JP5591023B2 - Electrophotographic image forming apparatus, developer carrier and method for producing developer carrier - Google Patents

Description

  The present invention relates to a developer carrier, a method for producing the same, and an electrophotographic image forming apparatus.

  Properties required for the developer carrying member of the electrophotographic apparatus include a stable charge imparting property to the developer and a stable developer transport property. Patent Document 1 includes a shaft, an elastic layer formed on the outer periphery of the shaft, and at least one resin coating layer formed on the outer periphery of the elastic layer, and fine particles are dispersed in the resin coating layer. Therefore, it is proposed to improve these characteristics.

JP-A-2005-258201

  However, according to the study by the present inventors, when an electrophotographic image is output using the developer carrier of Patent Document 1, the developer is developed on the white background portion of the electrophotographic image, so-called fogging. It sometimes occurred.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic image forming apparatus that stably provides high-quality electrophotographic images. Another object of the present invention is to provide a developer carrying member that hardly causes fogging in an electrophotographic image even when a large number of electrophotographic images are continuously formed, and a method for manufacturing the same.

  The present invention relates to an electrophotographic image forming apparatus comprising a negatively chargeable developer and a developer carrier that transports the developer to a development region, wherein the developer carrier comprises a urethane resin matrix. A surface layer including resin, and the surface layer has urethane resin particles fixed to the surface layer in a state where a part of the surface layer is exposed from the surface layer. Fluorine atoms derived from the perfluoroalkyl group are unevenly distributed on the surface of the portion containing a salt having an alkyl group in the molecule and exposed from the surface layer, whereby the developer carrier The electrophotographic image forming apparatus is characterized in that the surface has a configuration in which convex regions having fluorine atoms are scattered in the matrix resin.

  Further, the present invention is a developer carrying member having a surface layer containing a urethane resin as a matrix resin, and the surface layer is a urethane that is fixed to the surface layer with a part thereof exposed from the surface layer. The urethane resin particles contain a salt having a perfluoroalkyl group in the molecule, and are derived from the perfluoroalkyl group on the surface of the portion exposed from the surface layer. The developer carrying member is characterized in that fluorine atoms are unevenly distributed, whereby the surface of the developer carrying member has a configuration in which convex regions having fluorine atoms on the surface are scattered in the matrix resin. is there.

Furthermore, the present invention is a method for producing the developer carrier,
(1) forming a urethane resin raw material layer;
(2) Urethane resin particles impregnated with a liquid in which a salt having a perfluoroalkyl group in the molecule is impregnated are adhered to the surface of the urethane resin raw material layer, and then the urethane resin raw material layer is cured. And a step of forming the surface layer.

  ADVANTAGE OF THE INVENTION According to this invention, the electrophotographic apparatus which provides a high quality electrophotographic image stably can be provided. In addition, according to the present invention, it is possible to provide a developer carrier and a method for manufacturing the same that hardly cause fogging in an electrophotographic image even when a large number of electrophotographic images are continuously formed.

FIG. 3 is a cross-sectional view parallel to the axial direction showing an example of the developer carrier of the present invention. It is explanatory drawing of the surface side area | region A and the surface side area | region D in the convex area | region of the developer carrier surface of this invention. It is a conceptual diagram explaining the interface area | region B in the urethane resin particle used for this invention. 1 is a schematic view showing an example of an electrophotographic image forming apparatus using a developer carrying member of the present invention. It is the schematic of a dip coating machine. It is the schematic of a spray coating machine.

<Developer carrier>
The developer carrier according to the present invention has a surface layer containing a urethane resin as a matrix resin. And the surface layer has the urethane resin particle currently fixed to the surface layer in the state where a part was exposed from the surface layer. The urethane resin particles contain a salt having a perfluoroalkyl group in the molecule, and fluorine atoms derived from the perfluoroalkyl group are unevenly distributed on the surface of the urethane resin particles exposed from the surface layer. doing.

  As a result, the surface of the developer carrying member according to the present invention has a configuration in which convex regions having fluorine atoms are scattered in the matrix resin. According to such a configuration, it is possible to suppress the occurrence of fogging on the electrophotographic image when a large number of electrophotographic images are continuously formed.

  The inventors of the present invention examined the generation mechanism of fog generated in association with the formation of a large number of electrophotographic images, and obtained the following knowledge in the process.

  That is, since the convex region formed by dispersing fine particles in the coating layer on the surface of the developer carrying member as in Patent Document 1 is rubbed strongly with the developer, the developer is located in the vicinity of the convex region. May cause excessive charge. The excessively charged developer stays on the surface of the developer carrying member without contributing to the development of the electrostatic latent image on the photosensitive member by the electric reflection force. Such a developer is eventually fixed in the vicinity of the convex region on the developer carrying member by repeated rubbing with the developer regulating member and the photosensitive member. When the output of an electrophotographic image is continued using such a developer bearing member, a fixed substance of the developer grows with the developer fixed in the vicinity of the convex region as a nucleus. Then, at the portion of the developer carrying member where the developer is fixed, sufficient charge cannot be applied to the developer, and as a result, fog occurs in which the toner is developed on the white background portion of the electrophotographic image.

  In view of the mechanism as described above, the present inventors set the charging series on the surface of the developer carrying body as a charging series for the developer so as not to generate a developer having a large charge near the convex area on the surface of the developer carrying body. I tried to get closer. However, when the charging series on the entire surface of the developer carrying member is brought close to the charging series of the developer, the developer cannot be sufficiently charged and a sufficient image density may not be obtained.

  In view of this, the present inventor has a charging member having a configuration in which the surface of the developer carrying member has a convex region having a low charge imparting property to the developer and a non-convex region having a high charge imparting property to the developer. It was investigated. As a result, it has been found that such a charging member can suppress excellent charge imparting performance and fogging during long-term use, and has led to the present invention.

<Developer carrier>
The developer carrying member according to the present invention has a roller shape of a multilayer structure having an elastic layer 2 on the outer periphery of a conductive shaft core 1 and a surface layer 3 on the outer periphery as shown in FIG. Can do.

<Surface layer>
The surface layer 3 contains a urethane resin as a matrix resin. Further, urethane resin particles are fixed to the surface layer 3 in a state where a part thereof is exposed from the surface layer 3. The urethane resin particles contain a salt having a perfluoroalkyl group in the molecule, are exposed from the surface layer, and are formed on the surface of the portion forming the convex portion of the surface of the developer carrier. Fluorine atoms derived from fluoroalkyl groups are unevenly distributed. Thereby, the surface of the developer carrying member has a configuration in which convex regions having fluorine atoms on the surface are scattered in the matrix resin.

<< Matrix resin >>
As the matrix resin, a urethane resin having an excellent charge imparting property to a negatively chargeable developer is used. This is because the urethane resin is rich in positive chargeability, and by using it as a matrix resin, the negatively chargeable developer is better charged and an electrophotographic image having a sufficient image density is obtained. On the other hand, the convex region on the surface of the developer carrier for the purpose of conveying the developer has the following configuration.

  That is, urethane resin particles as roughened particles are fixed to the surface layer with a part thereof exposed from the surface layer, and form a convex region on the surface of the developer carrier. The urethane resin particles contain a salt having a perfluoroalkyl group in the molecule, and fluorine atoms derived from the perfluoroalkyl group are unevenly distributed on the surface of the portion exposed from the surface layer. . As a result, the surface of the developer carrying member has a configuration in which convex regions having fluorine atoms on the surface are scattered in the matrix resin.

  With such a configuration, it is possible to suppress the generation of a developer having a large charge in the vicinity of the convex region. And even if it uses for a long time in the state in which the resin particle was exposed to the surface layer, the fall-off of the resin particle from a matrix resin can be suppressed. In the present invention, urethane resin particles that are buried in the matrix resin and are not exposed on the surface may exist.

  Fluorine atoms have a high negative chargeability and a low charge imparting property to a negatively chargeable developer. Since the fluorine atom having such characteristics exists in the convex region on the surface of the developer carrying member that rubs strongly with the developer, the generation of a developer having a large charge in the vicinity of the convex region can be suppressed. On the other hand, a perfluoroalkyl group has low adhesion to other substances, and when a substance having a perfluoroalkyl group is used in a state where it is exposed to the surface layer, the substance having a perfluoroalkyl group has been May fall off the layer.

  In the present invention, by selecting the material of the matrix resin and the exposed resin particles and controlling the presence of perfluoroalkyl groups in the resin particles, the resin particles can be used for a long time with the surface layer exposed. Even in this case, it is possible to prevent the resin particles from dropping from the matrix resin.

  Specifically, (1) urethane resin particles are used as resin particles that form convex regions on the surface of the developer carrying member. Since the matrix resin is also a urethane resin, the adhesion between the matrix resin and the resin particles is very good. (2) The fluorine atom derived from the perfluoroalkyl group is unevenly distributed on the surface of the convex region, which is a portion where the urethane resin particles are exposed from the matrix resin. By reducing the amount of fluorine atoms at the interface between the matrix resin and the resin particles, it is possible to suppress the dropping of the resin particles from the matrix resin.

  As described above, the matrix resin 31 needs to be a urethane resin because of the chargeability of the developer, and is particularly preferably a polyether polyurethane resin that can reduce the hardness of the film and has high chargeability of the developer. The polyether polyurethane resin can be obtained by a reaction between a known polyether polyol and an isocyanate compound.

  Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. In addition, for these polyol components, prepolymers that are chain-extended with an isocyanate such as 2,4-tolylene diisocyanate (TDI), 1,4 diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI) in advance may be used.

  Specific examples of the isocyanate compound to be reacted with these polyol components are shown below. Aliphatic polyisocyanates (ethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), etc.); alicyclic polyisocyanates (isophorone diisocyanate (IPDI), cyclohexane 1,3-diisocyanate, cyclohexane 1,4-diisocyanate, etc.); aroma Group polyisocyanates (2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), etc.). Moreover, these modified substances, copolymers, and block bodies thereof can be used.

<< Urethane resin particles >>
The standard of the volume average particle diameter of the urethane resin particles 32 is 5 μm or more and 20 μm or less in order to form a convex shape on the surface of the developer carrier for the purpose of transporting the developer. Here, the volume average particle size can be measured using a laser diffraction particle size distribution measuring device (for example, SALD-3100 (trade name) manufactured by Shimadzu Corporation). Further, flexible urethane resin particles having a micro-compression hardness of 1 [mN / μm] or less are preferable because developer fusion is less likely to occur.

Examples of such urethane resin particles that are soft spherical urethane resin particles before containing a salt having a perfluoroalkyl group in the molecule include Art Pearl (trade name) manufactured by Negami Kogyo Co., Ltd. Chemical-made dimic beads (trade name) are commercially available. The micro compression hardness is a value measured under the following measurement conditions with an ultra micro hardness meter (trade name: ENT1100a, manufactured by Elionix).
Load range A, test load: 1 [mN], number of divisions: 1000, step interval: 10 [msec. ],
Indenter type: flat plate with a diameter of 20 μm.
The maximum displacement [μm] is read from the obtained displacement-load diagram, and the micro compression hardness is calculated by the following equation.
Micro compression hardness = Test load 1 [mN] / Maximum displacement [μm].

<< Salt having a perfluoroalkyl group in the molecule >>
Examples of the salt having a perfluoroalkyl group in the molecule include metal salts and ammonium salts of perfluoroalkyl sulfonic acids, metal salts and ammonium salts of perfluoroalkyl carboxylic acids, and the like. Here, from the viewpoint of uneven distribution on the surface of the urethane resin particle exposed portion (convex region), solubility in a solvent, and influence on the environment, the carbon number of the perfluoroalkyl group portion having an anion represented by the following structural formula Of 3 or more and 6 or less perfluoroalkyl sulfonate is preferable.
_{C n F 2n + 1 SO 3} - ··· (1)
(N represents an integer of 3 to 6.)
In the developer carrier according to the present invention, fluorine atoms derived from perfluoroalkyl groups are unevenly distributed on the surface of the convex region, and the convex region is scattered in the matrix resin on the surface of the developer carrier. Hereinafter, the uneven distribution and the interspersed will be described.

  FIG. 2 is an enlarged plan view of the vicinity of one urethane resin particle forming a convex region on the surface of the developer carrying member. The urethane resin particles 32 are exposed from the matrix resin 31 to form a convex region. Then, the ratio of fluorine atoms measured by energy dispersive X-ray fluorescence analysis (EDX) in the region A of 1 μm square at an arbitrary position on the surface of the exposed portion of the urethane resin particles 32 is Xa [at%]. And Note that reference numeral 4 in FIG. 2 indicates a minimum circumscribed circle with respect to the shape of the urethane resin particles projected onto the developer carrier surface.

  FIG. 3 is an enlarged cross-sectional view of one urethane resin particle forming a convex region on the surface of the developer carrier and the vicinity thereof when cut perpendicularly to the surface of the developer carrier. Points a and b are intersections between the matrix resin 31 and the convex regions of the urethane resin particles 32. In the cross section of the urethane resin particle 32, the ratio of fluorine atoms measured by EDX is defined as Xb [at%] in a 1 μm square region B in contact with the boundary with the matrix resin 31. At this time, it is defined as Xa> Xb that fluorine atoms derived from perfluoroalkyl groups are unevenly distributed on the surface of the portion exposed from the surface layer of the urethane resin particles.

  In the present invention, Xb is preferably 1.3 [at%] or less. Thereby, the drop-off from the surface layer of the urethane resin particles 32 can be more effectively suppressed.

  Next, in FIG. 2, the ratio of fluorine atoms measured by EDX in a 1 μm square region D on the surface of the developer carrying member without urethane resin particles is defined as Xd [at%]. In the present invention, when Xd is 0.1 [at%] or less and Xa> Xd, it is defined that convex regions having fluorine atoms on the surface are scattered in the matrix resin.

Further, an arbitrary 100 μm square region on the surface of the developer carrier is defined as a region C, and the ratio of fluorine atoms measured by energy dispersive X-ray fluorescence (EDX) analysis in this region C is determined per developer carrier. Measure at 5 points. From the viewpoint of image density, it is preferable to satisfy Xc ≦ 1.5 when the arithmetic average value of these five locations is Xc [at%]. In the present invention, the Xa [at%], Xb [at%], Xc [at%] and Xd [at%] can be measured under the following measurement conditions.
[measuring device]
Scanning electron microscope S-4800 (trade name, manufactured by Hitachi High Technology) and energy dispersive X-ray fluorescence analysis (EDX) Genesis 400 (trade name, manufactured by EDAX),
[Measurement condition]
Acceleration voltage 20KV.

<Shaft core>
As the shaft core 1, a cylindrical body made of metal such as aluminum, iron, and stainless steel (SUS) can be used.

<Elastic layer>
The elastic layer 2 can include rubber or elastomer and a conductive material for making the elastic layer conductive. Specific examples of rubber and elastomer are listed below. Polyurethane, natural rubber, butyl rubber, nitrile rubber, polyisoprene rubber, polybutadiene rubber, silicone rubber, styrene-butadiene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, chloroprene rubber, acrylic rubber, and mixtures thereof. Of these, silicone rubber having a low hardness and a high resilience is preferably used.

  Examples of the conductive material include electronic conductive materials such as carbon black, metal, and metal oxide, and ionic conductive materials such as sodium perchlorate. The elastic layer 2 preferably has an ASKER-C hardness of 25 ° to 60 °. Moreover, it is preferable that the thickness of an elastic layer is 0.5 mm or more and 5 mm or less.

<Method for producing developer carrier>
The developer carrying member according to the present invention can be obtained by forming an elastic layer on the outer periphery of the shaft core body using a known method and forming a surface layer on the outer periphery by a known method. Here, the method of forming the elastic layer is not particularly limited, but since the elastic layer can be formed with high dimensional accuracy, a method of forming the elastic layer by injecting an elastic material into the mold is preferable.

  Next, a surface layer that realizes a configuration in which convex regions having fluorine atoms on the surface are scattered in the matrix resin is formed. That is, first, the urethane resin particles are impregnated with a salt solution having a perfluoroalkyl group in the molecule. Next, a coating film (urethane resin raw material layer) for forming a surface layer containing isocyanate and polyol as raw materials for the urethane resin is formed on the elastic layer. Next, before the coating film is dried, urethane resin particle dispersion prepared by dispersing urethane resin particles impregnated with a liquid in which a salt having a perfluoroalkyl group in the molecule is dissolved in a poor solvent for the salt The urethane resin particles are adhered to the surface of the coating film by spraying a liquid. Next, by curing the coating film, it is possible to form a surface layer in which the urethane resin particles are fixed in a state where a part thereof is exposed.

  Here, as a solvent for dissolving a salt having a perfluoroalkyl group in the molecule, acetone, methyl ethyl ketone (MEK), etc. are used because of the solubility of the salt having a perfluoroalkyl group in the molecule and the impregnation property to urethane resin particles. Ketones are preferred.

  According to such a production method, it is possible to obtain a developer bearing member in which urethane resin particles are exposed on the surface layer, and fluorine atoms are unevenly distributed on the surface of the convex region which is the exposed portion. Here, it is considered that the reason why fluorine atoms are unevenly distributed on the surface of the exposed portion of the urethane resin particles is due to the following two reasons.

  (1) In the urethane resin particles, the salt having a perfluoroalkyl group impregnated in the urethane resin particles exists in a state dissolved in a solvent. On the other hand, since the urethane resin particles are present in a state exposed on the surface layer, the solvent impregnated in the urethane resin particles volatilizes toward the exposed portion. It is considered that the salt having a perfluoroalkyl group moves to the exposed portion of the urethane resin particles along with the flow of the solvent at the time of volatilization.

  (2) The perfluoroalkyl group portion of the salt having a perfluoroalkyl group moved to the vicinity of the exposed portion of the urethane resin particle as in (1) described above is in the direction of decreasing the surface free energy, that is, the exposure of the urethane resin particle. Oriented to the part surface.

  Here, the coating method of the urethane resin layer which is a matrix resin is not particularly limited, and a known method can be used, but dip coating is preferable from the viewpoint of productivity. FIG. 5 shows an example of a dip coater. FIG. 5 includes an immersion tank 25 filled with a paint for forming a surface layer having a urethane resin matrix, a transport pump 26 for circulating the paint in the direction of the arrow, and an agitation tank 27 for stirring the paint. ing. The urethane resin layer can be applied by gripping the developer carrier before forming the surface layer by the lifting device 28 and immersing it in the immersion tank 25.

  Further, the method for adhering the urethane resin particles to the surface of the urethane resin layer is not particularly limited, but the following method is preferable in consideration of productivity. That is, a method in which urethane resin particles impregnated with a salt having a perfluoroalkyl group in the molecule is spray-coated on the surface of the urethane matrix resin layer before drying and curing with a liquid in which the salt is dispersed in a poor solvent is preferable.

  FIG. 6 shows an example of a spray coating machine. FIG. 6 has a spray gun 29. The developer carrying body before adhesion of urethane resin particles is rotated by a rotating means (not shown), and the spray gun 29 is moved up and down by a spray gun lifting / lowering device (not shown) for spray application. can do. Here, as the poor solvent, alcohols such as methanol and ethanol are preferable because of the low solubility and volatility of the salt having a perfluoroalkyl group in the molecule and good spray coating properties. The method for drying and curing the urethane resin layer is not particularly limited, and a known method can be used.

<Additives>
In the present invention, the elastic layer 2 and the surface layer 3 are each made of an electronically conductive substance (carbon black, metal or metal oxide) or an ionic conductive substance (sodium perchlorate, modified aliphatic dimethyl) as an electric resistance adjusting agent. Ammonium etosulphate etc.) may be added. In the present invention, the method for dispersing the additive such as the resistance adjusting agent in the material forming the elastic layer 2 is not particularly limited, and a known apparatus such as a roll, a Banbury mixer, a pressure kneader or the like is used. Can be dispersed.

  Further, the method for dispersing the additive such as the resistance adjusting agent in the coating material forming the surface layer 3 is not particularly limited. For example, various additives can be added to a resin solution in which a matrix resin material is dissolved in an appropriate organic solvent, and dispersed using a known apparatus such as a sand grinder, a sand mill, or a ball mill.

<Electrophotographic image forming apparatus>
An electrophotographic apparatus according to the present invention includes a negatively chargeable developer and a developer carrier that transports the developer to the development region, and has the developer carrier described above as the developer carrier. ing. With such a configuration, even when a large number of electrophotographic images are continuously formed, fogging on the electrophotographic image is unlikely to occur, and an image having a sufficient density can be stably obtained.

  FIG. 4 is a schematic cross-sectional view of an electrophotographic apparatus provided with the developer carrying member of the present invention. The electrophotographic apparatus shown in FIG. 4 has a developing device 10 including a developer carrier 6, a developer coating member 7, a negatively chargeable developer 8, and a developing blade 9 having a mechanism capable of applying a blade bias. ing. Further, it has a photosensitive drum 5, a cleaning blade 14, a waste developer container 13, and a charging member 12.

  The photosensitive drum 5 rotates in the direction of the arrow, is uniformly charged by a charging member 12 for charging the photosensitive drum 5, and the surface thereof is exposed by laser light 11 which is an exposure means for writing an electrostatic latent image on the photosensitive drum 5. An electrostatic latent image is formed. The electrostatic latent image is developed by applying a negatively chargeable developer by the developing device 10 disposed in contact with the photosensitive drum 5 and visualized on the photosensitive drum 5 as a developer image. Development is so-called reversal development in which a negatively chargeable developer image is formed on the exposed portion.

  On the other hand, the paper 22 that is a recording medium is fed by the paper feed roller 23, and is then sucked onto the transfer conveyance belt 20 by the bias supplied from the bias power supply 18 to the suction roller 24, and the arrow is driven by the drive roller 16. Conveyed in the direction. The transfer / conveying belt 20 is stretched around the driving roller 16, the driven roller 21, and the tension roller 19. The visualized developer image on the photosensitive drum 5 is transferred by the transfer roller 17 as a transfer member onto the paper 22 adsorbed on the transfer conveyance belt 20 as described above. The paper 22 to which the developer image has been transferred is fixed by the fixing device 15 and discharged outside the device, thus completing the printing operation.

  On the other hand, the untransferred developer remaining on the photosensitive drum 5 without being transferred is scraped off by a cleaning blade 14 which is a cleaning member for cleaning the surface of the photoreceptor, and is stored in a waste developer container 13 and cleaned. The photosensitive drum 5 repeats the above operation. The developing device 10 includes a developing container that contains a negatively chargeable developer 8, and a developer carrier 6 that is located in an opening extending in the longitudinal direction in the developing container and is disposed to face the photosensitive drum 5. The electrostatic latent image on the photosensitive drum 5 is developed and visualized.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example and a comparative example, a present Example does not limit this invention at all.

<Example 1>
[Formation of elastic layer]
As the shaft core body 1, a core metal (made by SUM22) having an outer diameter of 6 mm was subjected to nickel plating, and a primer DY35-051 (trade name, manufactured by Toray Dow Corning Silicone) was applied and baked. Next, the shaft core body 1 is arranged concentrically with a cylindrical mold having an inner diameter of 11.5 mm, and the additional silicone rubber composition having the composition shown in Table 1 is injected into the cavity formed in the mold. did. Subsequently, the mold was heated to cure and cure the addition-type silicone rubber composition at 150 ° C. for 15 minutes. Thereafter, the mixture was further heated at 200 ° C. for 2 hours to complete the curing reaction, and the elastic layer 1 having a thickness of 2.75 mm was provided on the outer periphery of the shaft core 1.

[Polyol synthesis]
To 100 parts by mass of polytetramethylene glycol PTG1000SN (trade name, manufactured by Hodogaya Chemical Co., Ltd.), 20 parts by mass of an isocyanate compound (trade name: manufactured by Millionate MT Nippon Polyurethane Industry Co., Ltd.) was mixed stepwise in a MEK solvent. The solution was reacted at 80 ° C. for 7 hours under a nitrogen atmosphere to prepare polyether polyol 1 having a hydroxyl value of 20 [mgKOH / g].

[Synthesis of isocyanate]
Under a nitrogen atmosphere, 57 parts by mass of crude MDI (trade name: Cosmonate M-200, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.) is added to 100 parts by mass of polypropylene glycol having a number average molecular weight of 400 (trade name: Exenol, manufactured by Asahi Glass Co., Ltd.). The reaction was carried out at 2 ° C. for 2 hours. Thereafter, butyl cellosolve was added so as to have a solid content of 70% by mass, and an isocyanate compound having a mass ratio of NCO groups contained per unit solid content of 5.0% by mass was obtained. Thereafter, 22 parts by mass of MEK oxime was added dropwise under a reaction temperature of 50 ° C. to obtain block polyisocyanate 1.

[Production of surface layer paint]
Block Polyisocyanate 1 was mixed with Polyol 1 produced as described above so that the NCO / OH group ratio was 1.4. MEK is mixed with 20 parts by mass of carbon black (trade name: MA100, manufactured by Mitsubishi Chemical Corporation, pH = 3.5) with respect to 100 parts by mass of the solid content of this mixture so that the total solid content concentration becomes 35% by mass. Dissolved and mixed. This mixed solution was dispersed for 4 hours using a sand mill using glass beads having a particle diameter of 1.5 mm to prepare a surface layer coating material 1.

[Preparation of urethane resin particles 1]
Potassium perfluorobutanesulfonate (general formula C ₄ F ₉ SO ₃ K, trade name KFBS, manufactured by Gemco) was dissolved in methyl ethyl ketone (MEK) to prepare a salt solution 1 having a salt concentration of 2% by mass. In a sealed container, 100 parts by mass of the salt solution 1 was impregnated into 100 parts by mass of urethane resin particles (trade name: Art Pearl C600, volume average particle size 10 μm, manufactured by Negami Industrial Co., Ltd.). This is referred to as urethane resin particle 1.

[Preparation of dispersion of urethane resin particles 1]
100 parts by mass of urethane resin particles 1 were put into 900 parts by mass of ethanol, which is a poor solvent for potassium perfluorobutanesulfonate, and ultrasonically dispersed to prepare a dispersion of urethane resin particles 1. This is referred to as a resin particle dispersion 1.

[Formation of surface layer on elastic layer]
Immediately after forming the urethane resin layer 1 by dip-coating the surface layer-forming coating material 1 on the elastic layer 1 using the overflow type dip coating apparatus shown in FIG. The urethane resin layer 1 was spray coated using the spray coating apparatus shown in FIG. After air drying at room temperature for 30 minutes, the developer carrying member of Example 1 having the surface layer 1 on the elastic layer surface was obtained by heat treatment in a hot air circulating oven at 140 ° C. for 2 hours.

  In addition, the salt solution of Examples 2 to 21 to be described later, the urethane resin particles impregnated with the salt solution, and the resin particle dispersion are respectively salt solution 2 to 21, urethane resin particles 2 to 21, and resin particle dispersion 2 Referred to as ~ 21.

<Confirmation of resin particles>
Using a sharp razor blade, the surface layer of the developer carrying member was cut into a kamaboko shape together with the elastic layer to obtain an observation sample. The obtained observation sample was observed at an arbitrary magnification (for example, 500 times or more and 2000 times or less) using a video microscope, and the presence state of the particles was confirmed. As a result, the presence of urethane resin particles fixed to the surface layer in a state where a part thereof was exposed from the matrix resin was confirmed.

<Measurement of Fluorine Atom Ratio Xa [at%], Xb [at%], Xc [at%] and Xd [at%]>
In the observation sample, the fluorine atom ratio Xa [at%] of the surface side area A of the convex area, the fluorine atom ratio Xb [at%] of the interface area B with the matrix resin, and 100 μm square of the developer carrier surface. The fluorine atom ratio Xc [at%] in the region C was measured. Moreover, it measured similarly about the fluorine atom ratio Xd [at%] of the area | region D of the surface layers other than a convex area | region. The measurement results are shown in Table 2.

[Image output test]
The developer was extracted from two magenta cartridges of a laser printer (trade name: LBP5050, manufactured by Canon). This cartridge was filled with magenta negatively charged developer having an average particle diameter of 6.6 μm produced by the polymerization method described in Example 49 of JP-A-2006-106198, and two image output test cartridges were prepared. did. First, the developer carrier of Example 1 was attached to one of the cartridges, and the cartridge was loaded into the laser printer. Then, an image output test was conducted in an environment of a temperature of 15 ° C. and a relative humidity of 10% Rh, where developer fusion is most likely to occur. Color laser copier paper A4 (trade name, manufactured by Canon) was used for the image output test. First, one solid black image was output. This was the initial image.
Subsequently, images with a printing rate of 1% were continuously output, and 3000 images were output. Thereafter, the developer carrying member was taken out from the 3000-sheet endured cartridge and replaced with another image output test cartridge, and 3000 images were similarly output in an environment of a temperature of 15 ° C. and a relative humidity of 10% Rh. That is, as a developer carrier, an image corresponding to 6000 sheets is finally output, and finally a solid white image is output on glossy paper (trade name: Image Coat Gloss 158, manufactured by Canon), and a solid black image is output by a color laser. Output to Copier Paper A4 (trade name, manufactured by Canon). This was used as an image after durability. The following measurement and observation were performed on the output image and the developer carrier after the image output test.

[Measurement of image density]
The density was measured by a color reflection densitometer (trade name: X-RITE 404A: manufactured by X-Rite Co.) at nine locations on the paper surface of the output solid black image after the initial and endurance output. The average value of the 9 points of density at this time was defined as the image density. When the image density exceeds 1.30, it can be determined that the image is extremely good. When the image density is 1.20 or more and 1.30 or less, a good image having a sufficiently high density is obtained. If it is less than 1.20, the image has a low density.

[Measurement of fog]
Ten points of the reflection density of the solid white image portion of the solid white image after durability outputted on gloss paper (trade name image coat gloss 158, manufactured by Canon) were measured, and the average value was defined as Ds (%). On the other hand, the reflection density of gloss paper before printing was measured at 10 points, and the value calculated by the calculation formula: Ds-Dr (%) when the average value was Dr (%) was defined as the fogging amount. The reflection density was measured using a reflection densitometer (trade name: “REFLECTOMETER MODEL TC-6DS / A”, manufactured by TOKYO DENSHOKU CO. LTD). When the fogging amount is less than 0.6%, it can be determined that the image is extremely good. When the fogging amount is 0.6% or more and 2.0% or less, a good image with substantially no fogging is obtained. If it exceeds 2.0%, it is an unclear image with conspicuous fogging.

[Observation of developing roller surface]
The developer carrier after the image output test corresponding to 6000 sheets is taken out from the cartridge for image output test, the developer adhering to the surface is removed by air blow, the surface of the developer carrier is observed, and the resin of the surface layer The presence or absence of particle dropout was confirmed. For observation, a laser microscope (trade name: VK-8700, manufactured by Keyence Corporation) was used.

<Example 2>
A developer carrier was prepared in the same manner as in Example 1 except that the potassium perfluorobutanesulfonate used in the preparation of the salt solution 1 of Example 1 was changed to sodium perfluorohexasulfonate prepared as follows. Prepared and evaluated.

[Preparation of sodium perfluorohexanesulfonate]
A glass flask equipped with a stirrer, a condenser and a thermometer was charged with 100 parts by mass of perfluorohexanesulfonic acid, 100 parts by mass of ion-exchanged water, and 200 parts by mass of isopropyl alcohol. Thereafter, a solution prepared by dissolving 10 parts by mass of sodium hydroxide in 100 parts by mass of ion-exchanged water was added over 30 minutes at room temperature while stirring. The temperature was raised to 80 ° C. and stirring was continued for 2 hours. Thereafter, the wet powder obtained by removing ion-exchanged water and isopropanol under reduced pressure at the same temperature was heated with hot air at 80 ° C. for 20 hours to obtain sodium perfluorohexanesulfonate (general formula C ₆ F ₁₃ SO ₃ Na). Got.

<Example 3>
A developer carrier was prepared in the same manner as in Example 1 except that the salt concentration of the salt solution 1 used for preparing the urethane resin particles 1 of Example 1 was changed from 2.0% by mass to 1.5% by mass. ,evaluated.

<Example 4>
A developer carrier was prepared in the same manner as in Example 1 except that the salt concentration of the salt solution 1 used for preparing the urethane resin particles 1 of Example 1 was changed from 2.0% by mass to 3.0% by mass. ,evaluated.

<Example 5>
A developer carrier was prepared in the same manner as in Example 2 except that the salt concentration of the salt solution 2 used for preparing the urethane resin particles 2 in Example 2 was changed from 2.0% by mass to 2.5% by mass. ,evaluated.

<Example 6>
The potassium perfluorobutane sulfonate used in the preparation of the salt solution 3 of Example 3 was changed to lithium perfluoropropane sulfonate (general formula C ₃ F ₇ SO ₃ Li, trade name EF-35, manufactured by Gemco). . Further, the amount of ethanol used in the resin particle dispersion was changed from 900 parts by mass to 300 parts by mass. Otherwise, a developer carrier was prepared and evaluated in the same manner as in Example 3.

<Example 7>
The potassium perfluorobutane sulfonate used in the preparation of the salt solution 1 of Example 1 was changed to lithium perfluoropropane sulfonate (general formula C ₃ F ₇ SO ₃ Li, trade name EF-35, manufactured by Gemco). . The salt concentration of the salt solution 7 in which lithium perfluoropropane sulfonate was dissolved in MEK was 1.0% by mass. Otherwise, a developer carrier was prepared and evaluated in the same manner as in Example 1.

<Example 8>
The potassium perfluorobutane sulfonate used for the preparation of the salt solution 3 of Example 3 was changed to lithium perfluoroethane sulfonate (general formula C ₂ F ₅ SO ₃ Li, trade name EF-25, manufactured by Gemco). . Otherwise, a developer carrier was prepared and evaluated in the same manner as in Example 3.

<Example 9>
A developer carrier was prepared in the same manner as in Example 2 except that the salt concentration of the salt solution 2 used for preparing the urethane resin particles 2 in Example 2 was changed from 2.0% by mass to 3.0% by mass. ,evaluated.

<Example 10>
The potassium perfluorobutane sulfonate used for the preparation of the salt solution 3 of Example 3 was changed to sodium trifluoromethane sulfonate (general formula CF ₃ SO ₃ Na, trade name EF-13, manufactured by Gemco). Otherwise, a developer carrier was prepared and evaluated in the same manner as in Example 3.

<Example 11>
A developer carrier was prepared and evaluated in the same manner as in Example 9 except that the amount of ethanol used in the resin particle dispersion 9 of Example 9 was changed from 900 parts by mass to 600 parts by mass.

<Example 12>
The urethane resin particles used for the preparation of the urethane resin particles 1 of Example 1 were the same as those of Example 1 except that they were changed to Art Pearl C300 (trade name, volume average particle size 20 μm, manufactured by Negami Kogyo Co., Ltd.) having the same parts by mass. A developer carrier was prepared and evaluated.

<Example 13>
Example 2 The same as Example 2 except that the urethane resin particles used in the preparation of the urethane resin particles 2 of Example 2 were changed to Art Pearl C300 (trade name, volume average particle size 20 μm, manufactured by Negami Kogyo Co., Ltd.) of the same mass parts. A developer carrier was prepared and evaluated.

<Example 14>
Example 7 The same as Example 7 except that the urethane resin particles used in the preparation of the urethane resin particles 7 of Example 7 were changed to Art Pearl C300 (trade name, volume average particle size 20 μm, manufactured by Negami Kogyo Co., Ltd.) of the same mass parts. A developer carrier was prepared and evaluated.

<Example 15>
Example 8 The same as Example 8 except that the urethane resin particles used for the preparation of the urethane resin particles 8 of Example 8 were changed to Art Pearl C300 (trade name, volume average particle size 20 μm, manufactured by Negami Kogyo Co., Ltd.) having the same parts by mass. A developer carrier was prepared and evaluated.

<Example 16>
Similar to Example 10 except that the urethane resin particles used for the preparation of the urethane resin particles 10 of Example 10 were changed to Art Pearl C300 (trade name, volume average particle size 20 μm, manufactured by Negami Kogyo Co., Ltd.) having the same parts by mass. A developer carrier was prepared and evaluated.

<Example 17>
Similar to Example 1 except that the urethane resin particles used for the preparation of the urethane resin particles 1 of Example 1 were changed to Art Pearl C800 (trade name, volume average particle size 6 μm, manufactured by Negami Kogyo Co., Ltd.) of the same mass parts. A developer carrier was prepared and evaluated.

<Example 18>
Example 2 The same as Example 2 except that the urethane resin particles used for the preparation of the urethane resin particles 2 of Example 2 were changed to Art Pearl C800 (trade name, volume average particle size 6 μm, manufactured by Negami Kogyo Co., Ltd.) of the same mass parts. A developer carrier was prepared and evaluated.

<Example 19>
Example 7 The same as Example 7 except that the urethane resin particles used for the preparation of the urethane resin particles 7 of Example 7 were changed to Art Pearl C800 (trade name, volume average particle size 6 μm, manufactured by Negami Kogyo Co., Ltd.) of the same parts by mass. A developer carrier was prepared and evaluated.

<Example 20>
Example 8 The same as Example 8 except that the urethane resin particles used for the preparation of the urethane resin particles 8 of Example 8 were changed to Art Pearl C800 (trade name, volume average particle size 6 μm, manufactured by Negami Kogyo Co., Ltd.) of the same mass parts. A developer carrier was prepared and evaluated.

<Example 21>
Similar to Example 10 except that the urethane resin particles used in the preparation of the urethane resin particles 10 of Example 10 were changed to Art Pearl C800 (trade name, volume average particle size 6 μm, manufactured by Negami Kogyo Co., Ltd.) of the same mass parts. A developer carrier was prepared and evaluated.
The evaluation results of Examples 1-21 are shown in Tables 2-3.

<Comparative Example 1>
In Example 1, the surface layer coating material 1 was changed to the surface layer coating material 22 prepared as follows. Moreover, the spray coating of the resin particle dispersion 1 immediately after the surface layer coating 22 was dip-coated on the elastic layer was not performed. Otherwise, a developer carrying member having a surface layer on the elastic layer surface was obtained in the same manner as in Example 1. The obtained developer carrying member was evaluated in the same manner as in Example 1. As a result, in the surface layer of the developer carrying member of Comparative Example 1, a part of each particle was not exposed from the matrix resin for at least a part of all the urethane resin particles. Further, since the fluorine atom does not exist on the developer carrying surface, the fog was conspicuous.

[Production of surface layer paint]
First, a dispersion 22 was prepared by ultrasonically dispersing 24 parts by mass of Art Pearl C600 (trade name, volume average particle size 10 μm, manufactured by Negami Kogyo Co., Ltd.), which is urethane resin particles, in 60 parts by mass of MEK. The obtained dispersion liquid 22 was added to the surface layer coating material 1 of Example 1, and further dispersed for 30 minutes using a sand mill to prepare the surface layer coating material 22.

<Comparative example 2>
In Example 1, a developer carrier was prepared and evaluated in the same manner as in Example 1 except that the following fluororesin particle dispersion 23 was used instead of the resin particle dispersion 1. As a result, as shown in Tables 2 to 3, the surface of the developer carrier of Comparative Example 2 had a configuration in which convex regions having fluorine atoms on the surface were scattered in the matrix resin. Xc was very large and the image density was low from the beginning. Further, since the fluorine atoms were not unevenly distributed in the exposed portions of the resin particles from the matrix resin, the surface of the developer carrying member after the image output test was observed, and the fluororesin particles were almost removed. As a result, the convex area on the surface of the developer carrying member is in a direction in which the image density drops as the number of image output proceeds and the image density decreases, but Xc decreases and the image density increases. From the beginning, the results were low regardless of the number of output images.

[Preparation of fluororesin dispersion 23]
100 g of polytetrafluoroethylene resin dispersion KD-200AF (trade name, manufactured by Kitamura Co., Ltd., particle diameter of polytetrafluoroethylene particles: about 3.5 μm) was diluted with 200 g of xylene to obtain fluororesin dispersion 23.

<Comparative Example 3>
In Example 1, the surface layer coating material 1 was changed to the surface layer coating material 24 prepared as follows. Moreover, the spray coating of the urethane resin particle dispersion liquid 1 immediately after the surface layer coating 24 was dip-coated on the elastic layer was not performed. Otherwise, a developer carrying member having a surface layer on the elastic layer surface was obtained in the same manner as in Example 1. The obtained developer carrying member was evaluated in the same manner as in Example 1. As a result, as shown in Tables 2 and 3, in the surface layer of the developer carrying member of Comparative Example 3, a part of each particle was exposed from the matrix resin for at least a part of all the urethane resin particles. It wasn't. In addition, since fluorine atoms exist in regions other than the convex region, the image density was low from the beginning.

[Production of surface layer paint]
Block Polyisocyanate 1 was mixed with Polyol 1 produced as in Example 1 so that the NCO / OH group ratio was 1.4. Thereafter, 20 parts by mass of carbon black (trade name: MA100, manufactured by Mitsubishi Chemical Corporation, Ph = 3.5) is mixed with 100 parts by mass of the resin solids, and MEK is adjusted so that the total solids ratio is 35% by mass. Dissolved and mixed. Furthermore, 2 parts by mass of potassium perfluorobutanesulfonate (general formula C ₄ F ₉ SO ₃ K, trade name KFBS, manufactured by Gemco) was mixed, and 4 using a glass mill having a particle diameter of 1.5 mm using a sand mill. Dispersion with time was performed to prepare dispersion 24-1. On the other hand, a dispersion 24-2 was prepared by ultrasonically dispersing 24 parts by mass of Art Pearl C600 (trade name, volume average particle size 10 μm, manufactured by Negami Kogyo Co., Ltd.), which is urethane resin particles, in 60 parts by mass of MEK. The obtained dispersion liquid 24-2 was added to the dispersion liquid 24-1, and further dispersed for 30 minutes using a sand mill to prepare a surface layer coating material 24.

1 Axle core 2 Elastic layer 3 Surface layer

Claims (4)

An electrophotographic image forming apparatus comprising a negatively chargeable developer and a developer carrier for transporting the developer to a development region,
The developer carrier has a surface layer containing a urethane resin as a matrix resin,
The surface layer has urethane resin particles fixed to the surface layer in a state where a part of the surface layer is exposed from the surface layer,
The urethane resin particles contain a salt having a perfluoroalkyl group in the molecule, and fluorine atoms derived from the perfluoroalkyl group are unevenly distributed on the surface of the portion exposed from the surface layer. Thereby, the surface of the developer carrying member has a configuration in which convex regions having fluorine atoms on the surface are scattered in the matrix resin. The electrophotographic image forming apparatus according to claim 1, wherein the salt having a perfluoroalkyl group in the molecule has an anion represented by the following structural formula (1):
Structural formula (1)
_{C n F 2n + 1 SO 3} -
(In the structural formula (1), n represents an integer of 3 or more and 6 or less). A developer carrier having a surface layer containing a urethane resin as a matrix resin;
The surface layer has urethane resin particles fixed to the surface layer in a state where a part of the surface layer is exposed from the surface layer,
The urethane resin particles contain a salt having a perfluoroalkyl group in the molecule, and fluorine atoms derived from the perfluoroalkyl group are unevenly distributed on the surface of the portion exposed from the surface layer. Thereby, the surface of the developer carrying member has a configuration in which convex regions having fluorine atoms on the surface are scattered in the matrix resin. A method for producing a developer carrier according to claim 3,
(1) forming a urethane resin raw material layer;
(2) Urethane resin particles impregnated with a liquid in which a salt having a perfluoroalkyl group in the molecule is impregnated are adhered to the surface of the urethane resin raw material layer, and then the urethane resin raw material layer is cured. And a step of forming the surface layer.

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