JP2012215647A - Developing roller, electrophotographic process cartridge, and electrophotographic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing roller that prevents toner filming from growing in a low-temperature environment to stably form an image for a long time, and to provide an electrophotographic process cartridge for forming a favorable image and an electrophotographic image forming device.SOLUTION: The developing roller includes a shaft core body, an elastic layer formed around the shaft core body, and a surface layer formed around the elastic layer and containing a binder resin and a resin particle as a roughening particle. The elastic modulus of the binder resin is larger than that of the resin particle.

Description

  The present invention relates to a developing roller used in an image forming apparatus using an electrophotographic system such as a copying machine, a laser beam printer, a facsimile machine, and a printing machine. The present invention further relates to an electrophotographic process cartridge and an electrophotographic image forming apparatus provided with the developing roller.

  In recent years, with the progress of high speed and high image quality in electrophotographic image forming apparatuses, the required performance for developing rollers that supply toner to a photoreceptor on which an electrostatic latent image is formed has become sophisticated. ing.

  For example, particularly in a low-temperature environment, toner that has been continuously stressed from a contact member such as a developing roller adheres to the surface of the developing roller, which further grows into toner filming, and the toner is developed in the white portion of the image. There is a problem that causes image degradation of “fogging”. In order to improve this, the surface layer of the developing roller and rough surface forming particles contained in the surface layer (hereinafter also referred to as rough particles) have been extensively studied. With respect to such a problem, in Patent Document 1, particles for forming a rough surface having a desired hardness are included in a surface layer, and variation in indentation depth at the time of constant load indentation between a portion where particles are present and a portion where particles are not present. Is disclosed as a developing roller with less than 30%.

JP 2007-233255 A

  The inventors have further studied the configuration described in Patent Document 1. As a result, although the developing roller according to Patent Document 1 can reduce the stress on the toner, in a cartridge that is used for a long period of time for a high-speed machine, it is possible to suppress the toner fixed matter from growing to toner filming in a low temperature environment. Was found to need further improvement.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing roller capable of suppressing the growth of toner filming in a low temperature environment and capable of stably forming an image over a long period of time, an electrophotographic process cartridge having the developing roller, and an electrophotographic image forming apparatus. Is to provide.

  The developing roller according to the present invention includes a shaft core, an elastic layer formed around the shaft core, and a surface layer containing a binder resin and resin particles as rough particles around the elastic layer. A developing roller having an elastic modulus of the binder resin larger than an elastic modulus of the resin particles.

  The electrophotographic process cartridge according to the present invention includes a photoconductor on which an electrostatic latent image is formed, and a developing member for developing the electrostatic latent image on the photoconductor, and includes an electrophotographic image forming apparatus. In the electrophotographic process cartridge removable from the main body, the developing member is the developing roller of the present invention.

  Furthermore, an electrophotographic image forming apparatus according to the present invention includes a photoconductor on which an electrostatic latent image is formed, and a developing member for developing the electrostatic latent image on the photoconductor. The developing member is the developing roller of the present invention.

  According to the present invention, there are provided a developing roller capable of suppressing the growth of toner filming in a low temperature environment and capable of forming a stable image over a long period of time, an electrophotographic process cartridge having the developing roller, and an electrophotographic image forming apparatus. can do.

FIG. 2 is an example of the developing roller of the present invention, (a) is a schematic sectional view parallel to the longitudinal direction, and (b) is a schematic sectional view perpendicular to the longitudinal direction. 1 is a schematic configuration diagram illustrating an example of an electrophotographic image forming apparatus according to the present invention. 1 is a schematic configuration diagram illustrating an example of an electrophotographic process cartridge according to the present invention. It is explanatory drawing of the measuring method of the contact area ratio of the developing roller concerning this invention.

  The present inventors suppress the growth of toner filming in a low-temperature environment by making the elastic modulus of the binder resin in the surface layer of the developing roller larger than the elastic modulus of the resin particles, and stable images over a long period of time. The inventors have found that a developing roller capable of being formed can be provided, and have completed the present invention.

  When the growth process of toner film was observed in detail with a microscope, it was confirmed that toner filming occurred through the following process.

  First, the toner is dammed up at the base position on the upstream side of the convex portion formed by the resin particles contained in the surface layer with respect to the rotation direction of the developing roller. Next, of the blocked toner, a toner fixed by receiving pressure from an abutting member such as a toner regulating blade or a photosensitive member without being replaced with another toner is formed as a toner adhering matter. Next, the toner is further dammed and fixed and grows starting from the toner fixed matter, so that the toner filming that causes fogging and black spots on the image grows.

  Therefore, as a result of earnestly examining the relationship between the elastic modulus of the binder resin on the surface layer of the developing roller and the elastic modulus of the resin particles, the inventors have made the elastic modulus of the binder resin larger than the elastic modulus of the resin particles. It has been found that it is effective in suppressing the growth of toner filming. This is because the resin particle sinks when the toner regulating blade comes into contact, and the toner scraping effect by the toner regulating blade can be sufficiently obtained for the toner near the bottom position of the resin particle. It is guessed. As a result, it is considered that the dammed toner is prevented from being fixed and the toner filming growth can be suppressed.

  Further, in order to further obtain the effect of suppressing the growth of toner filming, the elastic modulus of the resin particles measured by a nanoindentation apparatus is set to 1200 MPa or less, and the elastic modulus of the binder resin of the surface layer is set to the elastic modulus of the resin particles. It has been found that the ratio is more preferably 1.5 times or more.

  By satisfying the above conditions, it is possible to promote the sinking of the resin particles when the toner regulating blade comes into contact, and the toner regulating blade has a scraping effect with respect to the toner near the bottom position of the resin particles. It is presumed that it has become available. As a result, it is considered that the toner fixed matter can be prevented from growing in toner filming.

  Further, the present inventors have found that by mounting the developing roller of the present invention on an electrophotographic process cartridge, it is possible to suppress toner film growth and to form a good image.

  Further, the present inventors have found that by mounting the developing roller of the present invention in an electrophotographic image forming apparatus, toner filming growth can be suppressed and good image formation can be achieved.

  Hereinafter, specific examples for carrying out the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

<Developing roller of the present invention>
An example of the developing roller of the present invention is shown in FIG.
1A shows a cross-sectional view in a plane parallel to the longitudinal direction of the developing roller, and FIG. 1B shows a cross-sectional view in a plane perpendicular to the longitudinal direction. It is. In FIG. 1, the developing roller 10 is formed with an elastic layer 12 around a cylindrical shaft core 11 and a surface layer 13 containing resin particles as rough particles around the elastic layer 12. Two or more surface layers 13 may be formed.
Hereinafter, the developing roller of FIG. 1 will be described in detail.

(Shaft core)
The shaft core 11 can be either cylindrical or cylindrical.
The material of the shaft core body 11 is not particularly limited as long as it can support the elastic layer on the outer periphery thereof and has sufficient strength to withstand the load in the electrophotographic process. When electrical conductivity is required, it can be appropriately selected from carbon steel, alloy steel, cast iron, and conductive resin. Examples of the alloy steel include stainless steel, nickel chrome steel, nickel chrome molybdenum steel, chromium steel, chromium molybdenum steel, nitriding steel to which Al, Cr, Mo and V are added. Furthermore, as a rust prevention measure, the shaft core body can be plated and oxidized. As the type of plating, either electroplating or electroless plating can be used, but electroless plating is preferable from the viewpoint of dimensional stability. Examples of the electroless plating used here include nickel plating, copper plating, gold plating, Kanigen plating, and other various alloy plating. Examples of the nickel plating include Ni-P, Ni-B, Ni-WP, and Ni-P-PTFE composite plating. The thickness of each plating is preferably 0.05 μm or more, more preferably 0.10 μm or more and 30.00 μm or less.

(Elastic layer)
The elastic layer is provided to give the developing roller the elasticity required in the electrophotographic apparatus to be used. As a specific configuration, either a solid body or a foam may be used. Further, the elastic layer may be a single layer or a plurality of layers. For example, since the developing roller is always in pressure contact with the photosensitive drum and the toner, an elastic layer having characteristics of low hardness and low compression strain is provided in order to reduce damage caused between these members.

  Examples of the material for the elastic layer include natural rubber, isoprene rubber, styrene rubber, butyl rubber, butadiene rubber, fluorine rubber, urethane rubber, and silicone rubber. These can be used alone or in combination of two or more.

  The thickness of the elastic layer 12 is preferably 0.5 mm or more and 10.0 mm or less, and more preferably 1.0 mm or more and 5.0 mm or less in order to give the developing roller 10 sufficient elasticity. By setting the thickness of the elastic layer 12 to 0.5 mm or more, more preferably 1.0 mm or more, it is possible to give the developing roller 10 sufficient elasticity and suppress wear of the photosensitive drum. Moreover, by making the thickness of the elastic layer 12 10.0 mm or less, more preferably 5.0 mm or less, the electrophotographic process cartridge and the electrophotographic image forming apparatus can be miniaturized.

  The hardness of the elastic layer 12 is preferably from 10 degrees to 80 degrees in terms of Asker-C hardness, and more preferably from 20 degrees to 70 degrees. By setting the hardness of the elastic layer 12 to 10 degrees or more, more preferably 20 degrees or more, it is possible to suppress the amount of depression of the developing roller caused by the toner regulating blade being pressed against the developing roller, and an image caused by deformation. The occurrence of adverse effects can be suppressed. Further, by making the hardness of the elastic layer 12 80 degrees or less, more preferably 70 degrees or less, it is possible to suppress the wear of the photosensitive drum.

  A filler may be added to the elastic layer 12 as long as the properties of low hardness and low compressive strain are not impaired. Examples of the filler material include the following. Quartz fine powder, fumed silica, wet silica, 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 fibers, organic reinforcing agents, and organic fillers. The surface of these fillers may be hydrophobized by treatment with an organosilicon compound such as polydiorganosiloxane.

  The developing roller 10 needs to have an electrical resistance of the semiconductor region. Therefore, it is preferable that the elastic layer 12 is made of a rubber material containing a conductive agent and appropriately adjusting the volume resistivity.

  As a means for making the material of the elastic layer 12 conductive, there is a technique of making the material conductive by adding a conductivity imparting agent based on an electronic conduction mechanism or an ionic conduction mechanism to the material.

  Examples of the conductivity-imparting agent based on the electronic conduction mechanism include the following. Carbon black, carbonaceous material of graphite, aluminum, silver, gold, tin-lead alloy, copper-nickel alloy metal or alloy, zinc oxide, titanium oxide, aluminum oxide, tin oxide, antimony oxide, indium oxide, silver oxide Metal oxide, various fillers plated with copper, nickel, silver conductive metal.

Moreover, the following are mentioned as an electroconductivity imparting agent by an ionic conduction mechanism. LiCF ₃ SO ₃ , NaClO ₄ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , NaSCN, KSCN, NaCl Group 1 metal salt, NH ₄ Cl, (NH ₄ ) ₂ SO ₄ , NH ₄ NO ₃ ammonium _{salts, Ca (ClO 4) 2,} Ba (ClO 4) 2 of the periodic table group 2 metal salts, these salts and 1,4-butanediol, ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol Complexes of polyhydric alcohols and their derivatives, complexes of these salts with ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether monool, and quaternary ammonium salt Ionic Surface active agents, fatty acid salts, alkyl sulfates, anionic surfactants alkyl phosphate salts, and amphoteric surfactants betaine.

  These conductivity-imparting agents based on the ion conduction mechanism and the electron conduction mechanism can be used alone or in a mixture of two or more in the form of powder or fiber. Among these, carbon black is preferably used from the viewpoint that the conductivity can be easily controlled and is economical.

(Surface layer)
Examples of the material used as the binder resin for the surface layer 13 include the following. Urethane resin, acrylic urethane resin, epoxy resin, diallyl phthalate resin, polycarbonate resin, fluorine resin, polypropylene resin, urea resin, melamine resin, silicon resin, polyester resin, styrene resin, vinyl acetate resin, phenol resin, polyamide resin, fiber Elementary resin, silicone resin, and water-based resin. It is also possible to use a combination of two or more of these. In the developing roller, it is particularly preferable to use a urethane resin or an acrylic urethane resin, which are nitrogen-containing compounds, in order to control charging of the toner, and it is more preferable to have a urethane resin obtained by reacting an isocyanate compound and a polyol. .

  The following are mentioned as an isocyanate compound. Diphenylmethane-4,4′-diisocyanate, 1,5-naphthalene diisocyanate, 3,3′-dimethylbiphenyl-4,4′-diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, p-phenylene diisocyanate, isophorone diisocyanate, Carbodiimide-modified MDI, xylylene diisocyanate, trimethylhexamethylene diisocyanate, tolylene diisocyanate, naphthylene diisocyanate, paraphenylene diisocyanate, hexamethylene diisocyanate, and polymethylene polyphenyl polyisocyanate. Moreover, these mixtures can also be used and the mixing ratio may be any ratio.

  Moreover, the following are mentioned as a polyol used here. As a bifunctional polyol (diol), ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, hexanediol, neopentyl glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, Xylene glycol, triethylene glycol. As a trifunctional or higher functional polyol, 1,1,1-trimethylolpropane, glycerin, pentaerythritol, sorbitol. Furthermore, high molecular weight polyethylene glycol, polypropylene glycol, and ethylene oxide-propylene oxide block glycol obtained by adding ethylene oxide and propylene oxide to diol and triol. Moreover, these mixtures can also be used and the mixing ratio may be any ratio.

  The elastic modulus of the binder resin in the surface layer is preferably 500 MPa or more and 4000 MPa or less, and more preferably 1000 MPa or more and 3000 MPa or less. By setting the pressure to 500 MPa or more, more preferably 1000 MPa or more, it is possible to suppress the amount of depression of the developing roller that is caused by the toner regulating blade being pressed against the developing roller, and to suppress the occurrence of image defects due to deformation. it can. Further, when the pressure is 4000 MPa or less, more preferably 3000 MPa or less, stress applied to the toner can be suppressed, and stable image formation can be achieved over a long period of time. The elastic modulus of the surface layer can be measured by a method conforming to ISO14577 using a nanoindentation measuring apparatus described later. In the present invention, the elastic modulus calculated from the result measured after controlling the sample temperature to 5 ° C. under vacuum was used. In order to make the binder resin of the surface layer have the above elastic modulus, it is preferable to use a urethanized polyol obtained by chain-extending a bifunctional polyether polyol component and a bifunctional isocyanate component. As a polyether polyol component of a urethanized polyol, a glycol such as methylene glycol, ethylene glycol, trimethylene glycol or tetramethylene glycol is specifically homopolymerized or obtained as a copolymer of two or more monomers of these glycols. Functional polyglycols can be exemplified, and polytetramethylene glycol can be particularly preferred. Specific examples of the isocyanate component of the urethanized polyol include isocyanic acid, methyl isocyanate, ethyl isocyanate and the like.

  Such a urethanized polyol preferably has a weight average molecular weight of 10,000 to 50,000 and a molecular weight dispersity of Mw / Mn = 3.0 or less and Mz / Mw = 2.5 or less. By using such a urethanized polyol, stress applied to the toner can be suppressed, and stable image formation can be achieved over a long period of time.

  The surface roughness of the developing roller 10 is not particularly limited, but may be appropriately adjusted and used for the purpose of obtaining a high-quality image by securing toner conveyance force and suppressing ghost and density unevenness with sufficient image density. Can do. In the present invention, the center line average roughness Ra in the standard of JIS B 0601: 1994 surface roughness is preferably 0.3 to 5.0 μm, more preferably 0.5 to 4.0 μm. By setting Ra to 0.3 μm or more, more preferably 0.5 or more, it is possible to obtain a stable toner coating amount regardless of the temperature, and to suppress deterioration in image quality such as reduction in image density and ghost. Can do. In addition, by setting Ra to 5.0 μm or less, more preferably 4.0 or less, it is possible to suppress deterioration in image quality such as fogging or roughness.

  In the present invention, the surface layer 13 contains resin particles whose elastic modulus is controlled as coarse particles as means for controlling the surface roughness to a desired level. Among these, resin particles that are highly flexible, have a relatively small specific gravity, and easily obtain the stability of the paint are more preferable. Examples of the resin particles include urethane particles, nylon particles, acrylic particles, and silicone particles. Among these, urethane particles are preferably used because of their high flexibility, relatively low specific gravity, and easy paint stability.

  These resin particles can be used alone or in combination of two or more. In the case where a plurality of surface layers are formed, all of the plurality of layers may contain particles, or at least one of the plurality of layers may contain particles. Further, when a plurality of types of resin particles are mixed and used, the effect of the present invention can be obtained if at least one type of resin particles has a desired elastic modulus.

  The volume average particle diameter of the resin particles is preferably 1.0 μm or more and 30.0 μm or less, more preferably 3.0 μm or more and 20.0 μm or less. By setting the thickness to 1.0 μm or more, more preferably 3.0 μm or more, the developing roller 10 can be controlled to have a desired surface roughness, and a sufficient image density can be obtained. In addition, by setting the thickness to 30.0 μm or less, more preferably 20.0 μm or less, it is possible to suppress deterioration in image quality such as fogging or roughness.

  The elastic modulus of the resin particles is preferably 500 MPa or more and 4000 MPa or less, and more preferably 800 MPa or more and 1200 MPa or less. By setting the pressure to 500 MPa or more, and more preferably 800 MPa or more, it is possible to prevent the resin particles from being dented too much when the toner regulating blade is brought into contact, and the toner coating amount from being insufficient. Further, when the pressure is 4000 MPa or less, the stress applied to the toner can be suppressed, and stable image formation can be achieved over a long period of time. Furthermore, by setting the pressure to 1200 MPa or less, sinking of the resin particles when the toner regulating blade comes into contact can be promoted, and the toner regulating blade has a scraping effect on the toner near the skirt position of the resin particles. It can be obtained sufficiently.

  Similar to the surface layer, the elastic modulus of the resin particles can be measured by a nanoindentation measuring device to be described later, and the elastic modulus calculated from the measurement result after controlling the sample temperature to 5 ° C. under vacuum was used. .

  Regarding the relationship between the elastic modulus of the binder resin in the surface layer and the elastic modulus of the resin particles, in the present invention, the binder resin in the surface layer needs to be larger than the elastic modulus of the resin particles. More preferably, the elastic modulus of the binder resin in the surface layer is 1.5 times or more that of the resin particles. By making the elastic modulus of the resin particles smaller than the elastic modulus of the binder resin of the surface layer, the resin particles sink when the toner regulating blade comes into contact with the toner near the skirt position of the resin particles. The scraping effect by the regulating blade can be exhibited. Furthermore, by making the elastic modulus of the binder resin in the surface layer 1.5 times or more that of the resin particles, it is possible to further exert a scraping effect by the toner regulating blade with respect to the toner near the base position of the resin particles. The surface layer 13 may contain a conductive agent in order to adjust the electric resistance of the developing roller. Specific examples of the conductive agent contained include those similar to those exemplified as the conductive agent used for the elastic layer.

  Although it does not specifically limit as a formation method of the surface layer 13, The spray by a coating material, immersion, or a roll coat is mentioned. In the dip coating, the method of overflowing the paint from the upper end of the dip tank as described in JP-A-57-5047 is simple and excellent in production stability as a method for forming the surface layer.

  The thickness of the surface layer 13 is preferably 1.0 μm or more and 500.0 μm or less. More preferably, they are 2.0 micrometers or more and 50.0 micrometers or less. By setting the surface layer 13 to 1.0 μm or more, more preferably 2.0 μm or more, durability can be imparted to the developing roller. Further, when the thickness is 500.0 μm or less, more preferably 50.0 μm or less, the stress applied to the toner can be suppressed, and stable image formation can be achieved over a long period of time. The thickness of the surface layer 13 in the present invention refers to a cross section in the thickness direction of the surface layer using a digital microscope VHX-600 manufactured by Keyence Corporation, and a flat portion of the surface layer surface from the interface between the surface layer and the elastic layer. The arithmetic mean value of arbitrary 5 points of the distance to.

  The MD-1 hardness of the developing roller 10 on which the surface layer is formed is preferably 20.0 ° or more and 50.0 ° or less, and more preferably 25.0 ° or more and 40.0 ° or less. By setting the angle to 20.0 ° or more, more preferably 25.0 ° or more, it is possible to suppress the amount of depression of the developing roller caused by the toner regulating blade being in pressure contact with the developing roller, and to prevent image damage caused by deformation. Occurrence can be suppressed. Further, when the angle is 45.0 ° or less, more preferably 40.0 ° or less, the stress applied to the toner can be suppressed, and stable image formation can be achieved over a long period of time. Here, MD-1 hardness means the value of micro rubber hardness measured in a room controlled at a temperature of 23 ° C. and a humidity of 50% RH using a micro rubber hardness meter MD-1 type manufactured by Kobunshi Keiki Co., Ltd. .

<Measurement of elastic modulus>
The elastic modulus of the binder resin and resin particles on the surface layer of the developing roller was measured with a nanoindentation measuring apparatus (manufactured by Hysitron Inc., Tribo Scope + NanoNavi station + E-sweep type, manufactured by SII Nanotechnology).

  The nanoindentation method is a method of measuring the relationship between the load and displacement until the indenter is removed (unloading) after the diamond indenter is pushed into the sample surface to a certain load (press-in). The press fit curve obtained at this time reflects the elastic-plastic deformation behavior of the material, and the unloading curve reflects the elastic recovery behavior. Therefore, the composite elastic modulus can be calculated from the initial slope of the unloading curve.

In the present invention, the measurement was carried out by the following procedure in accordance with ISO14577.
After the surface of the developing roller was cut out in a state of 5 mm square and 2 mm in thickness including the surface layer, a sample was prepared by cutting the surface of the developing layer by cutting with a microtome. Next, after controlling the sample temperature to 5 ° C. under vacuum using the nanoindentation measuring apparatus, three portions of the sample where the resin particles do not exist on the surface are measured, and the obtained measurement is performed. The arithmetic mean value of the result was calculated as the elastic modulus of the binder resin in the surface layer of the developing roller. Similarly, in the same sample, the central part of the resin particles where the resin particles are present on the surface was measured at three locations, and the arithmetic average value of the obtained measurement results was calculated as the elastic modulus of the resin particles. It was. In addition, the amount of indentation to the sample surface at the time of measurement was performed at 300 nm.

<Measurement of contact area ratio>
As an index of the growth suppression effect of the toner filming of the developing roller, the present inventors paid attention to the sinking of the resin particles when the toner regulating blade comes into contact. Therefore, the degree of sinking of the resin particles when the toner regulating blade comes into contact is determined by the contact area of the actual contact area with respect to the entire area of the nib portion when the developing roller is pressed against the transparent flat glass with a predetermined load. The ratio was evaluated.

In the present invention, the contact area ratio was evaluated by the following procedure.
After the developing roller 10 and the transparent flat glass 20 having a thickness of 1 mm are left in an environment of a temperature of 5 ° C. and a humidity of 10% RH for 24 hours, as shown in FIG. The flat glass 20 was pressed against the substrate at a linear pressure of 200 N / cm. At this time, the nip portion 21 formed at the contact portion between the developing roller 10 and the flat glass 20 is observed through the flat glass 20 at a magnification of 1000 times using a digital microscope VHX-500 manufactured by Keyence Corporation. And then shot. A schematic diagram of an image transmitted through the flat glass 20 and observed by the nip portion 21 is shown in FIG.

  The observed nip portion 21 is in the vicinity of the center in the longitudinal direction of the developing roller, and the circumferential direction is a 400 μm × 400 μm region in the vicinity of the center of the nip width, and this area is defined as the area (A) of the entire nib portion. As shown in FIG. 4B, the actual contact area (B) in the nip portion 21 is binarized into a contact portion 22 and a non-contact portion by image processing based on the density of the photographed image. It was calculated by adding the areas of.

  Based on these areas (A) and (B), the contact area ratio of the actual contact area to the entire area of the nib portion was calculated by the formula (A) / (B) × 100 (%).

<Electrophotographic image forming apparatus according to the present invention>
Next, an example of an electrophotographic image forming apparatus equipped with the developing roller of the present invention will be described with reference to FIG.

  An example of the electrophotographic image forming apparatus of the present invention is shown in FIG. In FIG. 2, the electrophotographic image forming apparatus 100 is provided with an image forming unit for each color toner of yellow toner, magenta toner, cyan toner, and black toner. Each image forming unit is provided with a photoreceptor 101 as an electrostatic latent image carrier that rotates in the direction of the arrow. Around each photoconductor, a charging roller 107 for uniformly charging the photoconductor, exposure means for irradiating the uniformly charged photoconductor with a laser beam 106 to form an electrostatic latent image, electrostatic A developing device 105 is provided for supplying toner to the photosensitive member on which the latent image is formed to develop the electrostatic latent image.

  On the other hand, a transfer conveyance belt 116 that conveys a recording material 118 such as paper supplied by a paper supply roller 119 is provided to be suspended from a driving roller 112, a driven roller 117, and a tension roller 115. The transfer / conveying belt 116 is charged with the charge of the attracting bias power source 121 via the attracting roller 120, and the recording material 118 is electrostatically attached to the surface and transported.

  A transfer bias power supply 114 is provided for applying a charge for transferring the toner image on the photosensitive member of each image forming unit to the recording material 118 conveyed by the transfer conveyance belt 116. The transfer bias is applied via a transfer roller 113 disposed on the back surface of the transfer conveyance belt 116. The toner images of the respective colors formed in the image forming units are sequentially superimposed and transferred onto a recording material 118 conveyed by a transfer conveying belt 116 that is moved in synchronization with the image forming unit. .

  Further, the color electrophotographic image forming apparatus includes a fixing device 111 that fixes the toner image superimposed and transferred onto the recording material by heating or the like, and a conveyance device (not shown) that discharges the image-formed recording material 118 to the outside of the device. Provided.

  On the other hand, each image forming unit is provided with a cleaning device 108 having a cleaning blade for removing residual toner remaining without being transferred onto each photoconductor and cleaning the surface. In addition, a waste toner container (not shown) that stores toner scraped off from the photoreceptor is provided. The cleaned photoconductor is set in an image-formable state and stands by.

  The developing device 105 provided in each of the image forming units is provided with a toner container 103 containing non-magnetic toner as a one-component developer and a toner container that closes the opening of the toner container, and a portion exposed from the toner container is exposed to light. A developing roller 10 as a developing member is provided so as to face the body.

  In the toner container, a toner supply roller 102 is provided for supplying toner to the developing roller and at the same time scraping off toner that is not used on the developing roller after development. In addition, a toner regulating blade 104 made of SUS304 is provided which forms toner on the developing roller in a thin layer and frictionally charges. These are disposed in contact with the developing roller 10, respectively.

  A toner regulating blade bias power source 109 is connected to the toner regulating blade 104, a developing roller bias power source 110 is connected to the developing roller, and a desired voltage is applied to each of the toner regulating blade 104 and the developing roller 10 during image formation. Is done.

<Electrophotographic process cartridge according to the present invention>
Next, an example of an electrophotographic process cartridge equipped with the developing roller of the present invention will be described with reference to FIG. The electrophotographic process cartridge 200 shown in FIG. 3 has a developing device 105, a photoconductor 101, and a cleaning device 108, which are integrated and removable from the main body of the electrophotographic image forming apparatus.

  An example of the developing device 105 is the same as that described in the electrophotographic image forming apparatus. A toner container 103 containing non-magnetic toner as a one-component developer and a developing roller 10 are provided so as to close the opening of the toner container, and the developing roller 10 is disposed so as to face the photoconductor at a portion exposed from the toner container. In FIG. 3, reference numeral 102 denotes a toner supply roller, 104 denotes a toner forming blade, and 107 denotes a charging roller.

  In addition to the above, the electrophotographic process cartridge of the present invention may be one in which a transfer member for transferring a toner image on a photosensitive member to a recording material is integrally provided with the above members.

Hereinafter, the present invention will be described in detail based on examples and comparative examples.
The following examples are examples of embodiments of the present invention, and the present invention is not limited to these examples.

[Example 1]
<Production of developing roller>
By the following procedure, a developing roller was prepared in which an elastic layer and a surface layer were provided as coating layers around a cylindrical shaft core.
As the shaft core body, a SUS304 metal core having a diameter of 6 mm and a length of 279 mm was used.
As a material for the elastic layer, liquid silicone rubber was prepared by the following method. First, the following materials were mixed to form a liquid silicone rubber base material.
-Dimethylpolysiloxane having a vinyl group at both ends and a viscosity at 25 ° C of 100 Pa · s (manufactured by Toray Dow Corning, weight average molecular weight 100,000): 100 parts by mass.
Non-reactive cyclic polysiloxane (trade name: DC246 Fluid, manufactured by Toray Dow Corning): 12 parts by mass.
Quartz powder as a filler (trade name: Min-USil, manufactured by Pennsylvania Glass Sand): 10 parts by mass.
Carbon black (trade name: Denka Black, powdered product, manufactured by Denki Kagaku Kogyo) 8 parts by mass.

  To 100 parts by mass of this base material, 0.05 part by mass of a platinum compound (manufactured by Toray Dow Corning, Pt concentration 1%) as a curing catalyst was blended to prepare a base material A. Separately, 3 parts by mass of organohydrogenpolysiloxane (manufactured by Toray Dow Corning Co., Ltd., weight average molecular weight 500) was blended with 100 parts by mass of the base material to prepare a base material B. The obtained base material A and base material B were mixed at a mass ratio of 1: 1 to obtain a liquid silicone rubber.

  A shaft core is placed in the center of a cylindrical mold with an inner diameter of 12 mm, and this liquid silicone rubber is injected into the cylindrical mold from the injection port, heated and cured at 120 ° C. for 5 minutes, and cooled to room temperature. The elastic layer integrated with the shaft core was removed. Further, the curing reaction was completed by heating at a temperature of 150 ° C. for 4 hours, and an elastic layer mainly composed of silicone rubber having a thickness of 3 mm was provided on the outer peripheral surface of the shaft core body.

Then, the excimer process of the elastic layer surface was performed on condition of the following.
The elastic layer surface is irradiated with a capillary excimer lamp (manufactured by Harrison Toshiba Lighting Co., Ltd.) capable of irradiating ultraviolet rays having a wavelength of 172 nm while rotating the shaft core at a rotation axis of 30 rpm so that the integrated light amount becomes 200 mJ / cm 2. Processed. The distance between the elastic layer surface and the excimer lamp at the time of irradiation was 2 mm.

Next, the surface layer was formed by the following method.
The following materials were used for the surface layer.
Polytetramethylene glycol (trade name: PTG850, number average molecular weight Mn = 850, f = 2 (f represents the number of functional groups; the same shall apply hereinafter), manufactured by Hodogaya Chemical Co., Ltd.): 100.0 parts by mass. Isocyanate (trade name: Millionate MT, MDI, f = 2, manufactured by Nippon Polyurethane Industry Co., Ltd.): 22.0 parts by mass.

  These materials were mixed stepwise in a methyl ethyl ketone solvent and reacted at 80 ° C. for 6 hours under a nitrogen atmosphere to obtain a bifunctional urethanized polyol. The obtained urethanized polyol had a weight average molecular weight of 30,000 and a molecular weight dispersity of Mw / Mn = 2.5 and Mz / Mw = 2.0.

  30.0 parts by mass of isocyanate (trade name: Coronate 2521, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to 100.0 parts by mass of this urethanized polyol so that the NCO equivalent was 1.4. The NCO equivalent represents a ratio ([NCO] / [OH]) between the number of moles of isocyanate groups in the isocyanate compound and the number of moles of hydroxyl groups in the polyol component.

  Further, 22.0 parts by mass of carbon black (trade name: # 1000, pH 3.0, manufactured by Mitsubishi Chemical Corporation) was mixed with stirring, dissolved and mixed in MEK so that the total solid content ratio was 30% by mass, and then a sand mill. And uniformly dispersed.

  Next, 50 parts by mass of Art Pearl JB-600T (trade name, manufactured by Negami Kogyo Co., Ltd.) is added as resin particles to the resulting dispersion, followed by stirring with a stirring motor for 10 minutes, and a coating for forming a surface layer. Got.

  Next, the shaft core on which the elastic layer was formed was immersed in the surface layer forming coating material, and then pulled up and dried naturally. Subsequently, a heat treatment was performed at a temperature of 140 ° C. for 60 minutes to cure the resin layer raw material liquid, thereby providing a surface layer having a thickness of about 12.0 μm. Furthermore, both ends of the coating layer were cut off and removed perpendicularly to the shaft core body to adjust the length of the coating layer.

  In this way, a developing roller having an outer diameter of about 12 mm, a coating layer length of 240 mm, and a centerline average roughness Ra of 2.2 μm according to JIS B 0601: 1994 surface roughness standards was produced.

  As a result of measuring the elastic modulus of the obtained developing roller using the above-mentioned nanoindentation measuring apparatus, the elastic modulus of the binder resin in the surface layer was 2400 MPa, and the elastic modulus of the resin particles was 1000 MPa.

<Evaluation of developing roller>
(Measurement of contact area ratio)
About the produced developing roller, the contact area ratio of the actual contact area to the entire area of the nib portion when the developing roller was pressed against the transparent flat glass with a predetermined load was evaluated according to the measurement procedure of the contact area ratio described above. As a result, the contact area ratio was 35%.

(Toner filming evaluation)
Next, image evaluation was performed with an electrophotographic image forming apparatus using the produced developing roller. For the electrophotographic image forming apparatus, Color LaserJet CP3520 (trade name) manufactured by Hewlett-Packard Company was used. A special magenta cartridge was used for the process cartridge, and the developing roller was replaced with the one prepared above. The process cartridge incorporating the developing roller of this example was mounted on the main body of the image forming apparatus, and left in an environment of temperature 5 ° C. and humidity 10% RH for 24 hours. Thereafter, in the same environment, an image having a printing rate of 1% was continuously output until the output image was blurred. Thereafter, 2000 solid white images were continuously output in the same environment, and the fogging value of the 2000th sheet was measured by the following method.

  The fog value is measured using a reflection densitometer TC-6DS / A (trade name, manufactured by Tokyo Denshoku Technology Center Co., Ltd.) and the reflection density of the recording material before the image formation and the recording material that outputs a solid white image. The increase in reflection density was taken as the fog value of the developing roller. The reflection density was measured over the entire image printing area of the recording material, and the minimum value was used for the recording material before image formation, and the maximum value was used for the recording material that output a solid white image.

  The smaller the fog value, the better. “A” if it is less than 1.0, “B” if it is 1.0 or more and less than 2.0, “C” if it is 3.0 or more and less than 5.0, 5 If it was greater than or equal to 0.0, it was evaluated as “D”. Here, the evaluation “A” and the evaluation “B” are levels at which “fog” cannot be recognized on the image by visual observation. On the other hand, the evaluation “C” and the evaluation “D” are levels at which “fogging” can be visually recognized on the image.

Normally, toner is not transferred onto a transfer paper on which a solid white image is formed, and the fog value is smaller than 2.0. However, in the developing roller where toner filming has grown, the charge amount of the toner coat layer formed on the toner filming is insufficient. For this reason, even when a solid white image is formed, the toner moves onto the photosensitive member and is further transferred onto the transfer paper to cause fogging, and the fog value becomes 3.0 or more. Accordingly, the fog value can be used as an index for toner filming of the developing roller.
The above evaluation results are shown in Table 1.

[Comparative Example 1]
The polytetramethylene glycol used as the material for the surface layer was changed to polytetramethylene glycol (trade name: PTG650, number average molecular weight Mn = 650, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl C-600T (trade name, manufactured by Negami Kogyo Co., Ltd.).
The evaluation results are shown in Table 1.

[Comparative Example 2]
A developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl C-400T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

[Comparative Example 3]
The polytetramethylene glycol used as the material for the surface layer was changed to polytetramethylene glycol (trade name: PTG1400, number average molecular weight Mn = 1400, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl C-800T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

[Comparative Example 4]
The polytetramethylene glycol used as the material for the surface layer was changed to polytetramethylene glycol (trade name: PTG1400, number average molecular weight Mn = 1400, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl P-400T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

[Example 2]
The polytetramethylene glycol used as the material for the surface layer was changed to polytetramethylene glycol (trade name: PTG1000, number average molecular weight Mn = 1000, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl P-400T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

Example 3
The polytetramethylene glycol used as the material for the surface layer was changed to polytetramethylene glycol (trade name: PTG650, number average molecular weight Mn = 650, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl P-600T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

Example 4
The polytetramethylene glycol used as the material for the surface layer was changed to polytetramethylene glycol (trade name: PTG1400, number average molecular weight Mn = 1400, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl P-800T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

Example 5
The polytetramethylene glycol used as the material for the surface layer was changed to modified polytetramethylene glycol (trade name: PTG-L2000, number average molecular weight Mn = 2000, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl JB-600T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

Example 6
The polytetramethylene glycol used as the material for the surface layer was changed to modified polytetramethylene glycol (trade name: PTG-L1000, number average molecular weight Mn = 1000, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl JB-800T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

Example 7
The polytetramethylene glycol used as the material for the surface layer was changed to polytetramethylene glycol (trade name: PTG1400, number average molecular weight Mn = 1400, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl JB-800T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

Example 8
A developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl JB-800T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

Example 9
The polytetramethylene glycol used as the material for the surface layer was changed to polytetramethylene glycol (trade name: PTG650, number average molecular weight Mn = 650, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl JB-400T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

Example 10
The polytetramethylene glycol used as the material for the surface layer was changed to polytetramethylene glycol (trade name: PTG2900, number average molecular weight Mn = 2900, f = 2, manufactured by Hodogaya Chemical Co., Ltd.). Further, a developing roller was produced in the same manner as in Example 1 except that the resin particles were changed to Art Pearl JB-600T (trade name, manufactured by Negami Kogyo Co., Ltd.). The evaluation results are shown in Table 1.

From the results of Examples 1 to 10 in Table 1, it was found that the contact area ratio can be increased and the toner filming can be improved by making the elastic modulus of the binder resin larger than the elastic modulus of the resin particles.
In addition, from the results of Example 1 and Tables 7 to 10 in Table 1, the elastic modulus of the resin particles is 1200 MPa or less, and the elastic modulus of the binder resin is 1.5 times or more of the elastic modulus of the resin particles. And found that the toner filming can be further improved.

DESCRIPTION OF SYMBOLS 10 Developing roller 11 Shaft core body 12 Elastic layer 13 Surface layer

Claims (4)

  A developing roller having a shaft core, an elastic layer formed around the shaft core, and a surface layer containing a binder resin and resin particles as rough particles around the elastic layer, A developing roller, wherein the elastic modulus of the binder resin is larger than the elastic modulus of the resin particles.   The developing roller according to claim 1, wherein the elastic modulus of the resin particles is 1200 MPa or less, and the elastic modulus of the binder resin is 1.5 times or more of the elastic modulus of the resin particles.   In an electrophotographic process cartridge comprising a photosensitive member on which an electrostatic latent image is formed and a developing member for developing the electrostatic latent image on the photosensitive member and detachable from a main body of an electrophotographic image forming apparatus, An electrophotographic process cartridge, wherein the developing member is the developing roller according to claim 1.   3. An electrophotographic image forming apparatus comprising: a photoconductor on which an electrostatic latent image is formed; and a developing member for developing the electrostatic latent image on the photoconductor. An electrophotographic image forming apparatus, characterized by being a developing roller of the above.