JP5734084B2 - Developing roller, electrophotographic process cartridge, and electrophotographic image forming apparatus - Google Patents

Description

  The present invention relates to a developing roller, an electrophotographic process cartridge, and an electrophotographic image forming apparatus used in an electrophotographic image forming apparatus.

  In the electrophotographic image forming apparatus, the developing roller plays a role of supplying a developer to the electrostatic latent image of the electrophotographic photosensitive member. Therefore, in order to stabilize the amount of developer carried on the surface of the developing roller, the surface of the developing roller is roughened by providing a surface layer containing roughening particles (Patent Document 1). 2).

Incidentally, in order to stabilize the coating amount of the developer on the surface of the developing roller, it is common to bring the developer regulating blade into contact with the surface of the developing roller. At this time, the coating amount of the developer carried on the developing roller depends on the size of the gap formed between the surface layer containing the resin particles and the developer regulating blade when the developer regulating blade is brought into contact therewith. . If the elastic modulus of the resin particles is large, the resin particles are difficult to dent, and the convex portions of the surface layer containing the resin particles support the developer regulating blade. As a result, a gap is formed at the contact portion between the surface layer and the developer regulating blade, and the coating amount of the developer carried on the developing roller increases. On the other hand, if the elastic modulus of the resin particles is small, the resin particles are easily dented, and it is difficult to form a gap at the contact portion between the surface layer and the developer regulating blade, and the amount of developer coating carried on the developing roller is reduced. Therefore, in the low temperature environment where the elastic modulus of the resin particles is relatively increased compared to the high temperature environment, the coating amount of the developer carried on the developing roller is larger than that in the high temperature environment. The image density may increase relatively.

JP-A-2005-258201 JP 2005-266500 A

  Therefore, an object of the present invention is to suppress an increase in the elastic modulus of the resin particles in a low temperature environment, thereby suppressing an increase in the developer coating amount in the low temperature environment and reducing the environmental temperature dependency of the electrophotographic image. An object of the present invention is to provide a developing roller that can be used.

  Another object of the present invention is to provide an electrophotographic image forming apparatus and an electrophotographic process cartridge in which the density of the electrophotographic image is less dependent on the environmental temperature.

。 According to the present invention, it has a shaft core, an elastic layer, and a surface layer, and the surface layer includes resin particles as roughened particles, the resin particles contain a urethane resin, and the urethane resins are adjacent to each other. Between two urethane groups, one or both structures selected from the structure represented by the following structural formula (1), the structure represented by the following structural formula (2) and the structure represented by the following structural formula (3) A developing roller is provided containing a urethane resin having:

.

  In addition, according to the present invention, the image forming apparatus includes a photoconductor on which an electrostatic latent image is formed and a developing member that develops the electrostatic latent image on the photoconductor, and is detachable from the main body of the electrophotographic image forming apparatus. An electrophotographic process cartridge is provided in which the developing member is the developing roller of the present invention.

  Furthermore, according to the present invention, the image forming apparatus includes a photosensitive member on which an electrostatic latent image is formed and a developing member that develops the electrostatic latent image on the photosensitive member, and the developing member is the developing roller of the present invention. An electrophotographic image forming apparatus is provided.

According to the present invention, the resin particles as rough particles contained in the surface layer are represented by the structure represented by the structural formula (1) and the structural formula (2) between two adjacent urethane groups. And a polyurethane particle having one or both structures selected from the structure represented by the structural formula (3) suppresses an increase in the coating amount of the developer in a low-temperature environment, and the concentration is independent of the temperature. A developing roller capable of stable image formation can be provided.
As a result, it is possible to obtain an electrophotographic process cartridge and an electrophotographic image forming apparatus capable of forming good images.

FIG. 2 is a schematic cross-sectional view illustrating an example of the developing roller of the present invention, wherein (a) it is parallel to the longitudinal direction and (b) is 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.

  As described above, the inventors of the present invention provide a resin particle as a rough particle contained in the surface layer between two adjacent urethane groups, the structure represented by the structural formula (1), and the structural formula ( The polyurethane particles having one or both of the structure represented by 2) and the structure represented by the structural formula (3) can suppress the increase in the coating amount of the developer in a low temperature environment, Regardless, the present inventors have found that it is possible to form an image with a stable density, and have completed the present invention.

The present inventors infer the reason as follows.
In the urethane resin contained in the resin particles according to the present invention, the structure represented by the structural formula (2) or (3) has remarkably low crystallinity in the low temperature region as compared with the structure represented by the structural formula (1). Thus, the urethane resin is less likely to increase its elastic modulus in the low temperature region due to the presence of a structure having low crystallinity in the low temperature region in the polymer chain.
On the other hand, since the structure represented by the structural formula (2) or (3) has a methyl group in the side chain, the molecular mobility in the high temperature range of the urethane resin is suppressed, and the elastic modulus is lowered in the high temperature range. Hateful. That is, the resin particles according to the present invention are less likely to increase in elasticity at low temperatures and less likely to decrease at high temperatures due to the properties of the urethane resin described above. That is, the temperature dependence of the elastic modulus is reduced. As a result, the developing roller having a surface roughened by the resin particles has a clearance between the developer regulating blade and the surface of the developing roller when pressed by the developer regulating blade even when the environmental temperature changes. Is hard to change. For this reason, the developing roller according to the present invention is less dependent on the coating amount of the developer carried on the surface even when the environmental temperature changes, and the dependency on suppressing the variation in image density with respect to the environmental temperature is stable. Image formation is possible.

  Further, the presence of the structural formula (2) or (3), which is more hydrophobic than the structural formula (1), reduces the affinity for water and can reduce the water absorption rate of the polyurethane particles. Further, in the high temperature range, the molecular mobility in the high temperature range is suppressed by the presence of the side chain methyl group. As a result, an increase in adhesiveness is unlikely to occur in a high-temperature and high-humidity environment, so that an increase in developer coating amount due to an increase in tack can be suppressed, and an image can be formed with a stable density.

  Furthermore, the urethane resin contains a polyether component in which the structure represented by the structural formulas (1) and (2) or (3) is randomly copolymerized, and the crystallinity is reduced in the low temperature range and in the high temperature range. This is preferable because of its higher molecular mobility control effect.

  Further, the urethane resin has a “molar ratio of the structure of the structural formula (1)”: “a molar ratio of at least one structure selected from the structural formula (2) or (3)” is 80:20 or more and 50:50 or less. It is preferable that When the molar ratio of each structural formula is within this range, excellent effects can be obtained in both the suppression of crystallinity in the low temperature range and the suppression of molecular mobility in the high temperature range. Furthermore, the urethane resin is obtained by reacting the structure of the structural formula (1) with the polyether diol having at least one structure selected from the structural formulas (2) and (3), or the polyether diol and an aromatic diisocyanate. It is preferable that the polymer be obtained by thermosetting a hydroxyl group-terminated prepolymer and an isocyanate group-terminated prepolymer obtained by reacting the polyether diol and aromatic isocyanate.

Furthermore, in this invention, it is preferable that a surface layer contains a urethane resin as a binder resin. This is considered to be because the strength of the surface layer is increased and the wear resistance can be improved by using polyurethane as the binder resin of the surface layer. In addition, the affinity between the binder resin of the surface layer and the polyurethane resin particles can be strengthened. As a result, the binder resin of the surface layer covering the resin particles is prevented from being broken, and the resin particles are prevented from falling off. I think it can be suppressed.
In the case where a urethane resin is used as the binder resin, it is preferable that the urethane resin in the resin particles has a smaller increase in elastic modulus when the temperature is lowered than the urethane resin as the binder resin. . The present inventors infer the reason as follows.
In general, in a low temperature environment, the elastic modulus of both the binder resin and the resin particles contained in the surface layer of the developing roller tends to increase and the pressure applied to the developer tends to increase. For this reason, filming in which the developer adheres to the surface of the developing roller easily occurs when image formation is repeatedly performed. In the portion where filming has occurred, the coating amount of the developer increases due to the adhesion between the developers, causing an increase in density. This tendency is likely to occur in the vicinity of the convex portion on the surface of the developing roller where the developer is subjected to high stress. The elastic modulus of the convex portion on the surface of the image roller is governed by the elastic modulus of the resin particles as rough particles. Therefore, the amount of increase in the elastic modulus of the resin particles when the temperature is decreased is smaller than the increase in the elastic modulus of the binder resin, so that the stress applied to the developer at the convex portion when the temperature decreases. It is possible to suppress filming that causes an increase in density.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments 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 according to the present invention>
An example of the developing roller according to the present invention is shown in the schematic view of FIG.
(A) in the drawing represents a cross section parallel to the longitudinal direction of the developing roller, and (b) represents a cross section perpendicular to the longitudinal direction. 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 polyurethane 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 material of the shaft core body 11 is not particularly limited as long as it is conductive, and 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.

(Elastic layer)
The elastic layer 12 is provided to give the developing roller the elasticity required in the apparatus 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 to 10.0 mm 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, sufficient elasticity is obtained for the developing roller 10 and wear of the photosensitive drum can be suppressed. Moreover, the cost of the developing roller 10 can be suppressed by making the thickness of the elastic layer 12 10.0 mm or less.

  The elastic layer 12 preferably has an Asker-C hardness of 10 to 80 degrees. By setting the hardness of the elastic layer 12 to 10 degrees or more, it is possible to suppress the occurrence of image defects due to deformation of the elastic layer. Further, by setting the hardness of the elastic layer 12 to 80 degrees or less, wear of the photosensitive drum can be suppressed.

  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 fiber, organic reinforcing agent, organic filler. 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, a method of making it conductive by adding a conductivity imparting agent by an ionic conduction mechanism or an electronic conduction mechanism to the material can be mentioned.

Examples of the conductivity imparting agent based on the ion conduction mechanism include the following. 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 phosphoric acid ester salt, an amphoteric surfactant betaine.

  Moreover, the following are mentioned as a conductive provision agent by an electronic conductive mechanism. 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. 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 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 Base resin, silicone resin, 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, for controlling the charging of the toner, and more preferably 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, 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 divalent 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. Examples of trivalent or higher polyols include 1,1,1-trimethylolpropane, glycerin, pentaerythritol, and 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.

  As a measure of the surface roughness of the developing roller 10, the center line average roughness Ra in the standard of JIS B 0601: 1994 surface roughness is preferably 0.3 to 5.0 μm. By setting Ra to 0.3 μm or more, a more stable coating amount of the developer can be obtained, which contributes to the formation of a high-quality electrophotographic image having a uniform image density.

  The surface layer 13 roughens and contains resin particles containing a urethane resin. The urethane resin contained in the resin particles includes a structure represented by the structural formula (1), a structure represented by the structural formula (2), and the structural formula (3) between two adjacent urethane groups. One or both of the structures selected from the structures represented by:

Usually, the following methods are used for the synthesis of polyurethane.
・ One shot method in which polyol component and polyisocyanate component are mixed and reacted,
A method of reacting an isocyanate group-terminated prepolymer obtained by reacting a part of polyol with isocyanate and a chain extender such as low molecular diol or low molecular triol.

  However, the polyether diol having the structure of the structural formula (1) and at least one structure selected from the structural formulas (2) and (3) is a low polarity material. Therefore, the compatibility with a highly polar isocyanate is low, and it is easy to microscopically separate into a portion having a high polyol ratio and a portion having a high isocyanate ratio in the system. Unreacted components are likely to remain in the portion where the ratio of polyol is high, and the remaining unreacted polyol may ooze out and cause surface toner fixation.

  In order to reduce the residual unreacted polyol, it is necessary to use an excessively high-polar isocyanate, and as a result, the water absorption rate of the polyurethane often becomes high. In any of the above-described methods, the reaction between isocyanates often occurs at a high ratio, resulting in a highly polar urea bond or allophanate bond.

  A polyether diol having the structure of the structural formula (1) and at least one structure selected from the structural formulas (2) and (3), or a hydroxyl group-terminated prepolymer obtained by reacting the polyether diol with an aromatic diisocyanate; The polarity difference between the polyol and the isocyanate can be reduced by thermally curing the isocyanate group-terminated prepolymer obtained by reacting the polyether diol with the aromatic isocyanate. Therefore, the compatibility between the polyol and the isocyanate is improved, and a polyurethane having a lower polarity can be obtained with a smaller isocyanate ratio than before. Furthermore, since it is possible to keep the unreacted polyol remaining very low, it is possible to suppress surface toner adhesion due to seepage of the unreacted polyol.

  When the polyether diol having the structure of the structural formula (1) and the structure of the structural formula (2) or (3) is used as a hydroxyl group-terminated prepolymer reacted with an aromatic diisocyanate, the number average molecular weight of the prepolymer is: 10,000 or more and 15000 or less are preferable.

  Moreover, when using as an isocyanate group terminal prepolymer, it is preferable that the isocyanate content of a prepolymer exists in the range of 3.0 to 4.0 mass%. When the molecular weight of the hydroxyl group-terminated prepolymer and the isocyanate content of the isocyanate group-terminated prepolymer are within this range, the balance between the reduction in water absorption of the resulting polyurethane and the suppression of residual unreacted components is good. Can be compatible at a higher level.

More preferably, the polyurethane is obtained by thermosetting the following.
-Number average molecular weight obtained by reacting aromatic diisocyanate with a polyether diol having a number average molecular weight of 2,000 to 3,000 comprising at least one structure selected from the structure of structural formula (1) and structural formulas (2) and (3) A polyether diol having a number average molecular weight of 2000 or more and 3000 or less and a fragrance comprising a hydroxyl-terminated prepolymer of 10,000 to 15000 and a structure of the structural formula (1) and at least one structure selected from the structural formulas (2) and (3) Isocyanate group-terminated prepolymer reacted with aromatic isocyanate

  When the polyether diol having a number average molecular weight of 2000 or more and 3000 or less is used with a hydroxyl group-terminated prepolymer and an isocyanate group-terminated prepolymer, it is possible to reduce the water absorption rate of the polyurethane to be formed and to prevent residual unreacted components. Furthermore, since the strength and adhesiveness of the surface layer are excellent, the durability can be improved.

  Between the two urethane groups, other than the structure of the structural formula (1) and at least one structure selected from the structural formulas (2) and (3), as necessary to the extent that the effects of the present invention are not impaired. And polypropylene glycol and aliphatic polyester. Aliphatic polyesters include 1,4-butanediol, 3-methyl-1.5-pentanediol, diol components such as neopentyl glycol, triol components such as trimethylolpropane, adipic acid, glutaric acid, sebacic acid and the like Aliphatic polyester polyols obtained by condensation reaction with dicarboxylic acids

  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), or isophorone diisocyanate (IPDI) as required.

  Components other than the structure of the structural formula (1) and at least one structure selected from the structural formulas (2) and (3) may be 20% by mass or less in the polyurethane from the viewpoint of the effect of the present invention. preferable.

The isocyanate compound to be reacted with these polyol components is not particularly limited, but aliphatic polyisocyanates such as ethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), cyclohexane 1, 3-diisocyanate, cycloaliphatic polyisocyanate such as cyclohexane 1,4-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), polymeric diphenylmethane Aromatic isocyanates such as diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, copolymers thereof, isocyanurate bodies, TMP adduct bodies, A biuret body and its block body can be used.
Among these, aromatic isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and polymeric diphenylmethane diisocyanate are more preferably used.

A polyurethane obtained by reacting a structural component (1) with a polyether component having at least one structure selected from structural formulas (2) and (3) between an aromatic isocyanate and a urethane group is flexible. In addition, it is excellent in strength and has low adhesiveness under high temperature and high humidity, which is preferable.
The mixing ratio of the isocyanate compound to be reacted with the polyol component is preferably such that the ratio of isocyanate groups is 1.2 to 4.0 with respect to 1.0 hydroxyl groups of the polyol.

  The polyurethane particles used in the present invention can be prepared by reacting the above materials by a known method such as suspension polymerization or emulsion polymerization. For example, desired polyurethane particles can be obtained by the suspension polymerization method described in JP-A-2008-280373.

  The polyurethane particles preferably have a volume average particle size of 1.0 μm to 30.0 μm. By setting the volume average particle diameter to 1.0 μm or more, it becomes easy to control the developing roller 10 to a desired surface roughness, and a sufficient image density can be obtained. Further, by setting the volume average particle diameter to 30.0 μm or less, it becomes easy to control the developing roller 10 to a desired surface roughness, and it is possible to suppress a decrease in image quality such as fogging and roughness.

  The particle size of the polyurethane particles can be adjusted, for example, by preparing resin particles by a suspension polymerization method and appropriately changing the polymerization conditions.

  The elastic modulus of the polyurethane particles is preferably 500 MPa to 1500 MPa. By setting the elastic modulus of the polyurethane particles to 500 MPa or more, it is possible to prevent the resin particles from being excessively depressed when the developer regulating blade is brought into contact with the polyurethane particles, so that the coating amount of the developer is insufficient. In addition, by setting the elastic modulus of the polyurethane particles to 1500 MPa or less, deterioration of the developer can be suppressed, and stable image formation can be achieved over a long period of time. The elastic modulus of the polyurethane particles can be measured by a method conforming to ISO14577 using a nanoindentation measuring apparatus described later.

  In the present invention, when the temperature of the developing roller is lowered, it is preferable to control the increase in elastic modulus of the polyurethane particles and binder resin contained in the surface layer.

  The elastic modulus of the binder resin in the surface layer is preferably 500 MPa to 1500 MPa. By setting the elastic modulus of the binder resin to 500 MPa or more, deformation due to the contact member can be suppressed. Further, by setting the elastic modulus of the binder resin to 1500 MPa or less, the deterioration of the developer can be suppressed, and stable image formation can be performed over a long period of time. The elastic modulus of the binder resin can be measured by a method conforming to ISO14577 using a nanoindentation measuring apparatus described later.

  The amount of increase in the elastic modulus of the resin particles contained in the surface layer is preferably 20 MPa or more and 40 MPa or less when changed from 23 ° C. to 10 ° C. By setting the amount of increase in the elastic modulus of the polyurethane particles within this range, it is possible to suppress an increase in the density of the printed image in a low temperature environment, and it is possible to form an image with a stable density regardless of the temperature.

  The amount of increase in the elastic modulus of the binder resin contained in the surface layer is preferably 20 MPa or more and 170 MPa or less when changed from 23 ° C. to 10 ° C. By setting the increase in the elastic modulus of the binder resin to 170 MPa or less, it is possible to suppress the deterioration of the developer in a low temperature environment, and it is possible to form a stable image over a long period of time.

  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.

  When a plurality of surface layers are formed, all of the plurality of layers may contain polyurethane particles, or at least one of the plurality of layers may contain polyurethane particles.

  The thickness of the surface layer 13 is preferably 1.0 μm to 500.0 μm. Further, it is more preferably 1.0 μm to 50.0 μm. By setting the thickness of the surface layer 13 to 1.0 μm or more, durability can be imparted to the developing roller. Further, by setting the thickness of the surface layer 13 to 500.0 μm or less, more preferably 50.0 μm or less, the deterioration of the developer can be suppressed, and stable image formation can be performed 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 the surface layer surface is flattened from the interface between the surface layer and the elastic layer. The arithmetic mean value of five arbitrary points of the distance to the part.

  The MD-1 hardness of the developing roller 10 on which the surface layer is formed is preferably 25.0 ° to 40.0 °. By setting the angle to 25.0 ° or more, deformation due to the contact member can be suppressed. Further, by setting the angle to 40.0 ° or less, deterioration of the developer can be suppressed, and stable image formation can be performed 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. .

<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.

  In FIG. 2, the electrophotographic image forming apparatus 100 is provided with an image forming unit provided 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 device 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 that supplies toner to the photoreceptor 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 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 developer regulating blade 104 made of SUS304 is provided which forms toner on the developing roller in a thin layer and is frictionally charged. These are disposed in contact with the developing roller 10, respectively.

  A developer regulating blade bias power source 109 is connected to the developer regulating blade 104, a developing roller bias power source 110 is connected to the developing roller, and voltages are applied to the developer regulating blade 104 and the developing roller 10 during image formation. Applied.

<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. An 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 detachably provided on 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 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 the best mode of the present invention, but the present invention is not limited to these examples.

[Molecular weight measurement of copolymer]
The apparatus and conditions used for the measurement of the number average molecular weight (Mn) and the weight average molecular weight (Mw) in this example are as follows.
Measuring instrument: HLC-8120GPC (manufactured by Tosoh Corporation)
Column: TSKgel SuperHZMM (manufactured by Tosoh Corporation) x 2 Solvent: THF (20 mmol / L triethylamine added)
Temperature: 40 ° C
THF flow rate: 0.6 ml / min
The measurement sample was a 0.1% by mass THF solution. Further, an RI (refractive index) detector was used as a detector for measurement.
As standard samples for preparing calibration curves, TSK standard polystyrene A-1000, A-2500, A-5000, F-1, F-2, F-4, F-10, F-20, F-40, F- A calibration curve was prepared using 80, F-128 (manufactured by Tosoh Corporation), and the weight average molecular weight was determined from the retention time of the measurement sample obtained based on this.

The synthesis example for obtaining the polyurethane of this invention is shown below.
(Synthesis of polyether diols A-1 to A-5)
In a reaction vessel, a mixture of 72.1 g (1 mol) of dry tetrahydrofuran and 258.3 g (3 mol) of dry 3-methyltetrahydrofuran (molar mixing ratio 25/75) was maintained at a temperature of 10 ° C. 70% perchloric acid (10.1 g) and acetic anhydride (120.1 g) were added, and the reaction was carried out for 10 hours. Next, the reaction mixture was poured into 500 g of a 20% aqueous sodium hydroxide solution for purification. Further, water and solvent components remaining under reduced pressure were removed to obtain 224 g of liquid polyether diol A-1. The number average molecular weight was 1350.
Polyether diols A-2 to A-5 were obtained under the same conditions except that the molar mixing ratio of dry tetrahydrofuran and dry 3-methyltetrahydrofuran and the reaction time were changed as shown in Table 1.

<Production of polyurethane particles>
A separable flask equipped with a 2 L stirrer was charged with 1000 g of water, and 40 g of hydroxypropylmethylcellulose (trade name: Metrolose 90SH-100, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved therein to prepare a dispersion medium. While this dispersion medium was stirred at 600 rpm, 250 g of polyol A-1 and a mixture of 180 g of HDI isocyanurate (trade name: TPAB80E, manufactured by Asahi Kasei Co., Ltd.) as isocyanate compound B-1 were added to prepare a suspension. Next, this suspension was heated to 60 ° C. with stirring and reacted for 6 hours, and then cooled to room temperature to obtain a suspension. This suspension was separated into solid and liquid, sufficiently washed with water, and then dried at 70 ° C. for 24 hours to obtain polyurethane particles C-1 having a volume average particle diameter of 10 μm. The volume average particle diameter was 50% D diameter measured by Coulter Multisizer II (trade name, manufactured by Coulter).

  Using the same method except that the polyol and isocyanate compound were changed as shown in Table 2, polyurethane particles C-2 to C-8 shown in Table 2 were obtained. The volume average particle diameter was 10 μm for all. Here, as the isocyanate compound B-2, polymeric MDI (trade name: PAPI122, manufactured by Dow Chemical Company) was used.

  Next, polyurethane particles C-9 shown in Table 2 were obtained using the same method except that the reaction time was changed to 3.5 hours. The volume average particle diameter was 6 μm. Furthermore, polyurethane particles C-10 shown in Table 2 were obtained using the same method except that the reaction temperature was changed to 70 ° C. and the reaction time was changed to 8 hours. The volume average particle diameter was 14 μm.

In addition, the polyurethane particle C-11 shown in Table 2 is the polyurethane particle used in Comparative Example 1.

[Example 1]
<Production of developing roller>
By the following procedure, a developing roller was produced in which an elastic layer and a resin layer as a surface layer were provided one by one as a coating layer around a cylindrical conductive shaft core.
As the conductive shaft core, 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.

This base material was prepared by blending a trace amount of a platinum compound (manufactured by Toray Dow Corning, Pt concentration 1%) as a curing catalyst. Next, what mix | blended 3 mass parts of organohydrogenpolysiloxane (the Toray Dow Corning company make, weight average molecular weight 500) with this base material was prepared. These were mixed at a mass ratio of 1: 1 to obtain a liquid silicone rubber.
A conductive shaft core is placed in the center of a cylindrical mold having an inner diameter of 12 mm, and this liquid silicone rubber is injected into the cylindrical mold from the injection port, and is heated and cured at a temperature of 120 ° C. for 5 minutes, until it reaches room temperature. After cooling, the elastic layer integrated with the conductive 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 conductive shaft core.
Then, the excimer process of the elastic layer surface was performed on condition of the following.
A thin tube excimer lamp (trade name, manufactured by Harrison Toshiba Lighting Co., Ltd.) capable of irradiating ultraviolet rays having a wavelength of 172 nm while rotating the surface of the elastic layer at 30 rpm with the conductive shaft core as the rotation axis, the accumulated light amount becomes 200 mJ / cm ² . Irradiation was performed as follows. The distance between the elastic layer surface and the excimer lamp at the time of irradiation was 2 mm.

Next, the resin layer as the surface layer was coated by the following method.
The following materials were used as the material for the resin layer.

  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 polyurethane prepolymer. The obtained polyurethane prepolymer had a weight average molecular weight Mw = 10000, a hydroxyl value of 20.0 (mg · KOH / g), a molecular weight dispersity Mw / Mn = 2.9, and Mz / Mw = 2.5.

  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 polyurethane prepolymer 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.

  Furthermore, 20.0 parts by mass of carbon black (trade name: # 1000, pH 3.0, manufactured by Mitsubishi Chemical Corporation) was added. An organic solvent was added to the raw material mixture, and the solid content was appropriately adjusted in the range of 20% by mass to 30% by mass so that a film thickness of about 13 μm was obtained.

  Further, 60.0 parts by mass of the aforementioned polyurethane particles C-1 were added, uniformly dispersed and mixed to obtain a raw material liquid for the resin layer.

  The conductive shaft core body on which the elastic layer was formed was immersed in the resin layer raw material liquid, and then pulled up and allowed to dry naturally. Next, a heat treatment was performed at a temperature of 140 ° C. for 60 minutes to cure the resin layer raw material liquid to obtain a resin layer having an average thickness of 13 μm as a surface layer. Here, this surface layer binder resin is referred to as a surface layer binder resin D-1.

  Furthermore, both ends of the coating layer were cut off and removed perpendicularly to the conductive shaft core, and the length of the coating layer was adjusted to 235 mm.

  In this way, a developing roller having an outer diameter of 12 mm, a coating layer length of 235 mm, and a centerline average roughness Ra of 2.0 μm in the standard of JIS B 0601: 1994 surface roughness was produced.

  The surface layer of the present invention has a structure represented by the structural formula (1) and one or both structures selected from the structure represented by the following structural formula (2) and the structure represented by the following structural formula (3). It can be confirmed by analysis by, for example, NMR, pyrolysis GC / MS, and FT-IR.

Using FT-NMR AVANCE500 (manufactured by BRUKER), the resin particles contained in each surface layer obtained in the examples were measured nuclei ¹ H, ¹³ C, (25 ° C. in deuterated chloroform, tetramethylsilane as a reference substance) Was used). As a result, it was confirmed that the structure represented by the structural formula (1) and one or both of the structures represented by the structural formula (2) and the structural formula (3) were selected. It was done.

<Measurement of elastic modulus>
The elastic modulus of the resin particles and the binder resin on the surface layer of the developing roller thus obtained was a value of a composite elastic modulus measured using a nanoindentation measuring apparatus (trade name: Triboscope, manufactured by Hystron).

  After the surface of the resin layer of the developing roller is cut out to include a surface layer of 5 mm square and 2 mm in thickness, a sample in which a cross section of the surface layer is formed by cutting with a microtome is prepared. Next, using the nanoindentation measuring apparatus, the sample temperature is controlled to 23 ° C. by a method in accordance with ISO14577, and the resin resin center part and the binder resin part of the surface layer where no resin particles are present, Each measurement was performed three times. From the measurement results, the composite elastic modulus at 23 ° C. of the resin particles of the surface layer and the binder resin was calculated and used as the elastic modulus at 23 ° C. of each.

  Next, the sample temperature was controlled at 10 ° C., and the composite elastic modulus at 10 ° C. of the resin particles and the binder resin in the surface layer was calculated in the same manner, and the elastic modulus at 10 ° C. was obtained. Further, for each of the resin particles and the binder resin of the surface layer, the elastic modulus of the resin particles and the binder resin when the temperature of the developing roller is lowered by subtracting the elastic modulus value at 23 ° C. from the elastic modulus value at 10 ° C. The increase was determined.

  As a result of measuring the elastic modulus at 23 ° C. for the developing roller produced in Example 1, the elastic moduli of the resin particles C-1 and the binder resin D-1 of the surface layer were 750 MPa and 720 MPa, respectively. Moreover, as a result of measuring the elastic modulus at 10 ° C., the elastic moduli of the resin particles C-1 and the binder resin D-1 of the surface layer were 780 MPa and 890 MPa, respectively. Further, by subtracting the value of the elastic modulus at 23 ° C. from the value of the elastic modulus at 10 ° C., the amount of increase in the elastic modulus of the resin particles and the binder resin when the temperature of the developing roller was decreased was found to be 30 MPa and 170 MPa, respectively. Met.

<Evaluation of developing roller>
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. The electrophotographic process cartridge used was a dedicated black one, and two developing rollers were prepared by replacing the developing roller of the electrophotographic process cartridge with that prepared above.

(Concentration evaluation)
One of the electrophotographic process cartridges was mounted in the black position of the main body of the electrophotographic image forming apparatus and left in an environment of a temperature of 23 ° C. and a humidity of 50% RH for 24 hours. In the same environment, 3000 sheets of images with a printing rate of 2% were output continuously, and then one solid black image was output. This was repeated a total of 5 times. The image density of each solid black image obtained was measured and averaged at any nine points using a reflection densitometer (trade name: GretagMacbeth RD918, manufactured by Macbeth Co., Ltd.) to obtain the image density of the solid black image. Here, the average value of the image density for five times was defined as the image density at a temperature of 23 ° C.
Next, a solid black image was similarly output from the other electrophotographic process cartridge in an environment of a temperature of 10 ° C. and a humidity of 10% RH to obtain an image density at a temperature of 10 ° C.
The image density difference was determined by subtracting the image density value at a temperature of 23 ° C. from the image density value at a temperature of 10 ° C. The image density difference was evaluated according to the following criteria.
A: The image density difference is less than 0.03.
B: The image density difference is 0.03 or more and less than 0.05.
C: The image density difference is 0.05 or more and less than 0.10.
D: The image density difference is 0.10 or more.

(Evaluation of resin particles falling off the surface layer)
Next, the new developing roller produced as described above was installed in a new black electrophotographic process cartridge, and an image with a printing rate of 2% was output continuously for 15000 sheets in an environment of temperature 10 ° C. and humidity 10% RH. . After repeating this a total of 3 times, the developing roller was taken out from the electrophotographic process cartridge. Thereafter, the surface of the developing roller was observed using a digital microscope (trade name: VH-2450, manufactured by Keyence Corporation). The presence or absence of the resin particles falling off the surface layer and the number of dropping points were evaluated, and the resin particles falling off the surface layer were evaluated according to the following criteria.
A: Particle dropout is not confirmed.
B: Particle dropout is confirmed, but it is less than 5 places.
C: Particle dropout is confirmed, and there are 5 or more and less than 30 places.
D: Particle dropout is confirmed, and there are 30 or more places.
The above evaluation results are summarized in Table 5.

[Comparative Example 1]
A developing roller was produced in the same manner as in Example 1, except that the polyurethane particles C-1 were changed to polyurethane particles (trade name: C600 transparent, diameter 10 μm, manufactured by Negami Kogyo Co., Ltd.) made of ester polyurethane. This polyurethane particle is designated as C-11. The elastic modulus of the polyurethane particles C-11 was 670 MPa.
Further, in the same manner as in Example 1, the elastic modulus and the elastic modulus increase amount of the resin particles and the binder resin on the surface layer of the developing roller were measured and the developing roller was evaluated. The evaluation results are shown in Table 5.

[Comparative Example 2]
A developing roller was produced in the same manner as in Example 1 except that the polyurethane particle C-1 was changed to C-2. Further, in the same manner as in Example 1, the elastic modulus and the elastic modulus increase amount of the resin particles and the binder resin on the surface layer of the developing roller were measured and the developing roller was evaluated. The evaluation results are shown in Table 5.

[Example 2]
A developing roller was produced in the same manner as in Example 1 except that the polyurethane particle C-1 was changed to C-3. Further, in the same manner as in Example 1, the elastic modulus and the elastic modulus increase amount of the resin particles and the binder resin on the surface layer of the developing roller were measured and the developing roller was evaluated. The evaluation results are shown in Table 5.

[Examples 3 to 7]
A developing roller was produced in the same manner as in Example 1 except that the polyurethane particles C-1 were changed to the polyurethane particles described in Table 5. Further, in the same manner as in Example 1, the developing roller prepared in each example was measured for the elastic modulus and the elastic modulus increase amount of the resin particles and the binder resin on the surface layer of the developing roller, and the developing roller was evaluated. The evaluation results are shown in Table 5.

Example 8
Implementation was performed except that polytetramethylene glycol used as a material for the resin 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.) A developing roller was produced in the same manner as in Example 1. This surface layer binder resin is referred to as a surface layer binder resin D-2. The elastic modulus of the binder resin D-2 of the surface layer was 780 MPa.
Further, in the same manner as in Example 1, the elastic modulus and the elastic modulus increase amount of the resin particles and the binder resin on the surface layer of the developing roller were measured and the developing roller was evaluated. The evaluation results are shown in Table 5.

Example 9
Implementation was performed except that polytetramethylene glycol used as a material for the resin 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.) A developing roller was produced in the same manner as in Example 1. This surface layer binder resin is referred to as a surface layer binder resin D-3. The elastic modulus of the binder resin D-3 in the surface layer was 740 MPa.
Further, in the same manner as in Example 1, the elastic modulus and the elastic modulus increase amount of the resin particles and the binder resin on the surface layer of the developing roller were measured and the developing roller was evaluated. The evaluation results are shown in Table 5.

[Examples 10 and 11]
A developing roller was produced in the same manner as in Example 1 except that the polyurethane particles C-1 were changed to the polyurethane particles described in Table 5. Further, in the same manner as in Example 1, the developing roller prepared in each example was measured for the elastic modulus and the elastic modulus increase amount of the resin particles and the binder resin on the surface layer of the developing roller, and the developing roller was evaluated. The evaluation results are shown in Table 5.

  From the results of Examples 1 to 11 in Table 5, by using the above-mentioned polyurethane particles as the resin particles of the surface layer, the increase in the density of the printed image was suppressed in a low temperature environment, and the density was stabilized regardless of the temperature. It has been found that a developing roller capable of image formation can be obtained.

  Furthermore, it has been found that the resin particles can be prevented from falling off by making the resin particles smaller than the binder resin of the surface layer by increasing the elastic modulus when the temperature of the developing roller is lowered. It was.

  From the results of Comparative Example 1 and Comparative Example 2 in Table 5, it was confirmed that when the above-mentioned polyurethane particles were not used as the resin particles in the surface layer, the density of the printed image increased in a low temperature environment. Furthermore, it was confirmed that the drop of the resin particles was worsened by making the increase in the elastic modulus when the temperature of the developing roller was lowered so that the resin particles were larger than the binder resin of the surface layer. .

DESCRIPTION OF SYMBOLS 10 Developing roller 11 Conductive shaft core 12 Elastic layer 13 Surface layer

Claims (4)

A developing roller having a shaft core, an elastic layer and a surface layer,
The surface layer includes resin particles as roughened particles,
The resin particles contain a urethane resin,
The urethane resin is selected from the structure represented by the following structural formula (1), the structure represented by the following structural formula (2), and the structure represented by the following structural formula (3) between two adjacent urethane groups. A developing roller containing a urethane resin having one or both of the following structures:

.   The developing roller according to claim 1, wherein the surface layer further contains a urethane resin as a binder resin.   An electrophotographic process cartridge comprising a photosensitive member and the developing roller according to claim 1, and configured to be detachable from a main body of an electrophotographic image forming apparatus.   An electrophotographic image forming apparatus comprising the photosensitive member and the developing roller according to claim 1.

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