JP4778705B2 - Magnet roller, developer carrier, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a magnet roller used in an image forming apparatus such as a copying machine, a facsimile, and a printer, a developer carrier having the magnet roller, a process cartridge having the developer carrier, and an image forming having the process cartridge. Relates to the device.

  In recent years, the “high-performance developing device that develops a latent image formed on an image carrier using a two-component developer composed of toner and magnetic particles” (SLIC developing device) has been attracting attention. In order to solve the image problem in the developing device, in the developing roller (magnet roller) mounted on the SLIC developing device, (A) the half width of the developing pole is 20 ° or less (conventional two-component development). And (B) the magnetic flux density is 120 to 140 mT (80 to 120 mT for the conventional two-component development). It is necessary to increase the density and to reduce the half width to half or less of the conventional one.

  As a developing roller (magnet roller) mounted on such an SLIC developing device, “a cylindrical shaft is formed and a shaft is fixed to a permanent magnet material provided with a plurality of magnetic poles extending in the axial direction on the outer peripheral surface. In a magnet roller, a permanent magnet material is made of a ferrite magnet material and formed into a substantially cylindrical shape, and at least a part is fixedly embedded in a specific magnetic pole of this main body or in a groove provided in the vicinity thereof. However, it was considered to use a magnet piece formed of a material made of a material composed of an isotropic R—Fe—B magnetic powder and a binding material (see Patent Document 1). In such a conventional magnet roller, if the half-value width is lowered, the magnetic flux density is also reduced, so that both the items (A) and (B) cannot be satisfied at the same time. Was Tsu.

  Moreover, as a plastic rare earth magnet molded object, what was manufactured by the injection molding method and the extrusion molding method using the compound containing isotropic Nd-Fe-B is marketed, but the magnetic force is (BH ) Since the maximum value is 6-9 MGOe, it was not sufficient.

  Therefore, the present inventors examined using an anisotropic Nd magnet material that exhibits the highest magnetic force at present in order to achieve a high magnetic force magnet of 13 MGOe or higher, but contains an anisotropic Nd magnet material. Even if a compound is used, in the injection molding method and the extrusion molding method, the magnetic force is currently limited to 10-12 MGOe at the (BH) max value, so that it is not possible to achieve a high magnetic force of 13 MGOe or more. was there.

  The present inventors also examined forming a compound containing an anisotropic Nd magnet material by a compression molding method that can expect the highest magnetic force. In order to compression-mold a magnet compound containing an anisotropic Nd magnet material, it is necessary to orient the melted compound in a mold by applying a magnetic field. Generally, in a compound used in compression molding, an epoxy-based material of a thermosetting resin is used as the binding resin (binder). In such a compound, 1 to 10 wt% of an epoxy resin / curing agent is blended in a magnet material and adhered around the magnet material to form a DRY compound. However, in order to make the epoxy resin a compound in the DRY state, it is necessary to use a solid epoxy resin and a solid curing agent. Solid curing agents include many materials such as aromatic amines, dicyandiamides, imidazoles, etc., all of which have a high curing temperature, require at least 150 ° C., have a long curing time, and 60 There was a problem that more than a minute was needed. In general, the magnet material has a property of being demagnetized by heat. In particular, since the anisotropic Nd magnet material is susceptible to thermal demagnetization, the heat treatment is performed at 150 ° C. for 60 minutes. There was a problem that the magnetic property (BH) max was reduced by about 15%.

In the compression molding method in the magnetic field, it is possible to increase the magnetic force by increasing the press pressure to improve the density of the magnet compact, and by applying a magnetic field to the melted compound to improve the orientation. In the case of an epoxy resin compound, since the density is difficult to increase, a large pressing pressure is required. In order to achieve 13 MGOe, 6.1 g / cm ³ is required as the density of the magnet molded product, so 7.0 ton / cm ² is required as the press pressure. Considering the demagnetization characteristic of 15%, 6.55 g / cm ³ is required as the density of the magnet compact, and 11.1 ton / cm ² is required as the press pressure. Now, when producing a magnet compact having a prismatic mag width of 6 mm, a height of 2.5 mm, and a length of 304 mm, the press area in transverse magnetic field molding (molding in which the press direction and the magnetic field direction are orthogonal) is 7. 6 cm ² (0.25 × 30.4), and the required pressing pressure is 84 tons, so a 100 ton class press is required. In the compression molding method in a magnetic field, a mold is placed between electromagnets, and the magnet is oriented by applying a magnetic field to the melted magnet compound, but the generated magnetic field depends on the gap between the electromagnets. A magnetic force is obtained, and therefore, the gap value is generally set to 10 mm. For this reason, the plate thickness of the mold cannot be increased, so that there is a problem that the mold is damaged when a high press pressure is applied.

Therefore, the present inventors can reduce the press pressure to 6 ton / cm ² or less by incorporating pigments, charge control agents and release agents into the thermoplastic resin fine particles contained as binders in the magnet compound. It was proposed that a magnet molded body of 13 MGOe or more can be obtained (see Patent Document 2).

  Inside such a magnet molded body, the magnet powder is fixed by the thermoplastic resin fine particles adhering to the periphery thereof, so the magnet powder will not rust, but on the surface of this magnet molded body, the magnet particles are not rusted. Since it was exposed, there was a problem that the magnet powder easily rusted under high temperature and high humidity. Currently, the magnet that exhibits the highest magnetic force among the magnets excluding the Sm—Co based magnet is an anisotropic Nd—Fe—B based magnet. However, since such a magnet contains an Fe component, it is oxidized. It is easy to be done.

  Generally, a resin-bonded rare earth magnet has improved corrosion resistance when a coating film of epoxy resin or acrylic resin is formed on the surface thereof. However, in the long magnet molded body proposed by the present inventors, magnet powder having an average particle size of several tens to several hundreds of μm is unevenly fixed with a small amount of thermoplastic resin fine particles having an average particle size of 30 to 200 μm. The surface of the long magnet molded body has a lot of irregularities, and therefore the applied coating film thickness becomes non-uniform, so that the rust prevention of the magnet powder in the long magnet molded body becomes insufficient. There was a problem that the magnetic force decreased. Further, the thermoplastic resin fine particles serving as a binder may be deteriorated by hydrolysis of the thermoplastic resin depending on the thermoplastic resin constituting the binder. Further, in such a long magnet molded body, the magnetic force concentrates on the end portion thereof, so that the binding force of the thermoplastic resin fine particles serving as the binder is weakened. There was a problem that a change occurred and the magnetic force waveform changed. Therefore, it is necessary to coat the surface of the long magnet molded body with a moisture-proof coating material. However, a resin coating film is formed at the corners of the long magnet molded body that has a high magnetic force concentration and is susceptible to deterioration. There was a problem that it was difficult to form.

And as a rust prevention process of such a long resin molding, although the plating process is proposed, such a plating process has a problem that the amount of capital investment is large, and the number of processes increases. Therefore, there is a problem that the manufacturing cost increases.
Japanese Patent No. 2545601 JP 2004-193543 A

  The present invention aims to solve this problem.

  That is, the present invention prevents the occurrence of rust on the surface of the magnet powder in the embedded long magnet molded body to prevent a decrease in magnetic force, and reduces variations in magnetic force due to the long magnet molded body. Magnet roller with improved axial magnetic force distribution of long magnet molded body, developer carrying member having the magnet roller, developing device having the developer carrying member, process cartridge having the developing device, and process cartridge It is an object to provide an image forming apparatus having a low cost.

In order to achieve the above object, the invention described in claim 1 is such that another member can be embedded in a portion corresponding to the pole of a cylindrical magnet molded body formed of a plastic magnet containing magnetic powder. At least one concave groove portion is provided, and the cylindrical magnet molded body has a higher magnetic force length than the plastic magnet fixed to the concave groove portion with magnet powder and thermoplastic resin fine particles attached to the periphery thereof. In the magnet roller in which the shaped magnet molded body is arranged,
(A) A moisture-proof resin film is coated on the upper surface of the long magnet molded body ,
(B) the moisture-proof resin film is filled in a gap between both side surfaces of the elongated magnet molded body and both wall surfaces forming the concave groove , and
(C) A magnet roller, wherein the moisture-proof resin film contains magnet fine particles .

  The invention described in claim 2 is the invention described in claim 1, wherein the moisture-proof resin film is a resin film formed of a resin composition containing a butadiene rubber and a methylcyclohexane solvent. It is characterized by.

The invention described in claim 3 is the invention described in claim 1 or 2 , wherein the moisture permeability when measured at a film thickness of the moisture-proof resin film: 50 μm is 0.01 g / cm ² · 24 hr. It is characterized by the following.

The invention described in claim 4 is the invention described in any one of claims 1 to 3 , wherein the long magnet molded body includes a magnet compound containing magnet powder and thermoplastic resin fine particles in a magnetic field. A long magnet molded body obtained by compression molding with
(A) The thermoplastic resin fine particles are composed of a thermoplastic resin, and at least one compounding material selected from a pigment, a charge control agent, and a release agent; and
(B) The thermoplastic resin fine particles have an average particle size of 10 μm or less.

According to a fifth aspect of the present invention, there is provided a developer carrier comprising a rotatable nonmagnetic cylindrical body on an outer periphery of the magnet roller according to any one of the first to fourth aspects.

According to a sixth aspect of the present invention, in the developing device having at least a developer carrier, a developer supply member, a developer layer regulating member, and a developer, the developer carrier according to the fifth aspect is used. A developing device having a developer carrying member.

A seventh aspect of the present invention is a process cartridge having at least a developing device, an image carrier, and a charging unit, wherein the developing device includes the developing device according to the sixth aspect. .

The invention described in claim 8 is an image forming apparatus including at least a process cartridge, an optical writing unit, a transfer member, and a fixing device, and has the process cartridge according to claim 7 as the process cartridge. An image forming apparatus.

According to the first and second aspects of the invention, (a) a moisture-proof resin film is coated on the upper surface of the long magnet molded body, and (b) the moisture-proof resin film is the long film. Filled in the gap between the both side surfaces of the scale magnet molded body and the both wall surfaces forming the concave groove , and (c) Since the fine moisture is contained in the moisture-proof resin film, moisture-proof The resin film can fill the concave portion of the irregularities formed by the magnetic powder on the surface of the long magnet molded body, and for that purpose, the surface of the long magnet molded body is further covered with a rust inhibitor. It is possible to further prevent the occurrence of rust on the surface of the magnet powder in the formed long magnet molded body, and further reduce the variation in magnetic force due to the long magnet molded body, thereby reducing the axial magnetic force of the long magnet molded body. Providing a magnet roller that can further improve the distribution Door can be.

According to the invention described in claim 3 , since the moisture permeability when measured at a film thickness of 50 μm is 0.01 g / cm ² · 24 hr or less, the long magnet molding is performed. The thickness of the moisture-proof resin film can be reduced while preventing deterioration of the magnet powder constituting the body and the resin as the binder material at high temperature and high humidity. Even if a non-magnetic cylindrical body (sleeve) is extrapolated to the magnet roller thus formed to form a developer carrier, there is no restriction on the design of the magnet roller.

According to the invention described in claim 4 , (a) the thermoplastic resin fine particles are composed of a thermoplastic resin and at least one compounding material selected from a pigment, a charge control agent and a release agent, And (b) since the average particle diameter of the thermoplastic resin fine particles is 10 μm or less, the magnet powder becomes slippery and the orientation of the magnet is improved, and the magnet molding density is increased, and therefore The long magnet molded body can be further increased in magnetic force.

According to the invention described in claim 5 , since the developer carrier having the nonmagnetic cylindrical body rotatable on the outer periphery of the magnet roller according to any one of claims 1 to 5, the carrier adheres. Therefore, high image quality can be achieved.

According to the invention described in claim 6 , in the developing device having at least the developer carrier, the developer supply member, the developer layer regulating member, and the developer, as the developer carrier, Since the developer carrying member described is included, high image quality can be achieved.

According to the seventh aspect of the present invention, in the process cartridge having at least the developing device, the image carrier, and the charging unit, the developing device according to the seventh aspect is provided as the developing device. Can be realized.

According to the invention described in claim 8 , in the image forming apparatus having at least the process cartridge, the optical writing means, the transfer member, and the fixing device, the process cartridge according to claim 8 is provided as the process cartridge. Therefore, high image quality can be achieved.

  FIG. 1 is a cross-sectional view of a developer carrier having a magnet roller according to an embodiment of the present invention. FIG. 2 is a partially enlarged cross-sectional view of a long magnet molded body in a magnet roller showing an embodiment of the present invention. FIG. 3 is a graph showing the relationship between the moisture permeability of the waterproof resin film and the thickness of the long magnet molded body. FIG. 4 is an explanatory diagram of the developing device showing one embodiment of the present invention. FIG. 5 is an explanatory diagram of a process cartridge showing an embodiment of the present invention. FIG. 6 is an explanatory diagram of an image forming apparatus showing an embodiment of the present invention.

As shown in FIGS. 1 and 2, in the magnet roller 10 of the present invention, other members are provided at portions corresponding to the poles of the cylindrical magnet molded body 1 made of a plastic magnet containing magnetic powder. At least one concave groove portion 2 that can be embedded is provided, and the cylindrical magnet molded body 1 fixed to the concave groove portion 2 with magnet powder 3a and thermoplastic resin fine particles 3b attached to the periphery thereof. A long magnet molded body 3 having a higher magnetic force than that of the plastic magnet is disposed. In the magnet roller 10, (a) a moisture-proof resin film 4 is coated on the upper surface of the long magnet molded body 3, and (b) the moisture-proof resin film 5 is formed into the long magnet molding. (C) The moisture-proof resin films 4 and 5 contain magnet fine particles , and are filled in a gap between both side surfaces of the body 3 and both wall surfaces forming the concave groove 2 . In FIG. 1, 6 is an adhesive for fixing the long magnet molded body 3 to the concave groove 2, 7 is another long magnet molded body, and 11 is a non-magnetic cylindrical body. Reference numeral 20 denotes a developer carrier.

Since the moisture-proof resin film contains magnetic fine particles,
As described above, (a) the moisture-proof resin film 4 is coated on the upper surface of the long magnet molded body 3, and (b) the moisture-proof resin film 5 is formed on both side surfaces of the long magnet molded body 3. is filled in the gap between the both wall surfaces to form the concave-like groove 2, and, (c) the moisture of the resin films 4 and 5, the magnet fine particles are contained, moisture-proof resin film 4 and 5 can fill the concave and convex portions formed by the magnetic powder on the surface of the long magnet molded body 3, and for this purpose, the surface of the long magnet molded body 3 is further coated with a rust inhibitor. It is possible to further prevent the rust on the surface of the magnet powder in the embedded long magnet molded body 3 and to further reduce the variation in magnetic force due to the long magnet molded body 3, thereby the long magnet molded body. 3 can further improve the axial magnetic force distribution of It can be provided.

In the present invention, the moisture permeability when measured at a film thickness of 50 μm of the moisture-proof resin films 4 and 5 is preferably 0.01 g / cm ² · 24 hr or less. Thus, when the moisture permeability when measured at a film thickness of 50 μm of the moisture-proof resin films 4 and 5 is 0.01 g / cm ² · 24 hr or less, the magnet powder constituting the long magnet molded body 3 is formed. Since the thickness of the moisture-proof resin films 4 and 5 can be reduced to 50 μm or less while preventing deterioration of the resin fine particles 3b as the binder material at high temperature and high humidity, the long magnet molded body 3 Even if the non-magnetic cylindrical body (sleeve) is extrapolated to the embedded magnet roller 10 to form the developer carrier 20, the design of the magnet roller 10 is not affected.

FIG. 3 is a graph showing the relationship between the moisture permeability of the waterproof resin film and the thickness of the long magnet molded body. The “thickness of the long magnet molded body” is NdFeB / polyester long It is the thickness of the NdFeB / polyester long magnet compact measured after leaving the magnet compact for 240 hours in an environment of temperature 60 ° C. and humidity 80%. From FIG. 3, it can be seen that when the moisture-proof rate exceeds 0.01 g / cm ² · 24 hr, the change in the thickness of the long magnet molded body increases.

  The moisture-proof resin film used in this test was formed using a styrene-butadiene rubber-based paint using methylcyclohexane as a solvent. The moisture-proof resin films 4 and 5 in the present invention may be formed with a general acrylic or urethane paint, but the acrylic or urethane paint uses a ruene / xylene solvent. Since there are many things, the use of such a ruene / xylene-based solvent is not preferable because it tends to deteriorate the resin (binder material) constituting the long magnet molded body. On the other hand, since styrene-butadiene rubber can use a methylcyclohexane solvent having a weak polarity, the one using such a methylcyclohexane solvent does not deteriorate the resin constituting the long magnet molded body. .

  The long magnet molded body 3 in the present invention is obtained by compressing and molding a magnet compound containing magnet powder 3a and thermoplastic resin fine particles 3b in a magnetic field, and (a) the thermoplastic resin fine particles 3b are: And (b) the average particle diameter of the thermoplastic resin fine particles 3b is 10 μm or less. The thermoplastic resin fine particles 3b are composed of at least one compounding material selected from a thermoplastic resin and a pigment, a charge control agent and a release agent. . Thus, (a) the thermoplastic resin fine particles 3b are composed of a thermoplastic resin and at least one compounding material selected from a pigment, a charge control agent and a release agent, and (b) the heat If the average particle size of the plastic resin fine particles 3b is 10 μm or less, the magnet powder 3a becomes slippery and the orientation of the magnet is improved, and the magnet molding density is increased. The molded body 3 can be further increased in magnetic force.

  The “magnet powder 3a” constituting the “long magnet molded body 3” is preferably composed of an Nd—Fe—B-based material or Sm—Fe—N-based material. It is -200 micrometers, Preferably, it is 80-150 micrometers, More preferably, it is 100-120 micrometers amorphous particles.

  The “thermoplastic resin” in the thermoplastic resin fine particles 3b constituting the “long magnet molded body 3” is, for example, a homopolymer composed of a styrene compound such as polystyrene, polychloroethylene, polyvinyltoluene, or the like, and a substitution product thereof, Styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer Polymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene- α-Chloromethyl methacrylate copolymer, styrene-acrylic Nitrile polymer, styrene-vinyl methyl ether polymer, styrene-vinyl methyl ketone polymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer And styrene copolymers such as styrene-maleic acid ester copolymer. The “thermoplastic resin” includes polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyvinyl butyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol. A resin such as a resin or an epoxy polyol resin may be used. These resins can be used alone or in combination.

  The “thermoplastic resin fine particles 3b” serve as a binder for the magnet powder 3a. In the case where the magnetic powder such as a conventional epoxy is fixed around the magnetic powder, the magnet powder is likely to aggregate and the orientation is often lowered. However, the “thermoplastic resin fine particles 3b” in the present invention are magnetic. Since it adheres electrostatically to the surface of the powder 3a, it is easier to orient and have a higher magnetic force than the conventional binder around the magnetic powder. In the “thermoplastic resin” constituting the “thermoplastic resin fine particles 3b” in the present invention, the magnet powder 3a can be bound at a temperature at which the thermoplastic resin melts or softens, so that the baking process can be performed in a short time. Therefore, thermal demagnetization due to temperature can be reduced.

  As described above, the “thermoplastic resin fine particles 3b” are composed of a thermoplastic resin and at least one compounding material selected from a pigment, a charge control agent, and a release agent. A mixture of a thermoplastic resin and at least one compounding material selected from a pigment, a charge control agent, and a release agent is melted, kneaded, and cooled by a heat kneading apparatus such as a heating kneader or a three roll mill. The solidified product can be obtained by pulverizing to a particle size of 1 to 50 μm with a pulverizer such as a jet mill or a ball mill. The “thermoplastic resin” acts as a binder, but those having a low softening point are liable to re-aggregate even when pulverized, so it is difficult to obtain fine particles of 10 μm or less. In such a case, re-aggregation after pulverization can be prevented by kneading a pigment such as carbon black in a thermoplastic manner. The added amount of the pigment is preferably 1 to 20 wt%, more preferably 5 to 10 wt%. The “charge control agent” is added to improve the dispersibility of the magnet powder 3a and the thermoplastic resin fine particles 3b. The addition amount of the charge control agent is preferably 1 to 20 wt%, more preferably 0.5 to 10 wt%. The “release agent” is added to those that improve mold release properties after molding. The amount of the release agent added is preferably 1 to 20 wt%, more preferably 2 to 10 wt%. The fluidity imparting agent can be added to the mixture of the pulverized thermoplastic resin, pigment, charge control agent and release agent to improve the fluidity of the mixture.

  The “pigment” is, for example, carbon black such as oil furnace black, channel black, lamp black, acetylene black, cadmium yellow, mineral fast yellow, nickel titanium yellow, molybdenum orange, permanent orange, bengara, cadmium red, methyl violet lake, Cobalt blue and alkali blue. The “charge control agent” is, for example, a complex compound of nigrosine, a quaternary ammonium salt, a metal-containing azo dye, and salicylic acid. Examples of the “release agent” include 1) synthetic waxes such as low molecular weight polyethylene and propylene, 2) plant waxes such as cadilla wax, carnauba wax, rice wax, wood wax, jojoba oil, and 3) beeswax. Animal waxes such as lanolin and spermaceti, 4) mineral waxes such as montan wax and ozokerite, and 5) fat waxes such as hardened castor oil, hydroxystearic acid, fatty acid amide, phenol fatty acid ester, etc. is there. These pigments can be used alone or in combination.

  As shown in FIG. 1, a developer carrier 30 according to the present invention includes a rotatable nonmagnetic cylindrical body 11 disposed on the outer periphery of a magnet roller 10 according to any one of claims 1 to 5. is there. As the nonmagnetic cylindrical body 11, for example, aluminum, SUS (stainless steel), or the like can be used. Aluminum is often used in terms of workability and lightness. In the case of aluminum, A6063, A5056, A3003, etc., and in the case of SUS, 303, 304, 316, etc. can be used. As described above, when the rotatable nonmagnetic cylindrical body 11 is disposed on the outer periphery of the magnet roller 10 according to any one of claims 1 to 5, adhesion of the carrier can be prevented. Thus, it is possible to provide the developer carrying member 20 that can achieve high image quality.

  As shown in FIG. 4, the developing device 30 of the present invention has at least a developer carrier (developing roller) 20, a developer supply member 21, and a developer layer regulating member 22. The developing device 30 includes the developer carrier according to claim 6 as the developer carrier 20. Thus, when the developer carrying member 20 according to any one of claims 1 to 5 is provided as the developer carrying member 20, the developing device 30 capable of improving the image quality can be provided. it can.

  As shown in FIG. 5, the process cartridge 40 of the present invention includes a developer carrier 20, a developer supply member 21, and a developing device 30 having at least a developer layer regulating member 22, as well as a charging roller 24 and an image carrier. It has a body 25. The process cartridge 40 includes the developing device according to claim 7 as the developing device 30. As described above, when the developing device according to the eleventh aspect is provided as the developing device 30, it is possible to provide the process cartridge 40 capable of improving the image quality.

  As shown in FIG. 6, the image forming apparatus 50 of the present invention includes at least a process cartridge 40, an optical writing unit 103, a transfer member 105, and a fixing device 117. The image forming apparatus 50 according to the present invention includes the process cartridge according to claim 8 as the process cartridge 40. As described above, when the process cartridge according to the eighth aspect is provided as the process cartridge 40, it is possible to provide the image device 50 capable of improving the image quality.

  In FIG. 6, the process cartridge 40 includes a developing device 30 having a developer carrier (developing roller) 20, a developer supply member 21, and a developer layer regulating member 22, as well as a charging roller 24 and an image carrier. 25. In FIG. 6, reference numeral 106 denotes a cleaning blade, 107 denotes a static elimination optical system, 113 denotes a toner supply unit, 114 denotes a registration roller, 115 denotes a toner collection blade, and 117. Is a fixing device, and 116 is a toner conveying coil.

( Example )
(1) (a) Average particle diameter composed of anisotropic Nd—Fe—B: 107 μm magnet powder (manufactured by Aichi Steel Corporation, MFP-13) 95% by weight, and (b) as a thermoplastic resin A resin comprising 89.8 parts by weight of a polyester resin and 9 parts by weight of a styrene acrylic resin, a thermoplastic resin at 75 ° C., and 1.2 parts by weight of hydrophobic silica as a fluidity-imparting agent. An average volume particle size constituted by the composition: 5% by weight of 5.5 μm thermoplastic resin fine particles were mixed, and these were stirred for 10 minutes with a tumbler mixer to obtain a compound. Then, after filling this compound into a cavity of a temperature-controlled mold having a cavity having a width of 2.5 mm, a height of 13.0 mm, and a length of 313 mm, a magnetic field of 18000 (Oe) is applied to the mold. A DC electric field was applied so as to generate, and subsequently, a compression molding compound filled in the cavity at room temperature was applied with a press pressure of 5.5 ton / cm ^{2 in} a magnetic field applied state. Next, a reverse magnetic field was applied to the mold to demagnetize both the work and the mold, and then the work was taken out of the mold. The long magnet molded body thus obtained has a width of 5.05 mm, a top height of 5.53 mm, and a length of 312.6 mm, and the width direction of the length of 312.6 mm is 11.1 mm in diameter. It was 3 mm in the R shape, and the molding density of the long magnet compact was 5.66 g / cm ³ . Next, this long magnet compact was heat-treated in an oven at 100 ° C. for 60 minutes to dissolve the binder and correct the undulation after molding.

  (2) The long magnet molded body obtained in the above (1) is magnetized with a 2.8T pulse magnetizer, and this is composed of a ferrite magnet provided with a groove having a width of 5.6 mm and a depth of 2.6 mm. A cyanoacrylate adhesive was applied to the center of the groove of the 25 mm diameter magnet roller. At that time, a gap of 0.29 mm was generated between both side surfaces of the long magnet molded body and both side walls of the groove. A coating composition comprising 80% by weight of a styrene-butadiene rubber-based paint (manufactured by Nitto Shinko Co., Ltd., ELEPCOAT LSS-520MH) and 20% by weight of an anisotropic SmFeN-based magnet powder having an average particle size of 2 μm is obtained. It is applied to the upper surface of the long magnet molded body by a spencer method, and the coating composition is filled in the gap between the both side surfaces of the long magnet molded body and the both side walls of the groove. A magnet roller formed by drying the coating material at 60 ° C. for 30 minutes to form a moisture-proof resin film having a surface film thickness of 0.075 ± 0.02 mm and a moisture-proof resin film having a thickness of 2.4 mm. Obtained.

(3) The moisture permeability of the moisture-proof resin film in the magnet roller thus obtained was 0.0040 g / cm ² · 24 hr. Then, the axial magnetic flux density distribution of the magnet roller thus obtained, that is, the axial magnetic flux density distribution at a position 1.2 mm away from the surface of the long magnet molded body was measured, and 91 mT ± 0. It was 8 mT. In addition, a non-magnetic cylindrical body (sleeve) and a flange were attached to this magnet roller, and this was left for 240 hours in an environment of a temperature of 60 ° C. and a humidity of 90%. It was. Moreover, the swelling of the long magnet molded body was small, and the film thickness change was 0.023 mm.

It is sectional drawing of the developer carrier which has a magnet roller which shows embodiment of this invention. It is a partial expanded sectional view of the elongate magnet molding in the magnet roller which shows embodiment of this invention. It is a graph which shows the relationship between the moisture permeability of a waterproof resin film, and the thickness of a long magnet molded object. It is explanatory drawing of the developing device which shows one Embodiment of this invention. It is explanatory drawing of the process cartridge which shows one Embodiment of this invention. 1 is an explanatory diagram of an image forming apparatus showing an embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 Cylindrical magnet molded body 2 Concave groove part 3 Long magnet molded body 3a Magnet powder 3b Thermoplastic resin fine particle as a binder material 4,5 Moisture-proof resin film 4b, 5b Magnet fine particle 6 Adhesive 7 Other long magnets Molded body 8 Recessed portion 10 Magnet roller 11 Nonmagnetic cylindrical body 20 Developer carrier (developing roller)
DESCRIPTION OF SYMBOLS 21 Developer supply member 22 Developer layer control member 24 Charging roller 30 Developing device 40 Process cartridge 50 Image forming apparatus

Claims (8)

At least one concave groove portion in which another member can be embedded is provided in a portion corresponding to the pole of a cylindrical magnet molded body composed of a plastic magnet containing magnetic powder, and the concave groove portion, In a magnet roller in which a long magnet molded body having a higher magnetic force than a plastic magnet of the cylindrical magnet molded body fixed with magnet powder and thermoplastic resin fine particles attached to the periphery of the magnet powder is disposed,
(A) A moisture-proof resin film is coated on the upper surface of the long magnet molded body ,
(B) the moisture-proof resin film is filled in a gap between both side surfaces of the elongated magnet molded body and both wall surfaces forming the concave groove , and
(C) A magnet roller characterized in that the moisture-proof resin film contains magnet fine particles .   The magnet roller according to claim 1, wherein the moisture-proof resin film is a resin film formed of a resin composition containing a butadiene rubber and a methylcyclohexane solvent. The moisture-proof resin film having a thickness: moisture permeability when measured at 50μm is, a magnet roller according to claim 1 or 2, characterized in that not more than 0.01g / cm ² · 24hr. The long magnet molded body is a long magnet molded body obtained by compression molding a magnetic compound containing magnet powder and thermoplastic resin fine particles in a magnetic field,
(A) The thermoplastic resin fine particles are composed of a thermoplastic resin, and at least one compounding material selected from a pigment, a charge control agent, and a release agent; and
(B) The magnet roller according to any one of claims 1 to 3 , wherein the thermoplastic resin fine particles have an average particle size of 10 µm or less. A developer carrying member, characterized in that it comprises a rotatable non-magnetic cylindrical body on the outer periphery of the magnet roller according to any one of claims 1-4. In a developing device having at least a developer carrying member, a developer supplying member, a developer layer regulating member, and a developer, the developer carrying member according to claim 5 is included as the developer carrying member. Developing device. A process cartridge having at least a developing device, an image carrier, and a charging unit, wherein the developing device includes the developing device according to claim 6 . An image forming apparatus having at least a process cartridge, an optical writing unit, a transfer member, and a fixing device, wherein the process cartridge according to claim 7 is used as the process cartridge.

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