JP2005206656A - Elastic member and image-forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyurethane-produced elastic member on which a toner is hardly flocculated or fused, whose surface is little shaven and which has excellent durability, and to provide an image-forming apparatus using the same. <P>SOLUTION: The elastic member comprises a polyurethane elastomer or polyurethane foam obtained by stirring and mixing a group (A): a polyol, a polyisocyanate, a catalyst, and temperature-controlling microcapsules, or a group (B): a urethane prepolymer synthesized from a polyol and a polyisocyanate, a chain extender, a catalyst, and temperature-controlling microcapsules. The image-forming apparatus using the elastic member as a developing roller 4, a developing blade 5, a toner-feeding roller 2, or the like, is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an elastic member and an image forming apparatus using the elastic member, and more particularly to an elastic member that is used in an electrophotographic process or the like and is difficult to agglomerate and fuse toner, difficult to scrape the surface, and excellent in durability. .

  In recent years, with the advancement of electrophotographic technology, medium resistance elastic members have attracted attention as transfer members, toner supply members, charging members and the like of dry electrophotographic apparatuses. For example, transfer resistance members, developing rollers, Used in toner supply rollers, charging rollers, and the like.

  Conventionally, as the material of the medium resistance elastic member, polymer elastomer or polymer foam having rubber elasticity has been used, and more specifically, conductivity imparting such as carbon black, metal oxide, ionic conductive agent, etc. Polymeric elastomers or foams such as NBR, EPDM, silicone rubber, polyurethane, etc., to which conductivity is imparted by adding an agent are used. Depending on the application, a non-conductive elastomer or foam to which the above-described conductivity imparting agent is not added may be used as an elastic member of an electrophotographic apparatus.

  Among the polymers, polyurethane is preferably used because it can form a low-hardness member suitable for the elastic member. In other words, when polyurethane is used, a foam-like, low-hardness elastic member can be obtained by a method using a foaming agent such as water, a low boiling point compound, or a method using mechanical stirring, and the chemical structure of the polyurethane is determined. The hardness of the elastic member can also be lowered by selecting the raw material and the composition to be used.

  Conventionally, urethane foam or silicone foam has been used as a toner supply member in an electrophotographic apparatus, but urethane foam is widely used because it has higher mechanical strength and is less expensive than silicone foam ( Patent Document 1).

  In the electrophotographic apparatus, toner is supplied from the toner cartridge onto the developing roller by the toner supply roller. At this time, the toner may agglomerate or fuse due to repeated compression or friction between the toner supply roller and the developing roller or between the developing roller and the developing blade. As a result, the developing roller In some cases, toner agglomerates or fused substances accumulate between the toner and the developing blade, causing streak-like image defects in electrophotography. In addition, toner agglomerates and fused products may cause local mechanical loads on the developing roller and the toner supply roller, causing the surfaces of these rollers to be scraped, and may cause image defects. In recent years, from the viewpoint of colorization and energy saving of an electrophotographic apparatus, since a toner having a lower melting point than ever has been used, image defects due to toner aggregation or toner fusion are likely to occur. Effective measures are strongly demanded.

JP 2003-137957 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an elastic member made of urethane which is hard to agglomerate and fuse, is hard to be scraped and has excellent durability. Another object of the present invention is to provide an image forming apparatus that uses such an elastic member and can form a good image over a long period of time.

  As a method for preventing the toner from agglomerating or fusing, the present inventor suppresses heat generation due to local friction between the toner supply roller and the developing roller or between the developing roller and the developing blade. It is considered effective to suppress the temperature rise of itself, and as a result of intensive studies to suppress heat generation due to such local friction, the elastic member such as the developing roller, toner supply roller, developing blade, etc. of the image forming apparatus Dispersing the temperature control microcapsules on the surface can reduce heat generation due to local friction between the elastic members such as between the developing roller and the toner supply roller and between the developing roller and the developing blade. As a result, it has been found that the toner can be prevented from agglomerating and fusing, and further, the surface of the elastic member can be suppressed and a good image can be obtained over a long period of time. This has led to the completion of the Akira.

  That is, the elastic member of the present invention comprises (A) group: polyol, polyisocyanate, catalyst and temperature control microcapsule, or (B) group: urethane prepolymer synthesized from polyol and polyisocyanate, chain extender, catalyst and It is characterized by comprising a polyurethane elastomer or polyurethane foam obtained by mixing and stirring temperature control microcapsules.

  In a preferred example of the elastic member of the present invention, the temperature control microcapsule contains an alkane having 23 to 27 carbon atoms as a main component. Here, as the alkanes, tetracosane, pentacosane and hexacosane are preferable.

  In another preferred embodiment of the elastic member of the present invention, the addition amount of the temperature control microcapsule is 5.0 to 50.0 mass with respect to 100 parts by mass of the polyol (A) group or the urethane prepolymer (B) group. Part.

  In another preferable example of the elastic member of the present invention, the group (A) or the group (B) further includes at least one of a foaming agent and a foam stabilizer. Moreover, the said (A) group and (B) group may also contain another additive as needed.

  The elastic member of the present invention is suitable as a developing roller, a developing blade, and a toner supply roller of an image forming apparatus. The image forming apparatus of the present invention is characterized by using the elastic member described above.

  According to the present invention, it is possible to provide an elastic member made of urethane that includes at least a temperature-controlled microcapsule, hardly aggregates and fuses toner, and is difficult to scrape the surface and has excellent durability. Further, it is possible to provide an image forming apparatus that can form a good image over a long period of time using such an elastic member.

  The present invention is described in detail below. The elastic member of the present invention comprises at least (A) group: polyol, polyisocyanate, catalyst and temperature control microcapsule, or (B) group: urethane prepolymer synthesized from polyol and polyisocyanate, chain extender, catalyst and temperature. It consists of a polyurethane elastomer or polyurethane foam obtained by mixing and stirring raw materials containing control microcapsules. Since the elastic member of the present invention includes a temperature-controlled microcapsule, when the temperature of the elastic member rises due to frictional heat, the components in the microcapsule melt from solid to liquid and the frictional heat is absorbed by the melting. The temperature rise of the elastic member itself is suppressed. Thereby, the temperature rise of the toner on the elastic member is suppressed, and toner aggregation and fusion are suppressed. Further, by suppressing aggregation and fusion of toner, for example, when an elastic member is used as a development roller, a toner supply roller, a development blade, etc., toner aggregation or fusion between the development roller and the development blade Can be prevented and the occurrence of image defects can be suppressed over a long period of time.

  The temperature-controlled microcapsule is formed by encapsulating a compound having a desired melting point in the microcapsule. From the viewpoint of the melting point of the toner, the temperature-controlled microcapsule used for the elastic member of the present invention preferably contains an alkane having 23 to 27 carbon atoms as a main component. Here, examples of the alkane having 23 to 27 carbon atoms include tricosane, tetracosane, pentacosane, hexacosane, heptacosane, and among these, tetracosane, pentacosane and hexacosane are preferable. These alkanes may be used alone or in a mixture of two or more. Moreover, urea resin etc. are mentioned as a material used for the said microcapsule.

  Examples of the temperature control microcapsule include FRISBY TECHNOLOGIES, INC. Are various temperature-controlled microcapsules commercially available, that is, THERMASORB (registered trademark). The THERMASORB (registered trademark) includes alkanes (paraffinic hydrocarbons) encapsulated in urea resin microcapsules, and the temperature control range can be selected according to the composition of the alkanes. That is, it is possible to control the temperature by utilizing endothermic and exothermic heat during the phase transition of the alkane (solid → liquid, liquid → solid). When an alkane having a large molecular weight is selected, the alkane has a melting point. Since the elastic member can be controlled to a high temperature because it is high, when an alkane having a small molecular weight is selected, the elastic member can be controlled to a low temperature because the alkane has a low melting point.

  The addition amount of the temperature control microcapsule is preferably in the range of 5.0 to 50.0 parts by mass, and in the range of 10.0 to 50.0 parts by mass with respect to 100 parts by mass of the polyol (A) group or the urethane prepolymer (B) group. Is more preferable, and the range of 20.0 to 40.0 parts by mass is even more preferable. If the amount of the temperature control microcapsule added to the elastic member is less than 5.0 parts by mass with respect to 100 parts by mass of the polyol or urethane prepolymer, the image forming apparatus incorporating the elastic member forms a good image over a long period of time. There are things that cannot be done. If the amount of the temperature control microcapsule exceeds 50.0 parts by mass, the inherent flexibility of the urethane is impaired, the mechanical strength is lowered, the properties such as compression residual strain are deteriorated, and a good image cannot be obtained. There are many cases.

  The polyol that can be used in the present invention is a compound having a plurality of hydroxyl groups, and specifically, as the polyol, polyether polyol, polyester polyol, isoprene polyol, butadiene polyol, PO (propylene oxide) -modified butadiene polyol. And silicone polyol. These polyols may be used alone or in combination of two or more.

  The polyisocyanate that can be used in the present invention is a compound having a plurality of isocyanate groups. Specifically, as the polyisocyanate, tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate (crude) MDI), isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, hexamethylene diisocyanate and other polyisocyanates having no unsaturated bond, and their isocyanurates, carbodiimides, glycols, polyols, etc. A thing etc. can be used conveniently. The amount of the polyisocyanate used is appropriately selected so that the ratio (NCO / OH) of the isocyanate group (NCO) of the polyisocyanate to the hydroxyl group (OH) of the polyol is in the range of 95/100 to 110/100. Is preferred.

  The polyisocyanate may be reacted with the polyol by a one-shot method, or may be reacted with a polyol in advance to form a urethane prepolymer and then reacted with a chain extender or the like in the presence of a catalyst. The amount of polyisocyanate and polyol used in the synthesis of the urethane prepolymer is preferably selected as appropriate so that the ratio of the NCO group of the polyisocyanate to the OH group of the polyol falls within the above range.

  The catalyst used in the present invention is a catalyst for urethanization reaction, and examples thereof include organotin compounds such as dibutyltin dilaurate, dibutyltin diacetate, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin thiocarboxylate, and tin octenoate; Organic lead compounds such as lead octenoate; monoamines such as triethylamine and dimethylcyclohexylamine; diamines such as tetramethylethylenediamine, tetramethylpropanediamine and tetramethylhexanediamine; pentamethyldiethylenetriamine, pentamethyldipropylenetriamine and tetramethylguanidine Triamines such as triethylenediamine, dimethylpiperazine, methylethylpiperazine, methylmorpholine, dimethylaminoethylmorpholine, Cyclic amines such as methylimidazole; alcohol amines such as dimethylaminoethanol, dimethylaminoethoxyethanol, trimethylaminoethylethanolamine, methylhydroxyethylpiperazine, hydroxyethylmorpholine; bis (dimethylaminoethyl) ether, ethylene glycol bis (dimethyl) ) Etheramines such as aminopropyl ether. Of these catalysts, organotin compounds are preferred. These catalysts may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the catalyst used is preferably in the range of 0.001 to 2.0 parts by mass with respect to 100 parts by mass of the polyol or urethane prepolymer.

  The chain extender that can be used in the present invention is a compound that links the urethane prepolymers, and specifically includes ethylene glycol, 1,4-butanediol, trimethylolpropane, and the like. The amount of the chain extender used is such that the ratio (NCO / OH) of the isocyanate group (NCO) of the urethane prepolymer to the hydroxyl group (OH) of the chain extender is in the range of 95/100 to 110/100. It is preferable to select appropriately.

  The groups (A) and (B) may further contain a foaming agent. In this case, the elastic member of the present invention is made of polyurethane foam. When the elastic member of the present invention is made of polyurethane foam, the foaming method of the polyurethane foam is not particularly limited, and any method such as a method using a foaming agent or a method of mixing bubbles by mechanical stirring may be used. Here, as the blowing agent, diethanolamine formate, salt of monoethanolamine and carbon dioxide, salt of N-methylethanolamine and carbon dioxide, reactive blowing agent such as water, n-pentane, isopentane, cyclohexane Pentane, methylene chloride, Freon 134a (1,1,1,2-tetrafluoroethane), Freon 245fa (1,1,1,3,3-pentafluoropropane), Freon 365mfc (1,1,1,3, Low boiling point such as 3-pentafluorobutane), Freon 356, Freon 141b (1,1-dichloro-1-fluoroethane), Freon 142b (1-chloro-1,1-difluoroethane), Freon 22 (chlorodifluoromethane) Compounds. These foaming agents may be used individually by 1 type, and may use 2 or more types together. The amount of the foaming agent used is preferably in the range of 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the polyol or urethane prepolymer.

  The groups (A) and (B) may further contain a foam stabilizer. As the foam stabilizer, in addition to silicone foam stabilizers such as polyether-modified silicone oil, ionic surfactants, nonionic surfactants, and the like can be used. The amount of the foam stabilizer used is preferably in the range of 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the polyol or urethane prepolymer.

  The elastic member of the present invention can be used as a non-conductive member or a conductive member. When used as a conductive member, in addition to the above compounds, a carbon conductive agent, an ionic conductive agent, a metal oxide powder, a metal powder It is preferable to include various conductive agents such as In addition, other known additives can be used in the elastic member of the present invention as necessary.

  In the polyurethane elastomer or polyurethane foam constituting the elastic member of the present invention, various additives such as a foaming agent, a foam stabilizer, and a conductive agent are appropriately selected and added to the group (A) or (B), and mixed and stirred. It is obtained by doing. Moreover, the elastic member of a desired shape can be manufactured by forming a polyurethane elastomer or a polyurethane foam in a mold of a desired shape.

  The elastic member of the present invention is suitable as a developing roller, a developing blade, and a toner supply roller of an image forming apparatus. In this case, the developing roller, the developing blade, and the toner supply roller may include other materials such as a metal shaft in addition to the polyurethane elastomer and the polyurethane foam. The developing roller and the toner supply roller, for example, inject a urethane raw material containing at least the group (A) or the group (B) into a mold having a desired shape with a metal shaft disposed in the center while mixing and stirring. The developing blade can be produced, for example, by mixing and injecting a urethane raw material into a mold having a desired shape and stirring and curing.

  The image forming apparatus of the present invention is characterized by using the elastic member described above, and preferably includes the elastic member as at least one of a developing roller, a developing blade, and a toner supply roller. The image forming apparatus of the present invention is not particularly limited except that the elastic member is used, and can be manufactured by a known method.

  The image forming apparatus of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a partial cross-sectional view of an example of the image forming apparatus of the present invention. The image forming apparatus of the illustrated example includes a toner supply roller 2 for supplying toner 1, a photosensitive drum 3 holding an electrostatic latent image, and a developing roller disposed between the toner supply roller 2 and the photosensitive drum 3. 4, a developing blade 5 provided above the developing roller 4, a transfer unit 6 located below the photosensitive drum 3, and a cleaning unit 7 provided adjacent to the photosensitive drum 3. The image forming apparatus of the present invention can further include known components (not shown) that are normally used in the image forming apparatus.

  The toner supply roller 2, the developing roller 4, and the photosensitive drum 3 rotate in the direction of the arrow in the drawing, so that the toner 1 on the toner supply roller 2 is sent to the photosensitive drum 3 through the developing roller 4. The toner 1 is adjusted to a uniform thin layer by the developing blade 5 on the developing roller 4 and further rotated while the developing roller 4 and the photosensitive drum 3 are in contact with each other. It adheres to the image and the latent image becomes visible. The toner 1 attached to the latent image is transferred to a recording medium such as paper by the transfer unit 6, and the toner 1 remaining on the photosensitive drum 3 after the transfer is removed by the cleaning blade 8 of the cleaning unit 7.

  In the image forming apparatus of the present invention, an elastic member containing the above-described temperature control microcapsule is used as the elastic member such as the toner supply roller 2, the developing roller 4, and the developing blade 5, and therefore, due to local friction between the elastic members. Heat generation is reduced and the temperature rise of the elastic member itself is suppressed. As a result, the temperature rise of the toner 1 in contact with each elastic member is also suppressed, and aggregation / fusion of the toner 1 is prevented. As a result, in the image forming apparatus of the present invention, toner 1 aggregates and fusion products are not accumulated between the developing roller 4 and the developing blade 5, and the surface of each elastic member is prevented from being scraped. A good image can be formed throughout.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(Example 1)
100 parts by weight of a polyether polyol having a molecular weight of 7,000 and a hydroxyl value of 25.0, 87.5% by weight of propylene oxide and 12.5% by weight of ethylene oxide added to glycerin, 1.8 parts by weight of highly conductive carbon, 0.01 parts by weight of dibutyltin dilaurate, and THERMASORB T122 [temperature control Microcapsule, FRISBY THECHNOLOGIES, INC. Manufactured] 30.0 parts by mass were mixed and stirred in advance and charged into the tank for component A (polyol component) of a two-component casting machine. On the other hand, modified pure MDI having an NCO content of 23.0% as an isocyanate component was charged into a B component (isocyanate component) tank of a two-component casting machine. The flow rate is adjusted so that the ratio of A component / B component is 131.81 parts by mass / 8.51 parts by mass, and the urethane raw material (with the A component and the A-component is injected into a cylindrical mold with a cored bar set from an injection nozzle equipped with an impeller for stirring and mixing. B component mixture) was injected. This mold was placed in a 100 ° C. hot air circulating oven and heated for 30 minutes. After the mold was taken out of the oven, the mold was cooled to prepare a urethane elastomer base material for a developing roller.

Next, after immersing this urethane elastomer base material in a thermosetting paint containing silica having an average particle size of 20 μm and a conductive agent, it was cured by heating in a hot air circulation oven at 110 ° C. for 30 minutes to obtain an elastic member for the developing roller. Obtained. The obtained elastic member had an Asker C hardness of 60 degrees and a roller resistance of 3.8 × 10 ⁴ Ω at 100V.

  This elastic member was incorporated into a dry electrophotographic apparatus as a developing roller, and left for 48 hours at a temperature of 20 ° C. and a humidity of 50% RH. After printing a gray image (8% density), a good image was obtained. Further, after continuous printing of 10,000 sheets, a gray image was printed. As a result, there was no image defect such as white streaks due to toner aggregation and fusion, and a good image was obtained. Further, when the used toner cartridge was disassembled and the surface of the developing roller was observed, it was found that the developing roller surface was not scraped. Further, when the toner near the developing roller was observed with a microscope, the toner maintained the initial state and no aggregation or fusion was observed.

(Comparative Example 1)
100 parts by mass of a polyether polyol having a molecular weight of 7,000 and a hydroxyl value of 25.0 obtained by adding 87.5% by mass of propylene oxide and 12.5% by mass of ethylene oxide to glycerol, 1.8 parts by mass of highly conductive carbon, and 0.01 parts by mass of dibutyltin dilaurate are mixed and stirred in advance. The A component (polyol component) tank of a two-component casting machine was charged. On the other hand, modified pure MDI having an NCO content of 23.0% as an isocyanate component was charged into a B component (isocyanate component) tank of a two-component casting machine. Adjust the flow rate so that the ratio of component A / component B is 101.81 parts by mass / 8.51 parts by mass, and place the urethane raw material (with component A and the cylindrical mold with the cored bar set from the injection nozzle equipped with the impeller for stirring and mixing. B component mixture) was injected. This mold was placed in a 100 ° C. hot air circulating oven and heated for 30 minutes. After the mold was taken out of the oven, the mold was cooled to prepare a urethane elastomer base material for a developing roller.

Next, after immersing this urethane elastomer base material in a thermosetting paint containing silica having an average particle diameter of 20 μm and a conductive agent, it was cured by heating in a hot air circulation oven at 110 ° C. for 30 minutes, and the elastic member for the developing roller was Obtained. The obtained elastic member had an Asker C hardness of 59 degrees and a roller resistance of 5.3 × 10 ⁴ Ω at 100V.

  This elastic member was incorporated into a dry electrophotographic apparatus as a developing roller, and left for 48 hours at a temperature of 20 ° C. and a humidity of 50% RH. After printing a gray image (8% density), a good image was obtained. Furthermore, after printing 10,000 sheets continuously, when printing a gray image, white streaks were generated in the image. Further, when the used toner cartridge was disassembled and the surface of the developing roller was observed, it was found that the surface of the developing roller corresponding to the position where the white streak occurred was scraped. Further, when the toner near the shaved portion was observed with a microscope, the toner was agglomerated and fused.

1 is a partial cross-sectional view of an example of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Toner 2 Toner supply roller 3 Photosensitive drum 4 Developing roller 5 Developing blade 6 Transfer part 7 Cleaning part 8 Cleaning blade

Claims (8)

  (A) group: polyol, polyisocyanate, catalyst and temperature control microcapsule, or (B) group: urethane prepolymer synthesized from polyol and polyisocyanate, chain extender, catalyst and temperature control microcapsule are mixed and stirred. The elastic member which consists of a polyurethane elastomer or polyurethane foam obtained.   The elastic member according to claim 1, wherein the temperature control microcapsule contains an alkane having 23 to 27 carbon atoms as a main component.   The elastic member according to claim 2, wherein the alkane is at least one selected from the group consisting of tetracosane, pentacosane, and hexacosane.   The addition amount of the temperature control microcapsule is 5.0 to 50.0 parts by mass with respect to 100 parts by mass of the polyol of the group (A) or the urethane prepolymer of the group (B). Elastic member.   The elastic member according to claim 1, wherein the group (A) further includes at least one of a foaming agent and a foam stabilizer.   The elastic member according to claim 1, wherein the group (B) further includes at least one of a foaming agent and a foam stabilizer.   The elastic member according to claim 1, wherein the elastic member is a developing roller, a developing blade, or a toner supply roller of an image forming apparatus.   An image forming apparatus using the elastic member according to claim 1.

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