JP5386090B2 - Developing roll for electrophotographic equipment - Google Patents

Description

  The present invention relates to a developing roll for electrophotographic equipment.

  In recent years, electrophotographic apparatuses such as copying machines, printers, and facsimiles that employ an electrophotographic system have been widely used. In general, a photosensitive drum is incorporated in the electrophotographic apparatus, and conductive rolls such as a charging roll, a developing roll, a transfer roll, and a toner supply roll are disposed around the photosensitive drum.

  Recently, this type of electrophotographic apparatus has been demanded to improve the quality of printed images. In order to obtain a high-quality print image, it is important that the developing roll is uniform and reliably conveys toner. Accordingly, the developing roll is required to have excellent toner transportability. For this reason, an uneven shape is often formed on the surface of the developing roll.

  In the developing roll, an elastic layer such as a rubber layer is usually formed on the outer periphery of the shaft, and one or two intermediate layers or surface layers such as a resistance adjusting layer and a protective layer are formed on the outer periphery of the elastic layer as necessary. It is formed as described above. Conventionally, in order to form an uneven shape on the surface of the developing roll, for example, a method of dispersing hard particles (roughness forming particles) such as urethane resin in an intermediate layer or a surface layer of the developing roll is known.

  There is also a method of forming a concavo-convex shape on the surface of the developing roll without using roughness forming particles. For example, Patent Document 1 discloses a developing roll in which a convex portion is formed on the surface of an elastic layer formed on the outer periphery of a shaft body by using a mold to form an uneven shape on the roll surface.

JP 2006-184608 A

  However, in the method in which hard particles (roughness forming particles) such as urethane resin are dispersed in the intermediate layer or surface layer of the developing roll, since the particles are hard, the photosensitive drum in which the roll surface on which the particles are present contacts the roll Pressure contact stress received from a contact member such as a blade or a blade increases. As a result, there is a problem that the convexity on the roll surface is scraped off and particles are dropped off, and the toner conveyance amount is not stable. Further, on the roll surface where the pressure stress is large, the convex portion is shaved and the contact surface becomes large, so that the toner is easily attached. As a result, there has been a problem that toner filming starts and image deterioration is caused.

  On the other hand, in the method of forming a convex portion on the surface of the elastic layer, a hard material is often used for the surface layer in order to reduce toner filming of the entire roll (particularly a portion other than the convex portion). For this reason, there is a problem in that the convexity formed on the elastic layer is damaged and destroyed during durability and the toner conveyance amount cannot be maintained.

  The problem to be solved by the present invention is to provide a developing roll for an electrophotographic apparatus that is excellent in toner filming resistance for a long period of time and can stably maintain a high toner conveyance amount for a long period of time. is there.

  In order to solve the above problems, a developing roll for an electrophotographic apparatus according to the present invention includes a shaft body, a rubber elastic layer formed on the outer periphery of the shaft body, and having a plurality of convex portions on the outer peripheral surface, and the rubber elastic layer. An intermediate layer formed on the outer periphery and containing a thermoplastic urethane and a thermosetting urethane, and a surface layer formed on the outer periphery of the intermediate layer and containing a silicone graft-modified urethane having a glass transition temperature (Tg) of −10 ° C. or higher. The concavo-convex shape resulting from the convex part of the rubber elastic layer is formed on the roll surface.

  In this case, the mass ratio of the thermosetting urethane to the thermoplastic urethane in the intermediate layer is preferably in the range of 20/80 to 80/20.

  At this time, the rubber elastic layer may contain one or more selected from silicone rubber and urethane rubber.

  And the thickness of the said intermediate | middle layer is good in it being in the range of 1-50 micrometers.

  The thickness of the surface layer is preferably in the range of 1 to 20 μm.

  Furthermore, the height of the convex portion of the rubber elastic layer is preferably in the range of 2 to 50 μm.

The number density of protrusions on the outer peripheral surface of the rubber elastic layer may be within the range of 50 to 1000 / mm ^2.

  According to the developing roll for electrophotographic equipment according to the present invention, the surface irregularities of the roll are formed by a large number of convex portions formed on the outer peripheral surface of the rubber elastic layer, and contains a silicone graft-modified urethane having a Tg of −10 ° C. or higher. Since the surface layer is formed of a material, the toner filming resistance is excellent. And, by providing an intermediate layer containing thermoplastic urethane and thermosetting urethane, the pressure stress received by a large number of convex portions formed on the outer peripheral surface of the rubber elastic layer is alleviated, and the convex portions at the time of durability are reduced. Damage destruction is suppressed. As a result, a high toner conveyance amount can be maintained stably over a long period of time. In addition, the toner filming resistance is excellent over a long period of time.

  In this case, when the mass ratio of the thermosetting urethane to the thermoplastic urethane in the intermediate layer is in the range of 20/80 to 80/20, it is suitable for alleviating the pressure stress applied to the convex portion of the rubber elastic layer. It becomes easy to form the intermediate layer with a small thickness, and the settling resistance is also improved.

  At this time, when the rubber elastic layer contains one or more selected from silicone rubber and urethane rubber, the anti-sag property is excellent.

  And when the thickness of the said intermediate | middle layer exists in the range of 1-50 micrometers, the effect which relieves the pressure stress which the convex part of a rubber elastic layer receives is excellent, and it is excellent in the inhibitory effect of damage destruction of the convex part at the time of durability.

  Further, when the thickness of the surface layer is in the range of 1 to 20 μm, the toner filming resistance is excellent, and it is difficult to scrape and is excellent in durability.

  Further, when the height of the convex portion of the rubber elastic layer is in the range of 2 to 50 μm, the toner transportability is excellent.

Further, when the number density of convex portions on the outer peripheral surface of the rubber elastic layer is in the range of 50 to 1000 / mm ² , the toner transportability is excellent.

  Next, a developing roll for an electrophotographic apparatus (hereinafter sometimes referred to as a developing roll) according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circumferential cross-sectional view illustrating a developing roll according to an embodiment.

  As shown in FIG. 1, a developing roll 10 according to an embodiment has a rubber elastic layer 14 formed along the outer peripheral surface of a conductive shaft 12 forming a shaft body, and an intermediate layer 16 formed on the outer peripheral surface. The surface layer 18 is formed on the outer peripheral surface. The developing roll 10 is a developing roll incorporated in an electrophotographic apparatus such as a copying machine, a printer, or a facsimile that employs an electrophotographic system, and is disposed around a photosensitive drum incorporated in the electrophotographic apparatus.

  Examples of the conductive shaft 12 include a cored bar made of a metal substance such as aluminum or stainless steel, a metal cylindrical body hollowed out inside, or those plated on these. If necessary, an adhesive or a primer may be applied to the outer peripheral surface of the conductive shaft 12 to form an adhesive layer. The adhesive or primer may be made conductive as necessary.

  The rubber elastic layer 14 becomes a base layer of the developing roll 10. As shown in FIG. 2, the rubber elastic layer 14 has a large number of convex portions on the outer peripheral surface thereof, and the large number of convex portions form surface irregularities of the developing roll 10. For example, the rubber elastic layer 14 is set by setting the conductive shaft 12 in a hollow portion of a cylindrical mold, and casting a rubber material in a gap portion between the cylindrical mold and the conductive shaft 12 to cause heat crosslinking. Then, it is formed by removing from the cylindrical mold. As the cylindrical mold, it is preferable to use a mold having a large number of recesses on the inner surface. When a rubber material is poured into a mold having a large number of concave portions, a large number of convex portions are transferred and formed on the outer peripheral surface of the rubber elastic layer 14.

  As a method of forming a large number of recesses on the inner surface of the cylindrical mold, for example, a method of shot blasting the inner surface of the cylindrical mold, a method of electric discharge machining the inner surface of the cylindrical mold, There is a method of performing electroless composite plating on the inner surface and forming pits (plating defects) on the surface of the electroless composite plating layer. Of these, the method of forming pits on the surface of the electroless composite plating layer is preferable in that the concave portion of the inner surface of the mold can be deepened and the convex portion of the rubber elastic layer 14 can be made larger.

  In order to form pits (plating defects) on the surface of the electroless composite plating layer, defective electroless composite plating is intentionally performed. The formation of this pit is due to the fact that hydrogen gas generated during the plating reaction is adsorbed on the surface of the deposited plating, and the further deposition of the plating is inhibited at the adsorbed portion. And the concave shape of each pit is normally formed in the curved surface shape (for example, hemisphere) which consists of a part of substantially spherical surface.

  Examples of the plating metal in the electroless composite plating include nickel, cobalt, copper, tin, palladium, gold, and alloys thereof. Of these, nickel or a nickel alloy is preferable from the viewpoint of easy formation of pits.

  As the electroless composite plating, a particle dispersion type electroless composite plating is preferable from the viewpoint of making the pit distribution density more uniform. The dispersed particles preferably have an average particle size in the range of 0.1 to 5 μm. Thereby, the uniform dispersibility in the plating bath of dispersed particles and the uniform eutectoid property in the electroless composite plating layer are improved, and the surface of the electroless composite plating layer can be formed in a more uniform rough surface.

Examples of the material for forming the dispersed particles include silicon carbide (SiC), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), polytetrafluoroethylene (PTFE), and boron nitride (BN). ) And the like. Among these, PTFE is preferable from the viewpoint of excellent releasability from the rubber material to be cast.

  The plating bath should contain a hydrocarbon-based cationic surfactant or amphoteric surfactant from the viewpoint of facilitating surface adsorption of hydrogen gas generated during the plating reaction and making pit formation easier. Is preferred.

The height of the protrusions formed on the outer peripheral surface of the rubber elastic layer 14 (height h in FIG. 2) is preferably in the range of 2 to 50 μm from the viewpoint of excellent toner transportability. Further, the number density of the convex portions on the outer peripheral surface of the rubber elastic layer 14 is preferably in the range of 50 to 1000 / mm ² from the viewpoint of improving toner transportability and fineness of image quality. In order to measure the height of the convex portion of the rubber elastic layer 14, for example, a laser microscope or the like may be used. In order to measure the number density of the convex portions, for example, a laser microscope or the like may be used.

  The material for forming the rubber elastic layer 14 may be any material having rubber elasticity. Specifically, silicone rubber, urethane rubber, butadiene rubber, hydrin rubber and the like can be exemplified. Of these, silicone rubber and urethane rubber are preferable from the viewpoint of good resistance to settling. Silicone rubber is also advantageous in that it hardly changes in volume with respect to environmental changes such as temperature changes and humidity changes, and the outer diameter fluctuation of the roll due to environmental changes is small.

  The rubber elastic layer 14 may include a conductive agent, a filler, an extender, a reinforcing agent, a processing aid, a curing agent, a vulcanization accelerator, a crosslinking agent, a crosslinking aid, an antioxidant, a plasticizer, as necessary. Various additives such as ultraviolet absorbers, pigments, silicone oils, auxiliaries, and surfactants are appropriately added. As the conductive agent, a general conductive agent such as an electronic conductive agent such as carbon black or an ionic conductive agent such as a quaternary ammonium salt can be used.

  The rubber elastic layer 14 may be a foam or a solid body. The thickness of the rubber elastic layer 14 is preferably in the range of 0.1 to 10 mm. More preferably, it may be within a range of 1 to 5 mm.

  The intermediate layer 16 formed on the outer periphery of the rubber elastic layer 14 is provided as a resistance adjustment layer and a stress relaxation layer. That is, it functions to adjust the resistance of the developing roll 10 and to relieve the pressure stress that a large number of convex portions formed on the outer peripheral surface of the rubber elastic layer 14 receive. The intermediate layer 16 is preferably formed into a thin film by coating.

  The mid layer 16 is formed of a material containing thermoplastic urethane and thermosetting urethane. By containing thermoplastic urethane, the material becomes sticky and easy to coat. When the forming material does not contain thermoplastic urethane, the material is greatly shrunk by crosslinking of the thermosetting urethane, so that it becomes difficult to form a coating layer of μm order and difficult to coat. On the other hand, the material becomes hard to stick due to containing thermosetting urethane. Further, the intermediate layer 16 can be made to have a low hardness, and the pressure stress applied to a large number of convex portions can be alleviated.

  The mixing ratio of thermosetting urethane and thermoplastic urethane (thermosetting urethane / thermoplastic urethane) is preferably in the range of 20/80 to 80/20 by mass ratio. When the mixing ratio is within this range, it becomes easy to form an intermediate layer with a thickness suitable for reducing the pressure stress applied to the convex part of the rubber elastic layer, and the pressure stress applied to the convex part is sufficiently reduced. Thus, the convex portion is prevented from being cut. Moreover, the settling resistance is also improved. More preferably, it exists in the range of 40 / 60-60 / 40.

  Examples of the thermoplastic urethane include caprolactone type, adipate type, and ether type. Among these, the caprolactone type is preferable from the viewpoint of ensuring high mechanical strength and elastic recovery. Thereby, high mechanical strength can be obtained while having low hardness. Further, from the viewpoint of ensuring coatability, the molecular weight is preferably relatively large. The preferred molecular weight range is in the range of 10,000 to 500,000.

  The thermosetting urethane is obtained by mixing a polyol and an isocyanate in the material forming the intermediate layer 16 and reacting them. The blending ratio of the polyol and the isocyanate is appropriately adjusted depending on the kind of the polyol and isocyanate, the crosslinking level, and the like.

  The polyol may be a compound having two or more hydroxyl groups in the molecule. Examples of the polyol include ether polyols, caprolactan polyols, ester polyols, and the like. Of these, ether-based polyols are preferable from the viewpoint of reducing resistance. When the resistance is low, the afterimage characteristics of the image are good.

  Examples of ether polyols include polyether polyols obtained by addition polymerization of one or more kinds such as ethylene oxide, propylene oxide, and butylene oxide to one or more kinds of relatively low molecular weight polyhydric alcohols, and tetrahydrofuran. And polytetramethylene ether glycol (PTMEG) obtained by ring-opening polymerization.

  On the other hand, the isocyanate may be a compound having one or more isocyanate groups in the molecule.

  The material for forming the intermediate layer 16 is preferably liquid so as to be coated on the outer peripheral surface of the rubber elastic layer 14. For example, the material constituting the thermosetting urethane may be liquid, or a solvent that dissolves or suspends the thermosetting urethane and the thermoplastic urethane may be used. Examples of the solvent include methyl ethyl ketone (MEK), methanol, toluene, isopropyl alcohol, methyl cellosolve, dimethylformamide and the like. These can be used alone or in combination of two or more. In particular, MEK is preferable from the viewpoint of the solubility of each component of the material. When using a solvent, it is preferable to adjust the solution concentration in the range of 5 to 30% by mass from the viewpoint of improving the coating property by adjusting the viscosity to be easy to coat.

  The material forming the intermediate layer 16 includes one or more various additives such as a conductive agent (electronic conductive agent and / or ionic conductive agent), a plasticizer, and a leveling agent as necessary. Also good.

  The thickness of the intermediate layer 16 is preferably in the range of 1 to 50 μm. When the thickness is less than 1 μm, it is difficult to form a layer on the apex of the convex portion of the rubber elastic layer. Therefore, the effect of alleviating the pressure contact stress received by the convex portions of the rubber elastic layer tends to be reduced. On the other hand, when the thickness exceeds 50 μm, surface irregularities caused by the convex portions of the rubber elastic layer are reduced, and the toner transportability is liable to be lowered. Moreover, the influence of the dimensional change by a urethane polymer tends to become large. Furthermore, the number of times of repeated coating increases, and the process tends to become complicated. The thickness of the intermediate layer 16 is more preferably in the range of 5 to 20 μm.

  In order to form the intermediate layer 16, first, a thermoplastic urethane, a polyol and an isocyanate that form a thermosetting urethane, and, if necessary, a solvent and other additives are mixed to prepare a coating liquid. Next, after the rubber elastic layer 14 is formed on the outer periphery of the conductive shaft 12, the coating liquid is coated on the outer peripheral surface of the rubber elastic layer 14. The coating method is not particularly limited, and general methods such as a dipping method, a spray method, and a roll coating method can be applied. If the coating is dried and heated and crosslinked, the intermediate layer 16 containing a mixture of thermoplastic urethane and thermosetting urethane can be formed.

  The surface layer 18 formed on the outer peripheral surface of the intermediate layer 16 functions to adjust the toner chargeability and protect the roll surface. The surface layer 18 is formed of a material containing silicone graft-modified urethane. Silicone graft-modified urethane imparts excellent releasability to the surface layer 18 because the silicone segment (polysiloxane segment) is chemically bonded to the side chain of the polyurethane. Thereby, toner filming can be reduced.

  As the silicone graft-modified urethane, those having a glass transition temperature (Tg) of −10 ° C. or higher are used. If the Tg is less than −10 ° C., the surface layer 18 becomes too soft and the toner tends to bite, and toner filming occurs. More preferably, Tg is 10 ° C. or higher. Further, the toner filming resistance is excellent.

Examples of silicone (polysiloxane) grafted on urethane include alkyl-substituted siloxanes such as dimethylsiloxane, diethylsiloxane, and dipropylsiloxane. The polysiloxane preferably has an active hydrogen-containing group (—OH, —NH _2, etc.) having reactivity with an isocyanate group of urethane in order to graft onto urethane. The amount of polysiloxane introduced (silicone modification amount) is preferably in the range of 1 to 20% by mass. If the silicone modification amount is less than 1% by mass, the releasability is hardly exhibited, and if it exceeds 20% by mass, the free silicone oil tends to bleed out, and the mechanical strength of urethane tends to decrease. is there.

  Examples of the polyol component that constitutes urethane include polyester polyol, polyether polyol, and polycaprolactone polyol.

  The acid component of the polyester polyol includes aliphatic dibasic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, dodecylsuccinic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid. Fats such as acid, 1,4-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2-bis (4-carboxycyclohexyl) methane, 2,2-bis (4-carboxycyclohexyl) propane Examples thereof include cyclic dibasic acids, or aromatic dibasic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 1,6-naphthalenedicarboxylic acid. An alicyclic dibasic acid and an aromatic dibasic acid improve the cohesive strength of the resin, while an aliphatic dibasic acid tends to improve the flexibility of the resin.

  Examples of the polyol component include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-propylene glycol, 1,3- Propylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-3-hydroxy Aliphatic glycols such as propyl-2 ′, 2′-dimethyl-3-hydroxypropanate, 2,2-diethyl-1,3-propanediol, 1,3-bis (hydroxymethyl) cyclohexane, 1,4- Bis (hydroxymethyl) cyclohexane, 1,4-bis (hydroxyethyl) cyclohexane 1,4-bis (hydroxypropyl) cyclohexane, 1,4-bis (hydroxymethoxy) cyclohexane, 1,4-bis (hydroxyethoxy) cyclohexane, 2,2-bis (4-hydroxymethoxycyclohexyl) propane, 2,2 -Bis (4-hydroxyethoxycyclohexyl) propane, bis (4-hydroxycyclohexyl) methane, 2,2-bis (4-hydroxycyclohexyl) propane, 3 (4), 8 (9), tricyclo [5.2.1 .02,6] alicyclic glycols such as decanedimethanol. Among these, ethylene glycol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, and 1,4-bis (hydroxymethyl) cyclohexane are particularly preferable.

  As the isocyanate component constituting the urethane, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, m-phenylene diisocyanate, 3,3′-dimethoxy- 4,4′-biphenylene diisocyanate, 2,6-naphthalene diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 4,4′-diphenylene diisocyanate, 4,4′-diisocyanate diphenyl ether, 1,5 -Of aromatic diisocyanates such as naphthalene diisocyanate and m-xylene diisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate Aliphatic such as 添化 thereof, alicyclic diisocyanate. Of these, 4,4'-diphenylmethane diisocyanate is particularly preferred.

  In addition to the above silicone graft modified urethane, the material forming the surface layer 18 includes diisocyanate that crosslinks urethane, various additives such as a conductive agent (electronic conductive agent and / or ionic conductive agent), a plasticizer, and a leveling agent. Seeds or two or more species may be included.

  The material for forming the surface layer 18 is preferably liquid so as to coat the outer peripheral surface of the intermediate layer 16. Examples of the solvent for forming a liquid include methyl ethyl ketone (MEK), methanol, toluene, isopropyl alcohol, methyl cellosolve, dimethylformamide and the like. These can be used alone or in combination of two or more. In particular, MEK is preferable from the viewpoint of the solubility of each component of the material. In the case of using a solvent, it is preferable to adjust the solution concentration within the range of 3 to 30% by mass from the viewpoint of improving the coatability by adjusting the viscosity to be easy to coat.

  In order to form the surface layer 18, a surface layer forming material is coated on the outer peripheral surface of the intermediate layer 18. The coating method is not particularly limited, and general methods such as a dipping method, a spray method, and a roll coating method can be applied. If the coating is dried and heated and cross-linked, the surface layer 18 can be formed on the outer periphery of the intermediate layer 18.

  The thickness of the surface layer 18 is preferably in the range of 1 to 20 μm. If the thickness of the surface layer 18 is less than 1 μm, the function as the surface layer may not be sufficiently exhibited. On the other hand, if the thickness of the surface layer 18 exceeds 20 μm, the surface hardness may be too high.

  The surface of the surface layer 18 may be impregnated with a specific substance. Specific substances include amino group-containing substances and isocyanate group-containing substances. These may be used alone or in combination of two or more. Of these, an isocyanate group-containing substance is preferable from the viewpoint of further less causing the toner charge amount to change more under high temperature and high humidity conditions. These specific substances may be monomers, polymers or oligomers. From the viewpoint of easy impregnation on the surface of the coating layer 16, the molecular weight of the specific substance is preferably relatively small. The preferred molecular weight range is in the range of 100 to 1000.

  Examples of the substance containing an amino group include melamine, benzoguanamine, and aniline. As the substance containing an amino group, those having an aromatic ring are preferred.

  On the other hand, examples of the substance containing an isocyanate group include diphenylmethane diisocyanate (MDI), polymethylene polyphenylene polyisocyanate (polymeric MDI), crude MDI (c-MDI) which is a mixture of MDI and polymeric MDI, and hexamethylene diisocyanate (HDI). ), Tolylene diisocyanate (TDI), or multimers thereof, such as MDI nurate, HDI nurate, TDI nurate, or modified products thereof, such as ureation, buretation, allophanate, carbodiimidation, urethanization, etc. . These may be used alone or in combination of two or more. Of these, crude MDI (c-MDI) is preferred from the standpoint that the toner charge amount is less likely to change under high temperature and high humidity conditions.

  In order to make the surface of the surface layer 18 impregnated with the specific material, the surface of the surface layer 18 is coated with the liquid specific material and then heat-treated. As the specific substance, a liquid substance may be used as it is, or a liquid substance or a solid substance may be diluted with a solvent. Examples of the solvent include ethyl acetate and methyl ethyl ketone (MEK). At this time, from the viewpoint of facilitating soaking into the surface of the surface layer 18, the solution concentration is preferably in the range of 1 to 5 mass%.

  The coating method is not particularly limited, and general methods such as a dipping method, a spray method, and a roll coating method can be applied. After coating on the surface of the surface layer 18 so that the coated specific substance penetrates well into the surface of the surface layer 18, it may be allowed to stand for several seconds to 1 hour. When heat treatment is performed after coating, volatile components such as a solvent are removed.

  The intermediate layer 16 and the surface layer 18 do not contain roughness-forming particles for forming the surface roughness of the developing roll 10. As shown in FIG. 2, the surface roughness is formed by convex portions formed on the outer peripheral surface of the rubber elastic layer 14.

  The surface hardness (MD-1 hardness) of the developing roll 10 is preferably in the range of 30 to 60 degrees. If the surface hardness is less than 30 degrees, the roll surface becomes too flexible, and the toner is likely to bite in, which tends to cause filming. On the other hand, if the surface hardness exceeds 60 degrees, it tends to cause stress of the mating member or toner that comes into contact with the roll surface, and the durability image tends to deteriorate.

  The surface hardness (MD-1 hardness) of the developing roll 10 can be suppressed to a low hardness by including not only the thermosetting urethane but also the thermoplastic urethane in the intermediate layer 16.

The volume resistance of the developing roll 10 is preferably in the range of 1 × 10 ³ to 1 × 10 ⁸ Ω. When the volume resistance is less than 1 × 10 ³ Ω, the volume ratio of the conductive agent increases and it is difficult to obtain a sufficient withstand voltage. On the other hand, when the volume resistance exceeds 1 × 10 ⁸ Ω, the volume ratio of the conductive agent is reduced and resistance unevenness is likely to occur.

  Hereinafter, the present invention will be described in detail using examples.

Example 1
<Preparation of rubber elastic layer composition (1)>
Conductive liquid silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd., “X34-264A / B”) was mixed with a static mixer to prepare a rubber elastic layer composition (1).

<Preparation of intermediate layer composition>
50 parts by weight of a thermoplastic urethane elastomer (manufactured by Nippon Polyurethane Co., Ltd., “N5196”), 30 parts by weight of an ether polyol (manufactured by Sanyo Chemical Co., Ltd., “PPG2000”), and isocyanate (manufactured by Dainippon Ink & Chemicals, “Bernock DN955”) ) 20 parts by mass, 30 parts by mass of an electronic conductive agent (manufactured by Denki Kagaku, “Denka Black”) and 1 part by mass of an ionic conductive agent (quaternary ammonium salt) were kneaded with a ball mill, and then 400 parts by mass of MEK was added. Then, an intermediate layer composition was prepared by mixing and stirring.

<Preparation of surface layer composition>
(Synthesis of polyester diol (a))
In a reaction vessel equipped with a thermometer, a stirrer, and a Liebig condenser, 83 parts by mass of terephthalic acid, 83 parts by mass of isophthalic acid, 74 parts by mass of ethylene glycol, and 2,2-dimethyl-1,3-propanediol 83 Then, 0.1 part by mass of tetrabutoxy titanate was added as a catalyst. The reaction was carried out at 240 ° C. for about 4 hours under normal pressure, and water produced was distilled off. Subsequently, the pressure was reduced at 245 ° C. for about 30 minutes to complete the reaction. The polyester diol (a) obtained had a hydroxyl value of 1020 eq / 10 ⁶ g and an acid value of 2.5 eq / 10 ⁶ g.

(Synthesis of silicone graft modified urethane)
After dissolving 60 parts by mass of the polyester diol (a) and 40 parts by mass of a polyester diol “ODX688” manufactured by Dainippon Ink & Chemicals, Ltd. in 76 parts by mass of methyl ethyl ketone (MEK), 4 manufactured by Nippon Polyurethane Co., Ltd. , 4′-diphenylmethane diisocyanate (MDI) “Millionate MT” (14 parts by mass) was dissolved and reacted at 75 ° C. for about 2 hours. Next, 106 parts by mass of MEK and 6 parts by mass of silicone oil “KF865” manufactured by Shin-Etsu Chemical Co., Ltd. (silicone oil containing an amino group in the side chain, viscosity at 25 ° C .: 90 cps, functional group equivalent: 4400) And dissolved at 75 ° C. for about 1 hour. Thereafter, 1 part by mass of trimethylolpropane was dissolved, 0.01 part by mass of dibutyltin dilaurate was added as a catalyst, and the reaction was carried out at 75 ° C. for about 2 hours. Thereby, a silicone graft-modified urethane was obtained. The obtained silicone graft-modified urethane had a molecular weight (Mn) of 25 × 10 ³ and a glass transition temperature (Tg) of 10 ° C.

  100 parts by mass of the above silicone graft-modified urethane (Tg = 10 ° C.), 20 parts by mass of isocyanate (manufactured by Dainippon Ink and Chemicals, “Bernock DN955”), and electronic conductive agent (manufactured by Denki Kagaku Kogyo, “Denka Black HS-100” ]) After kneading 15 parts by mass with a ball mill, 400 parts by mass of MEK was added, mixed and stirred to prepare a surface layer composition.

(Measurement method of glass transition temperature (Tg))
Each silicone graft-modified urethane was sampled, placed in an aluminum container, placed on a holder unit, and set in an electric furnace. And after heating from room temperature (20 degreeC) to 150 degreeC with the temperature increase rate of 10 degree-C / min, it maintained at 150 degreeC for 10 minutes. Subsequently, it cooled to room temperature (20 degreeC), and maintained for 10 minutes in the room temperature state. Next, DSC measurement was performed by heating again to 150 ° C. at a heating rate of 10 ° C./min in a nitrogen atmosphere. The glass transition temperature (Tg) was calculated from the tangent of the endothermic curve near the glass transition temperature (Tg) and the base line using a TG-DSC system TAS-100 (manufactured by Rigaku Corporation) analysis system.

<Production of cylindrical mold having a large number of recesses>
1. Nickel sulfate hexahydrate 20 g / liter, sodium hypophosphite monohydrate (reducing agent) 25 g / liter, lactic acid (complexing agent) 27 g / liter, propionic acid (complexing agent) 2. 5 g / liter, 5 g / liter of PTFE dispersed particles (average particle size 0.2 μm) and 0.1 g / liter of lauryltrimethylammonium chloride (cationic surfactant) are mixed to prepare a pH 4.8 plating bath. did.

  By immersing the cylindrical mold base in the plating bath, the inner surface of the cylindrical mold base is subjected to defective electroless composite plating, and an electroless composite plating layer in which many pits are uniformly distributed and formed A cylindrical mold (inner diameter: 12 mm) having a surface of the mold was obtained. At this time, the temperature of the plating bath was 90 ° C., the plating time was 120 minutes, and the electroless composite plating layer was formed to a thickness of 22 μm. The ten-point average roughness (Rz) of the surface of this electroless composite plating layer was 10 μm. The ten-point average roughness (Rz) was measured using a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., Surfcom 1400D).

<Preparation of developing roll>
A conductive shaft (φ6 mm, length 270 mm) is set coaxially in the cylindrical mold, the rubber elastic layer composition (1) is injected into the mold, heated at 150 ° C. for 30 minutes, cooled, Demolded. Thus, a roll body having a rubber elastic layer having a thickness of 3 mm on the outer periphery of the conductive shaft was produced. On the outer peripheral surface of the formed rubber elastic layer, a number of convex portions corresponding to the number of concave portions formed on the inner surface of the cylindrical mold are formed by mold transfer.

  Next, the intermediate layer composition was coated on the surface of the roll body by a roll coating method, and then heat treated at 170 ° C. for 60 minutes to form an intermediate layer having a thickness of 10 μm. Next, the surface layer composition was coated on the surface of the intermediate layer by a roll coating method, and then heat-treated at 150 ° C. for 60 minutes to form a surface layer having a thickness of 3 μm. As described above, the developing roll according to Example 1 was produced.

(Examples 2-3)
In the preparation of the intermediate layer composition of Example 1, development according to Examples 2 to 3 was carried out in the same manner as in Example 1 except that the blending amounts of thermoplastic urethane, polyol and isocyanate were the blending amounts shown in Table 2. A roll was produced.

(Examples 4 to 5)
In the preparation of the surface layer composition of Example 1, developing rolls according to Examples 4 to 5 were produced in the same manner as in Example 1 except that a silicone graft-modified urethane having a Tg value described in Table 2 was used.

(Example 6)
<Preparation of rubber elastic layer composition (2)>
100 parts by mass of urethane rubber (manufactured by Bayer, “Urepan 643G”), 1 part by mass of lubricant (stearic acid), 5 parts by mass of vulcanization accelerator (zinc white), and ionic conductive agent (trimethyloctadecyl ammonium perchlorate) 0 A rubber elastic layer composition (2) is prepared by stirring and mixing 5 parts by weight and 0.3 part by weight of an anti-aging agent (Onouchi Shinsei Chemical Co., Ltd., “NOCRAK NS-6”). did.

  In the production of the developing roll of Example 1, the same procedure as in Example 1 was used except that the rubber elastic layer composition (2) made of urethane rubber was used instead of the rubber elastic layer composition (1) made of silicone rubber. Thus, a developing roll according to Example 6 was produced.

(Comparative Example 1)
In the production of the developing roll of Example 1, a developing roll according to Comparative Example 1 was produced in the same manner as in Example 1 except that the surface layer was formed without forming the intermediate layer on the outer periphery of the rubber elastic layer.

(Comparative Example 2)
In the preparation of the surface layer composition of Example 1, a developing roll according to Comparative Example 2 was produced in the same manner as in Example 1 except that a silicone graft-modified urethane having a Tg value described in Table 2 was used.

(Comparative Example 3)
A developing roll according to Comparative Example 3 was produced in the same manner as in Example 1 except that the thermoplastic urethane was not blended in the preparation of the intermediate layer composition of Example 1.

  Prior to the evaluation of each developing roll, in the same roll configuration as in Example 1, the influence of the Tg value of the silicone graft-modified urethane in the surface layer on the toner filming resistance was examined. In Example 1, the Tg value of the silicone graft-modified urethane was adjusted by changing the blending ratio of the polyester diol (a), which is a diol component, and ODX688. The results are shown in Table 1.

<Evaluation of each developing roll>
For each developing roll according to the example and the comparative example, the toner transportability before and after durability was evaluated. In addition, the toner filming resistance and the degree of damage to the convex portions of the rubber elastic layer were evaluated. The results are shown in Table 2.

(Initial toner transportability)
The amount of toner adhered to the roll surface was measured using a so-called suction type Faraday gauge method. In other words, each developing roll is installed in a commercially available color laser printer (Canon, “LBP-2510”), and the printer is stopped while printing a solid black image in an HH environment (32.5 ° C. × 85% RH). did. Next, the toner adhered to the roll surface was sucked using a Faraday gauge, and the toner transport amount (M / A) was calculated from the suction area (A) and the suction amount (M). When the toner transport amount (M / A) is in the range of 4 to 7 g / m ² , the pass is “◯”, and the toner transport amount (M / A) is out of the range of 4 to 7 g / m ^2. A failure “×” was assigned.

(Toner transportability after endurance)
The initial toner transport is the same as that described above except that the printer was stopped while printing a solid black image under an HH environment (32.5 ° C x 85% RH). The toner transport amount (M / A) was calculated in the same manner as the property evaluation. When the toner transport amount (M / A) is in the range of 4 to 7 g / m ² , the pass is “◯”, and the toner transport amount (M / A) is out of the range of 4 to 7 g / m ^2. A failure “×” was assigned.

(Toner filming resistance)
Each developing roll was incorporated into a commercially available color laser printer (manufactured by Canon Inc., LBP-2510), and under an environment of 32.5 ° C. × 85% RH, 10,000 sheets (A4 size) of image output were passed through. The subsequent roll appearance was magnified and observed with a microscope (VK-9510, manufactured by Keyence Corporation). At this time, “◎” indicates that no toner adheres to the roll surface, and “○” indicates that the toner adheres to the roll surface, but the change is slight and does not affect the image. A case where toner adhered to the surface and a change in the conveyance amount or unevenness occurred in the image was judged as “Fail”.

(Damage on the convex part)
Each developing roll is incorporated into a commercially available color laser printer (manufactured by Canon Inc., LBP-2510), and 10000 sheets of paper (A4 size) are printed out in an environment of 32.5 ° C x 85% RH. Thereafter, the appearance of the roller was magnified and observed with a microscope (manufactured by Keyence Corporation, VK-9510). At this time, the case where the convex part was not damaged and the initial state was maintained was regarded as acceptable “◯”, and the case where the convex part was damaged was regarded as unacceptable “x”.

(Stick resistance)
Each developing roll is incorporated in a cartridge of a commercially available color laser printer (manufactured by Canon Inc., LBP-2510) and left for 2 weeks in an environment with an air temperature of 32.5 ° C. and a humidity of 80%, and then a halftone image Was imaged in an NN environment (23 ° C. × 53% RH). A case where there was no defect due to the pressure contact portion on the image was indicated as “◯”.

(Volume resistance)
Each developing roll was brought into line contact with the metal rod, and the metal rod was rotationally driven with a load of 500 g applied to both ends of the conductive shaft of the roll. Each developing roll was rotated at 30 rpm, and 100 VDC was applied. The electrical resistance between the conductive shaft and the metal rod in the state was measured and used as the volume resistance (Ω) of each developing roll.

(Surface roughness)
Arithmetic mean roughness (Ra) at any three points on the outer periphery of each position at three positions 5 mm inside in the axial direction and the center in the axial direction from both ends of the roll surface, surface roughness meter (Tokyo Seimitsu) The measurement was performed using a Surfcom 1400D manufactured by the company. And the average value of arithmetic average roughness (Ra) in the total of 9 points | pieces (3 points x 3 positions) was calculated, and the result was combined with the following Table 2, and was described.

(Residual charge)
Under an environment of a temperature of 15 ° C. and a humidity of 10% RH, a corona current of 100 μA is applied to the surface of the developing roll using a corona discharge wire (corotron) while rotating each developing roll at a roll rotation speed of 70 rpm. The surface was charged. Then, the residual charge on the surface of the developing roll was measured with a surface potentiometer disposed at a position one quarter cycle behind the corona discharge line. The measurement was performed while the roll was rotated.

(surface hardness)
The surface hardness of each developing roll was measured (N = 3) with an MD-1 hardness meter (manufactured by Kobunshi Keiki Co., Ltd., “Micro rubber hardness meter MD-1 type”).

  From Table 1, it was found that when the Tg value of the silicone graft modified urethane is −10 ° C. or more, the toner filming resistance is excellent. In particular, when Tg is 10 ° C. or higher, the toner filming resistance is further improved. On the other hand, it was found that when the Tg value is less than −10 ° C., the toner filming resistance is poor.

  In Comparative Example 1, no intermediate layer is provided between the rubber elastic layer and the surface layer. For this reason, during the durability, the convex portion on the surface of the rubber elastic layer was damaged, and the toner conveyance amount was reduced. In Comparative Example 2, the Tg of the silicone graft-modified urethane in the surface layer is too low. For this reason, the surface layer becomes too flexible, and the toner easily bites in, resulting in toner filming. In Comparative Example 3, an attempt was made to coat thermosetting urethane on the outer periphery of the rubber elastic layer. However, since the thermosetting shrinkage was large, film formation on the order of μm was difficult. Therefore, an intermediate layer (urethane thin film) made only of thermosetting urethane could not be formed on the outer periphery of the rubber elastic layer.

  On the other hand, each developing roll according to the example is provided with an intermediate layer containing thermoplastic urethane and thermosetting urethane between the rubber elastic layer and the surface layer, and the Tg of the silicone graft-modified urethane in the surface layer. Is −10 ° C. or higher. Therefore, damage to the convex portions of the rubber elastic layer that forms the surface irregularities of the roll during durability is suppressed, and a high toner conveyance amount is stably maintained over a long period of time, and the toner filming resistance is excellent over a long period of time. I was able to confirm.

  Further, in each developing roll according to the example, since the thermoplastic urethane is included in the coat layer, the coatability is good and film formation on the order of μm is possible. Further, when silicone rubber is used for the base layer, it is even more excellent in resistance to stickiness. From the product characteristics, it was confirmed that there was no problem in product performance.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said Example at all, A various change is possible in the range which does not deviate from the summary of this invention.

It is a circumferential direction sectional view showing the development roll for electrophotographic equipment concerning one embodiment. It is an axial direction sectional view showing the development roll for electrophotographic equipment concerning one embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Developing roll for electrophotographic equipment 12 Conductive shaft 14 Rubber elastic layer 16 Intermediate layer 18 Surface layer

Claims (7)

A shaft,
A rubber elastic layer formed on the outer periphery of the shaft body and having a plurality of convex portions on the outer peripheral surface;
An intermediate layer formed on the outer periphery of the rubber elastic layer and containing thermoplastic urethane and thermosetting urethane;
Formed on the outer periphery of the intermediate layer, and comprising a surface layer containing a silicone graft-modified urethane having a glass transition temperature (Tg) of -10 ° C or higher,
A developing roll for an electrophotographic apparatus, wherein a concavo-convex shape resulting from a convex portion of the rubber elastic layer is formed on a roll surface. 2. The developing roll for electrophotographic equipment according to claim 1, wherein a mass ratio of the thermosetting urethane to the thermoplastic urethane in the intermediate layer is in a range of 20/80 to 80/20. 3. The developing roll for electrophotographic apparatus according to claim 1 , wherein the rubber elastic layer contains one or more selected from silicone rubber and urethane rubber. 4. The electrophotographic apparatus developing roll according to claim 1 , wherein the intermediate layer has a thickness in the range of 1 to 50 μm. 5. 5. The developing roll for an electrophotographic apparatus according to claim 1 , wherein a thickness of the surface layer is in a range of 1 to 20 μm. 6. The developing roll for an electrophotographic apparatus according to claim 1 , wherein a height of the convex portion of the rubber elastic layer is in a range of 2 to 50 μm. 7. The electrophotographic apparatus development according to claim 1 , wherein the number density of the protrusions on the outer peripheral surface of the rubber elastic layer is in a range of 50 to 1000 / mm ^2. roll.

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