CN117111426A - Electrophotographic member, electrophotographic process cartridge, and electrophotographic image forming apparatus - Google Patents

Abstract

The invention relates to an electrophotographic member, an electrophotographic process cartridge, and an electrophotographic image forming apparatus. An electrophotographic member comprising a conductive substrate, an elastic layer, and a surface layer containing fine particles and a binder resin and having a thickness of less than 1.0 μm, the fine particles having an average particle diameter of 0.1 μm to 0.9 μm, the fine particles having a volume occupancy of 60% to 99% by volume relative to 100% by volume of the binder resin in the surface layer, an elastic modulus E1 of the fine particles being 1,000MPa or more, an elastic modulus E2 of the binder resin being 2MPa to 200MPa, an MD-1 hardness H1 of the surface layer being 50 ° to 100 °, a difference (H1-H2) between the H1 and an MD-1 hardness H2 of the elastic layer being 5 ° or more.

Description

Electrophotographic member, electrophotographic process cartridge, and electrophotographic image forming apparatus

Technical Field

The present disclosure relates to an electrophotographic member to be incorporated into an apparatus employing an electrophotographic system. The present disclosure also relates to an electrophotographic process cartridge and an electrophotographic image forming apparatus each using the electrophotographic member.

Background

A developing method including the use of a magnetic mono-component or non-magnetic mono-component toner has been known as an image forming method for an electrophotographic image forming apparatus (also referred to as an "electrophotographic apparatus") such as a copying machine, a facsimile machine, a printer, or the like. Specifically, image formation is performed by the steps of:

(1) A charging step of charging an electrophotographic photosensitive member as a rotatable electrostatic latent image bearing member with a charging unit such as a charging roller;

(2) A forming step of exposing a surface of the charged photosensitive member to laser light to form an electrostatic latent image;

(3) A developing step of applying the toner in the toner container to the developing member with a toner supplying member, then adjusting the applied toner with a toner adjusting member to form a toner layer, and developing the electrostatic latent image with the toner in a portion where the photosensitive member and the developing member are in contact with each other;

(4) A fixing step of transferring the toner image on the photosensitive member onto the recording paper in the transfer portion with or without passing through an intermediate transfer belt, and then fixing the toner image onto the recording paper with heat and pressure in a fixing device; and

(5) And a cleaning step of removing toner remaining on the photosensitive member with a cleaning blade after transfer onto the recording paper.

Specifically, for example, the following members are employed as electrophotographic members for the above-described development step:

(a) A toner supply roller that is present in the toner container, supplies toner to the developing member, and peels off the post-development toner on the developing member;

(b) A toner regulating blade that forms a toner layer on the developing member so as to make the toner amount on the developing member constant; and

(c) A developing roller configured to close an opening of a toner container storing toner and to be partially exposed to the outside of the container so that the exposed portion may face the photosensitive member, the developing roller serving as a developing member for developing an electrostatic latent image on the photosensitive member with toner.

In these electrophotographic members, a roller member rotates, and supply and adjustment of toner and development of an electrostatic latent image with toner are performed by friction between rollers or between a blade and each roller.

In recent years, development of toners aiming at fixing at a lower temperature to reduce energy in the fixing step has been accelerated from an environmental point of view. Meanwhile, in the development step, friction between members has occurred for uniform toner conveyance or the like, and stress is applied to the toner with this event. In order to develop a latent image with a toner fixable at a low temperature, it is necessary to further reduce stress on the toner. In addition, various techniques for preventing cracking (warming) of the electrophotographic member itself and the toner have been studied.

In japanese patent application laid-open No.2004-301872, a developing roller for an electrophotographic apparatus is disclosed, which is obtained by disposing a surface layer formed of a resin composition obtained by blending a fluorine-containing olefin resin, an acrylic resin, and inorganic fine particles on a surface of an elastic base layer having elasticity. In the tensile test of JIS K7113, the No.2 test piece of the resin composition has an elongation of 100% or more and does not have any yield point, and the stress at 100% elongation is 25MPa or less. Further, it is described that the surface layer is excellent in toner conveyability, flexibility, and followability, and therefore, the surface layer has almost no cracks even when used for a long time.

Disclosure of Invention

At least one aspect of the present disclosure is directed to providing an electrophotographic member that can be used as a developing member, that alleviates stress applied to toner, that can prevent occurrence of image defects due to melt adhesion of toner, and that is excellent in durability. Further, at least one aspect of the present disclosure is directed to providing an electrophotographic process cartridge that facilitates stable formation of high-quality electrophotographic images. Further, at least one aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus that can stably form high-quality electrophotographic images.

According to at least one aspect of the present disclosure, there is provided an electrophotographic member comprising: a conductive substrate; an elastic layer on the substrate; and a surface layer on the elastic layer, the surface layer containing fine particles and a binder resin, the thickness of the surface layer being less than 1.0 μm, the fine particles having an average particle diameter of 0.1 μm to 0.9 μm, the volume occupancy of the fine particles being 60% to 99% by volume with respect to 100% by volume of the binder resin in the surface layer, wherein E1 and E2 satisfy the relationship represented by the following formulas (1) and (2):

E1≥1,000MPa (1)

200MPa≥E2≥2MPa (2)，

wherein E1 represents the elastic modulus of the fine particles, E2 represents the elastic modulus of the binder resin, E1 and E2 are obtained by measuring a force curve with SPM in a section in the thickness direction of the surface layer, and wherein H1 and H2 satisfy the relationship represented by the following formulas (3) and (4):

100°≥H1≥50° (3)

H1-H2≥5° (4)

wherein H1 represents MD-1 hardness measured at an indentation depth of 2mm by bringing a C-shaped indenter into contact with a surface of the surface layer opposite to a surface facing the elastic layer, and H2 represents MD-1 hardness measured at an indentation depth of 2mm by peeling the surface layer from the electrophotographic member to expose the surface of the elastic layer and bringing the C-shaped indenter into contact with the exposed surface of the elastic layer.

Further, according to at least one aspect of the present disclosure, there is provided an electrophotographic process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, the electrophotographic process cartridge including the above-described electrophotographic member.

Further, according to at least one aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including: an image bearing member for bearing an electrostatic latent image; charging means for charging the image bearing member once; an exposure device for forming an electrostatic latent image on the primary charged image bearing member; a developing member for developing the electrostatic latent image with toner to form a toner image; and a transfer device for transferring the toner image onto a transfer member, wherein the developing member is the above-described electrophotographic member.

Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Drawings

Fig. 1A is a schematic diagram for illustrating a lateral cross section of a developing roller according to an aspect of the present disclosure.

Fig. 1B is a schematic view for illustrating a lateral cross section of a developing roller according to an aspect of the present disclosure.

Fig. 2 is a schematic view for illustrating an electrophotographic process cartridge according to one aspect of the present disclosure.

Fig. 3 is a schematic diagram for illustrating an electrophotographic image forming apparatus according to an aspect of the present disclosure.

Detailed Description

In order to stably form a high-quality electrophotographic image with a toner whose fixing temperature is further reduced, further alleviation of stress applied to the toner by a developing member in a developing step may be effective. Further, it may be effective to prevent the toner from fusion-adhering to the toner regulating member abutting against the developing member.

Here, the present inventors mount the electrophotographic member described in japanese patent application laid-open No.2004-301872 as a developing roller on an electrophotographic process cartridge (hereinafter also referred to as "CRG"), and continuously output an electrophotographic image of toner having a low fixing temperature under a high-temperature and high-humidity environment. As a result, as the number of output sheets increases, streak-like defects appear in the electrophotographic image. Then, the inventors removed and studied the CRG on which the defective electrophotographic image was formed, and as a result, recognized that fusion adhesion of the toner to the toner regulating member abutting against the developing roller occurred.

The present inventors speculate that, in the above-described experiments including the CRG using the electrophotographic member mounted with the electrophotographic member described in japanese patent application laid-open No.2004-301872 as a developing roller, the cause of the above-described defect occurring as the number of output sheets increases is as follows.

That is, the defect may be caused by the fact that: in the electrophotographic apparatus including the developing member according to japanese patent application laid-open No.2004-301872, fusion adhesion of the toner deteriorated due to long-term formation of an electrophotographic image to a toner regulating member (hereinafter also simply referred to as "regulating member") occurs, so that the state of a toner layer formed on the surface of the developing member is uneven.

In view of the above, the present inventors have studied with the object of obtaining a developing member capable of uniformizing the state of the toner layer itself even when used for a long period of time.

As a result, the present inventors have found that an electrophotographic member having the following constitution is advantageous in achieving the above object.

The electrophotographic member according to the first aspect of the present invention is an electrophotographic member including: a conductive substrate; an elastic layer formed on the substrate; and a surface layer formed on the elastic layer, wherein the surface layer contains fine particles and a binder resin, wherein the thickness of the surface layer is less than 1.0 μm, wherein the fine particles have an average particle diameter of 0.1 μm to 0.9 μm, wherein the volume occupancy of the fine particles is 60% by volume or more and 99% by volume or less with respect to 100% by volume of the binder resin in the surface layer.

In a cross section in the thickness direction of the surface layer, a force curve is measured by tracing the cross section with a probe of a Scanning Probe Microscope (SPM). At this time, the elastic modulus of the fine particles and the elastic modulus of the binder resin are represented by E1 and E2, respectively, which are elastic moduli calculated by the hertz theory. E1 and E2 satisfy the relationship represented by the following formulas (1) and (2).

E1≥1,000MPa (1)

200MPa≥E2≥2MPa (2)

In addition, the MD-1 hardness measured at an indentation depth of 2mm by bringing the C-shaped indenter into contact with the surface of the surface layer of the electrophotographic member opposite to the surface on the side facing the elastic layer is represented by H1. Further, the MD-1 hardness measured at an indentation depth of 2mm by peeling the surface layer from the electrophotographic member to expose the surface of the elastic layer and bringing the C-shaped indenter into contact with the exposed surface of the elastic layer is represented by H2. In this case, H1 and H2 satisfy the relationship represented by the following formulas (3) and (4).

100°≥H1≥50° (3)

H1-H2≥5° (4)

< mechanism of Effect expression >

The inventors speculate that the reason why the electrophotographic member having the above-described constitution can stably form a satisfactory electrophotographic image is as follows. The mechanism of action of the electrophotographic member according to one aspect of the present disclosure described below is only one possible assumption, and the present disclosure is not limited thereto. In addition, the following description is given by taking a developing member having a roller shape (hereinafter also referred to as a "developing roller") as one example of an electrophotographic member, but the electrophotographic member according to the present disclosure is not limited to the developing roller.

The developing roller according to this aspect has a higher surface hardness than a developing roller having only an elastic layer because a surface layer is present on the elastic layer.

The elastic modulus (E1) of the fine particles in the surface layer is 1,000mpa or more, and thus has high hardness among components to be incorporated into the developing roller. The fine particles are introduced into the binder resin having an elastic modulus (E2) of 2MPa to 200MPa at a volume occupancy of 60% by volume to 99% by volume with respect to 100% by volume of the binder resin. In addition, the surface layer thickness is less than 1.0 μm.

In the developing roller according to this aspect, the surface layer having a relatively high hardness is disposed on the relatively soft elastic layer with a small thickness. That is, the surface layer contains fine particles of high hardness, but has a small thickness. Therefore, the influence of the physical properties of the elastic layer can support the stress on the toner to a greater extent than the influence of the physical properties of the surface layer. Further, an excessive stress is hardly applied to the toner due to the presence of the soft elastic layer. That is, even if an electrophotographic image is formed for a long period of time, the toner hardly deteriorates. For the reasons described above, it is possible that the toner melt adhesion to the regulating member hardly occurs.

Further, when used for the formation of an electrophotographic image for a longer period of time, even a developing roller in which stress to be applied to the toner is relieved may repeatedly rub against the regulating member, resulting in stress accumulating on the toner. However, in the developing roller according to this aspect, the outer surface of the developing roller includes a high-hardness surface layer, and thus the tackiness of the developing roller surface is suppressed. As a result, contamination from the toner hardly accumulates on the surface of the developing roller. Further, even when toner melt adhesion to the regulating member occurs, since toner is satisfactorily scraped off by the high-hardness fine particles in the surface layer of the developing roller according to this aspect, contamination hardly accumulates on the regulating member. For these reasons, it is possible that the toner layer having a uniform thickness can be stably formed on the developing roller.

< preferable composition and physical Property Range of surface layer >

The thickness of the surface layer is less than 1.0 μm, preferably 0.8 μm or less, more preferably 0.5 μm or less. It is conceivable that when the thickness is set to less than 1.0 μm, the stress on the toner can be reduced, and thus filming on the surface of the developing roller due to the toner can be more satisfactorily prevented. Although the lower limit of the thickness of the surface layer is not particularly limited, the thickness is preferably such that the developing roller can hold fine particles more reliably. Specifically, for example, the thickness is preferably 0.1 μm or more, more preferably 0.2 μm or more. The thickness of the surface layer falls within a range of preferably 0.1 μm or more and less than 1.0 μm, particularly preferably 0.1 μm or more and 0.8 μm or less, more preferably 0.1 μm or more and 0.5 μm or less. The thickness of the surface layer was measured as follows. The entire thickness direction cross section of the surface layer was observed with an optical microscope or an electron microscope, and the thickness of the binder resin in the portion without any fine particles was measured. The measurement sites were a total of 9 sites determined as follows: at 3 positions in the circumferential direction of the developing roller, at 3 positions in the direction perpendicular to the circumferential direction (axial direction). Further, an average value of the thicknesses at the respective measurement sites was employed as the thickness of the surface layer.

Projections derived from fine particles are formed on the surface of the developing roller. Further, even when the fine particles are not exposed from the surface layer but embedded in the surface layer, the manner in which the portions of the surface layer containing the fine particles are recessed and the manner in which the portions of the surface layer containing no fine particles are recessed are different from each other due to the difference in elastic modulus between the fine particles and the binder resin under the condition that the surface of the developing roller is pressurized. It is conceivable that even when the toner melt adhesive adheres to the regulating member, the toner melt adhesive can be satisfactorily scraped off by such surface characteristics of the developing roller.

The fine particles to be incorporated into the surface layer have an average particle diameter of 0.1 μm to 0.9 μm, preferably 0.1 μm to 0.5 μm. In the case where the average fine particles of the fine particles is larger than 0.9 μm, the stress of the toner may become higher between the regulating member and the fine particles, thereby making the film formation remarkable. Meanwhile, in the case where the average particle diameter of the fine particles is less than 0.1 μm, there is a concern that the toner that has been fixed and melt-adhered to the regulating member in the durable second half of the developing roller cannot be scraped off properly. In this case, the following may occur: the contamination on the regulating member grows to cause streaks in the circumferential direction of the developing roller, the streaks serving as a coating thereon, and the streaks become apparent as an image-negative effect.

Further, the average particle diameter of the fine particles is preferably equivalent to the thickness of the surface layer, and preferably falls within a range from the thickness of the surface layer plus 3 μm to the thickness minus 3 μm. In the present disclosure, the average particle diameter of the fine particles is a number average particle diameter. Although the method of measuring the number average particle diameter is not particularly limited, for example, when the number average particle diameter of fine particles is measured from the fine particles themselves as a raw material used in the coating material for forming a surface layer, the measurement may be performed using, for example, a fine particle size distribution measuring device. Specifically, for example, a fine particle size distribution measuring device (trade name: manufactured by Coulter Counter Multisizer 3;Beckman Coulter,Inc) and dedicated software (trade name: beckman Coulter Multisizer 3Version 3.51,Beckman Coulter,Inc manufactured) by pore resistance method can be used. In the case of measuring the number average particle diameter using the above-described apparatus, the pore diameter was set to 100 μm, measurement was performed in 25,000 effective measurement channels, and then analysis and calculation were performed on the measurement data. As the aqueous electrolyte solution for measurement, a solution obtained by dissolving extra sodium chloride in ion-exchanged water to a concentration of 1 mass% can be used. As such an aqueous electrolyte solution, for example, "ISOTON II" (trade name; manufactured by Beckman Coulter, inc.) is available on the market. Here, the dedicated software is preferably set as follows before measurement and analysis.

On the "interface for changing standard measurement method (SOM)" of the dedicated software, the total count in the control mode was set to 50,000 particles, the number of measurements was set to 1, and the Kd value was set to a value obtained using (standard particles (10.0 μm), beckman Coulter, inc. The threshold and noise level are automatically set by pressing a threshold/noise level measurement button. Further, the current was set to 1,600 μA, the gain (gain) was set to 2, the electrolyte solution was set to "ISOTON II" (trade name), and the irrigation of the oral canal after measurement was checked. On the "interface of the pulse-to-particle size conversion setting" of the dedicated software, the element interval (bin interval) is set to logarithmic particle size, the particle size elements (particle diameter bin) are set to 256 particle size elements, and the particle size range is set to 2 to 60 μm.

At least one aspect of a specific measurement method is described below.

(1) About 200mL of the aqueous electrolyte solution was placed in a 250-mL round bottom glass beaker dedicated to Multisizer 3 and placed on a sample holder and stirred by a stirring bar counter clockwise at 24 revolutions per second. Dirt and air bubbles in the mouth tube are then removed by the "mouth tube flushing" function of the analysis software.

(2) About 30mL of the aqueous electrolyte solution was placed in a 100-mL flat bottom glass beaker. To this aqueous solution, about 0.3mL of a dilution liquid of "Contaminon N" (trade name; manufactured by Fuji Film-Wako Pure Chemical Industries, ltd.) was added by diluting 3 times by mass with ion-exchanged water. "Contaminon N" is a 10 mass% aqueous solution of a neutral detergent for cleaning a precision measuring instrument.

(3) To a water tank of an ultrasonic disperser (trade name: ultrasonic Dispersion System Tetora 150,Nikkaki Bios Co, manufactured by ltd.) having an electric output of 120W and introducing 2 oscillators having oscillation frequencies of 50kHz in a state of phase shift of 180 degrees, a predetermined amount of ion exchange water and about 2mL of Containan N (trade name) were then added.

(4) The beaker in the above (2) was set in a beaker fixing hole on the ultrasonic disperser, and the ultrasonic disperser was started. Then, the height position of the beaker is adjusted in such a manner as to maximize the resonance state of the liquid surface of the aqueous electrolyte solution in the beaker.

(5) While the aqueous electrolyte solution in the beaker in the above (4) was irradiated with ultrasonic waves, about 10mg of toner (particles) was added to the aqueous electrolyte solution in small portions and dispersed. Then, the ultrasonic dispersion treatment was continued for an additional 60 seconds. In the ultrasonic dispersion, the water temperature in the water tank is appropriately adjusted to 10 to 40 ℃.

(6) The aqueous electrolyte solution in which the toner (particles) in (5) was dispersed was dropped into the round-bottomed beaker provided on the sample holder in (1) above using a pipette, and the measured concentration was adjusted to about 5%. Then, measurement was performed until the measured particle number reached 50,000.

(7) The measurement data are analyzed with dedicated software connected to the apparatus to calculate the weight average particle size (D4). When the graph/volume% is set on the dedicated software, the "average diameter" at the analysis/volume statistics (arithmetic mean) interface is the weight average particle diameter (D4). When the graph/number% is set on the dedicated software, "average diameter" on the "analysis/number statistics (arithmetic average)" interface is the number average particle diameter (D1). In addition, when the average particle diameter of the fine particles is measured from the surface layer, the measurement can be performed by, for example, the method described below.

First, in the case where the electrophotographic member is a developing roller, a sample for measurement was cut according to the following method. The developing roller was cooled to-150 ℃ and a rubber sheet on which such a cross section in the thickness direction of the surface layer appeared and passed through the top of the convex portion on the outer surface of the developing roller was cut out using a cryo-microtome (UC-6 (product name), manufactured by Leica Microsystems). The number average particle diameter of the resin particles present in the surface layer can be measured as follows. First, from the sectional area of the resin particles in the obtained sample, the equivalent circle diameter (Ds) of each resin particle is calculated. Here, each resin particle is assumed to be a spherical particle, and the cross section is assumed to be a cross section obtained by randomly cutting the spherical particle. Then, the particle diameter D of each resin particle is calculated from the circular equivalent diameter Ds according to expression (1).

D＝4/π×D _S (1)

The above calculation was performed for a total of 100 particles per resin particle in the sample. This calculation was performed with respect to 9 samples taken from a total of 9 points, wherein 3 equidistant points in the axial direction of the developing roller and 3 equidistant points in the circumferential direction of the developing roller. Then, an arithmetic average value of the obtained particle diameters D of the respective samples was calculated, and the obtained value was determined as the number average particle diameter of the developing roller.

The volume occupancy of the fine particles with respect to 100% by volume of the binder resin to be incorporated into the surface layer is 60% by volume or more and 99% by volume or less. The volume occupancy is preferably 70% by volume or more and 95% by volume or less. When the volume occupancy falls within the above range, embrittlement of the surface layer due to excessive increase in the content of the resin fine particles relative to the binder resin in the surface layer can be satisfactorily suppressed, and thus scraping (shaving) and cracking of the surface layer can be satisfactorily prevented. Further, even when fixation or fusion adhesion of the toner to the above-described regulating member occurs, the toner can be satisfactorily scraped off. The method of measuring the volume occupancy of the fine particles with respect to the binder resin in the surface layer is explained below.

The volume occupancy of the fine particles in the surface layer is the same as the area ratio obtained from the sectional area in the thickness direction of the surface layer. Thus, the ratio of the sum of the areas of the fine particles observed in the cross section of the sample prepared as described above to the cross-sectional area of the sample was calculated. This calculation was performed with respect to the 9 samples prepared above, and the arithmetic average was taken as the volume occupancy of the fine particles in the surface layer.

The elastic modulus (E1) of the fine particles to be incorporated into the surface layer is 1,000MPa or more, as calculated by Hertz theory by measuring a force curve with SPM in a cross section in the thickness direction of the surface layer. The elastic modulus is preferably 1,500MPa or more. When the elastic modulus is 1,000mpa or more, the toner patch that has been fixed and melt-adhered to the toner regulating member can be scraped off more reliably.

In addition, the elastic modulus (E2) of the binder resin to be incorporated into the surface layer calculated by the above method is 2MPa or more and 200MPa or less. E2 is particularly preferably 25MPa or more and 200MPa or less. The surface layer according to the present disclosure contains fine particles having E1 of 1,000mpa or more, and although its thickness is as small as less than 1.0 μm, its content is as high as 60 to 99% by volume with respect to the binder resin in the surface layer. In general, a resin layer containing particles having a high elastic modulus at a high content tends to become brittle as its thickness becomes smaller. However, in the resin layer according to the present disclosure, the elastic modulus E2 of the binder resin falls within a range of 2MPa to 200 MPa. Probably for the above reasons, embrittlement of the surface layer can be prevented despite the fact that a large amount of fine particles having a high elastic modulus are put into the surface layer.

In order to obtain the elastic modulus E1 of the fine particles and the elastic modulus E2 of the binder resin in the thickness direction section of the surface layer, first, a force curve is measured with SPM. The mode of the SPM for measuring the force curve is set to the contact mode and its force distance and trigger point are set to 500nm and 0.01V, respectively. Further, a silicon cantilever of a dynamic mode such as "OMCL-AC-160TS" (manufactured by product name, olympus Corporation, spring constant=47.08N/m) was used as the cantilever, and the scanning frequency thereof was set to 1Hz.

MD-1 hardness (H1) is 50 ° or more and 100 ° or less measured at an indentation depth of 2mm by bringing a C-shaped indenter into contact with a surface of the surface layer of the electrophotographic member of the present disclosure opposite to the surface on the side facing the elastic layer. The hardness is preferably 70 ° or more and 95 ° or less. When the hardness is more than 100 °, occurrence of filming causes a concern due to an increase in stress to the toner. Meanwhile, when the hardness is less than 50 °, there is a concern that the contact area of the abutting portion between the toner and the developing roller increases, resulting in fixation (initial fixation) of the toner especially after it is left under a high-temperature and high-humidity environment for a long period of time.

MD-1 hardness measured at an indentation depth of 2mm by peeling the surface layer from the electrophotographic member of the present disclosure to expose the surface of the elastic layer and bringing the C-shaped indenter into contact with the exposed surface of the elastic layer is represented by H2. In this case, the difference (H1-H2) between the MD-1 hardness H1 and H2 is 5 DEG or more. When the value is less than 5 °, since the suppression of the tackiness of the electrophotographic member becomes insufficient, occurrence of filming causes a fear, and thus accumulation of toner contamination thereon is accelerated.

The 10% modulus value of the binder resin used in the electrophotographic member of the present disclosure is preferably 2MPa or more and 20MPa or less. The term "10% modulus" refers to the tensile stress when the resin is elongated by 10%. When the electrophotographic process cartridge including the member runs out of toner, the melt adhesion of the toner to the regulating member may be remarkable particularly when the frequency of toner replacement on the developing roller by new toner is reduced. At this time, the portion on the regulating member where the melt-adhesion of the toner occurs has a size, and thus penetration thereof into the surface of the developing roller occurs. At this time, when the binder resin of the developing roller has flexibility represented by the above characteristics, no particular crack or peeling occurs. Meanwhile, when the 10% modulus value of the binder resin is more than 20MPa, occurrence of cracks or peeling causes concern due to poor flexibility of the binder resin. Meanwhile, when the 10% modulus value of the binder resin is less than 2MPa, toner contamination on the surface of the developing roller causes concern because a state in which the molecular mobility of the resin is high is established. Therefore, occurrence of film formation causes concern.

< construction of developing roller >

A schematic view of a transverse cross section in a direction perpendicular to an axial direction of a developing roller according to an aspect of the present disclosure is shown in each of fig. 1A and 1B, but the shape of the developing roller is not limited thereto.

As shown in fig. 1A, the developing roller 1 includes a base body 2 having a cylindrical shape or a hollow cylindrical shape and a surface layer 4, and further includes an elastic layer 3 between the base body 2 and the surface layer 4. That is, the developing roller includes a substrate, an elastic layer on the substrate, and a surface layer on the elastic layer.

Other configurations of the developing roller 1 may be a three-layer structure in which the intermediate layer 5 is disposed between the elastic layer 3 and the surface layer 4, or a configuration in which a large number of intermediate layers 5 are disposed therebetween, as shown in fig. 1B. A known intermediate layer for a developing roller may be used as the intermediate layer.

< surface layer >

[ Fine particles ]

The fine particles according to the present disclosure satisfy the following features (I) and (II):

(I) The average particle diameter thereof is 0.1 μm to 0.9 μm; and

(II) when the elastic modulus of the fine particles, which is the elastic modulus calculated by the hertz theory by measuring a force curve in a thickness direction section of the surface layer with a probe of the SPM apparatus, is represented by E1, E1 satisfies the relationship represented by the following formula (1).

E1≥1,000MPa (1)

The fine particles according to the present disclosure may be used without any particular limitation as long as the fine particles satisfy the above-described features (I) and (II). Specifically, fine particles such as polyurethane resin, polyester resin, polyether resin, polyamide resin, acrylic resin, polycarbonate resin, phenolic resin, or the like may be used as the organic filler. Further, these particles are preferably crosslinked resin particles satisfying the formula (1).

In addition, insulating or conductive inorganic fillers may be used. Examples of the insulating inorganic filler include quartz fine powder, silica particles, diatomaceous earth, zinc oxide, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, mica powder, aluminum sulfate, calcium sulfate, barium sulfate, and glass fiber. The surface of each of these inorganic fillers may be hydrophobized by treatment with an organosilicon compound such as polydiorganosiloxane.

Examples of the conductive inorganic filler include: carbon-based substances such as carbon black and graphite; metals or alloys such as aluminum, silver, gold, tin-lead alloys and copper-nickel alloys; metal oxides such as zinc oxide, titanium oxide, aluminum oxide, tin oxide, antimony oxide, indium oxide, and silver oxide; and a substance obtained by conductive metal plating of various insulating fillers with copper, nickel or silver.

[ Binder resin ]

The binder resin satisfies the following requirement (i):

requirement (i): when the elastic modulus of the binder resin, which is the elastic modulus calculated by the hertz theory by measuring a force curve in a thickness direction section of the surface layer with a probe of the SPM apparatus, is represented by E2, E2 satisfies the relationship represented by the following formula (2).

200MPa≥E2≥2MPa (2)

The resin satisfying the above elastic properties may be used as the binder resin without any particular limitation. Specific examples thereof include polyurethane resins, acrylic resins, polyolefin resins, epoxy resins, polyester resins, and silicone resins (silicone resins). These resins may be used alone or as a mixture thereof.

Among them, polyurethane resin has moderate flexibility and is therefore suitable for satisfying the formula (2). The elastic modulus of even resins other than polyurethane resins can be adjusted within the above-mentioned elastic modulus range by a method such as adjusting the size of the molecular weight between the crosslinking points thereof, or the like.

The 10% modulus value of the binder resin preferably falls within a range of 2MPa or more and 20MPa or less. When the 10% modulus value falls within this range, the binder resin exhibits moderate elongation properties, and thus can satisfactorily follow deformation of the elastic layer. Meanwhile, when the 10% modulus value is 20MPa or less, the resin can follow the deformation of the elastic layer, and thus tearing and cracking thereof can be suppressed. In addition, when the 10% modulus value is 2MPa or more, the tackiness of the surface layer is suppressed from becoming remarkable, and thus the following is avoided: contamination of the surface layer occurs to cause film formation.

[ measurement of elastic modulus E1 and elastic modulus E2 ]

As described below, the elastic modulus E1 of the fine particles in the surface layer and the elastic modulus E2 of the binder resin therein were measured. Such a sample is produced from the surface layer such that a section corresponding to the entire thickness of the surface layer is exposed. Although the size of the sample is not particularly limited, the sample may be, for example, a cubic shape with a side length of 100 μm. Then, a probe of a Scanning Probe Microscope (SPM) is brought into contact with the fine particle portion and the binder resin portion exposed at the surface of the obtained sample (to which the entire thickness direction cross section of the surface layer is exposed) to measure a force curve. The elastic moduli E1 and E2 are determined from the resulting force curve based on hertz theory. For example, "MFP-3D-Origin" (manufactured by product name Oxford Instruments) may be used as the SPM. When the device is used, the elastic moduli E1 and E2 are automatically output from the measured force curve.

Here, the method of manufacturing the sample from the surface layer is not particularly limited, and is, for example, a method including using a sharp razor or a microtome, or a method including using a Focused Ion Beam (FIB).

In addition, the position where the sample is obtained is not particularly limited, and may be set to, for example, the center in a direction (longitudinal direction) perpendicular to the circumferential direction of the developing roller. Further, in the surface (observation surface) of the sample corresponding to the thickness direction cross section of the surface layer, the position of measuring the force curve with the SPM is not particularly limited, and the measurement needs only to be performed in the fine particle portion and the binder resin portion exposed to the observation surface. However, from the viewpoint of performing more stable measurement, it is preferable to perform measurement in a region of the observation surface ranging from T/3 to 2T/3 in the depth direction from the outer surface side of the surface layer, that is, a fine particle portion and a binder resin portion exposed in the central region when the observation surface is divided into three equal parts in the thickness direction thereof.

Further, the elastic modulus E1 in the present disclosure is a value determined as follows: measuring force curves at 10 arbitrary sites of the fine particle portion exposed to the observation surface with SPM, and calculating elastic moduli from the force curves; an arithmetic average of 8 values other than the maximum value and the minimum value in the calculated elastic modulus was used as E1.

Similarly, the elastic modulus E2 in the present disclosure is a value determined as follows: measuring force curves at 10 arbitrary sites of the binder resin portion exposed to the observation surface with SPM, and calculating elastic moduli from the force curves; an arithmetic average of 8 values other than the maximum value and the minimum value in the calculated elastic modulus was used as E2.

Regarding the measurement of the force profile, the mode of the SPM for force profile measurement was set to the contact mode, and the force distance and the trigger point thereof were set to 500nm and 0.01V, respectively. Further, a silicon cantilever of a dynamic mode such as "OMCL-AC-160TS" (manufactured by product name, olympus Corporation, spring constant=47.08N/m) was used as the cantilever, and the scanning frequency thereof was set to 1Hz.

[ measurement of MD-1 hardness ]

The electrophotographic member serving as a measurement object was placed under an environment of a temperature of 23 ℃ and a relative humidity of 53% for 24 hours. Next, by making 2mm indentations in the member, the hardness of the electrophotographic member was measured using a micro rubber durometer (product name: MD-1capa,Kobunshi Keiki Co, manufactured by ltd.) and a C-type indenter (diameter: 1.00 mm) at each of 12 points determined as follows: a central portion of the surface layer of the electrophotographic member and positions each 20mm inward from both end portions thereof were determined, and four points were determined in each of the three portions in increments of 90 ° in the circumferential direction thereof. The average of these measurements was used as the MD-1 hardness H1 of the surface layer.

Next, the surface layer was carefully removed from the above electrophotographic member, and measurement was performed by the above method in a state where the elastic layer was exposed. Thus, the MD-1 hardness H2 of the elastic layer was obtained. Although the method of removing the surface layer is not particularly limited, for example, a razor or a microtome may be used.

[ other Components ]

In addition to the above components, any one or more additives selected from the modified silicone compound (silicone compunds) or the modified fluorine compound may be incorporated into the surface layer to the extent that the function of the surface layer is not inhibited. In addition, components such as a crosslinking agent, a plasticizer, a filler, an extender, a vulcanizing agent, a vulcanization aid, a crosslinking aid, an antioxidant, an aging inhibitor, a processing aid, and a leveling agent may be incorporated therein.

< method for producing surface layer >

Although the method of producing the surface layer according to the present embodiment is not particularly limited, it preferably includes a coating molding method using a liquid coating material. The surface layer may be formed by: for example, each material for the surface layer is dispersed and mixed in a solvent to prepare a coating material, the coating material is applied onto an elastic roller having an elastic layer formed on a conductive substrate, and the applied coating material is dried to solidify the coating material or the coating material is heated to solidify the coating material.

When a crosslinked polyurethane resin is used as the binder resin, the solvent is preferably a polar solvent from the viewpoint of its compatibility with the polyol and isocyanate compound used as the resin raw materials. Examples of polar solvents 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. Solvents selected from these polar solvents and well compatible with other materials may be used alone or as a mixture thereof.

In addition, from the viewpoint of uniformly dispersing fine particles, it is preferable to adjust the solid content freely adjustable by the mixing amount of the solvent at the time of preparation of the coating material to 20 mass% or more and 40 mass% or less. Known dispersing devices using beads, such as sand mills, paint agitators, dinokill or pearl mills, may be used for dispersing and mixing. Further, any of dip coating, ring coating, spray coating, and roll coating may be used as a method of application.

The temperature at which the coating material is dried and solidified or heated and solidified is not particularly limited as long as the crosslinking of the polyurethane resin proceeds, but a temperature of 50 ℃ or higher is preferable, and a temperature of 70 ℃ or higher is more preferable.

< matrix >

The substrate serves as an electrode and a supporting member of the developing member, and includes any one of the conductive materials as described below: metals or alloys, such as aluminum, copper alloys or stainless steel; iron subjected to an electroplating treatment with chromium or nickel; and a synthetic resin having conductivity. The matrix may be solid or hollow.

< elastic layer >

A known material for an elastic layer or a material usable for an elastic layer may be used as the material for forming an elastic layer. It is generally preferable that the elastic layer is formed of a molded 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), fluoro rubber, silicone rubber, epichlorohydrin rubber, hydrogenated NBR, and urethane rubber. These rubbers may be used alone or as a mixture thereof.

Among them, silicone rubber is particularly preferable because rubber hardly causes permanent compression deformation in the elastic layer even when any other member is abutted against the elastic layer for a long time. Examples of the silicone rubber include a cured product of an addition-curable silicone rubber. In addition, a cured product of the addition-curable dimethylsiloxane is particularly preferable.

Various additives, such as conductivity imparting agents, non-conductive fillers, crosslinking agents, and catalysts, are suitably blended into the elastic layer. Fine particles of any of the following materials may be used as the conductivity imparting agent: carbon black; conductive metals such as aluminum or copper; and conductive metal oxides such as zinc oxide, tin oxide, or titanium oxide. At least one of these materials may be used. Among them, carbon black is particularly preferable because carbon black can be obtained in a relatively easy manner and provides satisfactory conductivity. When carbon black is used as the conductivity imparting agent, carbon black is preferably blended in an amount of 2 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the rubber material in the material for forming an elastic layer.

Examples of nonconductive fillers include silica, quartz powder, titanium oxide, zinc oxide, and calcium carbonate. At least one of them may be used.

Examples of the crosslinking agent include di-t-butyl peroxide, 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane, and dicumyl peroxide. At least one of them may be used.

< developing device >

The developing member according to each aspect of the present disclosure may be applied to a developing device using a magnetic one-component developer or a non-magnetic one-component developer. Further, the developing member according to each aspect of the present disclosure may be applied to a developing device that is not in contact with an electrophotographic photosensitive member and a developing device in which the developing member is in contact with an electrophotographic photosensitive member, and a developing device using a two-component developer.

< electrophotographic Process cartridge >

Fig. 2 is a schematic view for illustrating an electrophotographic process cartridge according to one embodiment of the present disclosure. The electrophotographic process cartridge includes: an image bearing member (photosensitive member) 21 such as a photosensitive drum; a charging device including a charging member (charging roller) 22; and a developing device including a developing member (developing roller) 24. Further, the developing device has built therein a supply roller 25 as a toner supply member that abuts against the developing member 24 and an adjusting blade 26 serving as a toner adjusting member. Further, a cleaning member (cleaning blade) 30 that removes residual toner on the image bearing member 21 is disposed in front of the charging member 22.

< electrophotographic image Forming apparatus >

Fig. 3 is a schematic view of an electrophotographic image forming apparatus in which the electrophotographic process cartridge of fig. 2 is mounted. Further, the electrophotographic process cartridge is supported by a housing (not shown), and is detachably mounted on the main body of the electrophotographic image forming apparatus.

The image bearing member 21 is uniformly charged (primary charging) by a charging member 22 connected to a bias power supply (not shown). At this time, the charging potential of the image bearing member 21 is-800V or more and-400V or less. Next, exposure light 23 for writing an electrostatic latent image is applied from an exposure device (not shown) onto the image bearing member 21 to form an electrostatic latent image on the surface thereof. The LED light and the laser light may each be used as the exposure light 23. The surface potential of the exposed portion of the image bearing member 21 is, for example, -200V or more and-100V or less.

Next, the toner charged to the negative polarity is applied to the electrostatic latent image by the developing member 24 to form a toner image on the image bearing member 21. Thus, the electrostatic latent image is converted into a visible image (development). At this time, a voltage of, for example, -500V or more and-300V or less is applied to the developing member 24 by a bias power supply (not shown). The developing member 24 is in contact with the image bearing member 21 with a nip width therebetween, for example, 0.5mm or more and 3mm or less. In the electrophotographic process cartridge of the present embodiment, the supply roller 25 is brought into abutment with the developing roller 24 in a rotatable state on the upstream side of the rotation of the developing roller 24 with respect to the abutment portion between the regulating blade 26 serving as the toner regulating member and the developing roller 24.

The toner image developed on the image bearing member 21 is primarily transferred onto an intermediate transfer belt 27 serving as a transfer unit. The primary transfer member 28 abuts against the rear surface of the intermediate transfer belt 27, and application of a voltage of +100deg.V or more and +1,500V or less to the primary transfer member 28 causes primary transfer of the toner image having the negative polarity from the image bearing member 21 onto the intermediate transfer belt 27. The primary transfer member 28 may be in the shape of a roller as shown in the figure, or any other shape, such as a blade shape.

Further, an example of the electrophotographic image forming apparatus of fig. 3 is a full-color image forming apparatus, and the above-described respective steps, that is, charging, exposure, development, and primary transfer, are performed for each of yellow, cyan, magenta, and black. Therefore, in the electrophotographic image forming apparatus shown in fig. 3, a total of four electrophotographic process cartridges each having toner of one of the respective colors built therein are detachably mounted to the main body of the electrophotographic image forming apparatus. Further, the above-described respective steps, that is, charging, exposure, development, and primary transfer are sequentially performed with a predetermined time difference therebetween to establish a state in which four-color toner images representing a full-color image are superimposed on the intermediate transfer belt 27.

As the intermediate transfer belt 27 rotates, the toner image on the intermediate transfer belt 27 is conveyed to a position facing the secondary transfer member 29. At a predetermined timing, the recording sheet is conveyed to a space between the intermediate transfer belt 27 and the secondary transfer member 29 along the recording sheet conveyance path 32, and application of a secondary transfer bias to the secondary transfer member 29 causes the toner image on the intermediate transfer belt 27 to be transferred onto the recording sheet. At this time, the bias voltage to be applied to the secondary transfer member 29 is +1000v or more and +4000V or less. The secondary transfer member 29 is also included in the transfer unit.

The recording paper on which the toner image has been transferred by the secondary transfer member 29 is conveyed to the fixing device 31 through the recording paper conveying path 32. In the fixing device 31, the toner image on the recording sheet is fused and fixed onto the recording sheet, and then the recording sheet is discharged to the outside of the electrophotographic image forming apparatus. Thus, the printing operation is completed.

The toner remaining on the image bearing member 21 from the image bearing member 21 that is not transferred onto the intermediate transfer belt 27 is scraped off by the cleaning member 30 for cleaning the surface of the image bearing member 21. Thus, the surface of the image bearing member 21 is cleaned.

Although the constitution including the intermediate transfer belt has been described above as the transfer unit, the unit is not limited thereto, and may be a transfer unit of a direct transfer system that directly transfers the toner image from the image bearing member onto the recording paper.

According to one aspect of the present disclosure, an electrophotographic member can be provided that can suppress adverse effects accompanying toner contamination and that has few cracks even when printing is performed on many sheets of paper. Further, according to another aspect of the present disclosure, an electrophotographic process cartridge and an electrophotographic image forming apparatus each including the electrophotographic member may be provided.

Examples

The present disclosure is specifically described below by way of manufacturing examples and embodiments. However, the present disclosure is not limited thereto.

< Fine particles >

[ Fine particles 1]

Crosslinked acrylic particles having an average particle diameter of 0.4 μm were synthesized by the same production method as in example 1 of Japanese patent application laid-open No. 2002-003511.

That is, 100 parts by weight of methyl methacrylate, 0.04 parts by weight of ethylene glycol dimethacrylate and 900 parts by weight of ion exchange water were charged into a four-necked flask having a capacity of 1 liter including a thermometer and a nitrogen inlet pipe, and these materials were mixed. Further, while the mixture was stirred in a nitrogen stream, the temperature of the mixture was raised to 80 ℃.

Next, 0.2 parts by weight of potassium persulfate was dissolved in 5 parts by weight of ion-exchange water, and 5.2 parts by weight of ion-exchange water was added to the reaction liquid in the above four-necked flask. The reaction liquid was reacted for 5.00 hours while maintaining the temperature of the reaction liquid at 80 ℃ to provide a dispersion of crosslinked acrylic particles. The number average particle diameter (or volume average particle diameter) of the obtained crosslinked acrylic particles was 0.40. Mu.m. Here, the number average particle diameter is a value measured by the following method. The number average particle diameter of the fine particles in this example is a value measured by the above-described method.

The crosslinked acrylic particles thus obtained were used as the fine particles 1.

[ Fine particles 2]

As the fine particles 2, "MX-80H3wT" (product name, material: crosslinked acrylic acid series, average particle diameter: 0.8 μm, manufactured by Soken Chemical & Engineering Co., ltd.) was prepared.

[ Fine particles 3]

Crosslinked acrylic particles having an average particle diameter of 0.9 μm were synthesized in the same manner as in the fine particles 1 except that the polymerization time was set to 11.25 hours. The resulting crosslinked acrylic particles were used as the fine particles 3.

[ Fine particles 4]

Crosslinked acrylic particles having an average particle diameter of 0.1 μm were synthesized in the same manner as the fine particles 1 except that the polymerization time was set to 1.25 hours. The fine particles thus obtained are used as the fine particles 4.

[ Fine particles 5]

"EPOSTAR S6" (product name, material: melamine, average particle size: 0.4 μm, manufactured by Soken Chemical & Engineering co., ltd.) was prepared as fine particles 5.

[ Fine particles 6]

Crosslinked acrylic particles having an average particle diameter of 0.8 μm were synthesized in the same manner as in the fine particles 1 except that the polymerization time was set to 10.00 hours. The resulting crosslinked acrylic particles were used as the fine particles 6.

[ Fine particles 7]

Crosslinked acrylic particles having an average particle diameter of 0.2 μm were synthesized in the same manner as in the fine particles 1 except that the polymerization time was set to 2.50 hours. The resulting crosslinked acrylic particles were used as the fine particles 7.

[ Fine particles 8]

Crosslinked acrylic particles having an average particle diameter of 0.7 μm were synthesized in the same manner as in the fine particles 1 except that the polymerization time was set to 8.75 hours. The resulting crosslinked acrylic particles were used as the fine particles 8.

[ Fine particles 9]

"SEAHOSTAR KE-S S" (product name, material: silica, average particle diameter: 0.5 μm, manufactured by Nippon Shokubai Co., ltd.) was prepared as the fine particles 9.

[ Fine particles 10]

"PT-301" (product name, material: titanium oxide, average particle diameter: 0.3 μm, ishihara Sangyo Kaisha, manufactured by Ltd.) was prepared as the fine particle 10.

[ Fine particles 11]

Crosslinked acrylic particles having an average particle diameter of 1.0 μm were synthesized in the same manner as the fine particles 1 except that the polymerization time was set to 12.50 hours. The obtained crosslinked acrylic particles were used as the fine particles 11.

[ Fine particles 12]

"MP-1000" (product name, material: non-crosslinked acrylic resin, average particle diameter: 0.4 μm, manufactured by Soken Chemical & Engineering Co., ltd.) was prepared as the fine particles 12.

[ Fine particles 13]

Crosslinked acrylic particles having an average particle diameter of 0.04 μm were synthesized in the same manner as in the fine particles 1 except that the polymerization time was set to 0.50 hours. The resulting crosslinked acrylic particles were used as the fine particles 13.

The materials and number average particle diameters (μm) of the fine particles 1 to 13 are shown together in table 1. The number average particle diameters of the respective fine particles nos. 1 to 13 were calculated according to the above-described calculation method.

TABLE 1

< Synthesis of resin raw Material >

[ Synthesis of isocyanate group-terminated prepolymer 1 ]

Under a nitrogen atmosphere, 100.0 parts by mass of a polytetramethylene glycol polyol (product name: PTMG 2000,Hodogaya Chemical Co, manufactured by Ltd.) was gradually dropped into 74.1 parts by mass of pure MDI (product name: MILLIONATE MT, manufactured by Tosoh Corporation) in a reaction vessel while maintaining the temperature in the reaction vessel at 65 ℃.

After completion of the dropwise addition, the mixture was subjected to a reaction at a temperature of 65℃for 2 hours. The resultant reaction mixture was cooled to room temperature to provide an isocyanate group-ended prepolymer 1 having an isocyanate group content of 5.1 mass%.

[ Synthesis of isocyanate group-terminated prepolymer 2 ]

Under a nitrogen atmosphere, 100.0 parts by mass of a polyester/polycarbonate-based polyol (product name: manufactured by NIPPOLAN 982,Tosoh Corporation) was gradually dropped into 74.1 parts by mass of the above-mentioned pure MDI in a reaction vessel while maintaining the temperature in the reaction vessel at 65 ℃.

After completion of the dropwise addition, the mixture was subjected to a reaction at a temperature of 65℃for 2 hours. The resultant reaction mixture was cooled to room temperature to provide an isocyanate group-ended prepolymer 2 having an isocyanate group content of 4.9 mass%.

< production of elastic roller >

A product obtained by applying a primer (product name: DY35-051,Dow Corning Toray Co, manufactured by ltd.) to a mandrel made of SUS304 having an outer diameter of 6mm and a length of 264mm, and heating the primer at a temperature of 150 ℃ for 20 minutes was prepared as a conductive substrate. The conductive substrate 2 was placed in a cylindrical mold having an inner diameter of 11.5mm so as to be concentric therewith.

Elastic rolls No.1 to 5

The following materials as materials for an elastic layer were mixed in the proportions shown in Table 2 using a kneading and stirring apparatus (product name: TRIMIX TX-15; manufactured by Inoue Mfg., inc.) to prepare an addition-curable liquid silicone rubber composition. The resulting addition-curable liquid silicone rubber composition was injected into the cavity of a mold heated to a temperature of 115 ℃. After injection, the composition was heated at a temperature of 120 ℃ for 10 minutes and cooled to room temperature. Thereafter, the matrix formed around the cured silicone rubber layer is removed from the mold. Thus, elastic rolls nos. 1 to 5 each having an elastic layer 3 having a thickness of 2.75mm and containing cured silicone (cured silicone) formed on the outer periphery of the conductive substrate 2 were obtained.

TABLE 2

[ elastic roll No.6]

The materials shown in "component (1)" of the following Table 3 were added to 100 parts by mass of styrene-butadiene rubber (SBR) (product name: TUFDENE 2003,Asahi Kasei Corporation) in the proportions shown in Table 3, and the mixture was kneaded with an internal mixer adjusted to a temperature of 80℃for 15 minutes. Next, the materials shown in "component (2)" of the following table 3 were added to the kneaded product in the proportions shown in table 3. Next, the mixture was kneaded with a twin roll machine cooled to a temperature of 25 ℃ for 10 minutes to provide a conductive rubber composition No.1.

TABLE 3 Table 3

A conductive vulcanized adhesive (product name: metaoc U-20,Toyokagaku Kenkyusho Co, manufactured by ltd.) was applied and baked to the outer peripheral surface of a cylinder made of stainless steel (SUS 304) having an outer diameter of 6mm and a length of 270mm to prepare a conductive base.

The outer peripheral surface of the base body serving as the center shaft was coated with the conductive rubber composition No.1 in a cylindrical manner by using an extrusion molding apparatus including a cross head. The thickness of the layer of the conductive rubber composition No.1 for coating was set to 2.75mm. The substrate having the layer of the conductive rubber composition No.1 coated on the outer peripheral surface thereof was charged into an air heating furnace and heated at 160℃for 1 hour, thereby vulcanizing the layer of the conductive rubber composition No. 1. Thus, a rubber layer is formed. After that, both end portions of the rubber layer were removed so that the length thereof became 235mm. Next, the outer peripheral surface of the rubber layer is polished with a polisher cutting into a grinding system so that the rubber layer is formed into a crown shape. The outer diameter of the cap rubber layer was measured at a pitch of 1mm in its longitudinal direction by a laser length measuring machine (product name: made by CONTROL-7000 and SENSOR HEAD LS-7030R,Keyence Corporation). Here, the difference between the average outer diameter at a position 10mm from the end in the longitudinal direction of the rubber layer to the center of the rubber layer and the average outer diameter at the center in the longitudinal direction is employed as the crown amount (crown amount). As a result, the average outer diameter at a position 10mm from the end in the longitudinal direction toward the center was 10.018mm, and the average outer diameter at the center was 10.068mm. Thus, the crown amount was 50. Mu.m. Thereafter, the base body including the cap rubber layer was charged into an air heating furnace and subjected to post heat treatment at a temperature of 195 ℃ for 1 hour under an air atmosphere to provide an elastic roll No.6.

< surface layer formation >

[ coating material intermediate No.1 to 9]

Coating material intermediate nos. 1 to 9 as raw materials of a coating material for forming a surface layer were prepared. That is, the following materials were stirred and mixed in the proportions shown in table 4. Next, methyl ethyl ketone (manufactured by Kishida Chemical co., ltd.) was added to each mixture so that the solid content concentration became 30 mass%, followed by mixing. Thereafter, the material was uniformly dispersed with a sand mill.

● Polyhydric alcohol

PTMG650: polytetramethylene glycol (molecular weight: 650,Hodogaya Chemical Co, manufactured by ltd.)

PTMG1000: polytetramethylene glycol (molecular weight: 1,000,Hodogaya Chemical Co, manufactured by ltd.)

PTMG2000: polytetramethylene glycol (molecular weight: 2,000,Hodogaya Chemical Co, manufactured by ltd.)

PTMG3500: polytetramethylene glycol (molecular weight: 3,500,Hodogaya Chemical Co, manufactured by ltd.)

NP-400: NEWPOL NP-400 (product name, sanyo Chemical Industries, manufactured by Ltd.)

● Isocyanate compound

MR-400: milliconate MR-400 (manufactured by product name Tosoh Corporation)

NCO1: the above isocyanate group-ended prepolymer 1

NCO2: the above isocyanate group-ended prepolymer 2

● Carbon black

SB X15: SUNBLACK X15 (product name, asahi Carbon Co., ltd.)

● Additive agent

TSF: TSF4445 (product name, polyether modified Silicone oil manufactured by Momentive Performance Materials Japan LLC)

TABLE 4 Table 4

[ coating material intermediate No.10]

The materials shown in table 5 below were mixed and stirred. Next, methyl ethyl ketone (Kishida chemical co., ltd.) was added to the mixture so that the solid content concentration became 30 mass%, followed by mixing. Thereafter, the material was uniformly dispersed with a sand mill to provide a coating material intermediate No.10.

TABLE 5

[ coating material intermediate No.11]

The materials shown in table 6 below were mixed and stirred. Next, methyl ethyl ketone (manufactured by Kishida Chemical co., ltd.) was added to the mixture so that the solid content concentration became 30 mass%, followed by mixing. Thereafter, the material was uniformly dispersed with a sand mill to provide a coating material intermediate No.11.

TABLE 6

[ preparation of coating Material for Forming surface layer ]

Fine particles nos. 1 to 13 were added to the resulting coated material intermediate nos. 1 to 11. The combination of the intermediate and the fine particles and the parts of the fine particles are shown in table 7 below. The materials were stirred and dispersed with a ball mill. The parts of the fine particles shown in table 7 are each relative to the amount of 100 parts by mass of the binder resin in the corresponding coating material intermediate. The amount of the binder resin represents the sum of parts by mass of the polyol and isocyanate compounds of the coating material intermediate. Next, methyl ethyl ketone (manufactured by Kishida Chemical co., ltd.) was added to the mixture to adjust their solid contents to the values shown in table 7. Thus, coating materials nos. 1 to 35 for surface layer formation were obtained.

TABLE 7

[ developing roller No.1]

The coating material No.1 for forming a surface layer was applied to the above elastic roll No.1 by roll coating so that the dry thickness of the coating film thereof was 0.4. Mu.m. Thereafter, the coating film was heated at a temperature of 130 ℃ for 60 minutes to be dried and cured, thereby forming a surface layer on the elastic layer of the roll. Thus, the developing roller No.1 was produced.

[ developing roller No.2 to 50]

Coating materials for forming a surface layer were each prepared in the same manner as described above except that the materials shown in table 7 were used as the materials of the surface layer. Then, as shown in table 8, the respective coating materials were applied onto the respective elastic rolls, and dried and heated in the same manner as described above. Thus, developing roller nos. 2 to 50 were produced.

TABLE 8

< evaluation of physical Properties of developing Member >

The following measurements and physical properties were carried out on the resulting developing roller. The results are shown in Table 9-1.

[ thickness measurement ]

The thickness of the surface layer of each developing roller was measured as described below. The cross sections of a total of 9 sites determined as follows were observed with an optical microscope or an electron microscope, and their thicknesses were measured: 3 sites in the axial direction of the surface layer and 3 sites in the circumferential direction thereof. The average of the measured values is used as the "thickness" of the surface layer.

[ measurement of elastic modulus E1 of fine particles in surface layer and elastic modulus E2 of binder resin therein ]

The elastic modulus E1 of the fine particles in the surface layer and the elastic modulus E2 of the binder resin therein were determined by the above-described method of measuring the elastic modulus with SPM.

[ measurement of elastic moduli E1 and E2 ]

As described below, the elastic modulus E1 of the fine particles in the surface layer and the elastic modulus E2 of the binder resin therein were measured. Such a sample is produced from the surface layer such that a section corresponding to the entire thickness of the surface layer is exposed. The sample was formed in a cube shape with a side length of 100 μm. Then, a probe of a Scanning Probe Microscope (SPM) is brought into contact with the fine particle portion and the binder resin portion exposed at the surface of the obtained sample (to which the entire thickness direction cross section of the surface layer is exposed) to measure a force curve. The elastic moduli E1 and E2 are determined from the resulting force curve based on hertz theory. "MFP-3D-Origin" (manufactured by product name Oxford Instruments) was used as the SPM. According to the device, the measurement of the force profile is automatically performed, and the elastic moduli E1 and E2 are automatically output from the measured force profile.

Here, a sample was produced from the surface layer as follows: samples of a cubic shape with a side length of 100 μm were produced from the surface layer using a freeze cutting system (product name: manufactured by EM FC6, leica Microsystems) and an ultra microtome (product name: manufactured by EM UC6, leica Microsystems). The sample was collected from the central portion of the surface layer in the longitudinal direction. The measurement was performed in a region ranging from T/3 to 2T/3 in the depth direction from the outer surface side of the surface layer, i.e., a fine particle portion and a binder resin portion exposed in the central region when the surface of observation was divided into three equal parts in the thickness direction thereof, of the surface (observation surface) corresponding to the entire thickness direction cross section of the surface layer of the sample.

In this measurement, as the elastic modulus E1, a value determined as follows: measuring force curves at 10 arbitrary sites of the fine particle portion exposed to the observation surface with SPM, and calculating elastic moduli from the force curves; an arithmetic average of 8 values other than the maximum value and the minimum value in the calculated elastic modulus was used as E1.

Further, in this measurement, as the elastic modulus E2, a value determined as follows is adopted: measuring force curves at 10 arbitrary sites of the binder resin portion exposed to the observation surface with SPM, and calculating elastic moduli from the force curves; an arithmetic average of 8 values other than the maximum value and the minimum value in the calculated elastic modulus was used as E2.

Regarding the measurement of the force curve, the mode of the SPM for force curve measurement was set to the contact mode, and the force distance and the trigger point thereof were set to 500nm and 0.01V, respectively. Further, a silicon cantilever of a dynamic mode such as "OMCL-AC-160TS" (manufactured by product name, olympus Corporation, spring constant=47.08N/m) was used as the cantilever, and the scanning frequency thereof was set to 1Hz.

[ measurement of the volume occupancy of fine particles relative to the binder resin in the surface layer ]

The volume occupancy of the fine particles in the surface layer was calculated according to the above calculation method.

[ measurement of MD-1 hardness ]

The electrophotographic roller serving as a measurement object was left to stand in an environment of a temperature of 23 ℃ and a relative humidity of 53% for 24 hours. Next, by making 2mm impressions with a roller, MD-1 hardness at each of 12 positions determined as follows was measured using a micro rubber durometer (product name: MD-1capa,Kobunshi Keiki Co, manufactured by ltd.) and a C-type indenter (diameter: 1.00 mm): the center portion of the surface layer of the electrophotographic roller and the positions each 20mm inward from both end portions thereof were determined, and four points were determined in each of the three portions in increments of 90 ° in the circumferential direction thereof. In this measurement, the average value of MD-1 hardness at each position was used as the MD-1 hardness H1 of the surface layer.

Next, the surface layer was removed from the electrophotographic roller serving as a measurement object with an ultra-micro microtome (product name: manufactured by EM UC6, leica Microsystems) to expose the surface of the elastic layer of the roller. Then, the MD-1 hardness H2 of the elastic layer was obtained in the same manner as described above, except that the portion where the indenter of the micro rubber durometer contacted was set as the exposed surface of the elastic layer.

Then, the difference (H1-H2) between the hardness H1 of the surface layer thus obtained and the hardness H2 of the elastic layer was calculated.

[ measurement of tensile modulus ]

The tensile modulus was measured by using test pieces produced from each of the surface layer-forming coating materials nos. 1 to 35 under the following conditions. The number of measurements "n" was set to 5 times, and the measurements were performed in a measuring environment at a temperature of 20℃and a humidity of 60% RH using a general tensile tester (product name: TENSILON RTC-1250A, manufactured by ORIENTEC). The average of the measured values was used as the tensile modulus.

< image evaluation >

The following image evaluation was performed. The results are shown in Table 9-1 and Table 9-2.

[ preparation for image evaluation ]

Cyan process cartridges (product name: manufactured by HP 656X High Yield Cyan Original LaserJet Toner Cartridge,Hewlett-Packard Company) for color laser printers (product name: HP Color LaserJet Enterprise M652dn, manufactured by Hewlett-Packard Company) were prepared, and developing rollers No.1 to 50 each in a state where the surface was coated with toner were each stored in a separate Cartridge (CRG) for initial fixation evaluation. Subsequently, these CRGs were left to stand at a temperature of 30 ℃ under a high-temperature and high-humidity environment of 95% relative humidity for 30 days.

[ evaluation 1: initial fixation evaluation ]

CRGs storing the developing roller nos. 1 to 50 are each stored in the main body of the color laser printer at a temperature of 30 ℃ and a relative humidity of 95%. Subsequently, a solid white image is output on 50 sheets of paper without rotating the CRG in advance. When an image adverse effect caused by an abnormal image occurs from the first sheet, the number of sheets required to eliminate the adverse effect is recorded. When no abnormal image is observed, the number is regarded as 0 sheets.

[ evaluation 2: evaluation of melt-adhering substances on the blade

The CRG is removed from the main body, and its developing roller and regulating blade are also removed. Thereafter, the surface of the regulation blade was observed with a laser microscope (product name: manufactured by VK-8700,Keyence Corporation) and an objective lens having a magnification of 20, and the size of the toner melt adhesive thereof was measured. When no melt adhesive is present, the size is considered to be 0.

[ evaluation 3: surface crack evaluation ]

Air is blown onto the surface of the developing roller removed from the CRG to remove the toner coating the surface. Subsequently, the surface state of the roller was observed with a laser microscope (product name: manufactured by VK-8700,Keyence Corporation) and an objective lens having a magnification of 20, and the size of the crack on the surface was measured. When no surface cracks were present, the size was considered to be 0.

[ evaluation 4: film formation evaluation

The surface of the above developing roller was observed using a laser microscope (product name: manufactured by VK-8700,Keyence Corporation) and an objective lens having a magnification of 20, and the area ratio of the film formed was calculated. When no film formation is present, the area ratio is considered to be 0.

TABLE 9-1

TABLE 9-2

[ discussion of evaluation results ]

In each of examples 1 to 39, each condition falls within the range described in the present disclosure, and therefore there is no problem in each of initial adhesion, image density, melt adhesion of toner to blade, surface cracking, and filming. Therefore, it is recognized that each of these developing rollers can exhibit satisfactory image performance.

In particular, in each of examples 1 to 7, 15, 19, the evaluation results were those of samples having a surface layer thickness as small as 0.5 μm or less, and therefore, substantially no melt adhesion of the toner to the blade was observed. This is considered to be because the melted adhesive on the blade is satisfactorily scraped off by the developing roller.

Furthermore, the following trends were observed: as the 10% modulus of the binder resin of the surface layer becomes smaller, the surface of the layer is more difficult to crack.

Meanwhile, in each of comparative examples 1, 2, 6, 8, film formation was remarkably observed. This is considered to be because the surface layer thickness, the average particle diameter of the fine particles, the elastic modulus of the binder resin, or the hardness of the surface layer deviates from the scope of the present disclosure, and thus stress on the toner becomes remarkable.

In comparative example 3, surface cracks were remarkably observed. This is considered to be because the volume occupancy of fine particles is large, and thus the surface layer is embrittled.

In each of comparative examples 4, 5, 10 and 11, the image density was low, and the melt adhesive on the blade was remarkably observed. This is considered to be because in each comparative example, the volume occupancy of the fine particles is smaller than the specification of the present disclosure, the elastic modulus of the fine particles is smaller than the specification thereof, the MD-1 hardness difference between the surface layer and the elastic layer is smaller than the specification thereof, or the average particle diameter of the fine particles is smaller than the specification thereof, and therefore the toner component that has been melt-adhered to the blade cannot be satisfactorily scraped off.

In each of comparative examples 7 and 9, initial fixation was significantly observed. This is thought to be due to the effect caused by: in each comparative example, the elastic modulus of the binder resin was smaller than the specification of the present disclosure, or the MD-1 of the surface layer was smaller than the specification thereof, and therefore the molecular mobility of the resin on the outermost surface of the developing roller was high, or the nip when the roller was abutted against the image bearing member became large.

The present disclosure encompasses the following constitution.

[ constitution 1]

An electrophotographic member comprising: a conductive substrate; an elastic layer formed on the substrate; and a surface layer formed on the elastic layer, wherein the surface layer contains fine particles and a binder resin, wherein a thickness of the surface layer is less than 1.0 μm, wherein an average particle diameter of the fine particles is 0.1 μm to 0.9 μm, wherein a volume occupancy of the fine particles is 60% by volume or more and 99% by volume or less with respect to 100% by volume of the binder resin in the surface layer, wherein when an elastic modulus of the fine particles and an elastic modulus of the binder resin (the elastic modulus is an elastic modulus calculated by hertz theory by a probe measurement force curve of an SPM device in a section in terms of a thickness of the surface) are each represented by E1 and E2, E1 and E2 satisfy a relationship represented by the following formulas (1) and (2):

E1≥1,000MPa (1)

200MPa≥E2≥2MPa (2)，

Wherein when the MD-1 hardness measured at an indentation depth of 2mm by bringing the C-type indenter into contact with the surface of the surface layer of the electrophotographic member opposite to the surface of the elastic layer is represented by H1, and the MD-1 hardness measured at an indentation depth of 2mm by peeling the surface layer from the electrophotographic member to expose the surface of the elastic layer and bringing the C-type indenter into contact with the exposed surface of the elastic layer is represented by H2, H1 and H2 satisfy the relationship represented by the following formulas (3) and (4).

100°≥H1≥50° (3)

H1-H2≥5° (4)

[ constitution 2]

The electrophotographic member according to constitution 1, wherein the binder resin has a 10% modulus value of 2MPa or more and 20MPa or less.

[ constitution 3]

The electrophotographic member according to constitution 1 or 2, wherein the thickness of the surface layer is 0.5 μm or less.

[ constitution 4]

An electrophotographic process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, the electrophotographic process cartridge comprising an electrophotographic member constituting any one of claims 1 to 3.

[ constitution 5]

An electrophotographic image forming apparatus comprising: an image bearing member for bearing an electrostatic latent image; charging means for charging the image bearing member once; an exposure device for forming an electrostatic latent image on the primary charged image bearing member; a developing member for developing the electrostatic latent image with toner to form a toner image; and a transfer device for transferring the toner image onto a transfer member, wherein the developing member is an electrophotographic member constituting any one of 1 to 3.

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

Claims (5)

1. An electrophotographic member, characterized in that the electrophotographic member comprises:

a conductive substrate;

an elastic layer on the conductive substrate; and

a surface layer on the elastic layer,

the surface layer contains fine particles and a binder resin,

the thickness of the surface layer is less than 1.0 μm,

the fine particles have an average particle diameter of 0.1 μm to 0.9 μm,

the volume occupancy of the fine particles is 60 to 99% by volume with respect to 100% by volume of the binder resin in the surface layer,

wherein E1 and E2 satisfy the relationship represented by the following formulas (1) and (2):

E1≥1,000 MPa (1)

200 MPa≥E2≥2 MPa (2)，

wherein E1 represents the elastic modulus of the fine particles, E2 represents the elastic modulus of the binder resin, E1 and E2 are obtained by measuring a force curve with SPM in a section in the thickness direction of the surface layer, and

wherein H1 and H2 satisfy the relationship represented by the following formulas (3) and (4):

100°≥H1≥50° (3)

H1-H2≥5° (4)

wherein H1 represents MD-1 hardness measured at an indentation depth of 2mm by bringing a C-shaped indenter into contact with a surface of the surface layer opposite to a surface facing the elastic layer, and H2 represents MD-1 hardness measured at an indentation depth of 2mm by peeling the surface layer from the electrophotographic member to expose the surface of the elastic layer and bringing the C-shaped indenter into contact with the exposed surface of the elastic layer.

2. The electrophotographic member as in claim 1 in which the 10% modulus value of the binder resin is 2MPa to 20MPa.

3. The electrophotographic member according to claim 1, wherein the thickness of the surface layer is 0.5 μm or less.

4. An electrophotographic process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, wherein said electrophotographic process cartridge comprises the electrophotographic member according to any one of claims 1 to 3.

5. An electrophotographic image forming apparatus, characterized by comprising:

an image bearing member for bearing an electrostatic latent image;

charging means for charging the image bearing member once;

an exposure device for forming an electrostatic latent image on the primary charged image bearing member;

a developing member for developing the electrostatic latent image with toner to form a toner image; and

a transfer device for transferring the toner image onto a transfer member,

wherein the developing member is an electrophotographic member according to any one of claims 1 to 3.