JP5686643B2 - Developing roller, electrophotographic process cartridge, and electrophotographic apparatus - Google Patents

Description

  The present invention relates to a developing roller, an electrophotographic process cartridge, and an electrophotographic apparatus used in an electrophotographic image forming apparatus (hereinafter referred to as “electrophotographic apparatus”).

In Patent Document 1, a developing roller having high developer transportability and low surface wear is provided with a resin layer cured by irradiation with ultraviolet rays or electron beams, and the resin layer contains fine particles dispersed therein. And a developing roller containing fluorine is disclosed.
Further, Patent Document 2 includes a resin layer cured by irradiation with ultraviolet rays or an electron beam as a developing roller having high developer transportability and low surface wear, and the resin layer disperses fine particles. A developing roller is disclosed that contains silicon and contains silicon.

JP 2005-352015 A JP 2005-352017 A

The developing roller according to the above patent document has excellent developer transportability by having convex portions derived from fine particles on the surface, and the resin layer contains fluorine or silicon, so that the friction resistance of the resin layer surface It is considered that the excellent developer transport performance is maintained over a long period of time since the wear of the convex portions is suppressed by the decrease in the thickness.
Here, the role of the developing roller used in the electrophotographic apparatus is to convey the developer to the developing area and to impart sufficient triboelectric charge to the developer.
According to the study by the present inventors, the resin layer of the developing roller according to the above patent document contains fluorine or silicon, so that the charging series on the surface thereof approaches the charging series of a general negatively chargeable developer. For this reason, the charge imparting ability of the developing roller with respect to the negatively chargeable developer is relatively lowered. That is, it can be said that the charging roller described in the above-mentioned patent document has a configuration that lowers the charge imparting ability to the developer, although it is excellent in the transportability of the developer over a long period of time.
SUMMARY OF THE INVENTION An object of the present invention is to provide a developing roller capable of achieving both a developer transport performance and a developer charging performance at a high level.
Another object of the present invention is to provide an electrophotographic process cartridge and an electrophotographic apparatus using the developing roller.

  A developing roller according to the present invention is a developing roller used together with a negatively chargeable developer, and has a conductive shaft core and a conductive urethane resin layer. Resin particles dispersed in the urethane resin and contained in an unexposed state on the surface of the urethane resin layer, and the developing roller has a plurality of resin particles derived from the resin particles on the surface. The surface of the developing roller is covered with a fluororesin or a silicone resin except for a valley between the protrusion and the protrusion, and the protrusion and the protrusion It is characterized in that the surface of the urethane resin layer is exposed in the valley between the two.

In the developing roller according to the present invention, the surface of the convex portion is covered with a fluororesin or a silicone resin, so that the convex portion is not easily worn. Therefore, the developer conveyance performance is maintained over a long period of time. On the other hand, since the urethane resin having high charge imparting performance with respect to the negatively chargeable developer is exposed in the valley between the convex portions, it has excellent charge imparting ability.
That is, according to the present invention, it is possible to obtain a charging roller capable of achieving both a stable developer transport performance and a developer charging performance at a high level.
In addition, an electrophotographic process cartridge and an electrophotographic apparatus that contribute to the formation of high-quality electrophotographic images over a long period of time can be obtained.

FIG. 3 is an axial sectional view showing an example of the developing roller of the present invention. FIG. 3 is a partially enlarged view of a cross-sectional view of the vicinity of the surface of the developing roller of the present invention. 1 is a schematic diagram illustrating an example of an electrophotographic apparatus using a developing roller of the present invention.

Hereinafter, embodiments of the present invention will be described, but the technical scope of the present invention is not limited thereto.
Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2 which are schematic views.
The present invention is a developing roller 1 that is used together with a negatively charged developer, and includes a conductive shaft body 102, an elastic layer 101, and a conductive urethane resin layer that is a surface layer 103. Yes. The urethane resin layer contains a urethane resin and resin particles 104 dispersed in the urethane resin, and the resin particles 104 are included in the urethane resin layer. That is, the resin particles 104 are contained in an unexposed state on the surface of the urethane resin layer.
The surface of the urethane resin layer (the surface of the developing roller) has a plurality of convex portions derived from the resin particles, and is thus roughened, and further, the surface of the urethane resin layer has the convex portions and the convex portions. Is covered with a fluororesin or a silicone resin 105. That is, the surface of the urethane resin layer is exposed in the valley portion 106.
The convex part described here refers to a portion of 2 μm or more from the minimum value by observing the surface of the urethane resin layer with a scanning confocal laser microscope (trade name: OLS3100, manufactured by Olympus Corporation) and drawing a cross-sectional curve.

  As the resin constituting the surface layer 103 of the developing roller of the present invention, urethane resin is used in consideration of the charge imparting property to the negatively chargeable developer. This is because the urethane resin has a property that is rich in positive chargeability, and by using the urethane resin having such characteristics as the resin constituting the surface layer, the developer is charged to obtain a sufficient image density. It is because it can do.

On the other hand, the technical significance of covering the convex portion on the surface of the developing roller for the purpose of transporting the developer with a fluororesin or a silicone resin will be described below.
That is, the resin particles 104 dispersed in the surface layer and causing protrusions on the surface of the surface layer are completely applied to the urethane resin as the surface layer 103 in order to prevent the resin particles 104 from falling off the surface layer during use. Covered with However, the surface layer 103 covering the resin particles 104 gradually wears when the convex portion continues to be subjected to strong rubbing with the developer regulating member, the developer, and the external additive after long-term use. . As the wear progresses, the resin particles 104 are exposed on the surface of the surface layer 103, and eventually the resin particles 104 may fall off the surface layer 103. As a result, it is conceivable that the roughness of the surface layer is lowered and the developer transportability is affected.
The fluororesin or silicone resin 105 covering the convex portion of the surface layer in the present invention alleviates stress concentration due to friction between the convex portion and the developer regulating member or the developer, and suppresses wear of the convex portion.
Suitable fluororesins for such applications include fluoroethylene / vinyl ether alternating copolymers, trifluoropropyltrimethoxysilane, and the like, and silicone resins include carbinol-modified silicone oil, carboxyl-modified silicone oil, amino acid. Examples include modified silicone oil. In general, fluororesins and silicone resins have high releasability and are difficult to adhere to the substrate. Therefore, it is desirable to have a functional group that reacts with the isocyanate group of the urethane resin that is the base material.

And it is important not to provide the said fluororesin or silicone resin in the trough part between a convex part. A film of fluororesin or silicone resin has a low ability to impart a triboelectric charge to the developer. Therefore, it is important to expose the surface of the urethane resin layer at the valleys between the convex portions so that sufficient frictional charge can be imparted to the toner at the exposed portions.
As a method of selectively providing the fluororesin or silicone resin film on the convex portion of the surface layer 103 in this manner, a method using a coating apparatus such as an applicator can be mentioned.
Specifically, a fluororesin or silicone resin is applied on a smooth plate such as a glass substrate using an applicator, and then the developing roller with a surface layer is rolled to roll the resin component on the developing roller. Transcript. At this time, the wet film thickness by the applicator needs to be thinner than the height of the convex portion provided by the resin particles. The “convex height” here is calculated by the following method. 1) First, the height from the valley between the projections to the projections obtained by using a scanning confocal laser microscope (trade name: OLS3100, manufactured by Olympus Corporation) is measured as the surface of the scanning area. Find on average. 2) Next, this height is obtained at a total of 18 points of 6 phases every 60 ° at three points 20 mm inside and center from both ends in the longitudinal direction of the developing roller, and the arithmetic average of the values at these 18 points is obtained. The above-mentioned “convex height” is used.

The developer is charged by being rubbed with the developing roller in the valley portion of the developing roller. Therefore, when the wet film thickness is larger than the height of the convex portion of the surface layer, the resin component is also applied to the valleys on the surface of the developing roller, reducing the charge imparting property to the one-component negatively chargeable developer. There is a possibility.
Moreover, since fluororesin and silicone resin have high releasability as described above, it is preferable to increase adhesion by reacting with an isocyanate group of a urethane resin as a base material. Therefore, it is preferable to go through the following steps. It is a so-called finger drying process that volatilizes only the organic solvent component of the coating film applied by dip coating, etc., a process of coating the convex part of the coating film with a fluororesin or silicone resin, and a baking process of the coating film . By passing through these steps in order, the fluororesin or silicone resin reacts with the isocyanate group in the coating film, and both are chemically bonded. For example, trifluoropropyltrimethoxysilane and the like are hydrolyzed to form a silanol group, chemically bonded to a highly reactive isocyanate group, and a urethane resin having a surface coated with a fluororesin is obtained.

  The material of the shaft core body 102 of the developing roller according to the present invention may be anything as long as it is conductive, and can be appropriately selected from carbon steel, alloy steel, cast iron, and conductive resin.

The elastic layer 101 is a molded body using rubber or resin as a raw material main component.
In addition, various rubbers can be used as the raw material rubber, and specific examples include the following. Ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), fluorine rubber, Silicone rubber, epichlorohydrin rubber, butadiene rubber (BR), NBR hydride, polysulfide rubber, urethane rubber.

  In addition, a thermoplastic resin is mainly used as the raw material resin. Specifically, the following can be mentioned. Polyethylene resins such as low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), and ethylene-vinyl acetate copolymer resin (EVA); polypropylene resins; polycarbonate resins; polystyrene resins ABS resin; Polyester resin such as polyethylene terephthalate and polybutylene terephthalate; Fluororesin; Polyamide resin such as polyamide 6, polyamide 66, MXD6;

And these rubber | gum and resin are used individually or in mixture of 2 or more types.
Among these, since it is important for the elastic layer 101 to have a moderately low hardness and sufficient deformation recovery force, it is preferable to use liquid silicone rubber or liquid urethane rubber as a material used for the elastic layer. In particular, it is more preferable to use an addition reaction cross-linkable liquid silicone rubber because it has excellent processability, high dimensional accuracy stability, and excellent productivity such that no reaction by-product is generated during the curing reaction.

Furthermore, in the developing roller of the present invention, conductive additives and non-conductive fillers necessary for the function required for the elastic layer itself, and various additive components used when forming rubber and resin moldings, for example, Further, a crosslinking agent, a catalyst, a dispersion accelerator and the like can be appropriately blended with the main rubber material.
As the conductive agent, there are an ionic conductive material based on an ionic conductive mechanism and a conductivity imparting agent based on an electronic conductive mechanism. Either one may be used, but they can also be used in combination.

  The following are mentioned as a conductive agent by an electronic conductive mechanism. Carbonaceous materials such as carbon black and graphite; metals or alloys such as aluminum, silver, gold, tin-lead alloys, copper-nickel alloys; zinc oxide, titanium oxide, aluminum oxide, tin oxide, antimony oxide, indium oxide, oxidation Conductive metal oxide such as silver; a substance obtained by subjecting various fillers to a conductive surface treatment with copper, nickel or silver.

Moreover, the following are mentioned as a conductivity imparting agent by an ionic conduction mechanism. _{LiCF 3 SO 3, NaClO 4,} LaClO 4, LiAsF 6, LiBF 4, NaSCN, KSCN, Group 1 metal salts periodic table, such as _{NaCl; NH 4 Cl, (NH} 4) 2 SO 4, NH 4 NO 3 Ammonium salts such as: salts of Group 2 metals of the periodic table such as Ca (ClO ₄ ) ₂ , Ba (ClO ₄ ) ₂ ; these salts and 1,4-butanediol, ethylene glycol, polyethylene glycol, propylene glycol, Complexes of polyhydric alcohols such as polypropylene glycol and their derivatives; complexes of these salts with monools such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether; Class Ammo Cationic surfactants such as ium salt; ampholytic agents such as betaines, aliphatic sulfonates, alkyl sulfates, such as anionic surfactants alkyl phosphates.

These conductive agents can be used alone or in admixture of two or more.
Among these, a carbon black-based conductive agent is preferable because it can be obtained relatively inexpensively and easily, and good conductivity can be imparted regardless of the type of the main rubber material. As means for dispersing the finely divided conductive agent in the raw material rubber material, a known means such as a roll kneader, a Banbury mixer, or a twin screw extruder can be used as appropriate depending on the rubber material. That's fine.

  The following are mentioned as a filler and a bulking agent. Silica, quartz fine powder, 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, glass fiber, organic Reinforcing agent, organic filler. These fillers may be hydrophobized by treating the surface with an organosilicon compound.

In order to press contact with the photosensitive drum and form a nip portion to ensure the nip width and to reduce the compression set, the thickness of the elastic layer is preferably 0.5 mm or more, and 1.0 mm. The above is more preferable. However, if the elastic layer is excessively thick, when the developing roller is left in pressure contact with the photosensitive drum or the developer amount regulating blade for a long time, the deformation of the press contact area increases and compression set is generated. Since it becomes easy to do, it is not preferable. Therefore, practically, the thickness of the elastic layer is suitably 6.0 mm or less, and more preferably 5.0 mm or less. In addition, in order to achieve the target nip width, the thickness of the elastic layer is desirably determined as appropriate according to the hardness.
In the present invention, a known molding method such as extrusion molding or injection molding can be used for molding the elastic layer. As long as it has the characteristic described in this invention as a layer structure, it will not be limited but can also be set as the structure of two or more layers.

As the surface layer 103 formed on the outer periphery of the elastic layer, it is necessary to use a polyurethane resin because of the charging property of the developer as described above, and in particular, polyether polyurethane that can reduce the hardness of the coating and has high charging property of the developer. Resins are preferred.
The polyether polyurethane resin can be obtained by a reaction between a known polyether polyol and an isocyanate compound. Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. In addition, these polyol components may be prepolymers that are chain-extended with an isocyanate such as 2,4-tolylene diisocyanate (TDI), 1,4 diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI) as required. Isocyanate compounds to be reacted with these polyol components are not particularly limited, but aliphatic polyisocyanates such as ethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), cyclohexane 1,3 -Arocyclic polyisocyanates such as diisocyanate, cyclohexane 1,4-diisocyanate, aromatic polyisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and these A modified product, a copolymer, or a block body thereof can be used.

Further, as a method of providing a convex portion for improving developer transportability on the surface of the developing roller, there is a method of dispersing resin particles 104 having a predetermined volume average particle diameter in a urethane resin as a surface layer. Examples of such resin particles 104 include polymethyl methacrylate particles, silicone resin particles, polyurethane particles, polystyrene particles, amino resin particles, or phenol resin particles.
As a standard of the content of the resin particles in the urethane resin, the content is preferably 5% by mass to 50% by mass with respect to the urethane resin component.

  In the present invention, various additives such as an electric resistance adjusting agent can be added to the surface layer 103 in the same manner as the elastic layer 101. Further, the method for dispersing the additive such as the resistance adjusting agent in the coating material forming the surface layer 103 is not particularly limited. Various additives can be added to a resin solution in which a urethane resin material is dissolved in an appropriate organic solvent, and dispersed using a known apparatus such as a sand grinder, a sand mill, or a ball mill.

  The one-component negatively chargeable developer that can be used in the electrophotographic apparatus of the present invention is not particularly limited, but may be a suspension polymerization method, an emulsion polymerization method, an interfacial polymerization method, an association polymerization method, or a pulverization method. Can be manufactured. Of these, the production of developer particles by suspension polymerization, association polymerization, or emulsion dispersion is preferred, and suspension polymerization methods that can easily obtain developer particles having a small particle diameter are more preferred.

When the developing roller of the present invention is used, the developing roller bears the developer in a state of being in contact with or pressed against the photosensitive drum as a latent image carrier that bears the latent image. The developing roller has a function of visualizing the latent image as a developer image by applying the developer to the photosensitive drum.
An example of a general electrophotographic process cartridge and an image forming apparatus equipped with the developing roller of the present invention is shown in FIG.

  The image forming apparatus includes image forming units 6a to 6d that form yellow, cyan, magenta, and black images, respectively, and are provided in a tandem manner. Further, the photosensitive drum 7, the charging roller 8, the developing device 10, and the cleaning device 11 are integrated to form an electrophotographic process cartridge. The electrophotographic process cartridge of the present invention includes a developing cartridge type equipped with the developing device 10. The electrophotographic process cartridge is detachable from the electrophotographic apparatus. The electrophotographic process cartridge contains a negatively charged developer.

  The developing device 10 includes a developing container 3 containing the one-component negatively chargeable developer 2 and a developing roller located in an opening extending in the longitudinal direction inside the developing container 3 and facing the photosensitive drum 7. 1, the electrostatic latent image on the photosensitive drum 7 is developed and visualized. Further, a developer application member 4 having both a function of supplying the one-component negatively chargeable developer 2 to the developing roller 1 and a function of scraping off the developer carried on the developing roller 1 without being used for development is provided. ing. Further, a developer regulating member 5 for regulating the carrying amount of the one-component negatively chargeable developer 2 on the developing roller 1 and frictionally charging is provided.

  The surface of the photosensitive drum 7 is uniformly charged to a predetermined polarity and potential by the charging roller 8, and exposure light 9 corresponding to image information is irradiated to the surface of the photosensitive drum 7 from an image exposure means (not shown), and electrostatically A latent image is formed. Next, the one-component negatively chargeable developer 2 is supplied to the formed electrostatic latent image from the developing roller 1 of the present invention, and the latent image is visualized. The developer image is transferred to the recording material 21 when the developer image comes to a place facing the transfer roller 12.

  In the image forming apparatus, four image forming units 6 a to 6 d are interlocked to form a predetermined color image on the recording material 21. The transfer / conveying belt 13 is wound around a driving roller 14, a tension roller 15, and a driven roller 16. The recording material 21 is conveyed to the transfer conveyance belt 13 in a form that is electrostatically adsorbed by the action of the adsorption roller 17. Reference numeral 18 denotes a supply roller for supplying the recording material 21, and 22 and 23 denote bias power sources for the transfer roller 12 and the suction roller 17, respectively.

  The recording material 21 on which the image has been formed is peeled off from the transfer conveyance belt 13 by the action of the peeling device 19 and sent to a fixing device 20 having a fixing member and a pressure member, and the developer image is fixed on the recording material 21. The printing is completed. The pressure member forms a nip portion with the fixing member, and conveys the recording material 21 (transfer material) in pressure contact with the nip portion. On the other hand, the photosensitive drum 7 after the transfer of the developer image to the recording material 21 is further rotated, the surface is cleaned by the cleaning device 11, and is neutralized by a neutralization device (not shown) if necessary. Thereafter, the photosensitive drum 7 is used for the next image formation.

  Here, the image forming apparatus that directly transfers the developer images of the respective colors onto the recording material has been described. For example, a monochrome monochrome image forming apparatus, an image forming apparatus that transfers to a transfer material via a transfer member such as an intermediate transfer roller or an intermediate transfer belt. Further, an image forming apparatus in which each color developing unit is arranged on a rotor or arranged in parallel with a photosensitive drum can be used. Further, instead of the electrophotographic process cartridge, a photosensitive drum, a charging roller, a developing device, and the like may be directly incorporated in the image forming apparatus.

[Formation of elastic roller]
A shaft core body 102 having an outer diameter of 6 mm and a length of 264 mm, coated with nickel and coated with a primer (trade name: DY39-051, manufactured by Toray Dow Corning Silicone). Was used. Next, the shaft core body 102 was disposed concentrically with a cylindrical mold having an inner diameter of 11.5 mm, and an addition type silicone rubber composition having the composition shown in Table 1 was injected into a cavity formed in the mold.

  Subsequently, the mold was heated to cure and cure the silicone rubber at a temperature of 150 ° C. for 15 minutes, and after demolding, it was further heated at a temperature of 200 ° C. for 2 hours to complete the curing reaction, and the thickness was 2.73 mm, length A 240 mm elastic layer 101 was provided on the outer periphery of the shaft core body 102. This is an elastic roller.

[Example 1]
[Formation of surface layer on elastic roller]
As the surface layer material, the materials shown in Table 2 were mixed and stirred with a stirring motor at 700 rpm for 1 hour.

Next, the stirring liquid was dispersed for 1 hour under the conditions of a peripheral speed of 7 m / sec, a flow rate of 1 cc / min, and a dispersion temperature of 15 ° C. using a horizontal disperser (trade name: NVM-03, manufactured by Imex Corporation).
After dispersion, MEK was further added to obtain a paint having a solid content of 25% by mass.
Next, this paint was circulated in a cylinder having a diameter of 32 mm at a liquid flow rate of 250 cc / min and a liquid temperature of 23 ° C. The elastic roller was immersed in the cylinder at an intrusion speed of 100 mm / second and stopped for 10 seconds. Then, it pulled up on the conditions of 400 mm / sec of initial speed, and 200 mm / sec of final speed, and naturally dried for 10 minutes, and obtained the elastic roller which provided the uncured surface layer.
Another elastic roller provided with the uncured surface layer was manufactured, and the surface layer material was cured by heat treatment at a temperature of 140 ° C. for 120 minutes. The height of the convex portion measured using this roller was 7.2 μm.

[Resin coating on surface layer protrusions]
Using the following doctor blade type applicator with a film thickness gap adjusted to 2 μm on a square glass substrate of 250 mm × 250 mm, thickness 5 mm, surface roughness Ra 0.1 mm, the following trifluoropropyltrimethoxy Silane was applied.
・ Doctor blade type applicator (trade name: Doctor blade type applicator, manufactured by Takumi Giken)
・ Trifluoropropyltrimethoxysilane (trade name: KBM-7103, manufactured by Shin-Etsu Silicone)
An elastic roller provided with an uncured surface layer on the glass substrate was rolled to transfer trifluoropropyltrimethoxysilane onto the surface layer convex portion.
Next, the surface layer was cured by heat treatment at a temperature of 140 ° C. for 120 minutes, and the fluororesin applied to the surface of the convex portion of the surface layer was cured.
[Development roller surface analysis]
On the surface of the developing roller, an area of 10 μm square centering on the apex of the convex part is A, and a 10 μm square area centering on the deepest point of the valley is B, and 20 energy dispersive fluorescent X Line analysis (EDX) was performed.
When the total ratio of fluorine element and silicon element measured by energy dispersive X-ray fluorescence analysis (EDX) was measured for the region A, and an arithmetic average value of 20 locations was obtained, it was 73.2 (wt%). there were. Further, regarding the region B, the total ratio of fluorine element and silicon element measured by energy dispersive X-ray fluorescence analysis (EDX) was measured, and the arithmetic average value was obtained. The result was 5.8 (wt%). In addition, it was confirmed that the region B had sufficiently less fluorine element and silicon element than the region A.
In this example, region A and region B were measured under the following measurement conditions.
[measuring device]
Scanning electron microscope (trade name: S-4800, manufactured by Hitachi High-Technology Corporation) and energy dispersive X-ray fluorescence analysis (EDX) (trade name: Genesis 400, manufactured by EDAX)
[Measurement condition]
Acceleration voltage 10kV
In this way, a developing roller was obtained in which the surface was covered with the fluororesin except for the valley between the protrusions, and the surface of the urethane resin layer was exposed in the valley.

[Image evaluation method]
Next, the image evaluation method performed in the present embodiment will be described.
First, the following electrophotographic process cartridge for an image output test was prepared. The developer was extracted from the electrophotographic process cartridge and filled with a magenta developer having a weight average particle diameter of 6.59 μm produced by the polymerization method described in Example 49 of JP-A-2006-106198. Five cartridges in which the developer was replaced by the same method were prepared.
Electrophotographic process cartridge (nominal life 1500 sheets, A4 size, printing rate 5%, product name: toner cartridge 316 magenta, manufactured by Canon Inc.)

Next, the developed developing roller is incorporated into one of the five electrophotographic process cartridges, and this cartridge is incorporated into an electrophotographic image forming apparatus (trade name: LBP5050, manufactured by Canon Inc., printing resolution 600 dpi). It is. Using this image forming apparatus, an intermittent durability test was performed in an environment of room temperature of 30 ° C. and humidity of 80% RH. When passing paper, perform a print operation in intermittent mode in which a character image with a printing rate of 2% is output on a genuine A4 paper (product name: Select Paper SC-250 A4, manufactured by Canon Inc.) every 20 seconds. 3000 images were output. After that, the developing roller was taken out from the 3000-sheet endured cartridge and replaced with another image output test cartridge, and 3000 images were similarly output. This image output was performed on all the cartridges prepared. That is, as the developing roller, an image corresponding to 15000 sheets was finally output, and finally a solid image was output to the recording material 21 (color laser A4 paper, trade name: Select Paper SC-250 A4, manufactured by Canon Inc.). .
The following evaluation and observation were performed on the output image and the developing roller after the image output test.

[Evaluation of change in image density]
The density was measured with a color reflection densitometer (trade name: X-RITE 404A, manufactured by X-Rite Co.) at nine locations on the paper surface of the entire solid image output initially and last. The arithmetic average value of nine measured values per sheet was taken as the density in the image, and the rate of density change was calculated as the density of the last output image / initial image density, and evaluated according to the following criteria.
A: The image density change rate exceeds 0.9 and is 1.0 or less.
B: The image density change rate exceeds 0.7 and is 0.9 or less.
C: The image density change rate is 0.7 or less.

[Observation of developing roller surface]
The developing roller after the image output test corresponding to 15000 sheets is taken out from the cartridge, the developer adhering to the surface is removed by air blow, the surface of the developing roller is observed, the abrasion of the surface layer convex portion, and the resin particles are removed. The presence or absence was confirmed. A scanning confocal laser microscope (trade name: OLS3100, manufactured by Olympus Corporation) was used for the observation. A total of 18 points of 6 phases every 60 ° were observed at an objective lens magnification of 50 times (total magnification of 1200 times) at three locations 6 mm inside from the both ends of the rubber part of the developing roller and the central part.
Tables 3 and 4 show the measurement results and the evaluation results.

[Example 2]
A developing roller was obtained in the same manner as in Example 1 except that the resin covering the convex portions of the surface layer was a fluoroethylene vinyl ether alternating copolymer (trade name: Lumiflon LF100, manufactured by Asahi Glass Co., Ltd.). Using the obtained developing roller, the same measurement and evaluation as in Example 1 were performed. The results are shown in Tables 3 and 4.

[Examples 3 to 13]
The developing roller was coated in the same manner as in Example 1 except that the type of resin coated on the surface layer protrusions and the average particle size and amount of resin particles added to the surface layer material were as shown in Table 3. Obtained.
Using the obtained developing roller, the same measurement and evaluation as in Example 1 were performed. The results are shown in Tables 3 and 4.

[Comparative Example 1]
A developing roller was obtained in the same manner as in Example 1 except that the surface layer protrusion was not coated with resin. Using the obtained developing roller, the same measurement and evaluation as in Example 1 were performed. The results are shown in Tables 3 and 4.

[Comparative Example 2]
In Example 1, a developing roller was prepared with a doctor blade type applicator having a film thickness gap of 20 μm. Since the film thickness gap was sufficiently larger than the average particle diameter of the resin particles, a developing roller was obtained in which not only the convex portions of the surface layer but also the valley portions were covered with the fluororesin. Using the obtained developing roller, the same measurement and evaluation as in Example 1 were performed. The results are shown in Tables 3 and 4.

[Comparative Example 3]
In Example 3, a developing roller was prepared with a doctor blade type applicator having a film thickness gap of 20 μm. Since the film thickness gap was sufficiently larger than the average particle diameter of the resin particles, a developing roller was obtained in which not only the convex portions of the surface layer but also the valley portions were coated with the silicone resin. Using the obtained developing roller, the same measurement and evaluation as in Example 1 were performed. The results are shown in Tables 3 and 4.

DESCRIPTION OF SYMBOLS 1 Developing roller 101 Elastic layer 102 Shaft core body 103 Surface layer 104 Resin particle 105 Fluorine resin or silicone resin

Claims (7)

A developing roller used together with a negatively chargeable developer, having a conductive shaft core and a conductive urethane resin layer,
The urethane resin layer is
Urethane resin,
Resin particles that are dispersed in the urethane resin and are contained in an unexposed state on the surface of the urethane resin layer,
The developing roller has a plurality of convex portions derived from the resin particles on its surface,
The surface of the developing roller is covered with a fluororesin or a silicone resin except for a valley between the protrusions and the valley between the protrusions and the protrusions. In the developing roller, the surface of the urethane resin layer is exposed. The developing roller according to claim 1, wherein the resin particles are polyurethane particles. The developing roller according to claim 1, wherein the resin particles have an average particle size of 10 to 22 μm. The developing roller according to any one of claims 1 to 3, wherein a content of the resin particles is 5 to 60% by mass with respect to the urethane resin. The developing roller according to claim 1, wherein the height of the convex portion is 4.8 to 12.3 μm. An electrophotographic process cartridge configured to be detachable from the electrophotographic apparatus,
The electrophotographic process cartridge has a developing roller and an electrophotographic photosensitive member, and contains a negatively charged developer .
Developing roller, electrophotographic process cartridge according to claim Oh Rukoto in developing roller according to any one of claims 1 to 5. And a current image roller and an electrophotographic photosensitive member, and an electrophotographic apparatus negatively chargeable developer is accommodated,
An electrophotographic apparatus , wherein the developing roller is the developing roller according to any one of claims 1 to 5 .

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