Developing device, process cartridge and electrophotographic image forming apparatus

Abstract

To provide a developing device that can stably form high-quality electrophotographic images with less fogging even when contributing to formation of a number of electrophotographic images by using developer including magnetic substances in a high temperature and high humidity environment for long period.SOLUTION: A developing device comprises developer and a developing member (developing roller) that carries the developer on its surface. The developing roller has a conductive substrate 2 and a single elastic layer as a surface layer 1 on the substrate. The surface layer 1 has a binder resin, and the binder resin includes a cross-linked urethane resin and a cross-linked acrylic resin. In a first area from an outer surface of the surface layer to a depth of 0.1 μm, the cross-linked urethane resin and the cross-linked acrylic resin constitute an interpenetrating polymer network structure. The developer includes at least developer particles containing a binder resin and magnetic substances.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a developing device incorporated in an apparatus employing an electrophotographic system, and also to an electrophotographic process cartridge and an electrophotographic image forming apparatus having the developing device. [Background technology]

[0002] In an electrophotographic image forming apparatus (also called an "electrophotographic apparatus"), a developing device has a developing roller that carries a developer on its surface, and plays a role in supplying the developer on the developing roller to an electrostatic latent image on an electrophotographic photosensitive member to form a developer image.

[0003] Patent Document 1 discloses an electrophotographic member used in an electrophotographic device, which includes a surface-treated layer made of a cured product of a photocurable composition impregnated into the surface of the rubber elastic body, and a rubber elastic body having rubber elasticity as a material for a portion including the surface of the electrophotographic member. The photocurable composition uses a modified rubber elastic body containing a (meth)acrylic monomer, a photopolymerizable polymer having a silicone group and / or a fluorine-containing group and a (meth)acryloyl group in the molecule, and a photopolymerization initiator. Patent Document 1 also describes that such an electrophotographic member achieves both developer releasability and low friction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-197064 Summary of the Invention [Problem to be solved by the invention]

[0005] When the electrophotographic member described in Patent Document 1 was used together with a developer containing a magnetic substance to output an image under a high-temperature and high-humidity environment, toner was sometimes transferred to areas of the electrophotographic image where toner should not have been transferred, resulting in so-called fogging.

[0006] One aspect of the present disclosure is to provide a developing device that can suppress the occurrence of fogging on an electrophotographic image even when the electrophotographic image is formed in a high-temperature, high-humidity environment using a developer containing a magnetic material. Another aspect of the present disclosure is directed to providing an electrophotographic process cartridge that contributes to the stable formation of high-quality electrophotographic images. Yet another aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus that can stably form high-quality electrophotographic images. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a developer and a developing member carrying the developer on its surface; 、 A developing device comprising: The developing member comprises: a conductive substrate; a single elastic layer as a surface layer on the substrate; 、 and the surface layer has a binder resin, the binder resin including a cross-linked urethane resin and a cross-linked acrylic resin; The volume resistivity of the binder resin is 1.0×10 10 Ω cm or more 1.0×10 18 Ω·cm or less, in a first region extending from the outer surface of the surface layer to a depth of 0.1 μm, the cross-linked urethane resin and the cross-linked acrylic resin form an interpenetrating polymer network structure, The crosslinked urethane resin is a polycarbonate-modified urethane resin having a structure having a side chain methyl group in a soft segment portion, The developer contains developer particles containing at least a binder resin and a magnetic material. 、 Characterized by A development apparatus is provided.

[0008] According to another aspect of the present disclosure, A developing device including a developer and a developing member carrying the developer on its surface, The developing member comprises: a conductive substrate; a single elastic layer as a surface layer on the substrate; 、 and the surface layer has a binder resin, the binder resin including a cross-linked urethane resin and a cross-linked acrylic resin; The volume resistivity of the binder resin is 1.0×10 10 Ω cm or more 1.0×10 18 Ω·cm or less, In a first region from the outer surface of the surface layer to a depth of 0.1 μm, the cross-linked urethane resin and the cross-linked acrylic resin Both Including, The crosslinked urethane resin is a polycarbonate-modified urethane resin having a structure having a side chain methyl group in a soft segment portion, A1 (°C) is the peak top temperature of the thermal chromatogram derived from the crosslinked acrylic resin measured from the first sample sampled from the first region; Applicable 1st The sample contains Applicable When the peak top temperature of a thermal chromatogram derived from the crosslinked acrylic resin measured from a second sample obtained by decomposing the crosslinked urethane resin is defined as A2 (°C), A1 and A2 satisfy the relationship represented by the following formula (1): Formula (1) A1>A2 The developer comprises at least Also Developer particles containing a resin and a magnetic material 、 A developing device characterized by .

[0009] According to another aspect of the present disclosure, the image forming apparatus is configured to be detachable from the main body of the electrophotographic image forming apparatus. Electrophotography A process cartridge including the developing device an electrophotographic A process cartridge is provided. Furthermore, according to another aspect of the present disclosure, there is provided a developing device including an image carrier for carrying an electrostatic latent image, a charging device for primarily charging the image carrier, an exposure device for forming an electrostatic latent image on the primarily charged image carrier, and a developing device for developing the electrostatic latent image with a developer. Drug image Development to form Device and the development Drug image and a transfer device for transferring the image onto a transfer material. In an electrophotographic image forming apparatus , The present The imaging device is Either It is a developing device , characterized in that An electrophotographic imaging apparatus is provided. [Effects of the Invention]

[0010] According to one aspect of the present disclosure, a developing device can be provided that can stably form high-quality electrophotographic images with little fog, even when used to form a large number of electrophotographic images over a long period of time in a high-temperature, high-humidity environment using a developer containing a magnetic material. According to another aspect of the present disclosure, an electrophotographic process cartridge and an electrophotographic image forming apparatus can be provided that are capable of forming high-quality electrophotographic images with little fog over a long period of time in a high-temperature, high-humidity environment using a developer containing a magnetic material. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic diagram illustrating a development roller according to one aspect of the present disclosure. [Figure 2] FIG. 1 is a schematic diagram of a development device according to one aspect of the present disclosure. [Figure 3] 1 is a schematic diagram of an electrophotographic image forming apparatus according to one aspect of the present disclosure. [Figure 4] FIG. 2 is a cross-sectional view of a surface layer of a developing roller according to one embodiment of the present disclosure. [Figure 5]1 is an explanatory diagram of a presumed mechanism of action of a developing member according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] As a result of the investigation, it was found that when forming an electrophotographic image using a developer containing a binder resin and a magnetic material (hereinafter also referred to as a "magnetic developer"), if a developing member having a specific structure is used, it is possible to form a high-quality electrophotographic image with little fogging even in a high-temperature, high-humidity environment. That is, a developing device according to one embodiment of the present disclosure includes a developer and a developing member carrying the developer on its surface. The developing member has a conductive substrate and a single-layer elastic layer as a surface layer on the substrate. The surface layer contains a binder resin, which includes a cross-linked urethane resin and a cross-linked acrylic resin. In a first region of the surface layer extending from the outer surface to a depth of 0.1 μm, the cross-linked urethane resin and the cross-linked acrylic resin form an interpenetrating polymer network structure. The developer also includes developer particles containing at least a binder resin and a magnetic material. A developing device according to another aspect of the present disclosure includes a developer and a developing member carrying the developer on its surface. The developing member has a conductive substrate and a single-layer elastic layer on the substrate as a surface layer. The surface layer contains a binder resin, which includes a cross-linked urethane resin and a cross-linked acrylic resin. A first region of the surface layer extending from the outer surface to a depth of 0.1 μm contains the cross-linked urethane resin and the cross-linked acrylic resin. A peak-top temperature of a thermal chromatogram derived from the cross-linked acrylic resin measured from a first sample sampled from the first region is defined as A1 (°C). Furthermore, A2 (°C) is defined as a peak-top temperature of a thermal chromatogram derived from the cross-linked acrylic resin measured from a second sample obtained by decomposing the cross-linked urethane resin contained in the first sample. A1 and A2 satisfy the relationship shown in the following formula (1): Formula (1) A1>A2 The developer contains developer particles containing at least a binder resin and a magnetic material.

[0013] The present inventors speculate as follows as to why a developing device configured as described above can form high-quality electrophotographic images even in a high-temperature, high-humidity environment. Note that the mechanism of action of a developing device according to one embodiment of the present disclosure described below is merely one possible speculation, and is not limited to this. Furthermore, in the following description, a developing member having a roller shape (hereinafter also referred to as a "developing roller") will be used as an example of the developing member, but the developing member according to the present disclosure is not limited to a developing roller.

[0014] A developing roller according to one embodiment of the present disclosure has an interpenetrating polymer network structure in a first region extending from its toner bearing surface (hereinafter also referred to as the "outer surface") to a depth of 0.1 μm. Hereinafter, the interpenetrating polymer network structure is also referred to as an "IPN structure." An IPN structure is defined as a structure in which the network structures of two or more polymer compounds are intertwined and entangled without being linked by covalent bonds. An IPN structure will not unravel unless the molecular chains of the polymer compounds forming the network are cut. In the IPN structure in the surface layer according to the present disclosure, as schematically shown in FIG. 5, a crosslinked acrylic resin 503 interpenetrates the three-dimensionally crosslinked network structure of a crosslinked urethane resin 501. In such an IPN structure, the role of imparting charge to the developer particles 505 is played by the electron cloud (not shown) of the highest occupied molecular orbital (also called HOMO) present on the nitrogen atom in the urethane bond of the cross-linked urethane resin.

[0015] 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 hydrogen atom bonded to the highly electronegative nitrogen atom has its bonding electrons attracted toward the nitrogen atom. In such a case, the nitrogen atom attracting the bonding electrons carries a slight negative charge (δ-), and the hydrogen atom to which the bonding electrons are attracted carries a slight positive charge (δ+). Such hydrogen atoms are also called active hydrogens.

[0016] Here, in the IPN structure according to the present disclosure, it is believed that the urethane bond in the cross-linked urethane resin 501 and the carbonyl bond in the cross-linked acrylic resin 503 are located in extremely close proximity to each other. When a molecule with a carbonyl bond is present nearby, the slightly positively charged urethane hydrogen forms an intermolecular hydrogen bond (507) with the oxygen atom in the carbonyl bond (also called carbonyl oxygen). In this case, the urethane hydrogen is attracted to the carbonyl oxygen, so the urethane nitrogen to which the urethane hydrogen is bonded can further attract the bonding electrons toward itself. As a result, the electron density of the electron cloud on the nitrogen atom increases, which is thought to significantly improve the ability to impart charge to the developer.

[0017] Furthermore, the magnetic developer according to the present disclosure contains a magnetic material. The magnetic material contains metal atoms. Magnetic materials suitable for use in the developer include the following: iron-based metal oxides such as magnetite, maghemite, and ferrite; and magnetic metals such as Fe, Co, and Ni. These magnetic materials also function as Lewis acids, and have room to accept electrons in their lowest unoccupied molecular orbitals (LUMOs). When a Lewis base with electron-donating ability approaches this room, the Lewis acid-base interaction is thought to facilitate the transfer of charge. In the present disclosure, the electron density of the urethane nitrogen that functions as a Lewis base is increased for the reasons described above, and therefore, it is believed that the magnetic metal atoms in the developer are more efficiently charged (see 509 in Figure 5). As a result, a sufficient charge is imparted to the developer even in a high-temperature, high-humidity environment where triboelectric charging is difficult. As a result, it is believed that the occurrence of fogging on electrophotographic images in a high-temperature, high-humidity environment can be effectively prevented.

[0018] In order to improve fogging, it is effective to increase the volume resistivity of the surface layer to prevent the charge acquired by the developer from leaking to the developing member. That is, charge leakage from the developer in contact with the outer surface of the developing member occurs when the charge escapes from the surface layer of the developing roller to the elastic layer and the base. To suppress such charge leakage, the volume resistivity of the binder resin in the surface layer of the developing member is preferably within the range exhibiting the following insulating properties: preferably 1.0×10 10 Ω cm or more, 1.0×10 18 Ω·cm or less, more preferably 1.0×10 13 Ω cm or more, 1.0×10 16 The volume resistivity is Ω·cm or less. This allows the charge efficiently imparted to the developer by the surface layer having the IPN structure described above to be more reliably retained in the developer. Examples of crosslinked urethane resins that provide such a volume resistivity include polyether-modified urethane resins, polyester-modified urethane resins, and polycarbonate-modified urethane resins. Among these, polycarbonate-modified urethane resins are preferably used because they can have a higher volume resistivity. An example of a polycarbonate urethane resin is a urethane resin that contains the chemical structure of the following structural formula (1) between two adjacent urethane bonds.

[0019] [ka]

[0020] It is also preferable to use a urethane resin having an alkyl group, such as a methyl group, in the soft segment. This side chain inhibits the crystallization of the soft segment, thereby suppressing the improvement in conductivity due to the development of a crystalline structure. This makes it possible for the binder resin to contribute to the formation of a surface layer with a higher volume resistivity. One example is a urethane resin having a structure in the soft segment portion with a side-chain methyl group between two adjacent urethane bonds, as shown in the following structural formula (2):

[0021] [ka]

[0022] <<Developing roller>> A developing roller according to one aspect of the present disclosure will be described in detail below with reference to the drawings. As shown in Figures 1(a) and 1(b), a developing roller according to one embodiment of the present disclosure has a conductive substrate 2 and a single elastic layer on the substrate as a surface layer 1. The surface layer 1 may be provided directly on the conductive substrate as shown in Figure 1(a), or, as shown in Figure 1(b), one or more intermediate layers 3 may be provided between the substrate 2 and the surface layer 1 as needed.

[0023] <Surface layer> To solve the problem of the present disclosure, it is necessary to arrange a cross-linked urethane resin and a cross-linked acrylic resin on the outermost surface of the developing roller and further create a spatial environment in which they interact with each other. To achieve this, it is effective to form an interpenetrating polymer network (IPN) structure of the cross-linked urethane resin and the cross-linked acrylic resin in a first region of the surface layer, which is located to a depth of 0.1 μm from the surface.

[0024] [How to check the IPN structure] The presence of an IPN structure in the surface layer (elastic layer) can be confirmed, for example, by a shift in the glass transition temperature (Tg) of the polymer that constitutes the IPN structure. That is, it is believed that the peak top temperature in the thermal chromatogram, which corresponds to the thermal decomposition temperature of the cross-linked acrylic resin, is shifted to a higher temperature in the IPN structure than when it exists alone. Therefore, by comparing the peak top temperatures of the thermal chromatograms of the cross-linked acrylic resin before and after decomposition of the cross-linked urethane resin in the surface layer, and finding that the peak top temperature after decomposition is lower than that before decomposition, it can be confirmed that the two resins form an IPN structure. Here, the thermal chromatogram is a mass spectrum that can be obtained by microsampling pyrolysis mass spectrometry.

[0025] The outline of the microsampling pyrolysis mass spectrometry method is as follows. First, a sample is prepared by cutting a thin section of the electrophotographic member to be measured using a microtome. In this embodiment, as shown in Figure 4, a sample is prepared from three regions designated as a first region 41, a second region 42, and a third region 43. The first region 41 is a region extending from the outer surface of the surface layer 44 to a depth of 0.1 µm, the second region 42 is a region extending from the back surface of the surface layer 44 (the surface facing the conductive substrate 45) to the outer surface, with a thickness of 0.1 µm, and the third region 43 is a region extending from the outer surface to a depth of 1.0 µm to 1.1 µm. From each region of the surface layer, a 100 μm square flake with a thickness of 0.1 μm is prepared. Measurements are performed using an ion trap mass analyzer, such as that installed in a gas chromatography-mass analyzer ("Polaris Q" (trade name, Thermo Electron)). A sample is attached to a filament at the tip of the probe and inserted directly into the ionization chamber. The sample is then rapidly heated from room temperature to 1000°C at a constant heating rate. The sample decomposes and vaporizes, and the resulting ions are irradiated with an electron beam and detected by a mass spectrometer. Under constant heating conditions, a thermal chromatogram similar to that obtained by simultaneous thermogravimetry-mass analysis (TG-MS) is obtained, which has a mass spectrum called a total ion chromatogram (TIC). Furthermore, a thermal chromatogram for a specific mass fragment can be obtained, allowing the peak temperature of the thermal chromatogram to be determined, corresponding to the decomposition temperature of the desired molecular structure. The peak temperature of the thermal chromatogram correlates with the cross-linking structure of the resin; the denser the cross-linking, the higher the peak temperature.

[0026] The formation of an IPN structure between the crosslinked acrylic resin and the crosslinked urethane resin can be confirmed as follows: by checking the difference in peak temperature in the thermal chromatogram of the fragment derived from the crosslinked acrylic resin before and after decomposition and removal of the crosslinked urethane resin in the composition. Here, the peak top temperature of the thermal chromatogram derived from the crosslinked acrylic resin measured from the first sample sampled from the first region is defined as A1 (°C). Furthermore, the peak top temperature of the thermal chromatogram derived from the crosslinked acrylic resin measured from the second sample obtained by decomposing the crosslinked urethane resin contained in the first sample is defined as A2 (°C). When an IPN structure is formed, A1 and A2 satisfy the relationship shown in the following formula (1): Equation (1) A1>A2.

[0027] Examples of methods for forming an IPN structure include the following methods i) and ii). i) A method in which a network structure of the first component polymer is first formed, and then the first component polymer is swelled with the second component monomer and polymerization initiator, and then a network structure of the second component polymer is formed (this method is also called the "sequential network formation method"). ii) A method in which a first component monomer, a second component monomer, and their respective polymerization initiators are mixed together to simultaneously form a network structure (this method is also called the "simultaneous network formation method"). A method for producing the surface layer (elastic layer) having an IPN structure in the first region according to this embodiment will be described later.

[0028] [Cross-linked urethane resin] Crosslinked urethane resins are obtained by reacting a polyol having a hydroxyl group with an isocyanate compound to form urethane groups. The term "crosslinked" here refers to the fact that one or both of the raw materials for the urethane resin, the polyol and the isocyanate compound, have three or more reactive functional groups, resulting in a three-dimensional network structure. Such crosslinked urethane resins have excellent flexibility and high strength. Urethane resins can be obtained from polyols, isocyanate compounds, and, if necessary, chain extenders. Examples of polyols that can be used as raw materials for urethane resins include polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, acrylic polyols, and mixtures thereof. Among these, it is preferable to use polyols that can provide the above structural formula (1) or (2). For example, polyether polyols having side chain methyl groups and polycarbonate polyols having side chain methyl groups can be suitably used. Examples of isocyanate compounds that are raw materials for urethane resins include the following: Tolylene 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.

[0029] Optional chain extenders 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. Prepolymer-type isocyanate compounds having terminal isocyanate groups may also be used, which are obtained by preliminarily reacting the above-mentioned various isocyanate compounds with various polyols in a state where the isocyanate groups are in excess relative to the hydroxyl groups. These isocyanate compounds may also be materials in which the isocyanate groups are blocked with various blocking agents such as methyl ethyl ketone (MEK) oxime. Regardless of which material is used, a urethane resin can be obtained by reacting a polyol with an isocyanate compound by heating. Preferably, either the polyol or the isocyanate compound, or both, have a branched structure and three or more functional groups, so that the resulting urethane resin is a crosslinked urethane resin.

[0030] [Cross-linked acrylic resin] The cross-linked acrylic resin forms an IPN structure together with the cross-linked urethane resin, and by the above-mentioned mechanism of action, brings about a significant improvement in the ability to impart charge to the magnetic developer on the surface layer of the developing member. Crosslinked acrylic resins are formed by the polymerization of acrylic monomers. The term "acrylic monomer" as used herein refers not only to acrylic monomers but also to methacrylic monomers. In other words, crosslinked acrylic resins are formed by the polymerization of either acrylic monomers, methacrylic monomers, or both.

[0031] To form an IPN structure between a cross-linked acrylic resin and a cross-linked urethane resin, a resin layer containing the cross-linked urethane resin is impregnated with a liquid acrylic monomer and then cured, as described above. The types of acrylic monomers used here include polyfunctional monomers having multiple acryloyl or methacryloyl groups as functional groups to form a cross-linked structure. On the other hand, if the functional groups are four or more, the viscosity of the acrylic monomer increases significantly, making it difficult for the acrylic monomer to penetrate into the surface of the resin layer made of the cross-linked urethane resin, and as a result, it becomes difficult to form an IPN structure. Therefore, the acrylic monomer is preferably a monomer having two or three acryloyl and methacryloyl groups in one molecule, and more preferably a bifunctional acrylic monomer having two acryloyl and methacryloyl groups in one molecule.

[0032] The molecular weight of the acrylic monomer is preferably in the range of 200 to 750. By using an acrylic monomer with a molecular weight in this range, an IPN structure can be easily formed relative to the network structure of the cross-linked urethane resin, and the strength of the surface layer can be effectively improved.

[0033] As described above, the acrylic monomer is impregnated into the resin layer containing the cross-linked urethane resin. To achieve this, it must have an appropriate viscosity. That is, if the viscosity is high, it is difficult to impregnate, and if the viscosity is low, it is difficult to control the impregnation state. Therefore, the viscosity of the acrylic monomer at 25°C is preferably 5.0 mPa·s or more and 140 mPa·s or less. That is, by selecting one or more acrylic monomers that satisfy the above-mentioned molecular weight and viscosity ranges, impregnating the resin layer, and polymerizing them, an IPN structure of cross-linked urethane resin and cross-linked acrylic resin can be formed.

[0034] The method for polymerizing the acrylic monomer is not particularly limited, and known methods can be used, such as thermal polymerization by heating and photopolymerization by ultraviolet irradiation. For each polymerization method, a known radical polymerization initiator or ionic polymerization initiator can be used.

[0035] Examples of the thermal polymerization initiator for thermal polymerization include peroxides such as 3-hydroxy-1,1-dimethylbutylperoxyneodecanoate, α-cumylperoxyneodecanoate, t-butylperoxyneoheptanoate, t-butylperoxypivalate, t-amylperoxynormaloctoate, t-butylperoxy2-ethylhexylcarbonate, dicumyl peroxide, di-t-butyl peroxide, di-t-amyl peroxide, 1,1-di(t-butylperoxy)cyclohexane, and n-butyl-4,4-di(t-butylperoxy)valerate; Examples of azo compounds include 2,2-azobisbutyronitrile, 2,2-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2-azobis(2,4-dimethylvaleronitrile), 2,2-azobis(2-methylbutyronitrile), 1,1-azobis(cyclohexane-1-carbonitrile), 2,2-azobis[2-(2-imidazolin-2-yl)propane], 2,2-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2-azobis(N-butyl-2-methoxypropionamide), and dimethyl-2,2-azobis(isobutyrate).

[0036] Examples of photopolymerization initiators for photopolymerization by irradiation with ultraviolet light include 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, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methylpropane. -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, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide are examples thereof.

[0037] These polymerization initiators may be used alone or in combination of two or more. Furthermore, the amount of the polymerization initiator is preferably 0.5 parts by mass or more and 10 parts by mass or less, when the total amount of the compounds for forming the specific resin (e.g., compounds having a (meth)acryloyl group) is taken as 100 parts by mass, from the viewpoint of efficiently progressing the reaction. Known devices for heating and UV irradiation can be used as appropriate. Examples of light sources for UV irradiation include LED lamps, high-pressure mercury lamps, metal halide lamps, xenon lamps, and low-pressure mercury lamps. The cumulative light intensity required for polymerization can be adjusted as appropriate depending on the type and amount of the compound and polymerization initiator used.

[0038] [Function of the surface layer] The surface layer is preferably flexible to reduce mechanical stress on the developer carried on its outer surface. On the other hand, the IPN structure increases the hardness of the surface layer. Therefore, the side of the surface layer facing the substrate preferably does not have an IPN structure, or, even if it does have an IPN structure, it preferably has an IPN structure in which the degree of penetration of the cross-linked acrylic resin into the cross-linked urethane resin is relatively weak compared to the IPN structure of the first region. This can suppress an increase in the hardness of the surface layer even if the outer surface side has a developed IPN structure. Specifically, when the second region is defined as a 0.1 μm-thick region extending from the surface of the surface layer facing the substrate toward the outer surface, the first and second regions preferably satisfy the relationship shown in the following formula (2), and particularly preferably satisfy the relationship shown in formula (3): where T1 (°C) represents the peak-top temperature of the thermal chromatogram derived from the crosslinked urethane resin measured from a sample sampled from the first region, and T2 (°C) represents the peak-top temperature of the thermal chromatogram derived from the crosslinked urethane resin measured from a sample sampled from the second region. Equation (2) T1>T2. Equation (3) (T1-T2)>1.0(℃).

[0039] Furthermore, in order to allow the surface layer to better exert its function of alleviating mechanical stress on the developer, the thickness of the surface layer is preferably 2.0 μm or more and 150.0 μm or less. In a surface layer of such thickness, when a region of 0.1 μm thickness extending from 1.0 μm to 1.1 μm deep from the outer surface of the surface layer is defined as a third region, it is preferable that an IPN structure is not present in the third region adjacent to the first region. Alternatively, even if an IPN structure is present, it is preferable that the degree of penetration of the crosslinked acrylic resin is weaker than that of the IPN structure in the first region.

[0040] Therefore, when the peak top temperature of the thermal chromatogram derived from the crosslinked urethane resin measured from the sample sampled from the third region is T3 (°C), it is preferable that T1, T2, and T3 satisfy the relationship of formula (4) and formula (5). Formula (4) T1>T3 Equation (5) |T1-T3|>|T3-T2|

[0041] [Volume resistivity of binder resin in surface layer and measurement method] As mentioned above, the volume resistivity of the binder resin in the surface layer is 1.0 × 10 10 Ω cm or more, 1.0×10 18 Ω·cm or less, especially 1.0×10 13 Ω cm or more, 1.0×10 16 It is preferable to set the resistivity to Ω·cm or less. This more reliably prevents the charge of the developer (called developer charge) from attenuating due to leakage to the developing member. It also prevents excessive charging of the developer. The volume resistivity of the binder resin can be measured using an atomic force microscope (AFM) in conductivity mode. A sample piece is cut out from the resin binder portion of the surface layer of the developing roller using a manipulator, and one side of the sample piece is subjected to metal deposition. A DC power source is connected to the metal-deposited surface, a voltage is applied, and the free end of a cantilever is brought into contact with the surface opposite the metal-deposited surface, and a current image is obtained through the AFM main body. The volume resistivity can be calculated from the current value thus obtained, the film thickness of the sample piece, and the contact area of ​​the cantilever.

[0042] [Other ingredients] In addition to the above, the surface layer may contain components such as crosslinkers, plasticizers, fillers, extenders, vulcanizing agents, vulcanization aids, crosslinking aids, antioxidants, antioxidants, processing aids, and leveling agents, provided that the functionality of the surface layer is not impaired. Furthermore, if the surface layer requires surface roughness, fine particles may be added to impart roughness to the surface layer. Specifically, fine particles of polyurethane resin, polyester resin, polyether resin, polyamide resin, acrylic resin, or polycarbonate resin can be used. The volume-average particle diameter of the fine particles is preferably 1.0 μm to 30 μm, and the surface roughness (ten-point average roughness) Rzjis formed by the fine particles is preferably 0.1 μm to 20 μm. Rzjis is a value measured according to JIS B0601 (1994).

[0043] [Additives] The surface layer preferably contains one or more additives, such as a modified silicone compound or a modified fluorine compound, because the acrylic monomer remains near the outer surface, allowing the IPN structure to be formed locally in the vicinity of the outer surface. The inclusion of such additives prevents the acrylic monomer from penetrating deep into the surface layer, thereby maintaining the surface layer's ability to impart a suitable charge to the developer. This allows for greater suppression of fogging.

[0044] [Method of manufacturing the surface layer] When the surface layer of this embodiment is produced by the sequential network formation method, the following steps are included: a step of forming a cross-linked urethane resin as a binder resin on a conductive substrate, a step of impregnating the outer surface of the resin layer with a liquid acrylic monomer, and a step of curing the impregnated acrylic monomer. The surface layer of this embodiment can be formed by going through the above steps. The method for forming the resin layer is not particularly limited, but a coating molding method using a liquid paint is preferred. For example, the resin layer can be formed by dispersing and mixing the materials for the resin layer in a solvent to form a paint, applying the paint to a conductive substrate, and drying and solidifying it or by heating and curing it. The solvent is preferably a polar solvent from the viewpoint of compatibility with the polyol and isocyanate compounds that are raw materials for the crosslinked urethane. For example, one or a mixture of two or more solvents that are compatible with other materials can be used, such as 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. The solid content of the paint can be freely adjusted by the amount of solvent mixed, but is preferably adjusted to 20% by mass or more and 40% by mass or less from the viewpoint of uniformly dispersing the carbon black. For dispersion and mixing, known dispersion devices using beads, such as a sand mill, paint shaker, dyno mill, or pearl mill, can be used. The coating method can be dip coating, ring coating, spray coating, or roll coating. The drying and solidifying or heat curing is not particularly limited as long as the crosslinking of the urethane resin proceeds, but a temperature of 50°C or higher is preferred, and a temperature of 70°C or higher is more preferred.

[0045] Next, the resin layer formed as described above is impregnated with a liquid acrylic monomer. By impregnating the surface with an impregnation treatment liquid prepared by appropriately diluting a liquid acrylic monomer with various solvents, a surface layer with a more uniform surface composition can be formed. The solvent can be freely selected as long as it has both affinity with the resin layer and solubility for the acrylic monomer. Examples 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. A polymerization initiator can also be mixed into the impregnation treatment solution. Details of the polymerization initiator will be described later. The method of impregnation with the impregnation treatment solution is not particularly limited, but dip coating, ring coating, spray coating or roll coating can be used.

[0046] After the impregnation treatment with the impregnation treatment solution is performed in this manner, the acrylic monomer is polymerized and cured to form a surface layer. The polymerization and curing method is not particularly limited, and known methods can be used. Specific examples include methods such as heat curing and ultraviolet irradiation. By this process, the cross-linked acrylic resin is introduced into the network structure of the cross-linked urethane resin of the resin layer in a mutually entangled manner, thereby forming an IPN structure. From the viewpoints of film strength and flexibility, the film thickness of the surface layer thus obtained is preferably 2.0 μm or more and 150.0 μm or less.

[0047] <Base> The conductive substrate 2 can be a cylindrical or columnar conductive substrate. The surface of the substrate may be subjected to a known surface treatment or provided with an adhesive layer in order to improve adhesion with an intermediate layer or surface layer provided on the outer periphery. The substrate may be made of the following conductive materials: metals or alloys such as aluminum, copper alloys, stainless steel; Chromium- or nickel-plated iron; A synthetic resin with electrical conductivity.

[0048] <Middle class> The intermediate layer 3 is preferably formed from a molded body of a rubber material. Examples of rubber materials 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, NBR hydride, and urethane rubber. These may be used alone or in combination of two or more. Among these, silicone rubber is particularly preferred because it is less likely to cause compression set in the conductive intermediate layer even when it comes into contact with other members (such as a developer control member) over a long period of time. Specific examples of silicone rubber include a cured product of addition-curing liquid silicone rubber.

[0049] The intermediate layer can be made conductive by blending the rubber material with a conductivity imparting agent such as an electronically conductive substance or an ionic conductive substance. The volume resistivity of the conductive intermediate layer is preferably 10 3 Ωcm or more 10 11 Ωcm or less, more preferably 10 4 Ωcm or more 10 10 It is adjusted to Ωcm or less. Examples of electronically conductive materials include the following: conductive carbon black, such as conductive carbon, carbon for rubber, and carbon for color (ink), and metals and their metal oxides. Examples include highly conductive carbon, such as Ketjenblack EC and acetylene black; carbon for rubber, such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT; carbon for color (ink) obtained by oxidizing carbon black powder; and metals and their metal oxides, such as copper, silver, and germanium. Among these, conductive carbon black (conductive carbon, carbon for rubber, and carbon for color (ink)) is preferred because it is easy to control conductivity with a small amount.

[0050] Examples of ion-conductive substances include the following: inorganic ion-conductive substances such as sodium perchlorate, lithium perchlorate, calcium perchlorate, and lithium chloride; and organic ion-conductive substances such as modified aliphatic dimethylammonium ethosulfate and stearylammonium acetate. These conductivity imparting agents are used in the amount necessary to adjust the intermediate layer to the appropriate volume resistivity as described above, but are used in the range of 0.5 parts by mass to 50 parts by mass per 100 parts by mass of the rubber material constituting the intermediate layer.

[0051] The intermediate layer may further contain various additives, such as plasticizers, fillers, extenders, vulcanizing agents, vulcanization aids, crosslinking aids, cure inhibitors, antioxidants, antioxidants, and processing aids, as needed. Examples of fillers include silica, quartz powder, and calcium carbonate. These optional components are blended in amounts that do not impair the function of the intermediate layer.

[0052] The intermediate layer has the elasticity required for the developing member, and preferably has an Asker C hardness of 20 degrees or more and 100 degrees or less, and a thickness of 0.3 mm or more and 6.0 mm or less.

[0053] The materials for the intermediate layer can be mixed using a dynamic mixer such as a single-screw continuous mixer, a twin-screw continuous mixer, a twin-roll mixer, a kneader mixer, or a trimix, or a static mixer such as a static mixer.

[0054] The method for forming an intermediate layer on a substrate is not particularly limited, and examples thereof include molding, extrusion, injection, and coating. In molding, for example, first, pieces for holding a mandrel in the mold are fixed to both ends of a cylindrical mold, and an injection port is formed in the pieces. Next, the mandrel is placed in the mold, and a material for the intermediate layer is injected through the injection port, and the mold is heated to a temperature at which the material hardens, followed by demolding. In the extrusion molding method, for example, a crosshead extruder is used to extrude the mandrel and the material for the intermediate layer together, and the material is then cured to form the intermediate layer around the mandrel. The surface of the intermediate layer can be modified by a surface modification method such as surface polishing, corona treatment, flame treatment, or excimer treatment in order to improve adhesion to the surface layer.

[0055] <<Developer>> The developer according to the present invention contains developer particles containing at least a binder resin and a magnetic material. The developer can be manufactured by a pulverization method or a polymerization method. When manufactured by a pulverization method, a known method is used. To prepare the developer according to the present disclosure, components necessary for the developer, such as a binder resin and a magnetic material, and optionally a release agent, a charge control agent additive, and other components, are thoroughly mixed in a mixer such as a Henschel mixer or a ball mill. The mixture is then melted and kneaded using a thermal kneader such as a heated roll, kneader, or extruder, cooled and solidified, pulverized, classified, and optionally surface-treated to obtain a developer. The order of classification and surface treatment is not important. In the classification step, a multi-division classifier is preferably used to improve production efficiency. The pulverization step can be performed using a known pulverization device, such as a mechanical impact type or a jet type.

[0056] Another method for directly producing spherical developers is to suspend a mixture mainly composed of a monomer that will become the binder resin of the developer in water and polymerize it to form a developer. The developer according to this embodiment requires a magnetic material as an essential component, and other commonly used polymerizable monomers, colorants, polymerization initiators, and, if necessary, crosslinking agents, charge control agents, release agents, and other additives, all of which are uniformly dissolved or dispersed to form a monomer composition. This monomer composition is then dispersed to an appropriate particle size in a continuous phase, such as an aqueous phase, containing a dispersion stabilizer using an appropriate stirrer, and further polymerized to obtain a developer having the desired particle size.

[0057] The spherical developer is preferably a developer with a high degree of sphericity, that is, an average circularity of 0.970 or more for a developer with an equivalent circle diameter of 3 μm to 400 μm measured with a flow particle image analyzer. By increasing the average circularity in this way, it becomes easier to uniformly triboelectrically charge the surface of each developer particle, resulting in excellent charging uniformity.

[0058] Furthermore, in order to achieve even higher image quality and faithfully develop even smaller latent image dots, the weight-average particle size of the developer is preferably 3 μm or more and 10 μm or less. When the weight-average particle size is 3 μm or more, it is possible to suppress a decrease in transfer efficiency, suppress an increase in residual developer on the photoreceptor, suppress photoreceptor abrasion during the contact charging process, and suppress developer fusion. Furthermore, it is easy to suppress an increase in the overall surface area of ​​the developer, suppress a decrease in powder flowability and agitation, and ensure uniform charging of individual developer particles. Therefore, it is easy to suppress fogging and deterioration of transferability and ensure image uniformity. Furthermore, when the weight-average particle size of the developer is 10 μm or less, scattering of characters and line images can be suppressed, and high resolution can be achieved.

[0059] To improve triboelectric charging characteristics, a charge control agent can be incorporated into the developer (internal addition) or mixed with the developer (external addition). This is because the charge control agent enables optimal charge control according to the development system. Positive charge control agents include the following: nigrosine, triaminotriphenylmethane dyes and modified fatty acid metal salts; and quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate. These can be used alone or in combination. Effective negative charge control agents include organometallic compounds and chelate compounds. Examples include aluminum acetylacetonate, iron(II) acetylacetonate, and chromium 3,5-ditertiarybutylsalicylate. Acetylacetone metal complexes, monoazo metal complexes, and metal complexes or salts of naphthoic acid or salicylic acid are particularly preferred.

[0060] Examples of magnetic materials for the magnetic substance contained in the developer include the following: iron-based metal oxides such as magnetite, maghemite, and ferrite; magnetic metals such as Fe, Co, and Ni; 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, and V; and mixtures of these.

[0061] It is preferable to blend a release agent in the developer. Examples of the release agent include: aliphatic hydrocarbon waxes such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, microcrystalline wax, and paraffin wax; and waxes containing fatty acid esters as the main component such as carnauba wax, Fischer-Tropsch wax, Sasol wax, and montan wax. Among these, waxes with low melting points are preferably used from the viewpoint of fixability.

[0062] Furthermore, to improve environmental stability, triboelectric charge stability, developability, fluidity, storage stability, and cleaning properties, it is preferable to externally add inorganic fine powders such as silica, titanium oxide, and alumina to the developer, i.e., to have them present near the surface of the developer. The amount of inorganic fine powder added is 0.1 to 5.0% by mass in the developer. Various external additives may be used in combination. External additives other than inorganic fine powders may also be added. 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. Among lubricants, polyvinylidene fluoride is preferred.

[0063] <<Developing device>> The developing device according to the present disclosure can be applied to any conventionally known developing device as long as it is a combination of the developing roller according to the present disclosure and a developer. For example, as shown in FIG. 2, the developing device includes a developer container 109 containing developer 105 and a developing roller 10 disposed at the opening of the developer container to transport the developer to the outside of the developer container. The developing device also includes a developing blade 107, which is a developer regulating member, and a developer supply roller 108, which is rotatably in contact with the developing roller 10 on the upstream side of the rotation of the developing roller 10. An end seal member (not shown) is also provided at the end of the opening of the developer container 109, which abuts against the developing roller 10. The end seal member is made of a material such as sponge or felt, and conforms to the shape of the developer container opening, which is formed to correspond to the shape of both end circumferential surfaces of the developing roller. It presses against both end circumferential surfaces of the developing roller to prevent developer from leaking to the outside. The developer and developing member according to the present disclosure are applied to the developer 105 and the developing roller 10. When a two-component developer is used, the developer container 109 may optionally include a stirring member for stirring the developer and carrier.

[0064] <<Electrophotographic process cartridge and electrophotographic image forming apparatus>> An electrophotographic process cartridge according to one aspect of the present disclosure is configured to be detachably mountable to the main body of an electrophotographic image forming apparatus, and is characterized by including the above-described developing device. An electrophotographic image forming apparatus according to one aspect of the present disclosure includes an image carrier for carrying an electrostatic latent image, a charging device for primarily charging the image carrier, an exposure device for forming an electrostatic latent image on the primarily charged image carrier, 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, and is characterized in that the developing device equipped with the developing member is the above-mentioned developing device.

[0065] A process cartridge and an electrophotographic image forming apparatus according to one embodiment of the present disclosure will be described. An example of the process cartridge of the present disclosure includes the above-described developing device and is configured to be detachably attached to the main body of the electrophotographic image forming apparatus. FIG. 3 is a schematic diagram showing an example of an electrophotographic image forming apparatus equipped with the above-described developing device or in which the process cartridge is detachably incorporated.

[0066] Around an image carrier 118 for carrying an electrostatic latent image, there are provided a charging roller 106 as a charging member arranged to be chargeable, a transfer member (transfer roller) 110, a cleaner container 111, a cleaning blade 112, a fuser 113, a pickup roller 114, and the like. The image carrier 118 is charged by the charging roller 106. Then, a laser generator 116 irradiates the image carrier 118 with laser light, thereby forming an electrostatic latent image corresponding to the desired image. The electrostatic latent image on the image carrier 118 is developed with a developer in a developer container 109 contained in a process cartridge serving as a developing device, thereby obtaining an image. The development is performed by so-called reversal development, in which the developer is developed in the exposed area. A transfer material (paper) P is transported into the device from a paper feed unit 115 by a pickup roller 114, and the image is transferred onto the transfer material (paper) P by a transfer member (transfer roller) 110 abutting against the image carrier 118 via the transfer material (paper) P. The transfer material (paper) P carrying the image is transported to a fixing device 113, where the developer is fixed onto the transfer material (paper) P. In addition, the developer remaining on the image carrier 118 is scraped off by a cleaning blade 112 and stored in a cleaner container 111. [Example]

[0067] The embodiments of the present disclosure will be described in detail below using specific examples, but the technical scope of the present disclosure is not limited to these examples.

[0068] <Preparation of Developing Roller D-1> [Production of Elastic Roller 1] A conductive substrate was prepared by coating a SUS304 core bar with an outer diameter of 6 mm and a length of 264 mm with a primer (product name: DY35-051, manufactured by Dow Corning Toray Co., Ltd.) and heating it for 20 minutes at a temperature of 150°C. This conductive substrate was placed concentrically in a cylindrical mold with an inner diameter of 11.5 mm. An addition-type silicone rubber composition prepared by mixing the materials shown in Table 1 below using Trimix (product name: TX-15, manufactured by Inoue Seisakusho) was used as the material for the intermediate layer, and the composition was poured into a mold heated to 115° C. After the material was poured, the mixture was heated and molded at 120° C. for 10 minutes, cooled to room temperature, and then demolded from the mold, yielding an elastic roller 1 in which a 2.71 mm-thick intermediate layer was formed on the outer periphery of a conductive substrate.

[0069] [Table 1]

[0070] [Formation of surface layer 1] First, a coating material for forming resin layer 1 was prepared. Specifically, all materials listed in Table 2 below, except for the roughness-forming particles, were mixed by stirring. Next, methyl ethyl ketone (Kishida Chemical Co., Ltd.) was added to the mixture to a solids concentration of 30% by mass, and after mixing, the mixture was uniformly dispersed using a sand mill. Further methyl ethyl ketone was added to the mixture to adjust the solids concentration to 25% by mass. The roughness-forming particles listed in Table 2 were then added, and the mixture was stirred and dispersed using a ball mill to obtain coating material for forming resin layer 1. The elastic roller 1 was immersed in coating material for forming resin layer 1 and coated so that the dry coating thickness was 15 μm. The coating was then dried and cured by heating at 130°C for 60 minutes, forming resin layer 1 on the intermediate layer.

[0071] [Table 2]

[0072] Subsequently, the resin layer 1 was impregnated with an impregnation treatment liquid 1 containing an acrylic monomer and cured to form a surface layer 1. First, the materials shown in Table 3 below were dissolved and mixed to prepare impregnation treatment solution 1. Next, the elastic roller on which the resin layer had been formed was immersed in this impregnation treatment solution 1 for 2 seconds to impregnate the acrylic monomer component. After that, it was air-dried at a temperature of 25°C for 30 minutes and then dried at a temperature of 90°C for 1 hour to volatilize the solvent. While rotating the dried elastic roller, it was exposed to an integrated light intensity of 15,000 mJ / cm. 2 The outer peripheral surface was irradiated with ultraviolet light so that the acrylic monomer impregnated in the resin layer was cured to form the surface layer 1. As the ultraviolet irradiating device, a high-pressure mercury lamp (product name: handy type UV curing device, manufactured by Mario Network Co., Ltd.) was used. In this way, the developing roller D-1 was obtained.

[0073] [Table 3]

[0074] [Production of developing rollers D-2 to D-32] Resin layer-forming paints 2 to 21 were prepared in the same manner as the resin layer-forming paint 1, except for the formulations shown in Tables 4-1 and 4-2. Impregnation treatment solutions 2 and 3 were prepared in the same manner as the impregnation treatment solution 1, except for the formulations shown in Table 5. Developing rollers 2 to 32 were produced in the same manner as in the method for forming surface layer 1, except that the combinations of the resin layer-forming paint and impregnation treatment liquid shown in Table 6 were used.

[0075] [Table 4-1]

[0076] [Table 4-2]

[0077] [Table 5]

[0078] *The numbers in Tables 4 and 5 represent the blend amount of each material in parts by mass. *The materials listed in Tables 4 and 5 are as follows: "C2090": Product name; Polycarbonate polyol with side chain methyl groups, manufactured by Kuraray Co., Ltd. "T5652": Product name; Polycarbonate polyol manufactured by Asahi Kasei Corporation "NP400": Product name; Nitrogen-containing polyol manufactured by Sanyo Chemical Industries, Ltd. "P2050": Product name; Polyester polyol manufactured by Kuraray Co., Ltd. "PTGL2000": Product name; Polyether polyol with side chain methyl groups, manufactured by Hodogaya Chemical Co., Ltd. PTMG2000: Product name; Mitsubishi Chemical Corporation, polyether polyol "MR-400" ("Millionate MR-400"; product name; Tosoh Corporation isocyanate compound (polymeric MDI) "SUNBLACK X15": Product name; Carbon black made by Asahi Carbon "TSF4445": Product name; Modified silicone oil manufactured by Momentive Performance Materials Japan, Inc. "Megafac F430": Product name; manufactured by DIC Corporation, oligomer containing fluorine groups, hydrophilic groups, and no lipophilic groups "UCN-5090" ("Daimic Beads UCN-5090"): Product name; Cross-linked urethane resin particles manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd. "LCB-19": Product name; Chain acrylic resin manufactured by Mitsubishi Chemical Corporation "EBECRYL145": Product name; Daicel-Allnex Corporation, bifunctional acrylic monomer; PO-modified neopentyl glycol diacrylate "NK Ester 9G": Product name; difunctional acrylic monomer manufactured by Shin-Nakamura Chemical Co., Ltd. NK Ester 14G: Product name; difunctional acrylic monomer manufactured by Shin-Nakamura Chemical Co., Ltd. "IRGACURE184": Product name; BASF photopolymerization initiator

[0079] [Table 6]

[0080] [Production of developing rollers DH-1 to DH-2] To 100 parts by mass of styrene-butadiene rubber (SBR) (product name: Tufden 2003, manufactured by Asahi Kasei Corporation), the other materials shown in the column for component (1) in Table 7 were added, and the mixture was kneaded for 15 minutes in an internal mixer adjusted to 80° C. To this mixture, the materials shown in the column for component (2) in Table 7 were added. The mixture was then kneaded for 10 minutes in a two-roll mill cooled to a temperature of 25°C to obtain conductive rubber composition No. 1.

[0081] [Table 7]

[0082] A cylindrical body made of stainless steel (SUS304) with an outer diameter of 6 mm and a length of 270 mm was prepared. A conductive vulcanizing adhesive (product name: Metalock U-20, manufactured by Toyo Kagaku Kenkyusho) was applied to the peripheral surface of the cylindrical body and baked to prepare a conductive substrate. Using an extrusion molding device equipped with a crosshead, the substrate was used as the central axis and its peripheral surface was cylindrically coated with the prepared conductive rubber composition No. 1. The thickness of the coated conductive rubber composition was adjusted to 2.75 mm. The extruded roller was vulcanized in a hot air oven at 160° C. for 1 hour, and then the ends of the rubber layer were removed to make a roller with a length of 235 mm, thereby producing a roller with a preliminary coating layer.

[0083] The outer peripheral surface of the roller with the preliminary coating layer obtained above was ground into a crown shape using a plunge-cut grinding machine to produce Roller No. 1. The outer diameter of the obtained Roller No. 1 was measured at 1 mm intervals using a laser length measuring device (product name: Controller LS-7000, Sensor Head LS-7030R, manufactured by KEYENCE Corporation). The difference between the average outer diameter at a position 10 mm from the end of Roller No. 1 and the average outer diameter at the center of Roller No. 1 was defined as the crown amount. As a result, the average outer diameter at a position 10 mm from the end was 10.018 mm, and the average outer diameter at the center was 10.068 mm. Therefore, the crown amount was 50 μm. Roller No. 1 was then heated in a hot air oven at 195°C for 1 hour in an air atmosphere to produce Elastic Roller H1. Developing rollers DH-1 and DH-2 were obtained in the same manner as for developing roller 1, except that the resin layer coating material and the impregnation treatment liquid for the obtained elastic roller H1 were changed to those shown in Table 8.

[0084] [Table 8]

[0085] <Developer> [Production of magnetic material 1] An aqueous solution containing ferrous hydroxide was prepared by mixing 1.00 to 1.10 equivalents of caustic soda solution relative to elemental iron, P2O5 in an amount equivalent to 0.15 mass% of phosphorus relative to elemental iron, and SiO2 in an amount equivalent to 0.50 mass% of silicon relative to elemental iron into an aqueous solution of ferrous sulfate. The pH of the solution was adjusted to 8.0, and an oxidation reaction was carried out at 85°C while blowing in air to prepare a slurry containing seed crystals. Next, 0.90 to 1.20 equivalents of aqueous ferrous sulfate relative to the initial alkali content (sodium content of caustic soda) were added to this slurry. The pH of the slurry was maintained at 7.6, and air was blown in to promote oxidation, yielding an aqueous slurry containing magnetic iron oxide. After filtration and washing, the aqueous slurry was temporarily removed. A small amount of aqueous sample was taken and its water content was measured. Next, without drying, this aqueous sample was placed in another aqueous medium and redispersed in a pin mill while stirring and circulating the slurry. The pH of the redispersed solution was adjusted to approximately 4.8. Then, 1.6 parts by mass of n-hexyltrimethoxysilane coupling agent was added per 100 parts by mass of magnetic iron oxide while stirring, and hydrolysis was carried out. The amount of magnetic iron oxide was calculated by subtracting the water content from the water-containing sample. The dispersion was then thoroughly stirred, the pH of the dispersion was adjusted to 8.6, and the surface was treated with a silane coupling agent. The resulting hydrophobic magnetic material was filtered using a filter press, washed with a large amount of water, and then dried at 100°C for 15 minutes and at 90°C for 30 minutes. The resulting particles were then crushed to obtain Magnetic Material 1, with a volume average particle size of 0.21 μm.

[0086] [Production of polyester resin 1] The materials shown in Table 9 below were placed in a reaction vessel equipped with a condenser, stirrer, and nitrogen inlet tube, and reacted at 230°C for 10 hours under a nitrogen stream while distilling off the water produced. The reaction was then carried out under a reduced pressure of 5 to 20 mmHg. When the acid value reached 2 mgKOH / g or less, the mixture was cooled to 180°C, 10 parts by mass of trimellitic anhydride was added, and the reaction was carried out under normal pressure and sealed for 2 hours. The reaction product was then removed, cooled to room temperature, and pulverized to obtain polyester resin 1. Polyester resin 1 had a main peak molecular weight (Mp) of 10,500 as measured by gel permeation chromatography (GPC).

[0087] [Table 9]

[0088] [Production of Developer Particles 1] A container was charged with 720 parts by weight of ion-exchanged water and 450 parts by weight of a 0.1M Na3PO4 aqueous solution, and the mixture was heated to 60°C. Then, 67.7 parts by weight of a 1.0M CaCl2 aqueous solution was added to obtain an aqueous medium containing a dispersion stabilizer. Meanwhile, the materials listed in the Component 1 column of Table 10 below were uniformly dispersed and mixed using an Attritor (trade name, manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) to obtain a polymerizable monomer composition. This polymerizable monomer composition was heated to 60°C, and the materials listed in the Component 2 column of Table 10 below were added, mixed, and dissolved. Then, the materials listed in the Component 3 column as a polymerization initiator were added, mixed, and dissolved to obtain a developer composition.

[0089] [Table 10]

[0090] The developer composition was added to the aqueous medium and granulated by stirring at 12,000 rpm for 10 minutes in a TK homomixer (trade name, manufactured by Tokushu Kika Kogyo Co., Ltd.) at 60°C under a N2 atmosphere. The mixture was then reacted at 74°C for 6 hours while being stirred with a paddle impeller. After the reaction was complete, the suspension was cooled, washed with hydrochloric acid, filtered, and dried to obtain developer particles 1. Developer particles 1, which were the resulting magnetic developer, had a weight average particle size of 8.0 μm and an average circularity of 0.938.

[0091] [Production of Developer T-1] The materials shown in Table 11 below were placed in a Henschel mixer FM10C (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) and mixed for 5 minutes at a constant rotation speed of 4000 rpm. After mixing, coarse particles and the like were removed using a circular vibrating sieve equipped with a screen with a diameter of 500 mm and openings of 75 μm, to obtain developer T-1.

[0092] [Table 11]

[0093] [Production of Developer T-2] 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.

[0094] [Manufacturing of Developer TH-1] A 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. The number of parts by mass of magnetic material per developer particle raw material component 1 is shown in Table 12 below.

[0095] [Table 12]

[0096] The resulting developing roller and developer were evaluated as follows. [Measurements of T1, T2, T3, A1, and A2] Using the above-described microsampling mass spectrometry, thermal chromatograms were obtained for a first region extending from the outer surface of the developing roller to a depth of 0.1 μm, a second region extending from the back surface of the surface layer to a thickness of 0.1 μm, and a third region extending from the surface to a depth of 1.0 μm to 1.1 μm. From the obtained thermal chromatograms, the peak-top temperatures T1, T2, and T3 derived from the cross-linked urethane resin in each of the first, second, and third regions were determined. Furthermore, the peak-top temperature A1 derived from the cross-linked acrylic resin in the first region was determined. Furthermore, the peak-top temperature A2 derived from the cross-linked acrylic resin was measured from a second sample obtained by decomposing the cross-linked urethane resin contained in the sample sampled from the first region. The samples from each region were collected using a microsampling method using an FIB-SEM (product name: NVision40, manufactured by SII Nano Technology Co., Ltd.). Specifically, a razor was used to cut a rubber piece from the surface of the developing roller toward the base, exposing the cross sections of the surface layer and intermediate layer. The rubber piece was placed on the SEM sample stage with the roller cross section facing up, and a sampling probe was fixed to the rubber piece at a position corresponding to the roller surface. A cutting process was then performed using an FIB at a position 0.1 μm inward from the surface corresponding to the roller surface, thereby obtaining a sample of the first region. The second region was cut using 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 surface. A sampling probe was fixed to the cut surface, and a cutting process using an FIB was performed at a position 0.1 μm inward from the cut surface to obtain a sample of the second region. For the third region, the same rubber piece as above was cut using an FIB at a position 1.0 μm inward from the surface corresponding to the roller surface, thereby exposing the third region. A sampling probe was fixed to the exposed surface, and a cutting process using an FIB was performed at a position 0.1 μm inward from the exposed surface, thereby obtaining a sample of the third region. In all cutting processes, the FIB acceleration voltage was 30 kV and the beam current was 27 mA.

[0097] [Pyridine decomposition method] The pyridine decomposition method is a method for selectively decomposing urethane bonds. By performing the pyridine decomposition method on a sample having an IPN structure of cross-linked acrylic resin and cross-linked urethane resin, the cross-linked acrylic resin can be obtained after removing the structure derived from the cross-linked urethane. The change in peak temperature of the thermal chromatogram of the obtained crosslinked acrylic resin due to the presence or absence of the IPN structure can be observed. The pyridine decomposition method was specifically carried out as follows. Using a microtome, a sample was cut out from the surface of the developing roller at a thickness of 0.1 μm, and 500 mg of the sample was collected. 0.5 mL of a 3:1 mixture of pyridine (Wako Pure Chemical Industries, Ltd.) and water was added to the resulting sample, and the sample was decomposed by heating at 130°C for 15 hours in a sealed container made of fluororesin (Teflon®) with a stainless steel jacket. The pyridine was removed by treating the resulting decomposition product under reduced pressure. The sample thus obtained was subjected to the above-mentioned microsampling mass spectrometry to obtain the A2 value.

[0098] [Film thickness measurement] The thickness of the surface layer was measured by observing the cross section of the surface layer at nine locations (three axial locations and three circumferential locations) using an optical microscope or an electron microscope, and the average value was taken as the "thickness" of the surface layer.

[0099] [Volume resistivity measurement] The volume resistivity of the surface layer was measured using an atomic force microscope (AFM) (Q-scope250: Quesant) in the conductivity mode. First, a sheet measuring 2 mm in width and 2 mm in length was cut from the surface layer of the conductive roller using a manipulator. 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 to a thickness of 80 nm on the surface side of the surface layer of the sheet. Next, a DC power supply (6614C: Agilent) was connected to the platinum-deposited surface and 10 V was applied, and the free end of a cantilever was contacted with the other surface of the surface layer, and a current image was obtained through the AFM main body. Measurements were performed at 100 randomly selected locations on the surface, and the volume resistivity was calculated from the average current value of the 10 lowest current values ​​and the film thickness measurement results. The measurement conditions are shown below. Measurement mode: contact Cantilever: CSC17 Measurement range: 10nm x 10nm Scan rate: 4Hz Applied voltage: 10V

[0100] Example 1 The following specification changes were made to a laser printer (product name: LaserJet Pro P1606, manufactured by HP) used as an electrophotographic image forming apparatus. First, the developing bias was changed from AC (alternating current) to DC (direct current). Next, the developing bias was set to -500V, the potential of the light areas on the photosensitive drum to -300V, and the potential of the dark areas to -800V. Therefore, in this image forming apparatus, Vcontrast was 200V and Vback was 300V. The developing roller D-1 prepared above was stored in the process cartridge with these specification changes, and the developer T-1 prepared above was filled in to prepare a developing device. Note that the developing device of this process cartridge is originally a magnetic non-contact type developing device, but by attaching a developing roller with an outer diameter of 11.4 mm, it was converted into a magnetic contact type developing device.

[0101] [Q / M measurement] The prepared process cartridge was loaded into the laser printer and aged for 7 days under a H / H environment. Then, without changing the environment, the laser printer was used to output a solid white image, resulting in the surface of the developing roller being coated with developer. Next, under the same environment, the developer carried on the developing roller was collected by suction using a metal cylindrical tube and a cylindrical filter. The charge amount Q (μC) stored in the capacitor through the metal cylindrical tube and the mass M (g) of the sucked developer were measured. From these values, the charge amount per unit mass Q / M (μC / g) was calculated. Note that when a negatively charged developer is used, the sign of Q / M is negative, and the larger the absolute value of Q / M, the higher the developing roller's ability to impart charge to the developer.

[0102] [Fog measurement] Immediately after the Q / M measurement, a fog measurement was performed using the following procedure. First, the printer was stopped while outputting a solid white image under an H / H environment. At this time, the developer adhering to the photoreceptor was removed with tape, and the decrease in reflectance (%) relative to the reference was measured using a reflection densitometer (product name "TC-6DS / A"; manufactured by Tokyo Denshoku Co., Ltd.), and this was taken as the fog value. The decrease in reflectance is caused by the developer being transferred to the white areas of the paper that should have been left unprinted and white. Therefore, the smaller the fog value, the better.

[0103] [Ghost Rating] The printer and cartridge used in the Q / M and fog measurements were aged for one day in an environment with a temperature of 15°C and a relative humidity of 10%. After that, an image for examining ghosting was printed on an area at the edge of the image equivalent to one rotation of the developing roller, with solid black marks (squares and circles) arranged at equal intervals on a white background, and a halftone image was printed in the other area. The degree to which the ghost of the mark appeared on the output halftone image was evaluated according to the following criteria. Rank AA: No difference in shading is observed. Rank A: Slight differences in shading can be seen depending on the viewing angle. Rank B: Ghosts can be seen for one revolution of the developing roller. Rank C: A ghost image covering one revolution of the developing roller is clearly visible. Rank D: The stain can be seen over two or more revolutions of the developing roller.

[0104] Example 7, 13, 19, 30, Reference examples 2~6, 8~12, 14~18, 20~29, 31~33 > Evaluation was carried out in the same manner as in Example 1, except that the developing roller and developer were changed to those shown in Table 13. The results are shown in Tables 13-1 and 13-2.

[0105] [Table 13-1]

[0106] [Table 13-2]

[0107] <Comparative Examples 1 to 3> Evaluation was carried out in the same manner as in Example 1, except that the developing roller and developer were changed to those shown in Table 14. The results are shown in Table 14.

[0108] [Table 14]

[0109] <Discussion of evaluation results> Example 1 , 7, 13, 19, 30, Reference examples 2~6, 8~12, 14~18, 20~29, 31~33 In Example 1, a developer containing a magnetic material was used to evaluate the developing device. Each of the developing rollers housed in the developing device had a single elastic layer as a surface layer, and the elastic layer contained a cross-linked urethane resin and a cross-linked acrylic resin as binder resins. , 7, 13, 19, 30, Reference examples 2~6, 8~12, 14~18, 20~29, 31~33 Since A1>A2 for all of the developing rollers, it can be confirmed that the cross-linked urethane resin and the cross-linked acrylic resin form an interpenetrating polymer network structure in the first region from the outer surface of the elastic layer to a depth of 0.1 μm. This confirms that the developer is well charged and has good anti-fogging properties even in high-temperature environments. Example 1: The binder resin of the surface layer of the developing roller is a cross-linked urethane containing a polycarbonate structure. Reference example 2. Example 7. Reference example 8. Example 13. Reference example 14. Example 19. Reference example 20, Reference example 25~ 29. Example 30, Reference example 32, Reference example Among these, Examples 1, 7, 13, 19, and 30, which contain methyl groups in the side chains, have particularly high volume resistivities and are excellent in fogging resistance. On the other hand, in Comparative Example 1, the preliminary coating layer is impregnated with acrylic, but does not contain a chemical structure (crosslinked urethane resin) that imparts charge to the developer, resulting in a low Q / M and poor fogging. Comparative Example 2 contains a crosslinked urethane resin and a chain acrylic resin, but does not contain an interpenetrating polymer network structure of crosslinked acrylic resin and crosslinked urethane resin. Furthermore, in Comparative Example 3, the developer does not contain a magnetic material. As a result, these Comparative Examples do not impart effective charge and also result in poor fogging performance. [Explanation of symbols]

[0110] 1: Developing roller 105: Developer 109: Developing device 41:First area 42:Second area 43:Third area 44: Surface layer 45: Conductive substrate

Claims

1. A developing device including a developer and a developing member carrying the developer on its surface, The developing member comprises: a conductive substrate; a single elastic layer as a surface layer on the substrate; and the surface layer has a binder resin, the binder resin including a cross-linked urethane resin and a cross-linked acrylic resin; the volume resistivity of the binder resin is 1.0×10 10 Ω·cm or more and 1.0×10 18 Ω·cm or less; in a first region extending from the outer surface of the surface layer to a depth of 0.1 μm, the cross-linked urethane resin and the cross-linked acrylic resin form an interpenetrating polymer network structure, The crosslinked urethane resin is a polycarbonate-modified urethane resin having a structure having a side chain methyl group in a soft segment portion, The developer contains developer particles containing at least a binder resin and a magnetic material. A developing device characterized by:

2. A1 (°C) is defined as the peak top temperature of the thermal chromatogram derived from the crosslinked acrylic resin measured from the first sample sampled from the first region; 2. The developing device according to claim 1, wherein A1 and A2 satisfy the relationship represented by the following formula (1), where A2 (°C) is the peak top temperature of a thermal chromatogram derived from the crosslinked acrylic resin measured from a second sample obtained by decomposing the crosslinked urethane resin contained in the first sample: Formula (1) A1>A2.

3. the peak top temperature of the thermal chromatogram derived from the crosslinked urethane resin in the first region is defined as T1 (°C); 3. The developing device according to claim 1, wherein T1 and T2 satisfy the relationship represented by the following formula (2), where T2 (°C) is a peak top temperature of a thermal chromatogram derived from the crosslinked urethane resin contained in a second region having a thickness of 0.1 μm from the back surface of the surface layer facing the substrate toward the outer surface: Formula (2) T1>T2.

4. 4. The developing device according to claim 3, wherein T1 and T2 satisfy the relationship represented by the following formula (3): Formula (3) (T1-T2)>1.0 (°C).

5. 5. The developing device according to claim 1, wherein the surface layer of the developing member has a thickness of 2.0 μm or more and 150.0 μm or less.

6. the peak top temperature of the thermal chromatogram derived from the crosslinked urethane resin in the first region is defined as T1 (°C); a peak top temperature of a thermal chromatogram derived from the crosslinked urethane resin contained in a second region having a thickness of 0.1 μm from the back surface of the surface layer facing the substrate toward the outer surface is defined as T2 (° C.); 6. The developing device according to claim 5, wherein T1, T2, and T3 satisfy the relationships represented by the following formulas (4) and (5), where T3 (°C) is a peak top temperature of a thermal chromatogram derived from the crosslinked urethane resin in a third region of the surface layer that is 1.0 μm or more and 1.1 μm deep: Formula (4) T1>T3; Equation (5) |T1-T3|>|T3-T2|.

7. 7. The developing device according to claim 1, wherein the surface layer of the developing member further contains one or more of a modified silicone compound and a modified fluorine compound.

8. 8. An electrophotographic process cartridge configured to be detachably mountable to a main body of an electrophotographic image forming apparatus, comprising the developing device according to claim 1.

9. 8. An electrophotographic image forming apparatus comprising: an image carrier for carrying an electrostatic latent image; a charging device for primarily charging the image carrier; an exposure device for forming an electrostatic latent image on the primarily charged image carrier; a developing device 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 is the developing device according to any one of claims 1 to 7.

10. 10. An electrophotographic image forming apparatus according to claim 9, wherein said developing device is a magnetic contact type developing device.

11. A developing device including a developer and a developing member carrying the developer on its surface, The developing member comprises: a conductive substrate; a single elastic layer as a surface layer on the substrate; and the surface layer has a binder resin, the binder resin including a cross-linked urethane resin and a cross-linked acrylic resin; the volume resistivity of the binder resin is 1.0×10 10 Ω·cm or more and 1.0×10 18 Ω·cm or less; a first region extending from the outer surface of the surface layer to a depth of 0.1 μm contains both the cross-linked urethane resin and the cross-linked acrylic resin; The crosslinked urethane resin is a polycarbonate-modified urethane resin having a structure having a side chain methyl group in a soft segment portion, A1 (°C) is the peak top temperature of the thermal chromatogram derived from the crosslinked acrylic resin measured from the first sample sampled from the first region; When the peak top temperature of a thermal chromatogram derived from the crosslinked acrylic resin measured from a second sample obtained by decomposing the crosslinked urethane resin contained in the first sample is defined as A2 (°C), A1 and A2 satisfy the relationship represented by the following formula (1): Formula (1) A1>A2 the developer contains developer particles containing at least a binder resin and a magnetic material; A developing device characterized by:

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