cumyl peroxyneodecanoate, tert-butyl peroxyneohexanoate, tert-butyl peroxyneopentanoate, tert-amyl peroxy-n-octanoate, tert-butyl peroxy-2-ethylhexylcarbonate, dicumyl peroxide, di-tert-butyl peroxide, di-tert-amyl peroxide, 1,1-di(tert-butylperoxy)cyclohexane, or n-butyl-4,4-di(tert-butylperoxy)valerate; or an azo compound such as 2,2-azobisisobutyronitrile, 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-butyl-2-methoxypropionamide), or dimethyl-2,2-azobis(isobutyrate).

[0070] The photopolymerization initiator when photopolymerization based on UV irradiation is performed is, for example, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, or 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0071] These polymerization initiators can be used alone or in combination thereof.

[0072] In addition, regarding the blending amount of the polymerization initiator, when the total amount of the compounds forming the specific resin (for example, the compound having a (meth) acryloyl group) is defined as 100 parts by mass, the amount of the initiator used is preferably 0.5 parts by mass or more and 10 parts by mass or less from the viewpoint of efficiently performing the reaction of resin formation. As the device for heating or the device for UV irradiation, a publicly known device can be appropriately used. For example, an LED lamp, a high-pressure mercury lamp, a metal halide lamp, a xenon lamp, and a low-pressure mercury lamp can each be used as a light source for applying UV light. The cumulative light amount required at the time of polymerization can be appropriately adjusted according to the kind and the added amount of the compound and the polymerization initiator used.

[0073] [Function of surface layer]

[0074] The surface layer is preferably soft to moderate the mechanical stress applied to the developer carried on the outer surface thereof. Meanwhile, the IPN structure causes the hardness of the surface layer to increase. Therefore, it is preferable that the side of the surface layer facing the substrate does not have any IPN structure, or even when this side has an IPN structure, the IPN structure causes the crosslinked acrylic resin to enter the crosslinked polyurethane resin to a relatively weak extent as compared with the IPN structure of the first region. Thus, even when the outer surface side of the surface layer has a developed IPN structure, the increase in the hardness of the surface layer can be suppressed.

[0075] Specifically, when a region having a thickness of 0.1 μm from the surface of the side of the surface layer facing the substrate toward the outer surface is defined as a second region, the first region and the second region preferably satisfy the relationship represented by the following formula (2), and particularly preferably satisfy the relationship represented by formula (3). Here, T1 (°C) represents the peak top temperature of the thermogram derived from the crosslinked polyurethane resin measured from a sample sampled from the first region, and T2 (°C) represents the peak top temperature of the thermogram derived from the crosslinked polyurethane resin measured from a sample sampled from the second region.

[0076] Formula (2) T1 > T2

[0077] Formula (3) (T1 - T2) > 1.0 (°C)

[0078] Further, in order to more satisfactorily exert the function of mitigating the mechanical stress of the developer applied to the surface layer, the thickness of the surface layer is preferably 2.0 μm or more and 150.0 μm or less. Further, in the surface layer having such a thickness, when a region having a thickness of 0.1 μm from a depth of 1.0 μm from the outer surface of the surface layer to a depth of 1.1 μm therefrom is defined as a third region, it is preferable that the IPN structure is not present in the third region adjacent to the first region. Alternatively, even when the IPN structure is present, it is preferable that the IPN structure in which the crosslinked acrylic resin is less incorporated into the crosslinked polyurethane resin than the IPN structure of the first region.

[0079] Therefore, when the peak top temperature of the thermogram derived from the crosslinked polyurethane resin measured from a sample sampled from the third region is represented by T3 (°C), Tl, T2 and T3 preferably satisfy the relationships represented by formula (4) and formula (5).

[0080] Formula (4) T1 > T3

[0081] Formula (5) |T1 - T3| > |T3 - T2|

[0082] [Volume resistivity of binder resin of surface layer and method for measuring the same]

[0083] As described above, the volume resistivity of the binder resin in the surface layer is preferably set to 1.0 x 10 10 Ω·cm or more and 1.0 x 10 18 Ω·cm or less, particularly preferably 1.0 x 10 13 Ω·cm or more and 1.0 x 10 16 Ω·cm or less. Therefore, charge decay due to leakage of the charge of the developer (referred to as "developer charge") to the developing member can be more reliably prevented. Further, excessive charging of the developer can be suppressed.

[0084] In the measurement of the volume resistivity of the binder resin, a measurement value measured by the conductive mode using an atomic force microscope (AFM) can be employed. A sample piece is cut from the resin binder portion of the surface layer of the developing roller with a robot, and metal deposition is performed on one surface of the sample piece. A direct current power source is connected to the surface on which the metal deposition is performed, and a voltage is applied thereto. The free end of a cantilever is brought into contact with the surface of the sample piece opposite to the surface on which the metal deposition is performed, and a current image is obtained by the main body of the AFM. The volume resistivity can be calculated from the current value thus obtained, the thickness of the sample piece and the contact area of the cantilever.

[0085] [Other components]

[0086] In addition to the above-mentioned components, components such as a crosslinking agent, a plasticizer, a filler, an extender, a vulcanizing agent, a vulcanization aid, a crosslinking aid, an antioxidant, an anti-aging agent, a processing aid, or a leveling agent can be introduced into the surface layer within a range not to hinder the function of the surface layer. In addition, when the surface layer is required to have surface roughness, fine particles for imparting roughness can be introduced into the surface layer. Specifically, fine particles of a polyurethane resin, a polyester resin, a polyether resin, a polyamide resin, an acrylic resin, or a polycarbonate resin can be used. The volume average particle diameter of the fine particles is preferably 1.0 μm or more and 30 μm or less, and the surface roughness (ten-point average roughness) Rzj formed by the fine particles is preferably 0.1 μm or more and 20 μm or less. Rzj is a value measured according to JIS B 0601 (1994).

[0087] [Additives]

[0088] It is preferable to introduce one or more additives selected from a modified organosilicon compound and a modified fluorine compound into the above-mentioned surface layer, because the acrylic monomer remains in the vicinity of the outer surface of the surface layer, and thus an IPN structure can be locally formed at a position very close to the outer surface. The introduction of the additive can inhibit the penetration of the acrylic monomer into the depth of the surface layer, and thus the appropriate property of the surface layer to impart a charge to a developer can be maintained. Thus, the fogging phenomenon can be inhibited in a higher dimension.

[0089] [Method for producing the surface layer]

[0090] When the surface layer of the present embodiment is produced by a sequential network formation method, the method includes the steps of impregnating a crosslinked polyurethane resin as a binder resin on an electrically conductive substrate, and then impregnating a liquid acrylic monomer on the outer surface of the resin layer, and the step of curing the impregnated acrylic monomer. The surface layer according to the present embodiment can be formed by each step.

[0091] Although the method for forming the resin layer is not particularly limited, a coating formation method using a liquid coating is preferable. The resin layer can be formed, for example, by preparing a coating by dispersively mixing each material for the resin layer in a solvent, coating the coating on an electrically conductive substrate, drying the coated coating to cure the coating, or heating the coating to cure the coating.

[0092] From the viewpoint of compatibility with the polyol or isocyanate compound as a raw material of the crosslinked polyurethane, the solvent is preferably a polar solvent. For example, one or two or more of the following solvents having good compatibility with other materials can be used in combination: alcohols such as methanol, ethanol, and n-propanol; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and esters such as methyl acetate and ethyl acetate.

[0093] Further, the solid content at the time of preparation of the paint can be freely adjusted by the amount of mixing of the solvent, and is preferably adjusted to 20 mass% or more and 40 mass% or less from the viewpoint of uniform dispersion of the carbon black. Known dispersing devices using beads, such as a sand mill, a paint shaker, a dinomill, or a bead mill, can be used for dispersion and mixing. Further, dip coating, ring coating, spray coating, or roll coating can be used as the coating method.

[0094] Although the temperature at which the paint is dried to be cured or heat-cured is not particularly limited, as long as crosslinking of the polyurethane resin proceeds, the temperature is preferably 50°C or higher, and more preferably 70°C or higher.

[0095] Next, a liquid acrylic monomer is impregnated in the resin layer formed as described above.

[0096] When the liquid acrylic monomer is impregnated as an impregnation treatment liquid appropriately diluted with any of various solvents, a surface layer having a more uniform surface composition can be formed.

[0097] A solvent satisfying both affinity for the resin layer and solubility for the acrylic monomer can be freely selected as the solvent. Examples thereof include alcohols such as methanol, ethanol, and n-propanol; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and esters such as methyl acetate and ethyl acetate. Further, the impregnation treatment liquid can be appropriately mixed with a polymerization initiator. Details of the polymerization initiator are described below. Although the impregnation method of the impregnation treatment liquid is not particularly limited, dip coating, ring coating, spray coating, or roll coating, or the like can be used.

[0098] The surface layer can be formed by impregnation treatment with the impregnation treatment liquid as described above, and then polymerization and curing of the acrylic monomer. The method of polymerization and curing is not particularly limited, and a publicly known method can be used. Specific examples thereof include methods such as thermal curing and UV irradiation.

[0099] By such a step, the crosslinked acrylic resin is introduced in a form of being entangled with the network structure of the crosslinked polyurethane resin of the resin layer, and thus an IPN structure can be formed. From the viewpoint of film strength and softness, the thickness of the surface layer thus obtained is preferably 2.0 μm or more and 150.0 μm or less.

[0100] <Substrate>

[0101] As the electrically conductive substrate 2, an electrically conductive substrate in a cylindrical or tubular shape can be used. In order to improve the adhesiveness to the intermediate layer or the surface layer provided on the outer periphery thereof, a publicly known surface treatment can be performed on the surface of the substrate. Alternatively, an adhesive layer can be provided thereon. As the material of the substrate, the substrate can include an electrically conductive material as described below:

[0102] a metal or an alloy, such as aluminum, a copper alloy, or stainless steel;

[0103] iron subjected to plating treatment with chromium or nickel; or

[0104] a synthetic resin having electrical conductivity.

[0105] <intermediate layer>

[0106] The intermediate layer 3 is preferably formed of a shaped body of a rubber material. Examples of the rubber material include 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. These rubbers can be used alone or in combination thereof. Among them, silicone rubber is particularly preferable because it hardly causes permanent compression set in the electrically conductive intermediate layer even when any other member (for example, a developer regulating member) is in contact with the layer for a long time. A specific example of the silicone rubber is a cured product of an addition-curable liquid silicone rubber.

[0107] The intermediate layer can be made into an electrically conductive intermediate layer by blending a rubber material with an electrically conductive imparting agent such as an electronic conductive substance or an ionic conductive substance. The volume resistivity of the electrically conductive intermediate layer is preferably adjusted to 10 3 Ω·cm or more and 10 11 Ω·cm or less, more preferably 10 4 Ω·cm or more and 10 10 Ω·cm or less.

[0108] Examples of the electronic conductive substance include the following substances: electrically conductive carbon black such as electrically conductive carbon, rubber carbon, and color (ink) carbon; and metals and metal oxides thereof. Specific examples thereof include highly conductive carbon such as Ketjen black EC and acetylene black; rubber carbon such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT; each color (ink) carbon obtained by oxidizing treatment of carbon black powder; and metals such as copper, silver, and germanium, and metal oxides thereof. Among them, electrically conductive carbon black [electrically conductive carbon, rubber carbon, and color (ink) carbon] is preferable because the electrical conductivity can be easily controlled with a small amount.

[0109] Examples of the ionic conductive substance include the following substances: inorganic ionic conductive substances such as sodium perchlorate, lithium perchlorate, calcium perchlorate, and lithium chloride; and organic ionic conductive substances such as modified aliphatic dimethyl ethylsulfate ammonium and stearyl acetate ammonium.

[0110] Each of these conductivity-imparting agents is used in an amount necessary to adjust the volume resistivity of the intermediate layer to the above-mentioned appropriate value, in a range of 0.5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the intermediate layer-forming rubber material.

[0111] In addition, the intermediate layer can also contain various additives, such as plasticizers, fillers, extenders, vulcanizing agents, vulcanization aids, crosslinking aids, cure inhibitors, antioxidants, anti-aging agents, and processing aids, as needed. Examples of fillers include silica, quartz powder, and calcium carbonate. The blending amount of these optional components is within a range that does not impede the function of the intermediate layer.

[0112] The intermediate layer preferably has the elasticity required for the developing member and an Asker C hardness of 20° or more and 100° or less, and its thickness is preferably 0.3 mm or more and 6.0 mm or less.

[0113] Each material for the intermediate layer can be mixed with a dynamic mixing device such as a single-screw continuous kneader, a twin-screw continuous kneader, a double roll, a kneader mixer, or a trimix, or a static mixing device such as a static mixer.

[0114] The method for forming the intermediate layer on the base body is not particularly limited, and examples thereof can include a mold forming method, an extrusion forming method, an injection forming method, and a coating forming method. An example of the mold forming method can be a method including the following: first, a die head for holding a mandrel inside a mold is fixed to both ends of a cylindrical mold; a injection port is formed in the die head; then the mandrel is disposed inside the mold; the intermediate layer material is injected from the injection port; the injected mold is heated at a temperature at which the material cures; and the cured product is taken out of the mold.

[0115] An example of the extrusion forming method can be a method including the following: a mandrel and an intermediate layer material are co-extruded with a crosshead-type extruder; and the material is cured to form an intermediate layer around the mandrel.

[0116] The surface of the intermediate layer can be modified by a surface modification method such as surface grinding, corona treatment, flame treatment, or excimer treatment, to improve its adhesion to the surface layer.

[0117] <<Developer>>

[0118] The developer according to the present disclosure contains developer particles each containing at least a binder resin and a magnetic substance. As a production method of the developer, a pulverization method or a polymerization method can be used. When the developer is produced by the pulverization method, a publicly known method is used. The developer according to the present disclosure can be obtained by sufficiently mixing components required for the developer, such as the binder resin and the magnetic substance, and additives, such as a release agent or a charge control agent, as needed, and any other components, with a mixer such as a Henschel mixer or a ball mill; then melting and kneading the mixture with a heated kneader such as a heated roll, a kneader, or an extruder; cooling the kneaded product to solidify the product; pulverizing the solidified product; then classifying the pulverized product; and surface-treating the classified product as needed. Either of the classification and the surface treatment can be performed first. In the classification step, a multi-stage classifier is preferably used in order to improve the production efficiency. The pulverization step can be performed by a method including the use of a known pulverizing device such as a mechanical impact type or a jet type pulverizing device.

[0119] In addition, as a method of directly producing a spherical developer, a method including suspending a mixture containing a monomer of a binder resin used as a developer as a main component in water; and polymerizing the monomer to obtain the developer is used. The developer according to this aspect is obtained as follows. A magnetic substance as a basic component and a polymerizable monomer, a colorant, and a polymerization initiator, which are generally used as other components, and a crosslinking agent, a charge control agent, a release agent, and any other additives as needed are uniformly dissolved or dispersed to obtain a monomer composition. Thereafter, the monomer composition is dispersed in a continuous phase containing a dispersion stabilizer such as an aqueous phase with a proper stirrer, made to have a moderate particle diameter, and the dispersion liquid is subjected to a polymerization reaction. Thereby, a developer having a desired particle diameter can be obtained.

[0120] The spherical developer is preferably a high-sphericity developer such that the average circularity of the developer particles each having an equivalent circle diameter of 3 μm or more and 400 μm or less, measured with a flow-type particle image measurement device, is 0.970 or more. This is because when the average circularity is set to be high as described above, uniform tribocharging of the surface of each developer particle is promoted, and thus the charging uniformity of the developer is excellent.

[0121] Further, in order to faithfully develop finer latent image dots in correspondence with higher image quality, the weight average particle diameter of the developer is preferably 3 μm or more and 10 μm or less. When the weight average particle diameter is 3 μm or more, it is possible to achieve suppression of reduction in transfer efficiency, suppression of increase in the amount of transfer residual developer on the photosensitive member, suppression of reduction in the photosensitive member in the contact charging step, and suppression of fusion adhesion of the developer. In addition, it is helpful to suppress increase in the surface area of the entire developer, to suppress reduction in flowability and stirrability of the developer as a powder, and to ensure uniform charging of each developer particle. Thus, it is helpful to suppress fogging of the developer and deterioration in transferability, and to ensure uniformity of the image. Further, when the weight average particle diameter of the developer is 10 μm or less, it is possible to suppress scattering of text or line images, thereby obtaining high resolution.

[0122] For the purpose of improving the triboelectric charging property of the developer, a charge control agent can be introduced (internal addition) into the developer, or can be used by mixing with the developer (external addition). This is because the charge control agent can optimize the charge amount in accordance with the developing system. Examples of the positive charge control agent include products modified with aniline black, triaminotriphenylmethane-based dyes, and fatty acid metal salts; and quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthalenesulfonate and tetrabutylammonium tetrafluoroborate. These positive charge control agents can be used alone or in combination thereof. Further, as the negative charge control agent, an organometallic compound or a chelate is effective. Examples thereof include acetylacetone aluminum, acetylacetone iron (II), and 3,5-di-t-butylsalicylic acid chromium. Among them, acetylacetone metal complexes, monoazo metal complexes, and naphthoic acid-based or salicylic acid-based metal complexes or salts are particularly preferable.

[0123] Examples of the magnetic material of the magnetic substance in the developer include: iron-based metal oxides such as magnetite, maghemite, and ferrite; magnetic metals such as Fe, Co, and Ni; and alloys of these metals with metals such as Al, Co, Cu, Pb, Mg, Ni, Sn, Zn, Sb, Be, Bi, Cd, Ca, Mn, Se, Ti, W, or V; and mixtures thereof.

[0124] It is preferable to blend a release agent into the developer. Examples of the release agent include: aliphatic hydrocarbon-based waxes such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, and paraffin wax; and waxes having fatty acid esters as a main component such as carnauba wax, Fischer-Tropsch wax, sasol wax, and montan wax. Among them, from the viewpoint of fixability, it is preferable to use a wax having a low melting point.

[0125] Furthermore, inorganic fine powders such as silica, titanium dioxide, or alumina are preferably externally added to the developer, i.e., present near the surface of the developer to improve its environmental stability, triboelectric stability, developability, flowability, and storage stability, and to improve its cleaning properties. The amount of inorganic fine powder added to the developer is from 0.1% to 5.0% by mass. Additionally, various external additives can be used in combination. External additives other than inorganic fine powders can be further added and used. Examples of external additives other than inorganic fine powders include lubricants such as polytetrafluoroethylene, zinc stearate, and polyvinylidene fluoride; and abrasives such as cerium oxide, strontium titanate, and strontium silicate. Polyvinylidene fluoride is preferred among lubricants.

[0126] <<Developing Apparatus>>

[0127] The developing apparatus according to this disclosure can be applied to any conventionally known developing apparatus, as long as the developing apparatus is a combination of developing rollers and developing agent according to this disclosure.

[0128] For example, such as Figure 2 As shown, the developing apparatus includes a developer container 109 in which developer 105 is stored, and a developing roller 10 disposed at the opening of the developer container for conveying developer to the outside of the developer container. Additionally, the developing apparatus includes a developing scraper 107 as a developer adjustment member, and a developer supply roller 108 located upstream of the developing roller 10 in a rotatable state and abutting against the developing roller 10. Furthermore, the developing apparatus includes an end sealing member (not shown) disposed at the end of the opening of the developer container 109, abutting against the developing roller 10. The end sealing member includes a member such as a sponge or felt corresponding to the shape of the opening of the developer container, which corresponds to the shape of both ends of the developing roller, and prevents developer leakage to the outside by pressing against each of the two ends of the developing roller. The developer and developing member according to this disclosure are applied to the developer 105 and the developing roller 10. When using a two-component developer, the developer container 109 may include, as needed, a stirring member inside it for stirring the developer and carrier.

[0129] <<Electrophotographic processing box and electrophotographic image forming apparatus>>

[0130] The electrophotographic processing cartridge according to one aspect of this disclosure is characterized in that it is detachably mounted to the main body of the electrophotographic image forming apparatus and includes the aforementioned developing apparatus.

[0131] An electrophotographic image forming apparatus according to one aspect of the present disclosure includes an image bearing member for bearing an electrostatic latent image; a charging device for primary charging the image bearing member; an exposure unit for forming an electrostatic latent image on the primary charged image bearing member; a developing member for developing the electrostatic latent image with a developer to form a developer image; and a transfer device for transferring the developer image. In addition, the electrophotographic image forming apparatus is characterized by including a developing device of the above-described developing member.

[0132] A process cartridge and an electrophotographic image forming apparatus according to one aspect of the present disclosure are described. As an example of the process cartridge of the present disclosure, a process cartridge including the above-described developing device can be given, which is detachably mounted to a main body of the electrophotographic image forming apparatus. In addition, Figure 3 A schematic configuration view for illustrating an example of the electrophotographic image forming apparatus including the above-described developing device or in which the process cartridge is detachably introduced.

[0133] A charging roller 106 configured to be able to charge a member in contact therewith as a charging member, a transfer member (transfer roller) 110, a cleaner container 111, a cleaning blade 112, a fixing unit 113, and a pickup roller 114, and the like are disposed around an image bearing member 118 for bearing an electrostatic latent image. The image bearing member 118 is charged by the charging roller 106. Then, laser is applied from a laser generator 116 to the image bearing member 118 to perform exposure, and thus, an electrostatic latent image corresponding to a target image is formed. The electrostatic latent image on the image bearing member 118 is developed with a developer in a developer container 109 of a process cartridge of a developing unit to obtain an image. The development performed here is so-called reverse development in which an exposed portion is developed with the developer. A transfer material (paper) P is transported from a paper feed section 115 into the apparatus by the pickup roller 114 and the like, and an image is transferred to the transfer material (paper) P by the transfer member (transfer roller) 110 abutting against the image bearing member 118 with the transfer material (paper) P interposed therebetween. The transfer material (paper) P on which the image is borne is transported to the fixing unit 113, and the developer is fixed on the transfer material (paper) P. In addition, the developer remaining on the image bearing member 118 is scraped off by the cleaning blade 112 and stored in the cleaner container 111.

[0134] According to one aspect of the present disclosure, it is possible to provide a developing device that can stably form a high-quality electrophotographic image with reduced fog even when many electrophotographic images are formed for a long time in a high-temperature high-humidity environment using a developer containing a magnetic substance.

[0135] Further, according to another aspect of the present disclosure, an electrophotographic process cartridge and an electrophotographic image forming apparatus each of which can form a high-quality electrophotographic image with reduced fogging for a long period under a high-temperature high-humidity environment using a developer containing a magnetic substance can be provided.

[0136] Example

[0137] Embodiments of the present disclosure will now be described in detail by way of specific embodiments. However, the technical scope of the present disclosure is not limited to this.

[0138] Production of the developing roller D-1

[0139] [Production of the elastic roller 1]

[0140] A base body obtained by applying a primer (product name: DY35-051, manufactured by Dow Corning Toray Co., Ltd.) on a core rod made of SUS304 having an outer diameter of 6 mm and a length of 264 mm and heating the primer at a temperature of 150°C for 20 minutes was prepared as an electrically conductive base body. The electrically conductive base body was concentrically disposed in a cylindrical mold having an inner diameter of 11.5 mm.

[0141] As a material of the intermediate layer, an addition type silicone rubber composition obtained by mixing the materials shown in Table 1 below with a ternary mixer (product name: TX-15, manufactured by Inoue Mfg., Inc.) was used, and the composition was injected into a mold heated to a temperature of 115°C. After injection, the material was heated and formed at a temperature of 120°C for 10 minutes, and cooled to room temperature, and then taken out of the mold. Thus, the elastic roller 1 in which the intermediate layer having a thickness of 2.71 mm was formed on the outer periphery of the electrically conductive base body was obtained.

[0142] Table 1

[0143]

[0144] [Formation of the surface layer 1]

[0145] First, a coating material for forming the resin layer 1 was prepared. That is, the materials in Table 2 below, except for the roughness-forming particles, were stirred and mixed. Next, methyl ethyl ketone (manufactured by Kishida Chemical Co., Ltd.) was added to the mixture so that the solid content concentration was 30 mass%, and the materials were mixed, and then uniformly dispersed with a sand mill. To the mixed solution, methyl ethyl ketone was further added to adjust the solid content concentration to 25 mass%. Thereafter, the roughness-forming particles in Table 2 were added to the mixture, and the materials were stirred and dispersed with a ball mill to obtain a resin layer-forming coating material 1. The elastic roller 1 was dipped in the resin layer-forming coating material 1, and the coating material was applied to the roller in such a manner that the dry thickness of the coating film became 15 μm. Thereafter, the coating film was dried and cured by heating at a temperature of 130°C for 60 minutes. Thus, the resin layer 1 was formed on the intermediate layer.

[0146] Table 2

[0147]

[0148] Subsequently, the impregnation treatment liquid 1 containing the acrylic monomer was impregnated in the resin layer 1, and cured to form the surface layer 1.

[0149] First, the materials shown in Table 3 below were dissolved and mixed to prepare the impregnation treatment liquid 1. Next, the elastic roller on which the resin layer was formed was treated by dipping in the impregnation treatment liquid 1 for 2 seconds so that the acrylic monomer component was impregnated in the layer. Thereafter, the elastic roller was air-dried at a temperature of 25°C for 30 minutes, and dried at a temperature of 90°C for 1 hour so that the solvent of the liquid volatilized. While the dried elastic roller was rotated, UV light was applied to the outer peripheral surface thereof so that the cumulative light quantity thereof became 15,000 mJ / cm2. 2 Thus, the acrylic monomer impregnated in the resin layer was cured. Thus, the surface layer 1 was formed. As the UV irradiation device, a high-pressure mercury lamp (product name: HANDY TYPE UV CURING DEVICE, manufactured by Marionetwork) was used. Thus, the developing roller D-1 was obtained.

[0150] Table 3

[0151]

[0152] [Production of developing rollers D-2 to D-32]

[0153] The resin layer-forming coating materials 2 to 21 were prepared in the same manner as the resin layer-forming coating material 1 except that the formulations shown in Tables 4-1 and 4-2 were used. In addition, the impregnation treatment liquids 2 and 3 were prepared in the same manner as the impregnation treatment liquid 1 except that the formulation shown in Table 5 was used.

[0154] Then, except for the combination of the resin layer forming paint and the impregnation treatment liquid shown in Table 6, the developing rollers D-2 to D-32 were respectively produced in the same manner as the method of forming the surface layer 1.

[0155]

[0156] Table 4-2

[0157]

[0158] Table 5

[0159]

[0160] *The values in Tables 4 and 5 represent the blending amounts of each material in mass parts.

[0161] *Each material shown in Tables 4 and 5 is described below.

[0162] • "C2090": product name; polycarbonate polyol having a side chain methyl group, manufactured by Kuraray Co., Ltd.

[0163] • "T5652": product name; polycarbonate polyol, manufactured by Asahi Kasei Corporation

[0164] • "NP400": product name; nitrogen-containing polyol, manufactured by Sanyo Chemical Industries, Ltd.

[0165] • "P2050": product name; polyester polyol, manufactured by Kuraray Co., Ltd.

[0166] • "PTGL2000": product name, manufactured by Hodogaya Chemical Co., Ltd.; polyether polyol having a side chain methyl group

[0167] • "PTMG2000": product name; polyether polyol, manufactured by Mitsubishi Chemical Corporation

[0168] • "MR-400" ("Millionate MR-400"; product name; isocyanate compound (polymeric MDI), manufactured by Tosoh Corporation

[0169] • "SUNBLACK X15": product name; carbon black, manufactured by Asahi Carbon Co., Ltd.

[0170] • "TSF4445": Product name; modified silicone oil manufactured by Momentive Performance Materials Japan LLC

[0171] • "MEGAFACE F-430": Product name; fluorine group-containing / hydrophilic group- containing / non-oleophilic group-containing oligomer manufactured by DIC Corporation

[0172] • "UCN-5090" ("DAIMIC BEAZ UCN-5090"): Product name; crosslinked polyurethane resin particles manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.

[0173] • "LCB-19": Product name; chain acrylic resin manufactured by Mitsubishi Chemical Corporation

[0174] • "EBECRYL 145": Product name; difunctional acrylic monomer; PO-modified neopentyl glycol diacrylate manufactured by Daicel-Allnex Ltd.

[0175] • "NK Ester 9G": Product name; difunctional acrylic monomer manufactured by Shin-Nakamura Chemical Co., Ltd.

[0176] • "NK Ester 14G": Product name; difunctional acrylic monomer manufactured by Shin-Nakamura Chemical Co., Ltd.

[0177] • "IRGACURE 184": Product name; photopolymerization initiator manufactured by BASF SE

[0178] Table 6

[0179]

[0180] [Production of developing rollers DH-1 and DH-2]

[0181] The other materials shown in the column of "Component (1)" of Table 7 were added to 100 parts by mass of a styrene-butadiene rubber (SBR) (product name: TUFDENE 2003, manufactured by Asahi Kasei Corporation), and the mixture was kneaded for 15 minutes using a closed-type mixer adjusted to 80°C. The materials shown in the column of "Component (2)" of Table 7 were added to the kneaded product. Subsequently, the mixture was kneaded for 10 minutes with a two-roll machine cooled to a temperature of 25°C, thereby obtaining an electrically conductive rubber composition No. 1.

[0182] Table 7

[0183]

[0184] A cylinder made of stainless steel (SUS304) having an outer diameter of 6 mm and a length of 270 mm was prepared. An electrically conductive vulcanized adhesive (product name: METALOC U-20, manufactured by Toyokagaku Kenkyusho Co., Ltd.) was applied to the outer peripheral surface of the cylinder and fired, thereby preparing an electrically conductive base.

[0185] The outer peripheral surface of the base serving as a center axis was coated in a cylindrical manner with the produced electrically conductive rubber composition No. 1 by using an extrusion molding device including a crosshead. The thickness of the electrically conductive rubber composition coating the outer peripheral surface was adjusted to 2.75 mm.

[0186] The extruded roll was vulcanized in a hot air furnace at 160°C for 1 hour, and then the end portion of the rubber layer thereof was removed so that the length of the obtained roll became 235 mm. Thus, a roll having a precoat layer was produced.

[0187] The outer peripheral surface of the obtained roll having a precoat layer was ground to have a crown shape by a grinder of a plunge-cut grinding method, thereby forming a roll No. 1 having a crown shape. The outer diameter of the roll No. 1 was measured with a laser length measuring machine (product names: CONTROLLER LS-7000 and SENSOR HEAD LS-7030R, manufactured by Keyence Corporation). The measurement was performed at an interval of 1 mm, and the difference between the average value of the outer diameter at a position 10 mm away from the end portion of the roll No. 1 and the average value of the outer diameter at the central position of the roll (precoat layer) No. 1 was defined as the amount of protrusion. The average outer diameter at the position 10 mm away from the end portion of the roll No. 1 was 10.018 mm, and the average outer diameter of the central portion thereof was 10.068 mm, and thus the amount of protrusion was 50 μm. Subsequently, the roll No. 1 was subjected to a post-heating treatment at a temperature of 195°C for 1 hour in an atmosphere of air using a hot air furnace, thereby obtaining an elastic roll H1.

[0188] In addition to the resin layer shown in Table 8 being used as a coating or impregnation treatment liquid for the resulting elastic roller H1, the developing rollers DH-1 and DH-2 were each obtained in the same manner as the developing roller D-1.

[0189] Table 8

[0190]

[0191] <Developer>

[0192] [Production of Magnetic Substance 1]

[0193] A ferrous sulfate aqueous solution was prepared by mixing the following materials into a ferrous sulfate aqueous solution: a 1.00 equivalent to 1.10 equivalent amount of caustic soda solution with respect to the iron element; 0.15 mass% of P2O5 with respect to the iron element in terms of the amount of phosphorus element; and 0.50 mass% of SiO2 with respect to the iron element in terms of the amount of silicon element. The pH of the aqueous solution was set to 8.0, and an oxidation reaction was performed at 85°C while air was blown into the solution. Thereby, a slurry having seeds was prepared.

[0194] Next, a ferrous sulfate aqueous solution was added to the slurry in an amount of 0.90 equivalent to 1.20 equivalent with respect to the initial amount of alkali (sodium component of caustic soda). Thereafter, the pH of the slurry was maintained at 7.6, and an oxidation reaction was performed while air was blown into the liquid. Thereby, an aqueous slurry containing magnetic iron oxide was obtained. The aqueous slurry was filtered and washed, and then taken out at once. At this time, a small amount of an aqueous sample was collected, and the water content thereof was measured. Next, the aqueous sample was put into another aqueous medium without drying, and the mixture was stirred. At the same time, the magnetic iron oxide was redispersed with a pin mill while circulating the slurry, so as to adjust the pH of the redispersion liquid to about 4.8. Then, 1.6 parts by mass of n-hexyltrimethoxysilane coupling agent was added to 100 parts by mass of the magnetic iron oxide in the liquid while stirring the liquid, so as to perform hydrolysis.

[0195] The amount of the magnetic iron oxide was calculated as a value obtained by subtracting the water content from the amount of the aqueous sample. Thereafter, stirring was performed sufficiently, and the pH of the dispersion liquid was set to 8.6, and then surface-treated with the silane coupling agent. The produced hydrophobic magnetic substance was filtered with a filter press, and washed with a large amount of water. Thereafter, the washed product was dried at 100°C for 15 minutes, and at 90°C for 30 minutes, and the resulting particles were subjected to a pulverization treatment, thereby obtaining a magnetic substance 1 having a volume average particle diameter of 0.21 μm.

[0196] [Production of Polyester Resin 1]

[0197] The materials shown in Table 9 below were charged into a reaction vessel including a cooling tube, a stirrer, and a nitrogen introduction tube, and allowed to react with each other at 230°C for 10 hours under a stream of nitrogen while distilling off water produced, under reduced pressure of 5 to 20 mmHg, the materials were allowed to react with each other, and at the time point when the acid value reached 2 mgKOH / g or less, the resultant was cooled to 180°C. To the cooled product, 10 parts by mass of trimellitic anhydride was added, and the materials were allowed to react with each other under normal pressure for 2 hours in a closed state. Thereafter, the reaction product was taken out and cooled to room temperature. Thereafter, the cooled product was pulverized, thereby obtaining a polyester resin 1. The main peak molecular weight (Mp) of the polyester resin 1 measured by gel permeation chromatography (GPC) was 10,500.

[0198] Table 9

[0199] Parts by mass Propylene oxide 2-mol adduct of bisphenol A Propylene oxide 3-mol adduct of bisphenol A 75 Terephthalic acid 25 Titanium-based catalyst (titanium dihydroxybis(triethanolamine)) 100 Developer 0.25

[0200] [Production of developer particles 1]

[0201] In a container, 450 parts by mass of a 0.1M aqueous Na3PO4 solution was charged into 720 parts by mass of ion exchange water, and the mixture was warmed to 60°C. Thereafter, 67.7 parts by mass of a 1.0M aqueous CaCl2 solution was added to the mixture to obtain an aqueous medium containing a dispersion stabilizer. Meanwhile, the materials shown in the column of "Component 1" in Table 10 below were uniformly dispersed and mixed with an ATTRITOR (product name, manufactured by Mitsui Miike Chemical Engineering Machinery, Co., Ltd.) to obtain a polymerizable monomer composition. The polymerizable monomer composition was warmed to 60°C, and the materials shown in the column of "Component 2" in Table 10 below were added, mixed, and dissolved in the composition. Thereafter, the materials shown in the column of "Component 3" were added as a polymerization initiator, mixed, and dissolved in the solution, thereby obtaining a developer composition.

[0202] Table 10

[0203]

[0204] The developer composition was put into an aqueous medium, and the mixture was stirred at 12,000 rpm with a T.K. HOMOMIXER (product name, manufactured by Tokushu Kika Kogyo Co., Ltd.) under a N2 atmosphere at 60°C for 10 minutes to granulate. Then, while stirring with a paddle blade, the granulation product was reacted at 74°C for 6 hours. After completion of the reaction, the suspension was cooled, and hydrochloric acid was added to wash the suspension. Thereafter, the washed product was filtered and dried, thereby obtaining developer granules 1. The obtained developer granules 1 were magnetic developers, which had a weight average particle diameter of 8.0 μm, and an average circularity of 0.938.

[0205] [Production of developer T-1]

[0206] The materials shown in Table 11 below were put into a HENSCHEL MIXER FM10C (manufactured by Mitsui Miike Chemical Engineering Machinery, Co., Ltd.), and mixed at a constant rotation speed of 4,000 rpm for 5 minutes. After the mixing, coarse particles and the like were removed with a circular vibrating screen classifier provided with a screen having a diameter of 500 mm and a mesh size of 75 μm. Thus, developer T-1 was obtained.

[0207] Table 11

[0208]

[0209] [Production of developer T-2]

[0210] Developer T-2 was obtained in the same manner as in the production of developer T-1, except that the amount of magnetic substance 1 was changed from 90 parts to 60 parts.

[0211] [Production of developer TH-1]

[0212] Developer TH-1 was obtained in the same manner as in the production of developer T-1, except that the amount of magnetic substance 1 was changed from 90 parts to 0 parts.

[0213] The mass parts of magnetic substance 1 in developer granule raw material component 1 are shown in Table 12 below.

[0214] Table 12

[0215] Parts by mass of magnetic substance 1 in developer granule raw material component 1 TH-1 T-1 90 T-2 60 ​ 0

[0216] The obtained developing roller and developer were evaluated as follows.

[0217] [Measurement of Tl, T2, T3, Al and A2]

[0218] A first region from the outer surface of each developing roller to a position 0.1 μm in depth from the outer surface of the surface layer, a second region 0.1 μm in thickness from the back surface of the surface layer toward the front surface thereof, and a third region corresponding to a depth of 1.0 μm or more and 1.1 μm or less from the front surface were obtained by the above-described micro-sampling mass spectrometry. The peak top temperatures T1, T2, and T3 of the thermogram originating from the crosslinked polyurethane resin in each of the first region, the second region, and the third region were obtained from the obtained thermogram. In addition, the peak top temperature Al of the thermogram originating from the crosslinked acrylic resin in the first region was obtained. Furthermore, the peak top temperature A2 of the thermogram originating from the crosslinked acrylic resin measured from a second sample obtained by decomposing the crosslinked polyurethane resin in the sample sampled from the first region was obtained.

[0219] The samples of each region were collected by using a micro-sampling method with an FIB-SEM (product name: NVision 40, manufactured by SII NanoTechnology Inc.).

[0220] Specifically, first, a notch was cut out from the surface of the developing roller toward the base with a razor to cut out a rubber sheet in a state where the surface layer and the intermediate layer were exposed in cross section. The rubber sheet was placed on the sample stage of the SEM with the roller cross section portion as the upper surface, and a sampling probe was fixed at a position corresponding to the roller surface. Further, cutting treatment with an FIB was performed at a position corresponding to the inside 0.1 μm from the surface corresponding to the roller surface to collect a sample of the first region.

[0221] For the second region, cutting treatment was performed with an FIB at a position 1.0 μm from the interface between the back surface of the surface layer and the intermediate layer toward the front surface. The sampling probe was fixed to the resulting cut surface, and cutting treatment with an FIB was performed at a position corresponding to the inside 0.1 μm from the cut surface to collect a sample of the second region.

[0222] In addition, regarding the third region, in the same rubber sheet as described above, cutting treatment with an FIB was performed at a position corresponding to the inside 1.0 μm from the surface corresponding to the roller surface to expose the third region. The sampling probe was fixed to the exposed surface, and cutting treatment with an FIB was performed at a position corresponding to the inside 0.1 μm from the exposed surface to collect a sample of the third region.

[0223] In each cutting treatment, the acceleration voltage and the beam current of the FIB were set to 30 kV and 27 mA, respectively.

[0224] [Pyridine decomposition method]

[0225] The pyridine decomposition method is a method of selectively decomposing a urethane bond. When the pyridine decomposition method is performed on a sample having an IPN structure of a crosslinked acrylic resin and a crosslinked polyurethane resin, a crosslinked acrylic resin after removal of a structure derived from the crosslinked polyurethane resin can be obtained.

[0226] A change in peak temperature of a thermogram caused by the presence or absence of an IPN structure can be grasped from the obtained crosslinked acrylic resin. The pyridine decomposition method is specifically performed by the following method.

[0227] A sample having a thickness of 0.1 μm was cut from the surface of the developing roller with a microtome, and 500 mg of the sample was collected. A mixed solution 0.5 mL obtained by mixing pyridine (manufactured by Wako Pure Chemical Industries, Ltd.) with water at 3:1 was added to the obtained sample, and the sample was decomposed by heating at 130°C for 15 hours in a closed container made of a fluorine resin (TEFLON (trademark)) having a stainless steel sheath. The obtained decomposition product was treated under reduced pressure to remove pyridine. The value of A2 was obtained by performing the above microsampling mass spectrometry using the sample thus obtained.

[0228] [Thickness Measurement]

[0229] The thickness of the surface layer was determined as follows: the cross sections of 3 parts in the axial direction and 3 parts in the circumferential direction of the surface layer, i.e., a total of 9 parts, were observed with an optical microscope or an electron microscope, and the thickness of the cross sections was measured; and the average of the measured values was taken as the "thickness" of the surface layer.

[0230] [Volume Resistivity Measurement]

[0231] The volume resistivity of the surface layer was measured by an atomic force microscope (AFM) (Q-scope 250: Quesant) by the conductive mode. First, a sheet having a width of 2 mm and a length of 2 mm was cut from the surface layer of the conductive roller with a mechanical hand. The sheet was cut from the surface layer so that one surface of the sheet included the surface of the surface layer. Next, platinum was vapor-deposited from the surface side of the surface layer of the sheet at a thickness of 80 nm. Subsequently, a direct current power source (6614C: Agilent Technologies) was connected to the surface on which the platinum was deposited, and a voltage of 10 V was applied thereto. The free end of the cantilever was brought into contact with the other surface of the surface layer, and an electric current image was obtained by the main body of the AFM. The electric current value was measured at 100 randomly selected sites on the surface, and the volume resistivity was calculated from the average electric current value of the sites having the 10 lowest electric current values and the measurement result of the thickness. The measurement conditions are described below.

[0232] Measurement mode: contact

[0233] Cantilever: CSC17

[0234] Measurement range: 10 nm x 10 nm

[0235] Scan rate: 4 Hz

[0236] Applied voltage: 10 V

[0237] <Example 1>

[0238] A laser printer (product name: LaserJet Pro P1606, manufactured by Hewlett-Packard Company) used as an electrophotographic image forming apparatus was subjected to the following specification change. First, the developing bias voltage of the printer was changed from alternating current (AC) to direct current (DC). Next, the developing bias voltage was set to -500 V, and the bright part potential and the dark part potential on the photosensitive drum of the printer were set to -300 V and -800 V, respectively. Thus, in the image forming apparatus, Vcontrast was 200 V, and Vback was 300 V.

[0239] The above-produced developing roller D-1 was housed in the process cartridge subjected to this specification change, and the above-produced developer T-1 was loaded therein to produce a developing device. Although the developing device of the process cartridge was originally a magnetic non-contact developing device, by installing the cartridge with a developing roller having an outer diameter of 11.4 mm, the developing device became a developing device of a magnetic contact system.

[0240] [Measurement of Q / M]

[0241] The produced process cartridge was loaded into the above laser printer, and the printer was aged for 7 days under a high-temperature high-humidity (H / H) environment. Then, while not changing the environment, an operation of outputting a white solid image was performed with the laser printer to establish a state in which the surface of the developing roller was covered with the developer. Next, under the same environment, the developer carried on the developing roller was sucked and collected with a metal cylinder tube and a cylinder filter. At this time, the amount of charge Q (pC) stored in a capacitor through the metal cylinder tube and the mass M (g) of the developer sucked therefrom were measured. The amount of charge per unit mass Q / M (pC / g) was calculated from these values. When a negatively charged developer is used, the sign of Q / M is negative. It can be said that the larger the absolute value of Q / M becomes, the higher the ability of the developing roller to impart charge to the developer becomes.

[0242] [Fogging measurement]

[0243] Immediately after the Q / M measurement, fogging measurement was performed by the following procedure. First, the printer was stopped during output of a white solid image in the H / H environment. At this time, the developer adhering to the photosensitive member was peeled off with a tape, and the amount of decrease (%) in reflectance with respect to a reference was measured with a reflection densitometer (product name: "TC-6DS / A"; manufactured by Tokyo Denshoku Co., Ltd.). The measured value was adopted as the fogging value. The decrease in reflectance is due to the developer being transferred to the white background portion where no image should be formed and a blank dot should be formed on the paper where no image was printed. Therefore, the fogging value is preferably as small as possible.

[0244] [Ghost evaluation]

[0245] The printer and cartridge used in the Q / M measurement and the fogging measurement were aged for 1 day in an environment at a temperature of 15°C and a relative humidity of 10%. Thereafter, an image for ghost check was generated by outputting an image in which solid black marks (squares and circles) were arranged at equal intervals on a white background in a region at the end of the image corresponding to one revolution of the developing roller, and outputting a halftone image in a region other than the above.

[0246] The degree to which the ghost of the marks appeared on the output halftone image was evaluated by the following criteria.

[0247] Grade AA: No concentration difference was observed.

[0248] Grade A: A slight concentration difference was observed depending on the angle at which the image was observed.

[0249] Grade B: A ghost corresponding to one revolution of the developing roller was observed.

[0250] Grade C: A ghost corresponding to one revolution of the developing roller was clearly observed.

[0251] Grade D: A ghost was observed over two or more revolutions of the developing roller.

[0252] [Examples 2 to 33]

[0253] Evaluation was performed in the same manner as in Example 1 except that the developing roller and the developer were changed to those shown in Table 13. The results are shown in Table 13-1 and Table 13-2.

[0254]

[0255]

[0256] [Comparative Examples 1 to 3]

[0257] The evaluation was performed in the same manner as in Example 1 except that the developing roller and the developer were changed to those shown in Table 14. The results are shown in Table 14.

[0258] Table 14

[0259]

[0260] <Discussion of Evaluation Results>

[0261] In Examples 1 to 33, the developing device was evaluated by using a developer each containing a magnetic substance. Each developing roller housed in the developing device had a single-layered elastic layer as a surface layer, and the elastic layer contained a crosslinked polyurethane resin and a crosslinked acrylic resin as its binder resin. Further, it was known that each developing roller of Examples 1 to 33 satisfied the relationship of Al > A2, and therefore, the crosslinked polyurethane resin and the crosslinked acrylic resin formed an interpenetrating polymer network structure in a first region from the outer surface of the elastic layer to a position 0.1 μm in depth from the outer surface of the surface layer. From the above, even in a high-temperature environment, the developer was satisfactorily charged, and therefore, the fogging performance of the developing device was satisfactory.

[0262] In each of Examples 1, 2, 7, 8, 13, 14, 19, 20, 25 to 30, 32, and 33 using a crosslinked polyurethane resin including a polycarbonate structure as the binder resin of the surface layer of the developing roller, Q / M was relatively high, and the fogging performance of the developing device was satisfactory. In each of Examples 1, 7, 13, 19, and 30 in which the crosslinked polyurethane resin contained a methyl group in the side chain thereof, the result was that the volume resistivity of the device was particularly high and the resistance to fogging was excellent.

[0263] Meanwhile, in Comparative Example 1, the precoat layer was subjected to an acrylic impregnation treatment, but no chemical structure (crosslinked polyurethane resin) that imparts a charge to the developer was introduced, and therefore, the result was that Q / M was low, and the fogging performance of the developing device was poor. In Comparative Example 2, a crosslinked polyurethane resin and a chain-like acrylic resin were introduced, but no interpenetrating polymer network structure of a crosslinked acrylic resin and a crosslinked polyurethane resin was introduced. Further, in Comparative Example 3, no magnetic substance was introduced to the developer. Therefore, in each of these comparative examples, the result was that no effective charge imparting was performed and the fogging performance of the developing device was insufficient.

[0264] While the present application has been described with reference to exemplary embodiments, it is to be understood that the application is not limited to the disclosed exemplary embodiments. The scope of the claims is intended to encompass all such improvements and equivalent structures and functions.

Claims

1. A developing apparatus, characterized in that, It includes: Developer; and A developing member configured to carry the developer on its surface. The developing component includes a conductive substrate and a single-layer elastic layer serving as a surface layer on the substrate. The surface layer comprises an adhesive resin, and the adhesive resin comprises a crosslinked polyurethane resin and a crosslinked acrylic resin. The crosslinked polyurethane resin and the crosslinked acrylic resin form an interpenetrating polymer network structure in a first region extending from the outer surface of the surface layer to a depth of 0.1 μm from the outer surface of the surface layer. The developer comprises developer particles, each containing at least a binder resin and a magnetic substance. The crosslinked polyurethane resin is a polycarbonate-modified polyurethane resin having a structure containing side-chain methyl groups in its soft segments, and The volume resistivity of the binder resin introduced into the surface layer of the developing member is 1.0 × 10⁻⁶. 10 Ω cm or larger and 1.0 × 10 18 Ω Less than cm.

2. The developing apparatus according to claim 1, Wherein, when a first sample is taken from the first region and the peak temperature of the thermochromatogram of the cross-linked acrylic resin originating from the first sample is defined as A1 in °C, and When a second sample is obtained by decomposing the crosslinked polyurethane resin in the first sample, and the peak temperature of the thermochromatogram of the crosslinked acrylic resin derived from the second sample is defined as A2 in °C, A1 and A2 satisfy the relationship expressed by equation (1): Equation (1) A1>A2.

3. The developing apparatus according to claim 1 or 2, wherein when the peak temperature of the thermochromatogram of the crosslinked polyurethane resin originating from the first region is defined as T1 in °C, and the peak temperature of the thermochromatogram of the crosslinked polyurethane resin originating from a second region of 0.1 μm thickness originating from the back side of the surface layer facing the substrate towards the outer surface is defined as T2 in °C, T1 and T2 satisfy the relationship expressed by equation (2): Equation (2) T1>T2.

4. The developing apparatus according to claim 3, wherein T1 and T2 satisfy the relationship expressed by equation (3): Equation (3) (T1-T2)>1.0℃.

5. The developing apparatus according to claim 1 or 2, wherein the thickness of the surface layer of the developing member is 2.0 μm or more and 150.0 μm or less.

6. The developing apparatus according to claim 5, wherein when the peak temperature of the thermochromatogram of the crosslinked polyurethane resin originating from the first region is represented by T1 in °C, the peak temperature of the thermochromatogram of the crosslinked polyurethane resin originating from a second region of 0.1 μm thickness on the back side of the surface layer facing the substrate towards the outer surface is represented by T2 in °C, and the peak temperature of the thermochromatogram of the crosslinked polyurethane resin originating from a third region corresponding to a depth of 1.0 μm or more and 1.1 μm or less from the outer surface of the surface layer is represented by T3 in °C, T1, T2, and T3 satisfy the relationship expressed by equations (4) and (5): Equation (4) T1>T3; and Formula (5)|T1-T3|>|T3-T2|.

7. The developing apparatus according to claim 1 or 2, wherein the surface layer of the developing member further comprises one or more modified organosilicon compounds and modified fluorine compounds.

8. An electrophotographic processing box that can be detachably mounted to the main body of an electrophotographic device, characterized in that, The electrophotographic processing box includes the developing apparatus according to any one of claims 1 to 7.

9. An electrophotographic image forming apparatus, characterized in that, It includes: Image carrier component used to carry electrostatic latent images; A charging device for energizing the image-carrying component once; An exposure apparatus for forming an electrostatic latent image on a charged image carrier component; A developing apparatus that develops the electrostatic latent image with a developer to form a developer image; and A transfer apparatus for transferring the developer image to a transfer material. The developing apparatus thereon is the developing apparatus according to any one of claims 1 to 7.

10. The electrophotographic image forming apparatus according to claim 9, wherein the developing device is a developing device of a magnetic contact system.

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