JP2007069240A - Cylindrical core body, its manufacturing method, and manufacturing method for endless-belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a cylindrical core body not forming a swelling and the like even when used in a heated state and being stably repeatedly usable and to provide a manufacturing method for an endless-belt, in which the cylindrical core body is used. <P>SOLUTION: A cylindrical billet is obtained by making a hole in the central part of one end surface of a columnar solid billet made of aluminum. The hole is made so as to penetrate the cylindrical body from the one end surface through the other end surface of the body, and the cross section of the hole is made to be concentric with the outer circle of the body. The cylindrical core body is manufactured using a material tube formed by extruding the cylindrical billet. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to, for example, a cylindrical core suitably used for the manufacture of photoconductors, transfer belts, fixing belts, and the like of electrophotographic apparatuses such as copying machines and printers, a method for manufacturing the same, and an endless using the cylindrical core The present invention relates to a method for manufacturing a belt.

  In an image forming apparatus using an electrophotographic process, a rotating body made of metal, plastic, or rubber is used for a photosensitive member, a charging unit, a transfer unit, and a fixing unit. For this reason, it may be preferable that these rotating bodies be deformable, and for this, a belt made of a plastic film having a small thickness is used. In this case, if the belt has a seam, a defect due to the seam occurs in the output image. Therefore, an endless belt without a seam is preferably used. As the material for the endless belt, a polyimide resin (hereinafter, polyimide is appropriately abbreviated as “PI”) is particularly preferably used in terms of strength, dimensional stability, heat resistance, and the like.

  As a method of producing an endless belt with a polyimide resin, for example, a polyimide molding solution is applied to the inner surface of a cylindrical core and dried while rotating (for example, refer to Patent Document 1). An inner surface coating method for developing a polyimide precursor solution (for example, see Patent Document 2) is known.

The cylindrical core used for manufacturing the endless belt is usually produced using an extruded element tube made of aluminum.
The aluminum base tube before being processed into a cylindrical core is manufactured by extruding a cast product called a billet. The billet includes a hollow billet cast in a cylindrical shape and a solid billet cast in a cylindrical shape.

  The hollow billet is produced, for example, by inserting the mandrel 20 into the center of the cylindrical mold 12 shown in FIG. 3A and injecting molten metal from the inflow port 11 (see, for example, Patent Document 3). In this case, when the outer diameter is a large diameter of 300 mm or more, it is preferable that there are two or more inflow ports 11. After cooling, the casting is drawn out from the mold 12 to obtain a cylindrical hollow billet 15 as shown in FIG.

  On the other hand, as shown in FIG. 1, the solid billet is produced by injecting molten metal into a cylindrical mold 2 from the inlet 1. In this case, if the diameter is large, the diameter of the inlet 1 may be increased, so the inlet 1 may be provided at one location. And after cooling, a casting is pulled out from the mold 2 to obtain a cylindrical solid billet.

When producing an extruded element tube from the billet obtained as described above, when the outer diameter is a large diameter of 300 mm or more, the hollow billet has been conventionally used because it cannot be extruded unless it is a cylindrical billet. .
However, when a cylindrical core body using a hollow tube made of hollow billet is used, a partial bulge may occur during heating, resulting in a cylindrical core body that is not suitable for manufacturing an endless belt. There was a case.
JP-A-57-74131 Japanese Patent Laid-Open No. 62-19437 JP-A-7-51800

The object of the present invention is to solve the above-mentioned problems of the prior art.
That is, the present invention relates to a cylindrical core that can be used repeatedly and stably without being raised on the surface even when heated and used, a method for manufacturing the same, and an endless belt using the cylindrical core It aims at providing the manufacturing method of.

The above-mentioned subject is achieved by the following present invention. That is, the present invention
<1> A cylindrical billet made of aluminum is formed at the center of one end face of a cylindrical solid billet by passing through the one end face to the other end face and forming a hole having a cross-section concentric with the outer circle, and extruding the resulting cylindrical billet This is a cylindrical core body using the raw pipe.

<2> The cylindrical core according to <1>, wherein the surface has no convex bumps after being allowed to stand at 300 ° C. for 30 minutes.

<3> At least a billet forming step in which molten aluminum flows into a mold to form a cylindrical solid billet, and a cross section is formed by drilling from one bottom surface to the other bottom surface by boring in the center of the cylindrical solid billet. It is a manufacturing method of a cylindrical core body which has a boring process which forms a hole of an outer circle and a concentric circle, and an extrusion process which extrudes the obtained cylindrical billet to make an element pipe.

<4> A resin coating film forming step in which a resin solution is applied to the surface of a cylindrical core to form a resin coating film, and a resin film formation in which the resin coating film is heated and dried and / or heated to react. And a resin film peeling step for peeling the resin film from the cylindrical core,
The cylindrical core is formed in a central portion of one end surface of a columnar solid billet made of aluminum to form a hole penetrating from the one end surface to the other end surface and having a cross section concentric with an outer circle. It is a manufacturing method of an endless belt which is a cylindrical core body using a raw tube obtained by extruding a billet.

  ADVANTAGE OF THE INVENTION According to this invention, even when it heats and uses, the cylindrical core body which does not generate | occur | produce a protrusion etc. on the surface and can be used repeatedly and stably, its manufacturing method, and an endless belt using this cylindrical core The manufacturing method of can be provided.

Hereinafter, the present invention will be described in detail.
<Cylindrical core and manufacturing method thereof>
The cylindrical core of the present invention is a cylinder obtained by forming a hole having a cross section concentric with an outer circle penetrating from the one end face to the other end face at the center of one end face of a cylindrical solid billet made of aluminum. It is characterized by using a raw pipe obtained by extrusion-molding a billet.
In the following, “aluminum” means both aluminum and an aluminum alloy.

  As described above, in a cylindrical core body made of a hollow tube manufactured using a hollow billet, a bulge may occur on the surface of the core body due to heating during use. As a result of investigating the cause, in the production of the hollow billet, as shown in FIG. 3, since there is a mandrel 20 when the molten aluminum flows into the mold 12, a hollow wall is formed at the place where the separated molten metal is mixed. I understood that. In this case, when there are two inflow ports 11, there are two places where they are mixed, and thus the empty wall is also generated at two places.

And when the cylindrical core body produced from the billet in which the above-mentioned empty wall exists is used, due to the expansion of the empty wall portion near the surface of the core body (about several hundred μm from the surface) during heating, It was found that convex bumps occurred.
Therefore, in order to eliminate the occurrence of the convex bulge in the cylindrical core body, it is necessary to allow molten aluminum to flow into the mold so that the empty wall is not generated in the billet when the billet is produced.

  As a result of investigations by the present inventors, it is difficult to reduce the generation of empty walls when producing hollow billets by the method shown in FIG. 3, and in particular, when trying to obtain a raw tube having an outer diameter of 300 mm or more. It turned out that the empty wall near the surface of the billet is unavoidable because the moving distance of the molten aluminum flowing in becomes long.

On the other hand, in the solid billet obtained by the method shown in FIG. 1, for example, the flow of molten aluminum flowing in from the inflow port 1 is not large, and the molten aluminum does not decompose and is uniformly filled without being mixed in the mold. It was confirmed that the empty wall was not present at all inside the billet.
However, if the solid billet is used as it is, an extruded element tube having an outer diameter of 300 mm or more cannot be obtained. Therefore, it has been necessary to form a cylindrical billet by some method.

As described above, the present inventors use a solid billet and produce an extruded element tube having an outer diameter of 300 mm or more by producing a billet in which a hole penetrating the other end surface is formed at the center of the bottom surface (one end surface) of the solid billet. Further, the present inventors have found that a cylindrical core body that does not generate convex protrusions on the surface even when heated can be obtained by using this raw tube.
In forming the through-hole, the method is not particularly limited, but it is preferable to perform by boring as described later in view of excellent positional accuracy and straightness.

Hereinafter, the cylindrical core of the present invention will be described together with its manufacturing method.
The cylindrical core of the present invention includes at least a billet forming step in which molten aluminum flows into a mold to form a columnar solid billet, and the center of the columnar solid billet is drilled from one bottom surface to the other. It is manufactured through a boring process that penetrates the bottom surface and forms a hole having a concentric cross section with an outer circle, and an extrusion process that extrudes the obtained cylindrical billet into a raw tube.

(Billette forming process)
In this step, as shown in FIG. 1, molten aluminum is poured into a cylindrical mold 2 to produce a solid billet.
The material of the mold 2 is preferably a material that has heat resistance, low thermal conductivity, and does not react with molten aluminum. Therefore, the material of the mold 2 is preferably iron or ceramic.

  The size of the inside of the mold 2 into which the molten aluminum is introduced is in the range of 500 to 600 mm in inner diameter and in the range of 600 to 800 mm in height (depth) due to the use of the cylindrical core of the present invention. Preferably there is.

  The mold 2 may be provided with a cooling device if necessary. As the cooling means, for example, cooling water may be sprayed around the mold 2, or the mold 2 is surrounded by a large water flow cooling tank so that the entire mold 2 can be covered with the cooling water. It may be configured.

  The composition of the aluminum billet is not particularly limited, and examples thereof include an Al—Mn alloy, an Al—Mn—Si alloy, an Al—Mg alloy, and pure Al. Among these, in the endless belt manufacturing application described later, it is preferable to use JIS H4080: 1999 alloy number A3003 aluminum alloy or JIS H4080: 1999 alloy number A6063 aluminum alloy.

Molten aluminum can be obtained by heating an aluminum ingot having the above composition to 700 ° C. or higher (more than the melting point of aluminum), preferably 750 to 900 ° C. This is poured from the inlet 1 of the mold 2. The inflow rate varies depending on the volume of the mold 2 but is preferably in the range of 100 to 700 ml / min. By setting the inflow rate within the above range, not only the generation of the vacant wall can be prevented, but also the crystal structure can be made more precise.
Prior to the inflow, it is preferable that degassing is performed after the dissolved aluminum is reduced with hydrogen gas and replaced with an inert gas.

Molten aluminum is allowed to flow up to the upper surface of the mold 2 and after the whole is cooled, a cast is drawn out by a predetermined method to obtain a cylindrical solid billet.
If necessary, the solid billet is cut into a predetermined length and applied to the next step.

(Boring process)
This step is a step of forming a hole having a cross section that is concentric with the outer circle by penetrating from one bottom surface to the other end surface by boring in the center of one end surface of the solid billet obtained as described above.
Here, the above boring is a processing method for producing a precise hole diameter, positional accuracy, and straightness. After normal drilling (casting, fusing, sawing, end mill contouring), intermediate finishing, finishing boring And done. Moreover, the said cross section is a cross section when cut | disconnected in a direction orthogonal to a billet axial direction.

  In the present invention, the diameter of the hole formed by boring is preferably in the range of 200 to 300 mm. In the cylindrical billet after processing, the ratio of the inner diameter (hole diameter) to the outer diameter (inner diameter / outer diameter) is preferably in the range of 0.4 to 0.5.

(Extrusion process)
This step is a step of extruding the cylindrical billet obtained in the above step by extrusion processing (extrusion molding) to obtain a raw pipe. The cylindrical core body of the present invention can be obtained by subjecting the obtained raw tube as it is or by surface polishing.

  The extrusion process is a method of obtaining a product having a predetermined cross-sectional shape by placing a billet in a pressure-resistant thick container (container), applying pressure to the billet with a push rod (ram), and extruding it from a die hole. . In the present invention, an aluminum base tube is obtained after extrusion using a cylindrical billet.

  In the present invention, hot extrusion for heating the billet may be performed, or cold extrusion without heating may be performed, but it is preferable to perform hot extrusion in order to reduce the deformation resistance of the billet. The extrusion temperature is preferably in the range of 450 to 500 ° C. from the viewpoint of reducing deformation in the length direction.

  The aluminum base tube thus obtained preferably has an outer diameter in the range of 370 to 380 mm, a thickness in the range of 24 to 28 mm, and a length in the range of 1000 to 1200 mm.

The aluminum base tube can be used as a cylindrical core as it is depending on the application, but when used in the method for producing an endless belt of the present invention described later, the surface is cut and polished, and then described later as necessary. It is preferable to perform roughening treatment and plating treatment.
In the cutting / polishing step, the raw tube is cut and polished by a lathe or the like to a thickness of about 5 mm to obtain a cylindrical core having a desired outer diameter.

The plating treatment is a surface treatment that makes the surface of the core body hard to be damaged. However, when the material of the core body is aluminum, it is preferably plated with chromium or nickel. Moreover, when performing nickel plating, it is preferable to process by electroless nickel plating.
The arithmetic average roughness Ra of the core surface after the plating treatment is preferably in the range of 0.2 to 0.5 μm.

  The outer diameter of the cylindrical core of the present invention obtained as described above is 300 mm or more, particularly 350 to 380 mm, the thickness is 8 to 20 mm, and the length is 1000 to 1150 mm. Is preferred.

As described above, the cylindrical core body of the present invention is formed by using the raw tube obtained from the solid billet, so that the surface of the core body does not rise even when heated.
Specifically, it is preferred that the cylindrical core is left at 300 ° C. for 30 minutes and then has no convex bumps on the surface. For the above-described reason, if the standing at the above temperature is repeated, a convex ridge is more likely to occur. In the present invention, it is preferable that no bulging occurs even if the standing at 300 ° C. for 30 minutes is repeated 10 times or more.

Here, the convex protrusion is an elliptical shape having a major axis of 1 to 5 mm and a minor axis of 0.1 to 0.8 mm and a height of about 50 to 300 μm when viewed from the surface side. Can be confirmed.
If such a convex bulge occurs, a protrusion defect corresponding to the bulge occurs in the belt when an endless belt or the like is produced using this core.

<Method for producing endless belt>
The method for producing an endless belt according to the present invention includes a resin coating film forming step of applying a resin solution to the surface of a cylindrical core and forming a resin coating film; A method for producing an endless belt, comprising: a resin film forming step for forming a film; and a resin film peeling step for peeling the resin film from the cylindrical core. The cylindrical core body of the invention is used.

  That is, in the present invention, in the method of applying the resin solution to the surface of the cylindrical core body and heating and drying and / or reacting with heat to form the resin film, the cylindrical core body of the present invention is used repeatedly. Even if it is used, the surface of the core is not raised, and a high-quality belt free from protrusion defects can be stably obtained.

The resin for the resin film that can be used in the present invention is not particularly limited, but thermoplastic resins such as polyimide, epoxy resin, acrylic resin, silicone resin, polyester resin, polycarbonate resin, polyamide resin, and polyamideimide resin, heat It can be selected from curable resins and the like.
Among these, polyimide is particularly preferable because it can ensure strength, flexibility and the like as an endless belt.

  In the present invention, a resin solution in which the above various resins are dissolved in a solvent is applied to the surface of the cylindrical core to form a resin film. The resin solution is a solution in which a high molecular weight resin is dissolved. As well as a polyimide precursor solution described later, a resin precursor solution that reacts to become a resin is also included.

  Hereinafter, as an example in which the method for producing a resin endless belt of the present invention is preferably used, a method for producing an endless belt made of polyimide resin will be described in detail for each step.

-PI precursor coating film forming process (resin coating film forming process)-
In this step, since the PI precursor coating film is formed as a coating film for forming the resin coating film, the resin coating film forming process in the present invention is the PI precursor coating film forming process.

In the PI precursor coating film forming step, first, a PI precursor solution in which the PI precursor is dissolved in an aprotic polar solvent is prepared.
As the PI precursor, those composed of various combinations listed above can be used. The PI precursors may be used as a mixture of two or more, or may be used as a copolymer obtained by mixing an acid or amine monomer.

  In particular, a polyimide precursor comprising 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter abbreviated as “BPDA” where appropriate) and p-phenylenediamine (hereinafter abbreviated as “PDA” where appropriate). It is preferable to use a polyimide precursor solution obtained by mixing an acid anhydride other than BPDA and a polyimide precursor made of any diamine. By using such a polyimide precursor, the required physical properties can be changed and the material price can be reduced while keeping the coefficient of thermal expansion of the produced polyimide resin low. This is because the thermal expansion coefficient of a polyimide resin manufactured using a polyimide precursor composed of BPDA and PDA (hereinafter referred to as “S type” as appropriate) is smaller than that of an aluminum cylindrical core, This is because there is a margin in the difference, so that other polyimide precursors may be mixed in a range where the thermal expansion coefficient is smaller than that of the aluminum cylindrical core.

  Other polyimide precursors that can be used in combination with the polyimide precursor composed of BPDA and PDA include those composed of BPDA and 4,4′-diaminodiphenyl ether, pyromellitic dianhydride (PMDA) and 4,4′-diamino. Composed of diphenyl ether, composed of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and 4,4′-diaminodiphenylmethane, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid What is necessary is just to select suitably from what consists of a dianhydride and 4,4'- diamino benzophenone, etc., but what consists of PMDA and 4,4'- diamino diphenyl ether is mixing suitability, a characteristic surface, material price Etc. are preferably used.

  The mixing ratio of the polyimide precursor composed of BPDA and PDA and the polyimide precursor composed of other composition is preferable in terms of price as the polyimide precursor composed of other composition increases, but if it is too much, the coefficient of thermal expansion is large. Since it becomes difficult to peel off from the cylindrical core body, (polyimide precursor composed of BPDA and PDA): (polyimide precursor composed of other composition) = adjustable from the range of about 5: 5 to 0:10 Is done. The larger the outer diameter of the cylindrical core body, the larger the dimensional difference from the polyimide resin film formed on the surface and the tendency to come off, so the mixing ratio of polyimide precursors of other compositions is increased. be able to.

  In the present invention, peeling of the polyimide resin film from the cylindrical core is not only performed by shrinkage of the cylindrical core by cooling after the heating reaction, but also by peeling with pressurized air. The mixing ratio of the polyimide precursor having another composition can be increased, and depending on the combination with the cylindrical core, a polyimide precursor having another composition can be used alone.

  The S-type PI resin film is known to have the strongest mechanical strength among polyimide resins, and has an advantage that it is not easily deformed when used as a fixing belt or a transfer belt. On the other hand, a member that is in direct contact with the surface of the photoconductor, such as a transfer belt, may damage or wear the surface of the photoconductor, so that it may be preferable that the mechanical strength is somewhat low. In such a case, it is effective to adjust the strength by mixing an S-type polyimide precursor and a polyimide precursor having another composition.

  The polyimide precursor is prepared as a polyimide precursor solution by dissolving in an aprotic polar solvent such as N-methylpyrrolidone, N, N-dimethylacetamide, acetamide, N, N-dimethylformamide. In addition, selection of the mixing ratio, concentration, viscosity, and the like of the polyimide precursor in the preparation is performed by appropriately adjusting.

  As described above, the cylindrical core body made of the aluminum of the present invention is used as the cylindrical core body. However, when the cylindrical core body is made of aluminum, the strength is lowered when heated to 350 ° C. and is likely to be deformed. . Such thermal deformation of aluminum is likely to occur when strain is accumulated during cold working into a cylindrical core shape. In order to remove such distortion, there is a method of annealing (annealing) aluminum. However, since thermal deformation also occurs by annealing, the processing to the predetermined shape needs to be performed after that. Annealing includes a method in which an aluminum material is heated to a range of 350 to 400 ° C. and naturally cooled in air.

  In addition, in the PI resin film forming step described later, the formed PI resin film may adhere to the surface of the cylindrical core, so that the surface of the cylindrical core may be provided with releasability. preferable. In particular, in the present invention, in the PI resin film peeling step, which will be described later, the film is peeled by injecting pressurized air into the gap between the cylindrical core and the PI resin film. It is preferable.

  In order to provide releasability, the surface of the cylindrical core body is plated with chromium or nickel, or the surface is coated with a fluorine resin or silicone resin, or the polyimide resin is not adhered to the surface. It is effective to apply a mold.

  In addition, when the PI precursor coating film is dried, if the residual solvent cannot be completely removed, or if water generated during heating cannot be removed completely, the PI resin film may partially swell like a lantern. This is a particularly serious problem when the thickness of the PI resin film is thicker than 50 μm. In that case, it is effective to roughen the surface of the cylindrical core body to an arithmetic average roughness Ra of about 0.2 to 2 μm. Thereby, the residual solvent or water vapor generated from the PI resin film can be discharged to the outside through a slight gap formed between the cylindrical core body and the PI resin film, and swelling can be prevented. For roughening the surface of the cylindrical core body, a method such as blasting, cutting, sandpapering or the like is used.

  In the PI precursor coating film forming step, the PI precursor solution (resin solution) is applied to the surface of the cylindrical core body to form a PI precursor coating film. Immersion method in which the core is immersed in the PI precursor solution to raise (pull up), flow coating method in which the PI precursor solution is discharged onto the surface while rotating the cylindrical core, and the coating is metalized with a blade A known method such as a blade coating method can be employed. In the above-described flow coating method or blade coating method, the coating portion is moved horizontally, so that the film is formed in a spiral shape. However, since the PI precursor solution is slow to dry, the seam is naturally smoothed. In addition, "applying on the surface of a cylindrical core body" means apply | coating to the surface of the layer of the side surface of a cylindrical core body also including a column, and when there is a layer in this surface. Further, “rising the cylindrical core body” is a relative relationship with the liquid level at the time of application, and includes the case of “stopping the cylindrical core body and lowering the coating liquid level”.

  In the PI precursor coating film forming step, when the PI precursor solution is applied by a dip coating method, the viscosity of the PI precursor solution is very high, and thus the film thickness may be too thick. In that case, the dip coating method which controls a film thickness with the annular body shown below is applicable.

A dip coating method for controlling the film thickness by an annular body will be described with reference to FIGS.
FIG. 5 is a schematic configuration diagram illustrating an example of an apparatus used in a dip coating method in which the film thickness is controlled by an annular body. However, in FIG. 5, only the application | coating main part is shown and the other apparatus is abbreviate | omitted.

  As shown in FIG. 5, in this dip coating method, an annular body 25 having a hole 26 larger than the outer diameter of the cylindrical core body 21 is floated on the PI precursor solution 22 filled in the coating tank 23 to form a cylinder. In this coating method, the core 21 is immersed in the PI precursor solution 22 through the hole 26 from the upper side in the drawing, and then the cylindrical core 21 is pulled up.

  The annular body 25 is configured to float on the liquid surface of the PI precursor solution, and any material may be used as long as the material is not affected by the PI precursor solution 22. For example, the annular body 25 is selected from various metals and plastics. . Further, for example, a hollow structure may be used so as to easily float, and legs or arms for supporting the annular body 25 may be provided on the outer peripheral surface of the annular body or the application tank 23 in order to prevent sinking.

  The annular body 25 needs to be able to move freely on the liquid surface of the PI precursor solution 22. Therefore, in addition to a method of floating the annular body 25 on the solution surface so that the PI precursor solution 22 can move with a slight force, a method of supporting the annular body 25 with a roll or a bearing, It is preferable to be installed so as to be freely movable by a method such as a method of supporting with air pressure.

  Moreover, you may provide the fixing means which fixes the annular body 25 temporarily so that the annular body 25 may be located in the center part of the application tank 23. FIG. Examples of such fixing means include means for providing a foot on the annular body 25, means for fixing the coating tank 23 and the annular body 25, and the like. However, when these fixing means are used, when the cylindrical core body 21 is dipped and then pulled up, the fixing means is detachably arranged so that the annular body 25 can move freely.

  The gap between the outer diameter of the cylindrical core 21 and the diameter of the hole 26 is adjusted in view of the desired coating thickness. The desired coating film thickness (dry film thickness) is the product of the wet film thickness and the non-volatile concentration of the PI precursor solution 22. From this, a desired wet film thickness is obtained. Further, the gap between the outer diameter of the cylindrical core 21 and the diameter of the hole 26 is preferably in the range of 1 to 2 times the desired wet film thickness. The reason why the range is 1 to 2 times is that the gap does not always become a wet film thickness due to the viscosity and / or surface tension of the PI precursor solution 22. Thus, the desired diameter of the hole 26 is determined from the desired dry film thickness and the desired wet film thickness.

  As shown in FIG. 5, the inner wall surface of the hole 26 provided in the annular body 25 has an inclined surface as shown in FIG. Further, a combined inclined surface may be used. Further, it may be stepped or curved.

  When performing dip coating, the cylindrical core body 21 is immersed in the PI precursor solution 22 through the holes 26. At this time, the cylindrical core body 21 is prevented from contacting the annular body 25. Next, the cylindrical core body 21 is pulled up through the hole 26. At this time, the thickness of the coating film 24 is determined by the gap between the cylindrical core body 21 and the hole 26. The pulling speed is preferably in the range of about 0.1 to 1.5 m / min. The solid content concentration of the PI precursor solution preferable for this coating method is in the range of 10 to 40% by mass, and the viscosity is in the range of 1 to 100 Pa · s.

  When the cylindrical core body 21 is pulled up through the hole 26, a frictional resistance is generated between the cylindrical core body 21 and the annular body 25 due to the presence of the polyimide precursor solution 22, and a rising force acts on the annular body 25. The annular body 25 is slightly lifted. At this time, the annular body 25 is in a freely movable state, and further, since the hole 26 of the annular body is circular and the outer periphery of the cylindrical core body 21 is also circular, the cylindrical core body 21 and the annular body 25. The annular body 25 can move so that the frictional resistance between the annular body 25 and the outer periphery is constant in the circumferential direction. That is, when the cylindrical core body 21 is pulled up, if the gap between the annular body 25 and the cylindrical core body 21 is narrowed at a certain position, the frictional resistance is increased in the narrowed portion, but on the opposite side. In this case, the frictional resistance becomes small, and the frictional resistance temporarily becomes non-uniform. However, since the annular body 25 moves freely, the outer periphery of the cylindrical core body 21 is circular, and the hole 26 of the annular body is circular, such frictional resistance is uniform from a non-uniform state. The annular body 25 moves so as to be in a stable state. Therefore, the annular body 25 does not come into contact with the cylindrical core body 21.

  Further, the position where the frictional resistance becomes uniform is a position where the circular shape of the outer periphery of the cylindrical core body 21 and the circular shape of the hole 26 of the annular body 25 are substantially concentric. Therefore, even if the center of the circle of the cross section of the cylindrical core body 21 is deviated within an allowable range in the axial direction, the annular body 25 moves so as to follow it. Therefore, the polyimide precursor coating film 24 having a certain wet film thickness can be formed on the surface of the cylindrical core body 21.

  Furthermore, the coating apparatus used for the dip coating method includes a cylindrical core body holding means for holding the cylindrical core body 21, and a first moving means for moving the holding means in the vertical direction in FIG. Alternatively, the container may contain a second moving means for moving the container for containing the polyimide precursor solution 22 in the vertical direction in FIG.

  By applying such a dip coating method in which the film thickness is controlled by the annular body 25, the sagging of the coating film at the upper end of the cylindrical core body 21 by using the high-viscosity polyimide precursor solution 22 is Therefore, the film thickness can be made uniform easily.

  In addition to using the above-described dip coating method in the PI precursor coating film forming step, an annular coating method shown in FIG. 6 can also be applied. Here, FIG. 6 is a schematic configuration diagram showing an example of an apparatus used for the annular coating method.

In FIG. 6, the difference from FIG. 5 is that an annular sealing material 28 having a hole slightly smaller than the outer diameter of the cylindrical core body is provided at the bottom of the annular coating tank 27. An annular sealing material 28 is attached to the bottom of the annular coating tank 27, the cylindrical core body 21 is inserted through the center of the annular sealing material 28, and the PI precursor solution 22 is accommodated in the annular coating tank 27. Thereby, the PI precursor solution 22 is prevented from leaking. The cylindrical core body 21 is sequentially lifted from the lower part to the upper part of the annular coating tank 27 in the drawing, and the coating film 24 is formed on the surface by inserting the annular sealing material 28. Intermediate bodies 29 and 29 ′ that can be fitted to the cylindrical core body 21 may be attached to the upper and lower sides of the cylindrical core body 21. The function of the annular body 25 is the same as described above.
In such an annular coating method, the annular coating tank 27 can be made smaller than the dip coating tank 23 of FIG.

-PI resin film formation process (resin film formation process)-
In this step, since the PI resin film is formed as the resin film, the resin film forming process in the present invention is the PI resin film forming process.

In the PI resin film forming step, the PI precursor film is heated and dried, and then heated to react to form a PI resin film.
First, in the PI resin film forming step, for the purpose of removing the solvent excessively remaining in the PI precursor coating film, heat drying is performed to such an extent that the coating film is not deformed even if left standing. The heating conditions are preferably 90 to 170 ° C. and 30 to 60 minutes. At that time, the higher the temperature, the shorter the heating time. In addition to heating, it is also effective to apply wind. Heating may be increased stepwise or at a constant rate over time.

  If the solvent is excessively removed from the PI precursor coating film, the coating film does not yet maintain the strength as a belt, and there is a risk of cracking. Therefore, it is better to leave the solvent to some extent (specifically, 15 to 45% by mass in the PI precursor coating film).

  The PI precursor coating film may be continuously dried from the heat drying to the heating reaction, but the temperature may be temporarily lowered during the process. Here, “reducing the temperature” means that the PI precursor coating film, which is in a high temperature state by heat drying, is cooled together with the cylindrical core body to reduce the temperature. The temperature to be lowered may be room temperature. Lowering the temperature is effective when the heat drying apparatus and the heat reaction apparatus are different.

At that time, the PI precursor coating film shrinks due to a decrease in temperature. The shrinkage rate is in a small range of 0.5 to 2% in the axial direction, but due to this shrinkage, the PI precursor coating film is displaced on the surface of the cylindrical core body, and is closer to the cylindrical core body. A wide gap occurs. Once such a gap occurs, residual solvent and the like are easily removed during the heating reaction.
When the heat drying apparatus and the heat reaction apparatus are the same, it is not necessary to lower the temperature once.

  In the PI resin film forming step, after the above-mentioned drying, the PI precursor film is heated and reacted in the range of preferably 300 to 450 ° C., more preferably around 350 ° C. for 20 to 60 minutes. Can be formed. During the heating reaction, if the aprotic polar solvent remains, the PI resin film may swell, so it is preferable to completely remove the residual solvent before reaching the final heating temperature. Before heating, it is heated and dried at a temperature of 200 to 250 ° C. for 10 to 30 minutes to remove the residual solvent, and then heated by gradually increasing the temperature stepwise or at a constant rate. It is preferable to form a resin film.

  In the PI resin film forming step, before heat drying, the PI precursor coating film is treated with a specific solvent that does not dissolve the PI precursor and can dissolve the aprotic polar solvent, You may perform the process of forming a PI precursor membrane | film | coat. Thereby, the aprotic polar solvent oozes out from the PI precursor coating film into the specific solvent, and the specific solvent penetrates instead. Individually, since the PI precursor is insoluble in a specific solvent, the PI precursor is precipitated and solidified to such an extent that the coating film does not deform even when left standing, and a PI precursor coating film is formed. As a result, the drying process described above is performed quickly, and the drying time can be shortened.

  The contact between the PI precursor coating film and the specific solvent is preferably performed immediately after the PI precursor coating film forming step. After the PI precursor solution is applied, the solvent contained in the coating film is slow to dry at room temperature as described above. Therefore, the coating film remains wet forever, and the coating film always hangs down under the influence of gravity. Therefore, immediately after the PI precursor is applied, the PI precursor coating film and the specific solvent are contacted to solidify the PI precursor coating film, thereby preventing dripping.

  As a method of contacting the PI precursor coating film with the specific solvent, a method of immersing the PI precursor coating film in the specific solvent is suitable, but in addition, the specific solvent is allowed to flow down or sprayed on the PI precursor coating film. May be. When the PI precursor coating method is centrifugal molding, the cylindrical core body may be stopped and immersed in a specific solvent, but the PI precursor coating on the inner surface may be applied while rotating the cylindrical core body. You may spray a specific solvent.

  When the PI precursor is deposited, the elution amount of the aprotic polar solvent from the PI precursor coating changes depending on the time for which the PI precursor coating is brought into contact with the specific solvent. When the aprotic polar solvent is completely removed from the coating film, the precipitated and solidified PI precursor film may become fragile. Therefore, the aprotic polar solvent remains in an amount of about 5 to 50% by mass. It is preferable. For this purpose, the contact time of the PI precursor coating film with the specific solvent is preferably about 10 seconds to 10 minutes, although it depends on the film thickness of the PI precursor coating film. The thicker the PI precursor coating film is, the more solvent is contained. Therefore, it is preferable to increase the contact time.

  As the specific solvent to be brought into contact with the PI precursor coating film, a solvent in which the PI precursor is insoluble and an aprotic polar solvent is dissolved is used. Specifically, water, alcohols (eg, methanol, ethanol, etc.), hydrocarbons (eg, hexane, heptane, toluene, xylene, etc.), ketones (eg, acetone, butanone, etc.), esters (eg, acetic acid, etc.) Ethyl etc.). These may be used alone or in combination, but water or a mixture containing water is particularly convenient and preferable.

In such a PI precursor film formation step, when the treatment for bringing the PI precursor film into contact with the specific solvent is performed, the specific solvent that has penetrated into the formed PI precursor film and the remaining aprotic polarity Drying is performed for the purpose of removing the solvent. Drying conditions are preferably performed at a temperature of 50 to 120 ° C. for 10 to 60 minutes. In the specific solvent and the aprotic polar solvent, since the aprotic polar solvent is less likely to evaporate, a state in which the aprotic polar solvent remains is formed in the PI precursor film. By entering into this state, the deposited PI precursor is again in a dissolved state and becomes transparent.
Thereafter, the PI precursor film is subjected to a PI resin film forming step in which a PI resin film is formed by heating and drying, followed by heat reaction.

-PI resin film peeling process (resin film peeling process)-
In this step, since the PI resin film is peeled from the cylindrical core as the resin film, the resin film peeling step in the present invention is the PI resin film peeling step.

  After the heating reaction, an endless belt made of PI resin is obtained through this step of peeling the formed PI resin film from the cylindrical core. As a peeling method, a method of inflating the gap by injecting pressurized air into the gap between the cylindrical core and the PI resin film is effective.

The extracted endless belt is inferior in film thickness uniformity at both ends or has a film fragment attached thereto, but the portion is cut as an unnecessary portion. As described above, the unnecessary portion is preferably within a range of 50 to 100 mm from the end.
An unnecessary portion of the end portion is cut to obtain an endless belt made of PI resin, but drilling (punching) processing, rib attaching processing, or the like may be performed as necessary.

When the endless belt is used as a transfer belt or a contact charging belt, a conductive substance is dispersed in the resin material as necessary. Examples of the conductive material include carbon black, carbon beads granulated from carbon black, carbon fiber, carbon materials such as graphite, metals or alloys such as copper, silver, aluminum, tin oxide, indium oxide, antimony oxide, Examples thereof include conductive metal oxides such as SnO ₂ —In ₂ O ₃ composite oxide, and conductive whiskers such as potassium titanate.
When an endless belt is used as a transfer belt, the thickness is preferably in the range of 50 to 100 μm.

  Further, when an endless belt is used as a fixing member, it is effective to form a non-adhesive resin film on the belt surface in order to improve the releasability of the toner adhering to the surface. Examples of the non-adhesive resin film material include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). A fluororesin is preferred. Further, carbon powder may be dispersed in the non-adhesive resin film in order to improve durability and electrostatic offset.

  In order to form these fluorine-based resin films, a method in which the aqueous dispersion is applied to the surface of the endless belt and baked is preferable. Moreover, when the adhesiveness of a fluorine resin film is insufficient, there is a method in which a primer layer is applied and formed in advance on the belt surface as necessary. Examples of the material for the primer layer include polyphenylene sulfide, polyethersulfone, polysulfone, polyamideimide, polyimide, and derivatives thereof, and it is preferable that at least one compound selected from fluorine-based resins is included.

  Thus, in order to form the primer layer and the fluorine-based resin film on the belt surface, the polyimide resin film (belt) is formed on the surface of the cylindrical core body by heating and curing, and then applied. Although the PI precursor solution is applied and the solvent is dried, or after contact with a specific solvent, the primer layer and the fluororesin dispersion are applied and then heated to complete the imide conversion reaction. And the fluororesin film may be fired at the same time. In this case, even if there is no primer layer, the adhesiveness of the fluororesin film may be strengthened.

When an endless belt is used as a fixing member, the thickness is preferably in the range of 25 to 500 μm. The thickness of the primer layer provided as needed is preferably in the range of 0.5 to 10 μm. The thickness of the fluororesin film is preferably in the range of 4 to 40 μm.
The primer layer and the fluororesin film have a certain degree of flexibility, and expansion and contraction can follow the polyimide resin film, so the coefficient of thermal expansion as a laminate is a value only for the polyimide resin. Can be considered the same.

Hereinafter, the present invention will be specifically described by way of examples. However, each example does not limit the present invention.
<Example 1>
(Production of cylindrical core)
The aluminum ingot was heated to 750 to 900 ° C. to form molten aluminum, reduced with hydrogen gas, and then replaced with inert gas. This was degassed in a casting furnace, and a trace element was added to become a component of JIS-A6063.

  Next, the cylindrical mold 2 shown in FIG. 1 was provided with a cooling means having a temperature-controlled water cooling structure, and the molten aluminum was introduced from one inlet 1 of the mold 2. In addition, the internal diameter of the casting_mold | template 2 is 584 mm and length is 700 mm. This was cooled to obtain a solid round bar (cylindrical) solid billet.

  As shown in FIG. 2, a hole 4 having an inner diameter of 254 mm was formed by boring using a lathe device at the center of the bottom surface (one end surface) to form an extrudable cylindrical billet 3. After extruding this directly at about 450 ° C, it is straightened, tempered, tempered, and then cut into a predetermined length to give an extruded element tube with an outer diameter of 377 mm, a wall thickness of 26 mm, and a length of 1100 mm was gotten.

  The surface of the extruded element tube was cut by a lathe process into a cylindrical body having an outer diameter of 369 mm. Next, the surface was roughened by blasting with spherical glass particles so that the arithmetic average roughness Ra was 0.40 μm, and then the surface was subjected to electroless nickel plating with a thickness of 10 μm. The arithmetic average roughness Ra of the surface after the plating treatment was 0.35 μm. Furthermore, a silicone release agent (trade name: Sepacoat, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface, and baked at 300 ° C. for 1 hour to obtain a cylindrical core.

  Even after heating in the baking process, no convex bumps were observed on the surface of the cylindrical core.

(Preparation of paint)
BPDA and PDA were reacted in equimolar amounts in N, N-dimethylacetamide to prepare a 22% by mass PI precursor solution A. Carbon black (trade name: Special Black 4, manufactured by Degussa Huls) was mixed with the precursor solution A so as to have a solid content of 23% by mass, and then dispersed by a jet mill. Further, a surfactant (trade name: LS009, manufactured by Enomoto Kasei Co., Ltd.) was added to make the coating film less susceptible to repellency so that the concentration became 500 ppm to obtain a paint. The viscosity of this paint was 45 Pa · s.

(Preparation of PI resin endless belt)
First, using the coating material, a PI precursor coating film was formed on a cylindrical core body by an annular coating method as shown in FIG. Next, the cylindrical core body on which the coating film was formed was leveled and rotated at 20 rpm, followed by drying at room temperature for 5 minutes, followed by heat drying at 80 ° C. for 20 minutes and at 100 ° C. for 1 hour. Thereby, a PI precursor coating film having a thickness of about 150 μm was obtained. Next, the core body was made vertical, placed on a heating table, placed in a heating apparatus, and reacted by heating at 200 ° C. for 30 minutes and at 300 ° C. for 30 minutes to form a PI resin film having a length of 900 mm.

After cooling to room temperature, pressurized air with a pressure of 0.5 MPa was injected into the gap between the cylindrical core and the film, and the PI resin film was extracted. Thus, a uniform PI resin endless belt with a film thickness of 80 μm could be obtained.
An end portion of the PI resin endless belt was cut from both ends to obtain an electrophotographic transfer belt.

  The production of the above endless belt was repeated using the same cylindrical core, but the cylindrical core did not bulge on the surface no matter how many times it was used, and the resulting PI resin endless belt There was no defect.

<Comparative Example 1>
A hollow billet 15 produced in the same manner as in Example 1 was used, except that a mold 12 having an inner diameter of 584 mm and a length of 700 mm as shown in FIG. 3A and having a mandrel 20 having a diameter of 254 mm in the center was used. In the same manner, extrusion and the like were performed to obtain an extruded element tube having the same shape. Note that molten aluminum was supplied to the mold 12 from a plurality of supply ports 11.

The extruded core tube was cut in the same manner as in Example 1 to produce a cylindrical core, and a PI resin endless belt was similarly produced using this cylindrical core.
As a result, the cylindrical core was able to be used without any problems at first. However, as shown in FIG. 4, the surface of the cylindrical core 6 has a major axis of about 2 mm and a minor axis of about 0.1 mm. A convex ridge 7 having an elliptical shape of 3 mm and a height of about 0.1 mm is generated at one place, and this is transferred to an endless belt produced using this core, resulting in a projection defect, and transfer for electrophotography. It was unsuitable for use as a belt.

  That is, although there was no bulge on the surface at the stage of cutting the extruded element tube, the bulge occurred by repeated heating at 300 ° C. When heating was further repeated, the number of bulges increased to five at the tenth time and was getting worse. In addition, the raised bumps generated were cut and flattened, but raised again at the same place, so that it could no longer be used as a cylindrical core.

It is a perspective view of the casting_mold | template for solid billet production. It is a perspective view of the billet used for this invention. (A) is a mold for producing a hollow billet, and (B) is a perspective view of the obtained hollow billet. It is a figure which shows the cylindrical core body which the protrusion generate | occur | produced. It is a schematic block diagram which shows an example of the coating device used for this invention. It is a schematic block diagram which shows another example of the coating device used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 Inlet 2,12 Mold 3,15 Billet 4 Hole 6,21 Cylindrical core 7 Convex ridge 20 Mandrel 22 Polyimide precursor solution (resin solution)
23 Coating tank 24 Polyimide precursor coating (resin coating)
25 annular body 26 annular body hole,
27 annular coating tank 28 annular sealing material 29, 29 ′ intermediate

Claims (4)

  A hollow tube formed by extruding the cylindrical billet obtained by forming a hole in the center of one end surface of a cylindrical solid billet made of aluminum that penetrates from the one end surface to the other end surface and has a cross section concentric with the outer circle. A cylindrical core body characterized by comprising the following.   2. The cylindrical core according to claim 1, wherein the cylindrical core body has no convex bumps on the surface after being left for 30 minutes at 300 ° C.   At least a billet forming step in which molten aluminum flows into a mold to form a cylindrical solid billet, and a central portion of the cylindrical solid billet penetrates from one bottom surface to the other bottom surface by boring, and a cross section is an outer circle. A method for producing a cylindrical core, comprising: a boring step for forming concentric holes; and an extrusion step for extruding the obtained cylindrical billet to form a blank tube. Applying a resin solution to the surface of the cylindrical core and forming a resin coating film; and a resin film forming process of forming a resin film by heating and drying and / or heating reaction of the resin coating film; A resin film peeling step for peeling the resin film from the cylindrical core, and a method for producing an endless belt,
The cylindrical core is formed in a central portion of one end surface of a columnar solid billet made of aluminum to form a hole penetrating from the one end surface to the other end surface and having a cross section concentric with an outer circle. A method for producing an endless belt, characterized in that the endless belt is a cylindrical core body using a raw tube obtained by extruding a billet.

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