JP2008304789A - Developing roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller capable of obtaining a satisfactory image for a long term by making the ability of an undercoat layer to be set and the low hardness of the undercoat layer compatible. <P>SOLUTION: The developing roller includes: a shaft 1; an elastic layer 2 held on the periphery of the shaft 1; one or more undercoat layers 3 and a surface layer 4 formed in that order on the peripheral face. The one or more undercoat layers 3 are all formed from a water-based resin. At least one of the undercoat layers 3 contains acrylonitrile and n-butyl acrylate at a monomer ratio of 1 to 25: 99 to 75. In addition, a water-based acrylic resin the molecule of which contains a group that has an active hydrogen is cross-linked by an oxazoline-based cross-linking agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing roller (hereinafter also simply referred to as “roller”), and more particularly to a developing roller used in an image forming apparatus such as an electrophotographic apparatus such as a copying machine or a printer or an electrostatic recording apparatus.

  In an image forming apparatus using an electrophotographic system such as a copying machine or a printer, a roller member imparted with conductivity is used in an electrophotographic process such as development, charging, and transfer (toner supply and cleaning).

  Conventionally, as a roller member used as a developing roller, a charging roller, a transfer roller (toner supply, cleaning) or the like, a conductive rubber or a polymer provided with conductivity by blending a conductive agent on the outer periphery of the shaft. Using a structure with an elastic layer made of elastomer, polymer foam, etc. as a basic structure, to obtain the desired surface roughness, conductivity, hardness, etc., one with one or more coatings on its outer periphery is used Has been.

  In this case, for example, in the case of an elastic layer made of urethane foam, since the cells are open on the foam surface, when the solvent-based paint is directly applied, problems such as dissolution of the elastic layer surface occur. For this reason, conventionally, an undercoat layer is formed on an elastic layer with a water-based paint using a water-based resin, and after sealing, a surface layer is formed with a solvent-based paint.

  As an improved technique related to such a developing roller, for example, in Patent Document 1, at least one lower conductive layer and a surface resin layer are sequentially provided on an elastic layer, and the elastic layer is made of a foam having a closed cell structure. A developing roller is disclosed in which the lower conductive layer is made of a water-based paint containing a conductive agent, and at least one of the lower conductive layers in contact with the elastic layer is mainly composed of a chloroprene / methacrylic acid copolymer.

Further, in Patent Document 2, as a coating material for forming a coating film layer in a charging roller having an elastic layer and a coating film layer formed directly or via another layer on the outside, 3 to 15 Patent Document 3 discloses a technique using an acrylic resin containing a mol% acrylonitrile residue, which has an elastic layer and a coating layer formed directly or through another layer on the outside. Each charging member is disclosed in which a film layer is an aqueous coating film obtained by crosslinking a resin having active hydrogen with an oxazoline-based crosslinking agent having two or more oxazoline groups.
Japanese Patent Laying-Open No. 2006-349741 (Claims etc.) JP 2002-072627 A (Claims etc.) Japanese Patent Application Laid-Open No. 11-084821 (claims, etc.)

  As described above, various types of roller members such as a developing roller have been conventionally studied. However, due to the recent improvement in image quality of printers, it is difficult to prevent image defects due to roller deformation with conventional materials. It has become to.

  In particular, there is a need for a developing roller that does not cause the problem of image defects due to deformation even in a state where it is assembled in a cartridge and stored for a long period of time and then pressed against the photosensitive drum for a long period of time. In recent years, the melting point of the toner has been lowered corresponding to the high-speed printing, and in order to reduce the toner damage during the durability, it is required to reduce the hardness of the developing roller.

  For these problems, the improvement of the compression set (set) performance of the undercoat layer using water-based paint and the reduction in hardness have been studied as problems, but it is difficult to achieve both of these performances. However, sufficient products have not been obtained yet, and there has been a demand for a developing roller that is soft and has good setting properties.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developing roller capable of solving the above-described problems and obtaining a good image over a long period of time by satisfying both the setting property of the undercoat layer and the reduction in hardness.

  As a result of intensive studies, the present inventors have found that by using a predetermined aqueous acrylic resin as the aqueous resin used for the undercoat layer, it is possible to realize both the setability and the reduction in hardness, thereby completing the present invention. It came to do.

Specifically, the developing roller of the present invention includes a shaft, an elastic layer carried on the outer periphery of the shaft, and one or more undercoat layers and surface layers sequentially provided on the outer peripheral surface of the elastic layer. In
All of the one or more undercoat layers are made of an aqueous resin, and at least one of the undercoat layers contains acrylonitrile and n-butyl acrylate in a monomer ratio of 1 to 25:99 to 75, and molecules A water-based acrylic resin containing a group having active hydrogen therein is crosslinked with an oxazoline-based crosslinking agent.

  In the present invention, preferably, the oxazoline-based crosslinking agent has two or more oxazoline groups. Further, the surface acid value of the water-based acrylic resin is preferably 10 mg / g or more, and the group having active hydrogen is preferably a carboxyl group. Furthermore, in the present invention, the elastic layer is preferably a polyurethane foam formed by a mechanical floss method.

  According to the present invention, by adopting the above-described configuration, it is possible to realize a developing roller capable of obtaining a good image over a long period while achieving both setability of the undercoat layer and reduction in hardness.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 is a sectional view in the axial direction of a developing roller according to an embodiment of the present invention. As shown in the figure, the developing roller 10 of the present invention includes a shaft 1, an elastic layer 2 carried on the outer periphery thereof, and one or more layers sequentially provided on the outer peripheral surface of the elastic layer 2. An undercoat layer 3 and a surface layer 4 are provided.

  In the present invention, it is important that all of the undercoat layers provided by one or more layers are made of a water-based resin, and at least one of the undercoat layers is made of a specific water-based acrylic resin described in detail below. is there.

  The water-based acrylic resin used for the undercoat layer 3 in the present invention contains acrylonitrile and n-butyl acrylate as essential components, and optionally contains other monomers. Examples of other monomers include ethyl acrylate and acrylic acid 2- Examples include ethylhexyl, acrylic acid, methacrylic acid and the like. The reason why acrylonitrile and n-butyl acrylate are essential components is that they contribute to improvement of elasticity (set property). From this viewpoint, the amount of n-butyl acrylate is increased as much as possible, and other components are added. It is preferable to reduce the monomer ratio of other monomer components other than the essential components. On the other hand, if the ratio of acrylonitrile is too high, the undercoat layer becomes hard, which is not preferable. Therefore, the monomer ratio of acrylonitrile, which is an essential component, and n-butyl acrylate is preferably in the range of 1 to 25:99 to 75, particularly 5 to 20:95 to 80 in terms of molar ratio.

  The aqueous acrylic resin used in the present invention needs to contain a group having active hydrogen in the molecule. Examples of the group having active hydrogen include a carboxyl group, a hydroxyl group, and an amino group, and a carboxyl group is preferable. In the present invention, the ratio of the monomer containing the group having active hydrogen is preferably in the range of 3 to 6% of the total monomer amount. In the present invention, a water-based acrylic resin having a surface acid value adjusted to 10 mg / g or more, for example, 10 to 20 mg / g is suitably used by setting the ratio of the monomer containing a group having active hydrogen within this range. be able to.

  Furthermore, the water-based acrylic resin according to the present invention is crosslinked with an oxazoline-based crosslinking agent to form an undercoat layer. Any oxazoline-based crosslinking agent may be used as long as it is water-soluble, but those having two or more oxazoline groups are preferred, and in particular, the oxazoline group equivalent is 300 to 1000, The thing of Tg = -50 degreeC-50 degreeC can be used conveniently. If the oxazoline group equivalent exceeds 1000, the molecular weight becomes large and handling at room temperature becomes difficult. On the other hand, if it is less than 300, the reactivity is too high and gelation occurs, so neither is preferred. The blending amount of the oxazoline-based crosslinking agent can be 5 to 50 parts by weight with respect to 100 parts by weight of the aqueous acrylic resin.

  In the present invention, only the point that at least one of the undercoat layers is made of the water-based acrylic resin is important, and other undercoat layers may or may not be provided. Examples of the water-based resin used for the other undercoat layer in the case of providing another undercoat layer include rubber-based, urethane-based, and acrylic-based resins other than those described above, and any one or two selected from these The above can be used suitably. As rubber type, natural rubber (NR), chloroprene rubber (CR), nitrile rubber (NBR), latex such as styrene butadiene rubber (SBR), etc., as urethane type, emulsion and dispersion such as ether type, ester type, As the acrylic, an emulsion such as acrylic or acrylic styrene can be suitably used.

  Moreover, a conductive agent is appropriately added to the undercoat layer to impart conductivity. Examples of the conductive agent include an ionic conductive agent and an electronic conductive agent. Examples of the ionic conductive agent include tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium (for example, lauryltrimethylammonium), hexadecyltrimethylammonium, and octadecyltrimethyl. Perchlorates such as ammonium (eg stearyltrimethylammonium), benzyltrimethylammonium, modified fatty acid dimethylethylammonium, chlorate, hydrochloride, bromate, iodate, borofluoride, sulfate, ethyl Ammonium salts such as sulfates, carboxylates and sulfonates, perchlorates, chlorates, hydrochlorides and odors of alkali metals and alkaline earth metals such as lithium, sodium, potassium, calcium and magnesium Salts, iodate salts, fluoroboric acid salts, trifluoromethyl sulfate, and sulfonic acid salts. Examples of the electronic conductive agent include conductive carbon such as ketjen black and acetylene black; carbon for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT; for ink subjected to oxidation treatment Examples thereof include carbon, pyrolytic carbon, natural graphite, and artificial graphite; conductive metal oxides such as tin oxide, titanium oxide, and zinc oxide; metals such as nickel, copper, silver, and germanium. These conductive agents may be used alone or in combination of two or more. Moreover, there is no restriction | limiting in particular in the compounding quantity, Although it can select suitably as desired, For example, it can be set as 1-20 weight part with respect to 100 weight part of resin components which comprise an undercoat layer.

  Furthermore, other vulcanizing agents, vulcanization accelerators, antiaging agents, and the like can be appropriately added to the undercoat layer as desired.

  The total thickness of the undercoat layer can be in the range of 20 to 600 μm. If the thickness is too thin, the solvent resistance deteriorates, but it is difficult to coat thicker than this range. In the present invention, the undercoat layer is coated on the elastic layer 2 using a known method such as dip coating, spray coating, roll coater coating, etc., dried, and heat-cured as desired. Can be formed.

  The shaft 1 of the developing roller of the present invention is not particularly limited as long as it has good conductivity, and any one can be used. For example, nickel or zinc can be used for steel materials such as sulfur free-cutting steel. A metal shaft such as a metal core made of a solid metal such as iron, stainless steel, or aluminum, or a metal cylindrical body hollowed out inside can be used.

  The elastic layer 2 of the developing roller of the present invention is preferably formed of polyurethane foam. The raw material for such polyurethane foam is not particularly limited as long as it contains a urethane bond in the resin. Examples of the polyol component include polyether polyol obtained by addition polymerization of ethylene oxide and propylene oxide, polytetramethylene ether glycol, polyester polyol obtained by condensing an acid component and a glycol component, polyester polyol obtained by ring-opening polymerization of caprolactone, polycarbonate diol, and the like. Can be used.

  Examples of polyether polyols obtained by addition polymerization of ethylene oxide and propylene oxide include water, propylene glycol, ethylene glycol, glycerin, trimethylolpropane, hexanetriol, triethanolamine, diglycerin, pentaerythritol, ethylenediamine, and methylglucotite. , Aromatic diamine, sorbitol, sucrose, phosphoric acid, etc. as starting materials, and those obtained by addition polymerization of ethylene oxide and propylene oxide. Particularly, water, propylene glycol, ethylene glycol, glycerin, trimethylolpropane. Those starting from hexanetriol are preferred. Regarding the ratio of ethylene oxide and propylene oxide to be added and the microstructure, the ratio of ethylene oxide is preferably 2 to 95% by weight, more preferably 5 to 90% by weight, and ethylene oxide is added to the terminal. preferable. In addition, the arrangement of ethylene oxide and propylene oxide in the molecular chain is preferably random.

  The molecular weight of the polyether polyol is bifunctional when water, propylene glycol, or ethylene glycol is used as a starting material, and preferably has a weight average molecular weight in the range of 300 to 6000, preferably in the range of 400 to 3000. Is more preferable. Further, when glycerin, trimethylolpropane, and hexanetriol are used as starting materials, they are trifunctional, and those having a weight average molecular weight in the range of 900 to 9000 are preferable, and those in the range of 1500 to 6000 are more preferable. Furthermore, a bifunctional polyol and a trifunctional polyol can be appropriately blended and used.

  Polytetramethylene ether glycol can be obtained, for example, by cationic polymerization of tetrahydrofuran, and those having a weight average molecular weight in the range of 400 to 4000, particularly in the range of 650 to 3000 are preferably used. It is also preferable to blend polytetramethylene ether glycols having different molecular weights. Furthermore, polytetramethylene ether glycol obtained by copolymerizing an alkylene oxide such as ethylene oxide or propylene oxide can also be used.

  Further, it is also preferable to use a blend of polytetramethylene ether glycol and a polyether polyol obtained by addition polymerization of ethylene oxide and propylene oxide. In this case, it is preferable to use such a blend ratio so that the weight ratio is in the range of 95: 5 to 20:80, particularly 90:10 to 50:50.

  In addition to the polyol component, a polymer polyol obtained by modifying the polyol with acrylonitrile, a polyol obtained by adding melamine to the polyol, a diol such as butanediol, a polyol such as trimethylolpropane, or a derivative thereof may be used in combination.

  As the isocyanate constituting the urethane foam, aromatic isocyanate or a derivative thereof, aliphatic isocyanate or a derivative thereof, alicyclic isocyanate or a derivative thereof is used. Among these, aromatic isocyanate or a derivative thereof is preferable, and tolylene diisocyanate (TDI) or a derivative thereof, diphenylmethane diisocyanate (MDI) or a derivative thereof is particularly preferably used.

  Tolylene diisocyanate or derivatives thereof include crude tolylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, these Urea-modified products, burette-modified products, carbodiimide-modified products, urethane-modified products modified with polyols, and the like are used. As diphenylmethane diisocyanate or a derivative thereof, for example, diphenylmethane diisocyanate or a derivative thereof obtained by phosgenating diaminodiphenylmethane or a derivative thereof is used. Examples of the derivatives of diaminodiphenylmethane include polynuclear bodies, and pure diphenylmethane diisocyanate obtained from diaminodiphenylmethane, polymeric diphenylmethane diisocyanate obtained from a polynuclear body of diaminodiphenylmethane, and the like can be used. Regarding the number of functional groups of polymeric diphenylmethane diisocyanate, a mixture of pure diphenylmethane diisocyanate and polymeric diphenylmethane diisocyanate having various functional groups is usually used, and the average number of functional groups is preferably 2.05 to 4.00, more preferably 2. .50 to 3.50 are used. Derivatives obtained by modifying these diphenylmethane diisocyanates or derivatives thereof, such as urethane modified products modified with polyols, dimers formed by uretidione formation, isocyanurate modified products, carbodiimide / uretonimine modified products, allophanate modified products , Urea-modified products, burette-modified products, and the like can also be used. Also, several types of diphenylmethane diisocyanate and its derivatives can be blended and used.

  In addition, the isocyanate may be prepolymerized with a polyol in advance. As a method for this, the polyol and the isocyanate are put in a suitable container and sufficiently stirred, and 30 to 90 ° C, more preferably 40 to 70 ° C, A method of keeping the temperature for 240 hours, more preferably 24 to 72 hours can be mentioned. In this case, the ratio of the amount of polyol and isocyanate is preferably adjusted so that the isocyanate content of the resulting prepolymer is 4 to 30% by weight, more preferably 6 to 15% by weight. If the isocyanate content is less than 4% by weight, the stability of the prepolymer is impaired, and the prepolymer may be cured during storage, making it impossible to use. If the isocyanate content exceeds 30% by weight, the content of isocyanate that has not been prepolymerized increases, and this polyisocyanate undergoes a prepolymerization reaction with the polyol component used in the subsequent polyurethane curing reaction. The effect of using the prepolymer method is diminished because it cures by a reaction mechanism similar to the one-shot process. In the case of using an isocyanate component in which isocyanate is prepolymerized with a polyol in advance, in addition to the above polyol component, diols such as ethylene glycol and butanediol, polyols such as trimethylolpropane and sorbitol, and derivatives thereof Can also be used.

  In the urethane foam raw material, in addition to these polyol component and isocyanate component, the same conductive agent as described above, foaming agent (water, low boiling point, gas body, etc.), crosslinking agent, surfactant, if desired Catalysts, foam stabilizers, and the like can be added, whereby an elastic layer can be formed as desired.

  Catalysts used for urethane foam curing reactions include monoamines such as triethylamine and dimethylcyclohexylamine, diamines such as tetramethylethylenediamine, tetramethylpropanediamine, and tetramethylhexanediamine, pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, tetra Triamines such as methylguanidine, triethylenediamine, dimethylpiperazine, methylethylpiperazine, cyclic amines such as methylmorpholine, dimethylaminoethylmorpholine, dimethylimidazole, dimethylaminoethanol, dimethylaminoethoxyethanol, trimethylaminoethylethanolamine, methylhydroxy Alcohol amines such as ethyl piperazine and hydroxyethyl morpholine; (Dimethylaminoethyl) ether, ether amines such as ethylene glycol bis (dimethyl) aminopropyl ether, stannous octoate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin marker peptide, dibutyltin thiocarboxylate, dibutyltin dimaleate, And organic metal compounds such as dioctyltin marker peptide, dioctyltin thiocarboxylate, phenylmercury propionate and lead octenoate. These catalysts may be used alone or in combination of two or more.

  In the present invention, it is preferable to blend a silicone foam stabilizer and various surfactants during the blending of the urethane foam in order to stabilize the cells of the foam material. As the silicone foam stabilizer, a dimethylpolysiloxane-polyoxyalkylene copolymer or the like is suitably used, and those composed of a dimethylpolysiloxane moiety having a molecular weight of 350 to 15000 and a polyoxyalkylene moiety having a molecular weight of 200 to 4000 are particularly preferable. . The molecular structure of the polyoxyalkylene moiety is preferably an addition polymer of ethylene oxide or a co-addition polymer of ethylene oxide and propylene oxide, and its molecular terminal is preferably ethylene oxide. Examples of the surfactant include cationic surfactants, anionic surfactants, ionic surfactants such as amphoteric, nonionic surfactants such as various polyethers and various polyesters. These may be used alone or in combination of two or more. The blending amount of the silicone foam stabilizer and various surfactants is preferably 0.1 to 10 parts by weight, and 0.5 to 5 parts by weight with respect to 100 parts by weight of the total amount of the polyol component and the isocyanate component. More preferably.

  As a foaming method of the urethane foam raw material in the present invention, a conventionally used method such as a mechanical froth method, a water foaming method, a foaming agent froth method, etc. can be used, particularly while mixing an inert gas. It is preferable to use a mechanical floss method in which foaming is performed by mechanical stirring. Here, the inert gas used in the mechanical froth method may be an inert gas in the polyurethane reaction, and in addition to inert gases in a narrow sense such as helium, argon, xenon, radon, krypton, nitrogen, carbon dioxide, drying The gas which does not react with urethane foam raw materials, such as air, is mentioned. In the present invention, the molding conditions of the elastic layer 2 made of such a urethane foam raw material are not particularly limited, and may be according to ordinary conditions.

  In the present invention, the surface layer 4 provided on the undercoat layer can be formed of a solvent-based paint such as urethane, acrylic, acrylurethane, or fluorine, and is shown in the enlarged cross-sectional view of FIG. As shown, the surface roughness can be adjusted by including spherical fine particles 5 made of urethane, acrylic, silica or the like. The surface roughness of the surface layer 4 is JIS arithmetic average roughness Ra, and can be usually 2 μm or less, particularly 0.5 to 1.5 μm. In addition, the surface layer 4 can be provided with desired conductivity by appropriately containing the above-described ionic conductive agent or electronic conductive agent as a conductive agent. The thickness of the surface layer 4 is not particularly limited, but is usually 1 to 50 μm, particularly about 1 to 40 μm. The surface layer 4 is formed by applying a predetermined solvent-based paint on the undercoat layer using a known method such as dip coating, spray coating, or roll coater coating, drying, and heating and curing as desired. Can be formed.

  The surface roughness of the developing roller 10 of the present invention obtained as described above can be suitably 0.5 to 1.0 μm in terms of arithmetic average roughness Ra. The developing roller 10 of the present invention preferably has a micro hardness of 55 ° or less, for example, 40 ° to 55 °, and the micro hardness is measured by, for example, a micro rubber hardness meter MD-1 type. It is possible.

Hereinafter, the present invention will be described in more detail with reference to examples.
As shown in FIG. 1, a developing roller 10 having a shaft 1 and an elastic layer 2, an undercoat layer 3 and a surface layer 4 sequentially formed on the outer periphery thereof was produced according to the following procedure.

  First, polyurethane foam was supported by the mechanical floss method on the outer periphery of a core bar (φ8 mm, length 260 mm, material: sulfur free cutting steel) as the shaft 1 to form an elastic layer 2 made of polyurethane foam.

  Specifically, it consists of 100 parts by weight of prepolymerized isocyanate (TDI + polyol), 20 parts by weight of polyether polyol, 2 parts by weight of acetylene black, and 0.2 parts by weight of ionic conductive agent (sodium perchlorate). A polyurethane raw material was prepared, and this polyurethane raw material was mechanically stirred by a mixer and mixed with dry air to foam. This urethane foam raw material was cast into a metal cylindrical mold in which a hole for penetrating the shaft was provided at the end, and a metal cap for supporting the shaft was installed. Inside the mold, the core metal 1 was disposed in a state where an adhesive was applied to the outer periphery. Next, the mold in which the urethane foam raw material was cast was left in a hot air oven adjusted to 90 ° C. for 4 hours to cure the urethane foam raw material.

  Next, the cured polyurethane foam was removed from the mold, and an undercoat layer-based aqueous coating composition shown in Table 1 below was dip-coated to form an undercoat layer 3 having a thickness of 100 μm on the outer periphery.

Further, on the outer periphery, a coating material for a surface layer in which 10 parts by weight of acetylene black and 10 parts by weight of spherical polyurethane particles having an average particle diameter D ⁵⁰ = 10 μm are blended with 100 parts by weight of polyurethane resin by dip coating using methyl ethyl ketone as a solvent. Thus, a surface layer 4 having a thickness of 10 μm was formed, and a developing roller having a roller main body portion of φ16 mm and a length of 240 mm was produced. The surface roughness of the obtained roller was 0.6 to 1.0 μm in terms of JIS arithmetic average roughness Ra.

<Dent evaluation>
A load of 500 g was applied to both ends of each of the obtained rollers to be brought into contact with the photoreceptor, and left for 7 days at a high temperature and high humidity of 40 ° C. × 95%. Thereafter, the roller was taken out, and the amount of dent at the contact portion was measured using a surface roughness meter (manufactured by Tokyo Seimitsu).

<Roller hardness>
The roller hardness of each obtained roller was measured with a micro hardness meter (MD-1 manufactured by Kobunshi Keiki Co., Ltd.).

<Image output evaluation>
Each roller after the evaluation of the dent was mounted on a printer cartridge as a developing roller and incorporated in a Laser Jet 4050 manufactured by Hewlett-Packard Co., and an image test was performed.
These results are also shown in Table 1 below.

＊１）水系アクリル樹脂以外は、水系アクリル樹脂１００重量部に対する重量部を示す。
＊２）（株）日本触媒製，品名：エポクロスＫ−２０１０Ｅ（オキサゾリン価５５０ｇｓｏｌｉｄ／ｅｑのオキサゾリン基を有するオキサゾリン系架橋剤）
＊３）ケッチェンブラック

* 1) Except for the water-based acrylic resin, it indicates parts by weight relative to 100 parts by weight of the water-based acrylic resin.
* 2) Made by Nippon Shokubai Co., Ltd., product name: Epocross K-2010E (oxazoline-based crosslinking agent having an oxazoline group having an oxazoline value of 550 g solid / eq)
* 3) Ketjen Black

  As can be seen from Table 1 above, the roller of each example using a water-based acrylic resin that satisfies the predetermined conditions according to the present invention for the undercoat layer has a desired low hardness and is excellent in setability. It was confirmed.

(A) is an axial sectional view showing a developing roller according to an embodiment of the present invention, and (b) is an enlarged sectional view showing the vicinity of the surface.

Explanation of symbols

1 Shaft 2 Elastic layer 3 Undercoat layer 4 Surface layer 5 Spherical fine particle 10 Developing roller

Claims (5)

In a developing roller comprising a shaft, an elastic layer carried on the outer periphery of the shaft, and one or more undercoat layers and a surface layer sequentially provided on the outer peripheral surface of the elastic layer,
All of the one or more undercoat layers are made of an aqueous resin, and at least one of the undercoat layers contains acrylonitrile and n-butyl acrylate in a monomer ratio of 1 to 25:99 to 75, and molecules A developing roller obtained by crosslinking a water-based acrylic resin containing a group having active hydrogen therein with an oxazoline-based crosslinking agent.   The developing roller according to claim 1, wherein the oxazoline-based cross-linking agent has two or more oxazoline groups.   The developing roller according to claim 1 or 2, wherein a surface acid value of the water-based acrylic resin is 10 mg / g or more.   The developing roller according to claim 1, wherein the group having active hydrogen is a carboxyl group.   The developing roller according to claim 1, wherein the elastic layer is a polyurethane foam formed by a mechanical floss method.

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