JP4222909B2 - Composite tubular body - Google Patents

Description

  The present invention relates to a member that is used in an electrophotographic image forming apparatus such as a copying machine, a laser beam printer, and a facsimile, and that conveys or fixes a copy sheet. More particularly, the present invention relates to a belt member that is excellent in preventing wrinkles of a transported sheet such as copy paper, printing deviation, and toner contamination.

2. Description of the Related Art Conventionally, as an electrophotographic image forming apparatus for forming and recording an image by an electrophotographic system, a copying machine, a laser beam printer, a facsimile, or a complex machine of these is known. In this type of apparatus, a fixing method using an endless belt is employed for the purpose of speeding up image formation and saving energy. As an endless belt used in the belt fixing method as described above, a composite tubular body including a polyimide resin inner layer and a fluororesin outer layer excellent in heat resistance and mechanical strength is known (see Patent Document 1). The endless belt used in the belt fixing method is required to have excellent heat resistance and mechanical strength. Further, as a belt that can return the meandering while suppressing the meandering of the belt, a tubular belt having a difference in circumferential length between the center and both ends is known (see Patent Document 2).
Japanese Patent Laid-Open No. 3-130145 Japanese Patent No. 2625021

  In recent years, this type of apparatus has noticeably increased image density, speed, and large screen. For this reason, various obstacles have occurred in the belts produced so far. For example, at the temperature at which the toner is melted and fixed, the rubber layer of the driving roller expands thermally, and the outer peripheral length varies, so that the rotational speed of the belt may fluctuate. Alternatively, when the transfer conveyance sheet becomes large and is conveyed at high speed, wrinkles are generated on the sheet. In addition, when digital fine toner is used to form a fine image quality, fine toner dragging (generally, a defect called dust or beard) that does not occur is generated. Furthermore, there is a risk that the belt sticks to the built-in heater during continuous use.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an endless belt that can withstand continuous use by suppressing image deviation, conveyance sheet wrinkling, toner drag, and the like accompanying image densification, speeding up, and large screens of image forming apparatuses. There is to do.

  As a result of intensive research to solve the above-mentioned problems, the present inventor has found that a belt having a fixing property that satisfies the following conditions is obtained, and has completed the present invention.

That is, the composite tubular body of the present invention has a fluororesin tubular outer layer containing a conductive material and a polyimide resin tubular inner layer containing a fluororesin powder, and a conductive property between the outer layer and the inner layer. adhesive layer is formed Rutotomoni a composite tubular body polyimide resin is made a base material of substantially the polyimide resin tubular in the inner layer, the outer diameter of the tubular body, the tubular body ends toward the central portion The surface resistivity of the fluororesin tubular outer layer alone is 10 ¹³ Ω / □ or more, and the surface resistivity of the conductive adhesive layer is 10 ⁻¹ to 10 ⁵ Ω / □. The apparent surface resistivity of the fluororesin tubular outer layer when the layer is the base is 10 ⁵ to 10 ¹² Ω / □.

The surface resistivity of the conductive adhesive layer is preferably 10 ⁻¹ to 10 ⁴ Ω / □. The apparent surface resistivity of the fluororesin tubular outer layer is preferably 10 ⁷ to 10 ¹² Ω / □, and more preferably 10 ⁹ to 10 ¹¹ Ω / □.

  In the composite tubular body, the fluororesin of the fluororesin tubular outer layer is preferably tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and the conductive material is carbon black. The carbon black content is preferably 0.1 to 2.5% by weight, more preferably 0.5 to 1% by weight, based on the PFA. The thickness of the tubular outer layer is preferably 5 to 25 μm. More preferably, it is 10-15 micrometers.

  In the composite tubular body, the ratio of the outer diameter of the end portion of the tubular body to the outer diameter of the central portion of the tubular body is preferably 1: 1.0004 to 1: 1.0035. 0009 to 1: 1.003 is more preferable.

  According to the composite tubular body of the present invention, it has a fluororesin outer layer substantially comprising a polyimide resin as a base material and containing a conductive material, and the surface resistivity of the outer layer satisfies a predetermined requirement, A fixing belt which is excellent in heat resistance and mechanical strength and does not cause toner contamination and offset can be formed. The conductive material is carbon black, and by making the content ratio and the thickness of the fluororesin outer layer within a predetermined range, the surface resistivity can be easily controlled and a fixing belt excellent in toner fixing property is expressed. can do.

  According to the composite tubular body of the present invention, by having the polyimide resin tubular inner layer containing the fluororesin powder, even when the heater in the apparatus is abnormally heated, the driving of the belt is continued satisfactorily. There is no sticking of the belt.

  According to the composite tubular body of the present invention, the outer diameter of the tubular outer layer tubular body is gradually reduced from both ends toward the central portion, so that a tubular body having an inverted crown shape is constructed and used as a transfer belt. Is difficult to meander, and even if meandering occurs, it can be easily restored. Accordingly, even if a large transfer conveyance sheet is conveyed at high speed, the sheet does not wrinkle. When the ratio of the outer diameter of the end portion of the tubular body to the outer diameter of the central portion of the tubular body is 1: 1.0009 to 1: 1.003, the wrinkle prevention effect is particularly excellent.

  The composite tubular body of the present invention includes a tubular inner layer, a conductive adhesive layer formed on the outer peripheral surface of the inner layer, and a tubular outer layer formed on the outer peripheral surface of the conductive adhesive layer.

  The thickness of each of these layers is appropriately selected depending on the design of the apparatus used. Usually, the tubular inner layer is 20 to 60 μm, the conductive adhesive layer is 0.3 to 5 μm, and the tubular outer layer is 5 to 25 μm.

  The fluororesin constituting the tubular outer layer is effective against toner stains, especially when tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) is used, but any known fluororesin can be used without limitation. It is.

  Specifically, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoroethylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE) and the like, and these may be used alone or in combination of two or more.

  The conductive material contained in the tubular outer layer is a conductive or semiconductive material, such as carbon black such as ketjen black and acetylene black, metals such as Al and Ni, metal oxide compounds such as tin oxide, graphite, titanium Although potassium acid etc. can be used, the carbon black which can express a desired surface resistivity with small addition is preferable. The conductive material can be blended by dispersing it in a solvent in advance.

  The material used for the conductive adhesive layer is not particularly limited as long as it is a material capable of bonding the tubular inner layer and the tubular outer layer. Specific examples include a polyimide resin, a polyamideimide resin, and a polyamide resin. Examples thereof include resins and fluorine resins.

  The surface resistivity of the conductive adhesive layer can be controlled by the amount (thickness) of the adhesive layer. The conductive material may be added as long as the function as an adhesive layer is not lost.

  The polyimide resin that constitutes the tubular inner layer and serves as the base material of the composite tubular body of the present invention can be any known polyimide resin that is used in the field of fixing belts and the like, and can be used from the viewpoint of heat resistance and mechanical strength. The use of an aromatic polyimide resin is preferred.

  The fluororesin powder contained in the polyimide resin can be used without limitation as long as it is a known fluororesin powder. Specifically, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoroethylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer Examples include coalescence (ETFE). Especially, use of polytetrafluoroethylene (PTFE) excellent in heat resistance is preferable.

  The addition amount of the fluororesin powder is usually 1 to 20 parts by weight and preferably 1 to 5 parts by weight with respect to 100 parts by weight of the polyimide resin solid content. By setting the addition amount in such a range, the mechanical strength and flexibility of the belt can be maintained.

  The tubular inner layer is formed by forming a polyamic acid solution containing a fluororesin powder into a predetermined shape and performing an imide conversion reaction after removing the solvent. The polyamic acid solution contains a polyamic acid which is a polyimide precursor, and can be obtained, for example, by reacting approximately equimolar amounts of tetracarboxylic dianhydride or its derivative and diamine in an organic polar solvent. it can. The blending of the fluororesin powder into the polyamic acid solution is performed by dispersing it in an organic polar solvent before or after the production of the polyamic acid. Dispersion can be performed by a known method.

  Specific examples of the tetracarboxylic dianhydride constituting the preferred polyimide resin in the present invention include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3 , 3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) propane dianhydride Bis (3,4-dicarboxyphenyl) sulfone dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether Things, ethylene tetracarboxylic dianhydride, and the like.

Specific examples of diamines to be reacted with such tetracarboxylic dianhydrides include 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, and 3,3′-. Dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3′-dimethyl-4,4′- Biphenyldiamine, benzidine, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfide, 4,4′-diaminodiphenylpropane, 2, 4-bis (β-amino-t-butyl) toluene, bis (p-β-amino-t- Butylphenyl) ether, bis (p-β-methyl-t-aminophenyl) benzene, bis-p- (1,1-dimethyl-5-amino-pentyl) benzene, 1-isopropyl-2,4-m-phenylene Diamine, m-xylylenediamine, p-xylylenediamine, di (p-aminocyclohexyl) methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3- Methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2 , 5-Dimethylheptamethyle Diamine, 3-methylheptamethylenediamine, 5-methylnonamethylenediamine, 2,11-diaminododecane, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10- Dimethyldecane, 1,12-diaminooctadecane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, piperazine, H ₂ N (CH ₂ ) ₃ O (CH ₂ ) ₂ OCH ₂ NH ₂ ,
H ₂ N (CH ₂ ) S (CH ₂ ) ₃ NH ₂ ,
H ₂ N (CH ₂ ) ₃ N (CH ₂ ) ₂ (CH ₂ ) ₃ NH ₂ ,
Etc.

  One or more of these tetracarboxylic dianhydrides or their derivatives and diamines can be appropriately selected and reacted. As the diamine, it is particularly desirable to use an aromatic diamine as a main component.

  The organic polar solvent used when the tetracarboxylic dianhydride and diamine are reacted has a dipole whose functional group does not react with tetracarboxylic dianhydride or diamine. It must be inert to the system and act as a solvent for the product polyamic acid. Moreover, it must act as a solvent for at least one of the reaction components, preferably both. As the organic polar solvent, N, N-dialkylamides are particularly useful, and examples thereof include N, N-dimethylformamide and N, N-dimethylacetamide, which have low molecular weight. They can be easily removed from the polyamic acid and the polyamic acid molded article by evaporation, displacement or diffusion. Other organic polar solvents include N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethylsulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine , Tetramethylene sulfone, dimethyltetramethylene sulfone and the like. These may be used alone or in combination. Furthermore, phenols such as cresol, phenol and xylenol, benzonitrile, dioxane, butyrolactone, xylene, cyclohexane, hexane, benzene, toluene and the like can be mixed alone or in combination with the organic polar solvent. However, it is preferable to avoid the use of water in order to prevent lowering the molecular weight due to hydrolysis of the produced polyamic acid.

The composite tubular body of the present invention can be produced, for example, by the following steps.
(1) First, a cylindrical mold is prepared as a molding mold, and a polyamic acid solution containing fluororesin powder is applied to the inner peripheral surface or outer peripheral surface of the cylindrical mold. After coating, the coated film is dried and cured until it can support at least itself, or heated until imide conversion is completed to form a tubular inner layer containing a fluororesin powder, and the obtained tubular inner layer is Remove from the cylindrical mold.
(2) A conductive adhesive layer is formed on the outer peripheral surface of the tubular inner layer by applying a conductive primer or the like.
(3) A fluororesin outer layer containing a conductive material (preferably carbon black) is formed on the outer peripheral surface of the formed conductive adhesive layer.
(1) Formation of Tubular Inner Layer When the polyamic acid solution is used, if the solution viscosity is high, it can be used by diluting with a suitable solvent to lower the viscosity. For example, the viscosity of the polyamic acid solution is set according to the coating thickness, coating method, coating conditions, solution temperature, etc., but is usually 0.01 to 1000 Pa · s (measured with a B-type viscometer at the temperature during the coating operation). Viscosity). In the above manufacturing method, any cylindrical mold can be used as a molding mold as long as it is conventionally used for manufacturing a tubular body, and the material is a metal from the viewpoint of heat resistance. Various types such as glass, ceramics and the like are exemplified. As a method of applying the polyamic acid solution (containing fluororesin powder) to the cylindrical mold, the cylindrical mold is immersed in the polyamic acid solution to form a coating film on the outer surface, and this is formed with a cylindrical die or the like. Or a method of running a traveling body (bullet shape, spherical shape) having a certain clearance with the cylindrical mold after supplying a polyamic acid solution to one end portion of the inner surface of the cylindrical mold. Examples include a method of rotating around an axis, supplying a polyamic acid solution to the inner surface, and forming a uniform film by centrifugal force.

  As a method of traveling the above-mentioned traveling body, in addition to the self-weight traveling method (a method in which a cylindrical mold is set up vertically and the traveling body is traveled downward by its own weight), a method using compressed air or gas explosive force, The method of pulling with a pulling wire etc. is mentioned.

  The heating temperature after applying the polyamic acid solution is not particularly limited and can be appropriately set. In particular, after heating at a low temperature of about 80 to 200 ° C. to remove the solvent, the temperature is raised to about 250 to 400 ° C. Thus, a multi-stage heating method for completing the imide conversion is preferable. Moreover, after peeling the tubular body which became a state which can support itself after low-temperature heating and forming a conductive adhesive layer or a fluororesin layer (tubular outer layer), high-temperature heating may be performed to perform imide conversion. Although the time required for heating is appropriately set according to the heating temperature, both the low temperature heating and the subsequent high temperature heating are usually about 20 to 60 minutes. If such a multistage heating method is used, generation | occurrence | production of the microvoid in the tubular body resulting from ring-closing water and solvent evaporation which generate | occur | produce with imide conversion can be prevented.

The tubular inner layer thus obtained is peeled from the cylindrical mold. As a method for peeling the tubular inner layer made of polyimide resin from the cylindrical mold, for example, a method in which air is pumped to a minute through-hole provided in advance on the peripheral wall surface of the cylindrical mold end can be cited. In addition, it is preferable to perform release treatment with a silicone resin or the like in advance on the inner peripheral surface of a cylindrical mold that forms the tubular inner layer, so that the workability of peeling the tubular inner layer is improved.
(2) Formation of conductive adhesive layer The conductive adhesive layer is formed, for example, by a method of applying a primer solution to the outer peripheral surface of the obtained tubular inner layer. Examples of the application method include roll coating, brush coating, spray coating, and the like.
(3) Formation of tubular outer layer A fluororesin tubular outer layer is a method in which a tubular tubular body obtained by melt extrusion is applied to the outer surface of a conductive adhesive layer, and a solution-like (including dispersion) fluororesin is made conductive. It is formed by a method of coating the outer surface of the adhesive layer. As a method for coating the solution-like fluororesin solution, for example, methods such as spray coating, spin coating, roll coating, and brush coating are conceivable. As a procedure of coating and heating, in order to prevent voids from being generated in the outer layer, after coating the fluororesin outer layer and removing the solvent in the fluororesin solution, the temperature is raised to the melting point of the fluororesin or higher, and the fluororesin outer layer Can be formed. At this time, the imide conversion of the tubular inner layer may be performed simultaneously.

  The composite tubular body thus obtained has substantially no difference in peripheral length between the end portion and the central portion of the tubular body. The desired deformed composite tubular body is formed by the following deformation process.

  In the present invention, it is preferable to form a polyimide tubular product in which 1 to 30% by weight of a volatile component such as an organic polar solvent remains, and then peel from the cylindrical mold. Next, it is preferable that the conductive adhesive layer and the fluororesin outer layer are formed as described above, and the obtained composite tubular body is deformed in the next step and imide conversion and sintering of the fluororesin layer are completed.

The deformation step is performed by inserting a heat-resistant core body (reverse crown shape) having a required circumference difference as shown in FIG. 1 into the obtained composite tubular body, and heating and firing. The material of the heat-resistant core used in this case is not particularly limited, but a material having a linear thermal expansion coefficient of 2 × 10 ⁻⁵ cm / cm / ° C. or more is required in order to easily remove the core after forming the deformed tubular body. It is preferable to use, for example, a core made of a material such as aluminum, fluorine resin, or polyimide resin is preferable.

  In the above deformation step, the heat treatment conditions for heating and baking are usually not less than the glass transition temperature of the material forming the tubular body and not more than the thermal decomposition temperature. After the heat treatment, it is cooled to room temperature and taken out from the core.

Examples Hereinafter, examples and the like specifically showing the configuration and effects of the present invention will be described.
[Example 1]
Disperse 3.06 g of fluororesin (PTFE) powder (made by Kitamura Co., Ltd.) in 723 g of N-methyl-2-pyrrolidone, and 41 g of p-phenylenediamine and 3,3 ′, 4,4′-biphenyltetracarboxylic acid. The dianhydride 112g was melt | dissolved (solid content concentration of 20 weight%), and it was made to react at room temperature in nitrogen atmosphere, stirring, and the 300 Pa.s polyamic acid solution was obtained. After applying the above polyamic acid solution to the inner surface of a cylindrical mold having an inner diameter of 24.2 mm, the bullet-shaped traveling body is dropped by its own weight, and then defoaming is performed to remove bubbles in the coating film, thereby obtaining a uniform coating film surface. Obtained.

  Next, the mold having the coating surface was heated stepwise from 150 ° C. to 250 ° C. to remove the solvent, cooled to room temperature, and then peeled from the mold to obtain a 50 μm seamless belt.

  A PFA dispersion (solid content concentration 35% by weight) prepared by adjusting carbon black (W311N manufactured by Lion Corporation) to 1% by weight with respect to the solid content of the fluororesin was stirred for 12 hours to obtain a fluorine coating solution.

  A conductive adhesive layer was formed on the outer peripheral surface of the seamless belt by spray coating with a conductive primer. Next, the fluorine coating solution was spray coated on the outer peripheral surface of the conductive adhesive layer to form a fluororesin tubular outer layer. The obtained composite tubular body was inserted into a heat-resistant core body having an effective length of 500 mm (having an inverted crown shape with an outer diameter of both ends of 24.1 mm and a central outer diameter of 24.04 mm) and fired at 400 ° C. for 20 minutes. The ring-closing water was removed and the imide conversion was completed to obtain a seamless belt having a 10 μm fluororesin tubular outer layer.

When the outer diameter of the obtained seamless belt was measured with a laser-type outer diameter measuring machine, the outer diameter of both end portions was 24.2 mm, and the outer diameter of the central portion was 24.14 mm. At this time, the surface resistivity of the conductive adhesive layer is 2 × 10 ⁴ Ω / □, and the fluororesin tubular outer layer alone (when there is no conductive adhesive layer) has a surface resistivity of 10 ¹³ Ω / □ or more. The apparent surface resistivity of the fluororesin tubular outer layer when using the adhesive layer as a base was 1 × 10 ⁷ Ω / □.

The obtained seamless belt was set as a fixing belt in a commercially available digital multifunction peripheral, and continuous printout fixing was performed. As a result, a good image was obtained.
[Comparative Example 1]
A seamless belt having a 10 μm fluororesin tubular outer layer was obtained in the same manner as in Example 1 except that the polyamide solution did not contain fluororesin powder. When this was set as a fixing belt on a commercially available digital multi-function peripheral and printed out and fixed, an image with no problems was obtained initially. However, when continuous printing and fixing were performed, a drive failure occurred. Stopped.
[Comparative Example 2]
A seamless belt having a 10 μm fluororesin tubular outer layer was obtained in the same manner as in Example 1 except that the heat-resistant core had a straight shape of 24.1 mm. When the outer diameter of the obtained seamless belt was measured, it was 24.2 mm at both ends and the center. When this was set as a fixing belt on a commercially available digital multi-function peripheral and printout fixing was performed, wrinkles were generated parallel to the paper in the transport direction.
[Comparative Example 3]
A seamless belt having a 10 μm fluororesin tubular outer layer was obtained in the same manner as in Example 1 except that the carbon black contained in the fluororesin tubular outer layer was 3% by weight. When this was set as a fixing belt on a commercially available digital multi-function peripheral and subjected to print-out fixing, toner smearing occurred in many of the prints.

The perspective view which shows the shape of the heat resistant core used in order to obtain the composite tubular body of this invention

Claims (3)

Contains fluorine resin tubular outer layer and the fluororesin powder comprising a conductive material and a polyimide resin tubular inner layer comprising, Rutotomoni is conductive adhesive layer between the outer layer and the inner layer is formed, substantially A composite tubular body in which the polyimide resin in the polyimide resin tubular inner layer is a base material ,
The outer diameter of the tubular body gradually decreases from both ends of the tubular body toward the center, the surface resistivity of the fluororesin tubular outer layer alone is 10 ¹³ Ω / □ or more, and the surface resistance of the conductive adhesive layer A composite tubular body having a rate of 10 ⁻¹ to 10 ⁵ Ω / □ and an apparent surface resistivity of the fluororesin tubular outer layer of 10 ⁵ to 10 ¹² Ω / □ when the conductive adhesive layer is used as a base.   The fluororesin of the fluororesin tubular outer layer is tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), the conductive material is carbon black, and the content of the carbon black is 0.1 with respect to the PFA. The composite tubular body according to claim 1, wherein the composite tubular body is -2.5 wt%, and the thickness of the tubular outer layer is 5-25 µm.   The composite tubular body according to claim 1 or 2, wherein the ratio of the outer diameter of the central portion of the tubular body to the outer diameter of the end portion of the tubular body is 1: 1.0004 to 1: 1.007.

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