JP4286414B2 - Developer supply member and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developer supply member used in a developing device of an electrophotographic or electrostatic image forming apparatus such as a copying machine, a facsimile, or a printer, and an image forming apparatus equipped with the developer supplying member.
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the advancement of electrophotographic technology, polyurethane members have attracted attention as image forming apparatuses such as dry electrophotographic apparatuses for charging, developing, transferring, toner supplying, cleaning, and the like. It is used in the form of an elastic roller such as a charging roller, a developing roller, a transfer roller, a toner supply roller, and a cleaning roller, an elastic blade such as a toner layer regulating blade, and a cleaning blade. When the polyurethane member is used for applications such as transfer, toner supply, and cleaning that are particularly required to have low hardness, it is preferable to apply polyurethane foam.
The polyurethane member is produced by reacting and curing a polyisocyanate component and a polyol component. As a method for forming polyurethane into a foam body, a method of introducing a gas by mechanical stirring while blowing a gas such as nitrogen gas at the time of this reaction hardening (mechanical floss method), adding water as a blowing agent to a polyol component, A method of generating carbon dioxide by reaction with an isocyanate component (water foaming method), a low-boiling liquid such as chlorofluorocarbons and low-boiling hydrocarbons is added to a polyol component, and this low-boiling liquid is increased by a temperature rise during reaction curing. There is a method such as a method for vaporizing (foaming agent froth method).
On the other hand, the developer supply member is a member for supplying a developer such as a toner to a developer carrier such as a developing roller, and is usually a polyurethane foam or a silicone foam in which a member such as a metal shaft is disposed in the center. It is used in the form of a roller made of A member made of polyurethane foam is preferred to a member made of silicone foam because the raw material is inexpensive.
[0003]
[Problems to be solved by the invention]
However, when a toner supply roller made of polyurethane foam is used for a long period of time, depending on how the toner supply roller is used, the toner may melt and adhere to the surface of the toner supply roller, causing image defects.
The present invention has been made in view of the above circumstances, and in a developer supply member made of polyurethane foam at least on its surface, a developer such as toner is melted and fixed on the surface of the developer supply member, thereby causing an image defect. It is an object of the present invention to provide a developer supply member that does not have any.
[0004]
[Means for Solving the Problems]
The inventors of the present invention have intensively studied to achieve the above object. In particular, research was repeated from the viewpoint of preventing the developer from being melted and fixed on the surface of the polyurethane foam forming the surface in contact with the developer in the developer supply member. As a result, it was found that the substance that migrates from the inside of the polyurethane foam to the vicinity of the surface of the polyurethane foam melts the developer such as toner that comes into contact with the developer supply member. Further, when the surface of the developer supply member is formed of polyurethane foam having a low molecular weight component evaluated by the acetone extraction rate and a polyurethane foam having Asker F hardness in a specific range, migration of the substance can be prevented. It has been found that the developer does not melt and adhere to the developer supply member, and when used in an image forming apparatus, a good image can be maintained over a long period without causing image defects. The present invention has been completed based on such findings.
That is, according to the present invention, in a developer supply member that is made of polyurethane foam and is used in contact with a developer, the polyurethane foam is produced using a polyol and a polyisocyanate as main raw materials, and acetone at 90 ° C. is used as a solvent. And a developer supply member having an Asker hardness of 20 to 80 ° and an image forming apparatus equipped with the developer supply member. Is to provide.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
A component of the polyurethane foam forming at least the surface of the developer supply member of the present invention that is extracted with acetone as a solvent (acetone extraction component) is acetone at 90 ° C., and is a method that complies with the method for soft rubber of JIS K6350. Refers to the ingredients extracted in The acetone extraction component of the polyurethane foam used in the present invention is 5% by weight or less, preferably 3% by weight or less, by weight of the resin (polyurethane foam). If the resin weight ratio (acetone extraction rate) of this acetone extract component exceeds 5% by weight, the amount of substances transferred to the surface of the developer supply member increases, which causes developer fusion.
The method of setting the acetone extraction rate of polyurethane foam to 5% by weight or less is a method of washing the produced polyurethane foam with steam, a method of immersing the polyurethane foam in ion-exchanged water for a long time, and a polyurethane foam using an organic solvent such as acetone. For example, a method for washing polyurethane, a blending formulation for polyurethane raw materials, and a method for producing polyurethane foam. Among these, the method of specifying the blending formulation of the polyurethane raw material and the polyurethane foam production method is most preferable.
Moreover, the Asker F hardness of the polyurethane foam used by this invention is 20-80 degrees, Preferably it is 30-70 degrees. When the Asker F hardness is less than 20 °, there is a disadvantage that the amount of developer supply is insufficient. When the Asker F hardness exceeds 80 °, the material to be transferred to the surface of the developer supply member and the developer are caused by the pressing force. The inconvenience of fusing occurs.
[0006]
The polyurethane foam forming at least the surface of the developer supply member of the present invention is produced using polyol and polyisocyanate as main raw materials. As the polyisocyanate constituting the polyurethane raw material, aromatic isocyanate or a derivative thereof, aliphatic isocyanate or a derivative thereof, alicyclic isocyanate or a derivative thereof is used. Among these, aromatic isocyanates or derivatives thereof are preferable, and tolylene diisocyanate or derivatives thereof, diphenylmethane diisocyanate or derivatives thereof are 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 These are urea-modified products, burette-modified products, carbodiimide-modified products, and the like.
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. As for 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 from 2.05 to 4.00, more preferably 2. The thing of 50-3.50 is used. Derivatives obtained by modifying these diphenylmethane diisocyanates or their derivatives, such as urethane modified products modified with polyols, dimers formed by uretidione, 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.
[0007]
In the present invention, diphenylmethane diisocyanate or a derivative thereof is preferable among the polyisocyanates when the acetone extraction rate of the polyurethane foam is set to 5% by weight or less by selection of the formulation. Tolylene diisocyanate or its derivatives are preferable from the viewpoint of the strength of the polyurethane foam, but when the polyurethane foam is produced by a one-shot production method in which polyisocyanate and polyol are reacted directly, the acetone extraction rate cannot be reduced to 5% by weight or less. . Therefore, by using a prepolymer method in which a hydroxyl group of a polyol described later is reacted with polyisocyanate in advance to make a prepolymer having a high molecular weight with a chain extender, the acetone extraction rate of polyurethane foam is 5 wt. % Or less. The prepolymer method can also be applied when polyisocyanate other than tolylene diisocyanate or a derivative thereof is used.
As a method of prepolymerizing a polyol with a polyisocyanate in advance, the polyol and the polyisocyanate are put in a suitable container and sufficiently stirred, and the temperature is preferably 30 to 90 ° C., more preferably 40 to 70 ° C., for 6 to 240 hours. A method of keeping the temperature for 24 to 72 hours is preferable. In this case, the ratio of the amount of polyol and polyisocyanate 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 non-prepolymerized polyisocyanate increases, and this polyisocyanate reacts with the polyol component used in the subsequent polyurethane curing reaction and the prepolymerization reaction. The effect of using the prepolymer method is diminished because it cures by a reaction mechanism similar to the one-shot manufacturing method that does not pass.
When the obtained prepolymer is cured with a chain extender, it is necessary to select a chain extender having a specific reaction activity in order to achieve an acetone extraction rate of 5% by weight by selecting a formulation. A chain extender containing 50 to 100% by weight, more preferably 70 to 100% by weight of a chain extender whose terminal molecular structure is a primary hydroxyl group or a primary amino group is suitable. Examples of the chain extender used include ethylene glycol, diethylene glycol, 1,4-butanediol, polyethylene glycol having a molecular weight of 200 to 1000, polytetramethylene ether glycol having a molecular weight of 400 to 3000, glycerin, trimethylolpropane, and sorbitol. Further, water that also serves as a foaming agent can be used as a chain extender.
[0008]
Polyol components constituting the polyurethane raw materials include polyether polyols obtained by addition polymerization of ethylene oxide and propylene oxide, polytetramethylene ether glycols obtained by ring-opening polymerization of tetrahydrofuran, polyester polyols obtained by condensing acid components and glycol components, and caprolactone. A ring-polymerized polyester polyol, polycarbonate diol, or the like can be used. Among these, polyether polyol and polytetramethylene ether glycol are preferable from the viewpoint of hydrolysis resistance.
Polyether polyols obtained by addition polymerization of ethylene oxide and propylene oxide are, for example, water, propylene glycol, ethylene glycol, glycerin, trimethylolpropane, hexanetriol, triethanolamine, diglycerin, pentaerythritol, ethylenediamine, methylglucotite, Examples include aromatic diamines, sorbitol, sucrose, phosphoric acid, etc. as starting materials, and addition polymerization of ethylene oxide and propylene oxide. Especially, water, propylene glycol, ethylene glycol, glycerin, trimethylolpropane, Those starting from hexanetriol are preferred. About 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 what has ethylene oxide added to the terminal is preferably used. Further, 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, particularly preferably in the range of 400 to 3000. . When glycerin, trimethylolpropane, and hexanetriol are used as starting materials, they are trifunctional and preferably have a weight average molecular weight in the range of 900 to 9000, particularly preferably in the range of 1500 to 6000. Further, a bifunctional polyol and a trifunctional polyol can be appropriately blended and used.
[0009]
Polytetramethylene ether glycol is obtained, for example, by cationic polymerization of tetrahydrofuran, and those having a weight average molecular weight 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 alkylene oxide such as ethylene oxide or propylene oxide can also be used.
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, polytetramethylene ether glycol, addition polymerization of ethylene oxide and propylene oxide was performed. It is preferably used so that the ratio with the polyether polyol is in the range of 95: 5 to 20:80, particularly in the range of 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 can be used in combination.
[0010]
Polyurethane raw materials include conductive agents such as electrolytes, conductive materials such as carbon black, fillers such as carbon black and inorganic carbonates, foam stabilizers such as silicone foam stabilizers and various surfactants, phenol and phenylamine, etc. Antioxidants, low friction agents, charge control agents, and the like can be added. In the case where the acetone extraction rate of the polyurethane foam is set to 5% by weight or less by the selection of the blending formulation, it is necessary to thoroughly examine the blending amounts of the electrolyte, carbon black and filler to be added. That is, when a large amount of liquid or grease-like electrolyte or carbon black with a large amount of volatilization (for example, channel black) is blended, the acetone extraction rate increases, while when carbon black with a large oil absorption (for example, acetylene black) or a filler is blended. The acetone extraction rate can be reduced. Also, when blending foam stabilizers such as silicone foam stabilizers and surfactants, incorporate reactive hydroxyl groups into the foam stabilizer and incorporate foam stabilizers into the polyurethane backbone during polyurethane curing by reaction with polyisocyanates. Thus, the acetone extraction rate can be effectively reduced.
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, and nonionic surfactants such as various polyethers and various polyesters.
The blending amount of the silicone foam stabilizer and various surfactants is preferably 0.1 to 10 parts by weight, and more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the polyurethane material.
The blending amount of the silicone foam stabilizer and various surfactants is preferably 0.1 to 10 parts by weight, and more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the polyurethane raw material.
[0011]
Catalysts used for the curing reaction of polyurethane raw materials include monoamines such as triethylamine and dimethylcyclohexylamine, diamines such as tetramethylethylenediamine, tetramethylpropanediamine and tetramethylhexanediamine, pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, tetra Triamines such as methylguanidine, cyclic amines such as triethylenediamine, dimethylpiperazine, methylethylpiperazine, 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, Examples thereof include organometallic compounds such as dioctyl tin marker peptide, dioctyl tin thiocarboxylate, phenylmercury propionate, and lead octenoate. These catalysts may be used alone or in combination of two or more.
[0012]
Methods for forming polyurethane foam include mechanical flossing with mechanical agitation and foaming while mixing inert gas, water foaming with carbon dioxide generated by the reaction of water and polyisocyanate components, low freon and pentane, etc. There is a method such as a blowing agent froth method in which a polyol component is added to a polyol component and the low boiling point compound is vaporized by increasing the temperature during reaction curing. Here, the inert gas used in the mechanical froth method may be an inert gas in the polyurethane reaction. 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 polyisocyanate, such as air, is mentioned. The density of the polyurethane foam, from the viewpoint of adjusting the Asker F hardness of above, preferably 0.06~0.6g / cm ^3, more preferably 0.07~0.4g / cm ^3.
[0013]
In the present invention, the polyurethane foam is preferably produced by a water foaming method from the viewpoint of obtaining a polyurethane foam having a bottom density and a low hardness. In the polyurethane foam manufacturing process, the setting of the conditions for curing the polyurethane is to reduce the acetone extraction rate of the polyurethane foam by making the blending formulation of the polyurethane raw material and the polyurethane foam manufacturing method specific. If the curing conditions are unsuitable even if the formulation is optimized, the acetone extraction rate of the polyurethane foam cannot be reduced. That is, it is necessary to effectively incorporate into the polyurethane main chain a compounding component formulated to sufficiently increase the reaction completion rate of the polyurethane and introduce a hydroxyl group into the main chain of the polyurethane. Methods for increasing the reaction completion rate and incorporating the compounding components into the polyurethane main chain include increasing the curing temperature of the polyurethane raw material injected into the mold, increasing the curing time, or reusing the polyurethane foam after demolding. There is a method of increasing the reaction completion rate by heating. Of these, the method of reheating after demolding is the most effective, and within 5 minutes to 2 days after demolding, the polyurethane foam is preferably 40 to 140 ° C., more preferably 60 to 110 ° C., preferably 30 minutes. A method of heating for 120 hours, more preferably 1 to 48 hours is suitable.
[0014]
FIG. 1 is an explanatory view showing an example of an electrophotographic image forming apparatus equipped with a developer supply member of the present invention, which holds a developer supply member (toner supply roller) 3 and a latent electrostatic image. A developer carrier (developing roller) 2 is disposed between the image forming body 1 and the outer peripheral surface thereof close to the surface of the image forming body 1, and a recording medium 8 such as paper is provided on the image forming body 1. A structure in which a transfer member (transfer roller) 5 is in contact with each other is shown. By rotating the developer supply member 3, the developer carrier 2 and the image forming body 1 in the direction of the arrow, the developer (toner) is supplied to the surface of the developer carrier 2 by the developer supply member 3 and developed. After being adjusted to a uniform thin layer by the agent layer forming blade 4, it adheres to the latent image on the image forming body 1, and the latent image is visualized. The developer (toner) image on the image forming body 1 is transferred to the recording medium 8 by generating an electric field between the image forming body 1 and the transfer member (transfer roller) 5. Reference numeral 6 denotes a cleaning member (cleaning roller), which removes the developer remaining on the surface of the image forming body 1 after the transfer. Reference numeral 7 denotes a charging member (charging roller).
Specific examples of the image forming apparatus include a plain paper copying machine, a plain paper facsimile machine, a laser beam printer, a toner jet printer, and the like.
[0015]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these examples.
Example 1
90 g of a polyether polyol having a weight average molecular weight of 5000 obtained by addition polymerization of ethylene oxide and propylene oxide using glycerin as a starting material, and a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 8: 2. After mixing with 20 g and stirring sufficiently, the mixture was kept at 60 ° C., and stirring was repeated every 12 hours. After 48 hours, the prepolymerization of the polyether polyol was completed. The isocyanate content of the obtained prepolymer was 6.7% by weight.
100 g of this prepolymer, 20 g of water, 0.1 g of a dipropylene solution (33% by weight) of tetramethylethylenediamine (amine catalyst), 0.1 g of N-methylmorpholine (amine catalyst), and a silicone foam-stabilized silicone introduced with a hydroxyl group at the terminal 2.5 g of the agent and 2.5 g of acetylene black were mixed. The mixture was cast on a cylindrical form with an inner diameter of 17.0 mm and a length of 210.0 mm, and the inner surface of the cylinder was coated with Teflon and the end was sealed with a removable cap. When left in a hot-air oven adjusted to 0 ° C. for 8 hours, the polyurethane expanded and expanded, filling the mold and cured. The cured polyurethane foam was demolded by removing the cap at the end of the mold, and passed through a roll for crushing treatment. The acetone extraction rate of the polyurethane foam was 4.5% by weight, the density was 0.09 g / cm ³ , and the Asker F hardness was 65 °.
Next, a hole having an inner diameter of 5 mm was made in the center of the circle at the end face of the cylinder, and a shaft made by galvanizing sulfur free-cutting steel having an outer diameter of 6.0 mm and a length of 240 mm coated with an adhesive was press-fitted. After heat-bonding for 15 minutes in an oven at 60 ° C., a toner supply roller was prepared by polishing with a grindstone so that the outer diameter of the cylinder was 16.5 mm.
The obtained toner supply roller was incorporated into the image forming apparatus shown in FIG. 1, and a test was performed to print 5000 sheets of 8% grayscale images 100 times a day for a total of 50 days, from the initial test to the end of the test. A good image free from image defects was obtained.
[0016]
Comparative Example 1
90 g of polyether polyol having a weight average molecular weight of 5000 obtained by addition polymerization of ethylene oxide and propylene oxide using glycerin as a starting material, and 20 g of a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a weight ratio of 8: 2. 20 g of water, 0.1 g of tetramethylethylenediamine, 0.1 g of N-methylmorpholine, 2.5 g of a silicone foam stabilizer introduced with a hydroxyl group at the terminal, and 2.5 g of acetylene black were mixed in the same manner as in Example 1. A polyurethane foam was formed in the mold. The cured polyurethane foam was demolded by removing the cap at the end of the mold, and passed through a roll for crushing treatment. The acetone extraction rate of the polyurethane foam was 7.5% by weight, the density was 0.09 g / cm ³ , and Asker F hardness was 58 °.
Next, a toner supply roller was prepared in the same manner as in Example 1, and the obtained toner supply roller was incorporated in the image forming apparatus shown in FIG. 1 and tested in the same manner as in Example 1. However, an image defect was observed from the 2000th sheet, and a serious defect was observed in which a gray-scaled stripe pattern appeared at the time of printing 5000 sheets. When the image forming apparatus was disassembled and examined, the toner was melted and fixed on the surface of the toner supply roller.
[0017]
【The invention's effect】
When the developer supply member of the present invention is used in an electrophotographic or electrostatic recording type image forming apparatus, a good image can be obtained even if the number of printed sheets is increased, and an image defect is also observed after printing durability. It does not cause
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of an electrophotographic image forming apparatus equipped with a developer supply member of the present invention.
[Explanation of symbols]
1: Image forming body 2: Developer carrier 3: Developer supplying member 4: Developer layer forming blade 5: Transfer member 6: Cleaning member 7: Charging member 8: Recording medium

Claims (3)

  In a developer supplying member which is made of polyurethane foam and is used in contact with a developer, the polyurethane foam is water-foamed using a polyol containing a polyether polyol and a polyisocyanate containing diphenylmethane diisocyanate or a derivative thereof as main raw materials. The polyisocyanate produced by the above method contains a prepolymer obtained by reacting a hydroxyl group of a polyol with a polyisocyanate in advance, and the component extracted using acetone at 90 ° C. as a solvent is 5% by weight or less by weight of the resin. A developer supply member having an Asker F hardness of 20 to 80 °. At least the surface is made of polyurethane foam, the developing agent supplying member for use in contact with the developer, the polyurethane foam, a polyol containing a polyether polyol, a polyisocyanate containing tolylene diisocyanate or a derivative thereof as main components The polyisocyanate produced by the water foaming method contains a prepolymer obtained by reacting the hydroxyl group of the polyol with the polyisocyanate in advance, and the component extracted using 90 ° C. acetone as a solvent is 5% by weight of the resin. A developer supply member having an Asker F hardness of 20 to 80 ° as follows.   An image forming apparatus comprising the developer supply member according to claim 1.

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