JP2010241123A - Tubular body, transfer unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tubular body hardly carrying partial electric current in the thickness direction. <P>SOLUTION: The tubular body includes a laminated body of outer layer 121 and an inner layer 122, and includes a region exhibiting higher conductivity than other regions (the inner layer 122 region and the outer layer 121 region other than a conductivity point uneven distribution region 124A) in the thickness direction in the inner layer 122. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tubular body, a transfer unit, and an image forming apparatus.

  In an image forming apparatus using an electrophotographic method, conventionally, an electrostatic latent image is formed on an image carrier such as an electrophotographic photosensitive member, the electrostatic latent image is developed with toner, and the obtained toner image is transferred to an endless belt. 2. Description of the Related Art Image forming apparatuses are known that form an image after electrostatically transferring (primary transfer process) onto an intermediate transfer belt, and then transferring again to a transfer medium such as transfer paper (secondary transfer process). . In particular, an intermediate transfer belt is preferably used in an image forming apparatus of a system (tandem system) that obtains a full color image by superimposing different color toner images. In this type of image forming apparatus, a conductive intermediate transfer belt having conductivity has been widely used.

  For example, in Patent Document 1, the intermediate transfer member has a three-layer structure, the volume resistivity of the central portion is 3.0 to 7.0 LogΩ · cm, and the volume resistivity of both layers is 9.0 LogΩ · cm. The technology described above is disclosed.

JP 9-34269 A

  An object of the present invention is to provide a tubular body in which local current hardly flows in the thickness direction of the tubular body as compared with the case where the conductivity of the inner layer is constant in the thickness direction.

The above object is achieved by the present invention described below.
That is, the invention according to claim 1
The invention according to claim 1
Having at least two layers of an outer layer and an inner layer including resin and conductive particles,
The tubular body in which the inner layer has a region having higher conductivity than other regions in the thickness direction.

The invention according to claim 2
A transfer unit comprising: a transfer belt that is a tubular body according to claim 1; and a plurality of rolls that hang the transfer belt in a tensioned state, and is detachable from an image forming apparatus main body.

The invention according to claim 3
An image carrier,
Charging means for charging the surface of the image carrier;
Latent image forming means for forming a latent image on the surface of the image carrier;
Developing means for developing a latent image on the surface of the image carrier with toner to form a toner image;
An intermediate transfer member to which the toner image formed on the surface of the image carrier is transferred;
Primary transfer means for primarily transferring the toner image formed on the surface of the image carrier to the surface of the intermediate transfer member;
Secondary transfer means for secondary transfer of the toner image transferred to the surface of the intermediate transfer member to a transfer medium;
Fixing means for fixing the toner image transferred to the recording medium;
With
The image forming apparatus according to claim 1, wherein the intermediate transfer body is a tubular body.

According to the first aspect of the present invention, compared to the case where the conductivity of the inner layer is constant in the thickness direction, a local current is less likely to flow in the thickness direction of the tubular body.
According to the second aspect of the present invention, when used in the image forming apparatus, image defects such as density unevenness or white spots are suppressed as compared with the case without this configuration.
According to the third aspect of the present invention, image defects such as density unevenness or white spots are suppressed as compared with the case without this configuration.

It is a schematic perspective view which shows the transfer belt which concerns on this embodiment. It is an AA schematic sectional drawing of FIG. It is a schematic sectional drawing which shows the transfer belt which concerns on other this embodiment. The cross-sectional schematic of a surface resistivity measuring apparatus is shown. The cross-sectional schematic of a volume resistivity measuring apparatus is shown. The plane schematic diagram of the electrode used for a surface resistivity measuring device or a volume resistivity measuring device is shown. It is process drawing which shows the manufacturing method of the transfer belt which concerns on this embodiment. It is a schematic diagram for demonstrating the spin coating method. It is process drawing which shows the manufacturing method of the transfer belt which concerns on other this embodiment. It is process drawing which shows the manufacturing method of the transfer belt which concerns on other this embodiment. It is a schematic diagram for demonstrating the other spin coating method. It is a schematic perspective view which shows the transfer unit which concerns on this embodiment. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. It is a figure which shows the change of the surface resistivity of the outer peripheral surface of an outer layer with respect to the grinding | polishing amount from the inner peripheral surface of an inner layer in a tubular body produced in Example 1. FIG. The change of the surface resistivity of the inner peripheral surface of the inner layer with respect to the polishing amount from the outer peripheral surface of the outer layer in the tubular body manufactured in Example 1 and the specified boundary position 2 are shown. It is a figure which shows the cross-sectional photograph of the tubular body 23 produced in Example 17. FIG. FIG. 10 shows a cross-sectional photograph of a tubular body 27 produced in Example 18. It is a figure which shows the cross-sectional photograph of the tubular body 25 produced in the comparative example 8. FIG.

(Transfer belt: tubular body)
FIG. 1 is a schematic perspective view showing a transfer belt according to the present embodiment. FIG. 2 is a schematic cross-sectional view taken along the line AA of FIG. FIG. 3 is a schematic cross-sectional view showing a transfer belt according to another embodiment. 3 corresponds to a cross-sectional view taken along the line AA in FIG.

  As shown in FIGS. 1 and 2, the transfer belt 120 according to the present embodiment is formed in an endless shape, and includes a laminate of an outer layer 121 and an inner layer 122 that include at least a resin and conductive particles 124. It is comprised by the tubular body. The transfer belt 120 according to the present embodiment includes a two-layer laminate, but is not limited thereto, and an intermediate layer including at least a resin and conductive particles is provided between the inner layer 122 and the outer layer 121. You may provide, and you may provide another functional layer in a belt outer peripheral surface (further outside of an outer layer) and an inner peripheral surface (further inner side of an inner layer).

  In the inner layer 122, there is a conductive point uneven region in which the conductive particles 124 serving as conductive points are unevenly distributed in the thickness direction. Specifically, for example, the conductive point uneven distribution region 124A exists in a layered manner along the belt circumferential direction on the belt outer circumferential surface side. The conductive point uneven distribution region 124A contains the conductive particles 124 in a more dense state than the other regions (the inner layer 122 region and the outer layer 121 region other than the conductive point uneven distribution region 124A). The region is also highly conductive.

  The conductive point uneven distribution region 124A is not limited to the outer peripheral surface side of the belt and is not particularly limited as long as it exists inside the inner layer 122. For example, as shown in FIG. 3, the conductive point uneven region 124A exists on the inner peripheral surface side of the inner layer 122. You may do it.

  Here, when a discharge occurs on the inner peripheral surface of the belt, electric charges may accumulate on the inner peripheral surface of the transfer belt 120 and local charging may occur. In addition, when electrons flow in from the inner peripheral surface of the belt, the flowing electrons flow through the belt and reach the outer peripheral surface of the belt, and positive charges and electrons are annihilated in the belt thickness direction on the outer peripheral surface of the belt. A current path due to discharge is formed, the current due to discharge increases, and a local current may flow in the thickness direction.

  Therefore, in the transfer belt 120 according to the present embodiment, in at least a two-layer configuration of the outer layer 121 and the inner layer 122, conductivity is higher than other regions (the inner layer 122 region other than the conductive point unevenly distributed region 124A and the outer layer 121 region). By applying the inner layer 122 having a high conduction point unevenly distributed region 124A, even when electric charges are supplied to the inner peripheral surface of the belt when a discharge occurs on the inner peripheral surface of the belt, the conductive point unevenly distributed region 124A in the inner layer 122 is obtained. The charge is considered to flow in the circumferential direction of the belt (in the direction intersecting the belt thickness direction), and the charge is less likely to accumulate on the inner circumferential surface of the belt, and it is assumed that local charging is suppressed. The

  Further, even when electrons flow from the inner peripheral surface of the belt, the electrons that have flown reach the conduction point unevenly distributed region 124A in the inner layer 122, but are closer to the outer peripheral surface side of the belt than the conductive point unevenly distributed region 124A. Since the region has lower conductivity than the conductive point uneven distribution region 124A, it is considered that it is difficult to reach the outer peripheral surface of the belt beyond the conductive point uneven distribution region 124A. For this reason, it is presumed that a current path due to discharge is less likely to be formed in the belt thickness direction, and local current is less likely to flow in the thickness direction.

  Therefore, in the transfer belt 120 according to the present embodiment, it is difficult for a local current to flow in the thickness direction. In addition, local charging is less likely to occur on the inner peripheral surface.

  When the transfer belt 120 according to the present embodiment is applied to an image forming apparatus as an intermediate transfer belt, image defects such as density unevenness (for example, scale-like density unevenness) or white spots are suppressed. The reason for this is not clear, but is thought to be due to the following reasons.

  In an image forming apparatus using an intermediate transfer belt, density unevenness (for example, scale-like density unevenness) occurs on an output image, or a toner image is partially whitened (a minute) white spot on the output image. May occur.

  The phenomenon that the density unevenness (for example, the scale-like density unevenness) occurs is that, in the secondary transfer process, discharge occurs between the backup roll contacting the inner peripheral surface of the intermediate transfer belt and the back surface of the intermediate transfer belt. As a result, charges are accumulated on the back surface of the intermediate transfer belt, and an electric field corresponding to the accumulated charges reaches the outer peripheral surface of the intermediate transfer member and disturbs the toner image. It is considered that scale-like density unevenness occurs.

  Similarly, in the secondary transfer step, a discharge is generated between the secondary transfer roll contacting the outer peripheral surface of the intermediate transfer belt via the recording medium and the outer peripheral surface of the intermediate transfer belt, and positive charges are supplied. . At this time, when electrons flowing from the backup roll to the back surface of the intermediate transfer belt flow through the intermediate transfer belt and reach the surface of the intermediate transfer belt, positive charges and electrons are annihilated on the surface of the intermediate transfer belt, and the A current path is formed by the discharge leading to the secondary transfer roll, and the current due to the discharge is increased. Then, current flows locally in the thickness direction of the belt, and the toner on the surface of the intermediate transfer belt is charged with a reverse polarity and is not transferred to the transfer medium, so that a small white spot is generated on the output image. It is done.

  For this reason, when the intermediate transfer belt is unlikely to be locally charged on the inner peripheral surface and a local current is difficult to flow in the thickness direction, image defects such as density unevenness (for example, scale-like density unevenness) or white spots. Is considered to be suppressed.

In the transfer belt 120 according to the present embodiment, the conductivity of the conductive point unevenly distributed region 124A of the inner layer 122 is, for example, a large value of a current detected in a conductive atomic force microscope observation image with an applied voltage of 5 V on the belt cross section of 20 pA or more. It is 150 pA or less (desirably 25 pA or more and 150 pA or less), and the root mean square current value is 2 pA or more and 20 pA or less (desirably 2.3 pA or more and 20 pA or less).
On the other hand, regarding the conductivity of the region other than the conductive point unevenly distributed region 124A, the maximum value of the current detected in the conductive atomic force microscope image of the applied voltage 5V on the belt cross section is 11 pA or more and less than 20 pA (preferably 17 pA or more and 20 pA or less). In addition, the root mean square current value is preferably 2 pA or more and 3 pA or less (preferably 2.1 pA or more and 3 pA or less).

  For the measurement of the current value of the belt cross section with this conductive atomic force microscope (cAFM), a system comprising an atomic force microscope (Dimension 3000 made by Veeco Instruments) and a controller (Nanoscope IIIa made by Veeco Instruments) is used.

And a measurement sample is produced as follows. The belt is cut into a size of about 1 mm × 10 mm and embedded in a two-component mixed curing type epoxy resin. After allowing it to stand for a whole day and night and confirming that the epoxy resin is cured, a belt cross section is prepared using an ultramicrotome.
The current value at the belt cross section as the measurement sample is measured by the cAFM system. The obtained cAFM image is analyzed by image processing software attached to the system, and the maximum current value and the root mean square current value are calculated. In the present embodiment, in the cAFM image obtained by observing the target region in the belt section, the maximum current value and the root mean square current value are calculated at two locations, and the mean values are calculated as the maximum current value and the root mean square current. Value.

  In the transfer belt 120 according to the present embodiment, both the outer layer 121 and the inner layer 122 are configured to include at least a resin and conductive particles dispersed therein. The conductivity of the outer layer 121 and the inner layer 122 (the inner layer 122 region other than the conductive point unevenly distributed region 124A) may be the same or different. However, the conductivity of the outer layer 121 is smaller than the conductive point uneven distribution region 124 </ b> A of the inner layer 122.

  Hereinafter, constituent materials and characteristics of the transfer belt 120 according to the present embodiment will be described.

First, a resin (hereinafter referred to as a resin material) will be described.
Although the Young's modulus of the resin material varies depending on the belt thickness, it is preferably 3500 MPa or more, more preferably 4000 MPa or more, and the mechanical properties as a belt are satisfied. The resin is not limited as long as the above Young's modulus is satisfied. For example, a polyimide resin, a polyamide resin, a polyamideimide resin, a polyether ether ester resin, a polyarylate resin, a polyester resin, a polyester resin obtained by adding a reinforcing material. Etc.

  The Young's modulus is obtained by performing a tensile test according to JIS K7127 (1999), drawing a tangent line to the curve of the initial strain region of the obtained stress / strain curve, and determining the inclination. As the measurement conditions, a strip-shaped test piece (width 6 mm, length 130 mm), dumbbell No. 1, test speed 500 mm / min, and thickness are measured by each setting of the thickness of the belt body.

  Among the resin materials, polyimide resin is preferable. Since the polyimide resin is a material having a high Young's modulus, deformation due to driving (stress of a support roll, a cleaning blade, etc.) is less than that of other resins, so that the transfer belt is less prone to image defects such as color misregistration. The polyimide resin is usually obtained as a polyamic acid solution by polymerizing an equimolar amount of tetracarboxylic dianhydride or its derivative and a diamine in a solvent. As tetracarboxylic dianhydride, what is shown by the following general formula (I) is mentioned, for example.

(In the general formula (I), R is a tetravalent organic group, which is aromatic, aliphatic, cycloaliphatic, a combination of aromatic and aliphatic, or a substituted group thereof.)

  Specific examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, and 3,3 ′, 4,4′-biphenyltetracarboxylic acid. Acid dianhydride, 2,3,3 ′, 4-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid Dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) sulfonic dianhydride, perylene-3,4,9,10 -Tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, ethylenetetracarboxylic dianhydride, etc. are mentioned.

On the other hand, specific examples of the diamine include 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 3,3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenylsulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3′-dimethyl4,4′-biphenyldiamine, benzidine, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylpropane, 2,4-bis (β-aminotert-butyl) toluene, bis (p-β-amino-tertiary) Tributylphenyl) ether, bis (p-β-methyl-δ-aminophenyl) benzene, bis- -(1,1-dimethyl-5-amino-benzyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, 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-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-methylnonamethylenediamine, 2 , 1 7-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 12-diaminooctadecane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, _{piperazine, H 2 N (CH 2)} 3 O (CH 2) 2 O (CH 2) NH 2, H 2 N (CH 2) 3 S (CH 2) 3 NH 2, H 2 N (CH 2) 3 N _{(CH 3) 2 (CH 2} ) 3 NH 2 and the like.

  As a solvent for the polymerization reaction of tetracarboxylic dianhydride and diamine, a polar solvent (organic polar solvent) is preferably mentioned from the viewpoint of solubility. As the polar solvent, N, N-dialkylamides are desirable, and specific examples thereof include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide, which are low molecular weight compounds thereof. N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethyl sulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine, tetramethylenesulfone, dimethyltetramethylenesulfone and the like. These may be used singly or in combination.

  The solid content concentration of the polyamic acid solution is preferably 5% by weight or more and 40% by weight or less, and more preferably 10% by weight or 30% by weight or less. When the solid content concentration is within 40% by weight, the coating can be easily performed and the uniformity of the coating film is ensured. Moreover, when the solid content concentration is 5% by weight or more, a film thickness having strength can be easily obtained. Although there is no restriction | limiting in particular about the viscosity of a polyamic acid solution, Generally the thing of the viscosity of 1 Pa.s or more and 500 Pa.s or less is easy to handle.

Next, the conductive particles will be described.
As the conductive particles, conductive or semiconductive powder can be used, and there is no limitation on the conductivity if a specific electric resistance can be stably obtained as a belt. For example, Ketchen black, acetylene black, Examples thereof include carbon blacks such as oxidized carbon black having a pH of 5 or less, metals such as aluminum and nickel, metal oxide compounds such as tin oxide, and potassium titanate. These may be used alone or in combination, but carbon black which is advantageous in terms of price is desirable. Here, “conductive” means that the volume resistivity is less than 10 ⁷ Ωcm. “Semiconductive” means that the volume resistivity is 10 ⁷ or more and 10 ¹³ Ωcm or less. Others are the same.

Next, characteristics of the transfer belt according to the present embodiment will be described.
When the transfer belt according to the present embodiment is an intermediate transfer belt, the surface resistivity of the outer peripheral surface is preferably 9 (LogΩ / □) or more and 13 (LogΩ / □) or less in common logarithmic values, and 10 (LogΩ). / □) and more preferably 12 (LogΩ / □) or less. If the common logarithmic value of the surface resistivity after 30 msec of voltage application exceeds 13 (LogΩ / □), the recording medium and the intermediate transfer belt may be electrostatically adsorbed during the secondary transfer, and the recording medium may not be peeled off. is there. On the other hand, if the common logarithm of the surface resistivity after 30 msec of voltage application is less than 9 (Log Ω / □), the holding power of the toner image primarily transferred to the intermediate transfer belt is insufficient, and the graininess of the image quality and the image disturbance May occur. The common logarithmic value of the volume resistivity is controlled by the type of conductive agent and the amount of conductive agent added, which will be described later.

Here, the measurement method of the surface resistivity is performed as follows. FIG. 4 shows a schematic cross-sectional view of the surface resistivity measuring apparatus. An insulating sheet 24 is disposed on the back electrode 23 connected to the GND, and a measurement sample 27 is disposed thereon. The front surface electrode 21 and the guard electrode 22 are arranged on the measurement sample 27, and the measurement sample 27 is sandwiched between the back surface electrode 23, the front surface electrode 21, and the guard electrode 22 via the insulating sheet 24. A direct current voltage is applied by a direct current power source 25 connected to the guard electrode 22, the amount of current flowing by the microammeter 26 connected to the surface electrode 21 is measured, and the surface resistivity is calculated.
FIG. 6 shows a schematic plan view of electrodes used in the surface resistivity measuring apparatus. A guard electrode 22 is arranged concentrically with the surface electrode 21 as the center. Here, d1 to d3 represent the diameter of the surface electrode 21, the diameter of the inner circumference of the guard electrode 22, and the diameter of the outer circumference of the guard electrode 22, respectively. These values can be arbitrarily set according to the size and shape of the measurement sample. In addition, in the measurement of the surface resistivity in a present Example, UR probe (made by Mitsubishi Chemical Corporation) was used, and d1-d3 was set to the following values, respectively.
d1 = 16mm
d2 = 30mm
d3 = 40mm
The surface resistivity ρs was calculated by the following formula.
Formula: ρs = [π (d2 + d1) / (d2−d1)] × (V / I)
(Here, V represents the voltage value (V) applied to the surface electrode 21, and I represents the current value (A) detected by the microammeter 26. In the measurement of the surface resistivity in this example, The voltage applied to the electrode 21 was 500 V. The current value I was 10 seconds after applying the voltage V. The surface resistivity was measured in an environment at a temperature of 20 ° C. and a relative humidity of 40%. )

  When the transfer belt according to this embodiment is an intermediate transfer belt, the entire volume resistivity is desirably 8 (Log Ωcm) or more and 13 (Log Ωcm) or less as a common logarithmic value. If the common logarithmic value of the volume resistivity is less than 8 (Log Ωcm), the electrostatic force that holds the charge of the unfixed toner image transferred from the image carrier to the intermediate transfer belt is less likely to act. The electrostatic repulsive force between the images and the fringe electric field at the image edge may cause the toner to scatter around the image and form a noisy image. On the other hand, if the common logarithmic value of the volume resistivity exceeds 13 (Log Ωcm), the charge holding power is large, so that the surface of the transfer belt is charged by the transfer electric field in the primary transfer, and thus a static elimination mechanism is required. There is a case. The common logarithmic value of the volume resistivity is controlled by the type of conductive agent and the amount of conductive agent added, which will be described later.

Here, the volume resistivity is measured as follows. FIG. 5 shows a schematic sectional view of the volume resistivity measuring apparatus. A measurement sample 27 is placed on the back electrode 23 connected to the GND via the DC power supply 25. The front surface electrode 21 and the guard electrode 22 are arranged on the measurement sample 27, and the measurement sample 27 is sandwiched between the back surface electrode 23, the front surface electrode 21, and the guard electrode 22. The guard electrode 22 is connected to GND. A direct current voltage is applied from a direct current power source 25 connected to the back electrode 23, a current amount flowing through a microammeter 26 connected to the front electrode 21 is measured, and a volume resistivity is calculated.
FIG. 6 shows a schematic plan view of electrodes used in the volume resistivity measuring apparatus. A guard electrode 22 is arranged concentrically with the surface electrode 21 as the center. Here, d1 to d3 represent the diameter of the surface electrode 21, the diameter of the inner circumference of the guard electrode 22, and the diameter of the outer circumference of the guard electrode 22, respectively. These values can be arbitrarily set according to the size and shape of the measurement sample. In addition, in the measurement of the volume resistivity in a present Example, UR probe (made by Mitsubishi Chemical Corporation) was used, and d1-d3 was set to the following values, respectively.
d1 = 16mm
d2 = 30mm
d3 = 40mm
The volume resistivity ρv was calculated by the following formula.
Formula: ρv = [(π × d1 ² ) / 4] × (V / I) × (1 / t)
(Here, V represents the voltage value (V) applied to the surface electrode 21, I represents the current value (A) detected by the microammeter 26, and t represents the film thickness (cm) of the measurement sample. In the measurement of volume resistivity in the examples, the voltage applied to the surface electrode 21 was 500 V. The current value I was a value 10 seconds after the voltage V was applied. For the measurement of t, any known method such as a micrometer or an eddy current film thickness system can be suitably used. In this example, an eddy current film thickness meter ISOSCOPE MP30 (manufactured by Fischer) is used. (The film thickness was measured. The volume resistivity was measured in an environment of a temperature of 20 ° C. and a relative humidity of 40%.)

  Hereinafter, a method for manufacturing the transfer belt according to the present embodiment will be described. FIG. 7 is a process diagram showing a method for manufacturing a transfer belt according to the present embodiment.

  In the method for manufacturing the transfer belt 120 according to the present embodiment, first, an inner layer coating solution containing conductive particles 124, a resin material, and a solvent is prepared. Then, as shown in FIG. 7A, the inner layer coating solution is applied to the outer peripheral surface of the cylindrical tube 11 to form an inner layer coating film 122A of the coating solution.

  Here, an example of preparing a polyamic acid solution in which carbon black (conductive particles) is dispersed is illustrated as a coating solution, but the material is not limited thereto. First, purified carbon black is prepared and dispersed in an organic polar solvent to prepare a carbon black dispersion. As a dispersion method, a method of dispersing by a disperser or a homogenizer after preliminary stirring is desirable. As with the carbon black purification method, the mixing of fine media reduces the carbon black purification effect. Therefore, a media-free dispersion method that does not use media is desirable, especially jets that suppress dispersion of high-viscosity solutions and disperse them. A mill is preferred.

  A polyamic acid solution in which carbon black is dispersed is prepared by dissolving and polymerizing a diamine component and an acid dianhydride component in the obtained carbon black dispersion.

  In this case, the monomer concentration (concentration of the diamine component and the acid anhydride component in the solvent) is set according to various conditions, but is preferably 5% by weight or more and 30% by weight or less. The reaction temperature is preferably set to 80 ° C. or less, particularly preferably 5 ° C. to 50 ° C., and the reaction time is 5 hours to 10 hours.

  Since the polyamic acid solution in which carbon black is dispersed is a highly viscous solution, the air bubbles mixed at the time of production do not escape naturally, and defects such as belt protrusions, dents and holes due to the air bubbles are generated by application. . For this reason, defoaming is desirable. It is desirable to defoam as much as possible just before application.

  In addition, the method of applying the inner layer coating liquid onto the cylindrical tube 11 is not particularly limited, for example, using a method of immersing in the outer peripheral surface, a method of spin-coating on the outer peripheral surface or the inner peripheral surface, etc. The inner layer coating film 122A is formed endlessly. In forming the belt, it is preferable to perform mold release treatment.

  As a specific example of the method of applying the inner layer coating liquid onto the cylindrical tube 11, a spin coating method will be described. In the spin coating method, as shown in FIG. 8, for example, a cylindrical forming tube 11 having an outer diameter corresponding to the length of the transfer belt 120 is prepared. A nozzle 15 for discharging the coating liquid 16 onto the outer peripheral surface of the cylindrical molded tube 11 is disposed at a position along the outer peripheral surface of the cylindrical molded tube 11, and the nozzle 15 is connected to the coating liquid container 14 through the pipe. Further, the coating solution container 14 is connected to the pressurizing device 17 through a pipe. A blade 18 for leveling the discharged coating solution 16 on the outer peripheral surface of the cylindrical tube 11 is disposed below the nozzle 15.

  The cylindrical molding tube 11 is rotated in the direction of the rotation of the cylindrical molding tube (arrow D), and the coating liquid 16 (inner layer coating liquid) is discharged from the nozzle 15 onto the outer peripheral surface of the cylindrical molding pipe 11. Level on the outer peripheral surface of the molded tube 11. The nozzle 15 and the blade 18 move at a constant speed in the nozzle and blade movement direction (arrow E), and the coating liquid 16 is applied on the outer peripheral surface of the cylindrical tube 11 with a constant thickness. The coating liquid 16 is adjusted so that a predetermined amount is discharged from the nozzle 15 by the pressurizing device 17. As a result, a coating film of the coating liquid 16 is formed on the outer peripheral surface of the cylindrical tube 11.

  Next, the inner layer coating film 122A applied to the cylindrical tube 11 is dried. The main drying is preferably performed so that the residual solvent amount of the inner layer coating film 122A is 50% by weight or less, particularly 25% or less, desirably 20% or less, and more desirably 16% or less. If the amount of residual solvent in the inner layer coating film 122A is too large, uneven distribution (increase in density) of the conductive particles 124 described later is difficult to occur. On the other hand, as the residual solvent amount is lower, uneven distribution (increase in density) of conductive particles 124 described later is more likely to occur. By controlling the residual solvent amount of the inner layer coating film 122A, that is, the drying state of the inner layer coating film 122A, the degree of uneven distribution (concentration) of conductive particles 124 described later is controlled, and in the obtained transfer belt 120 Position control in the thickness direction of the region where the conductive particles 124 are unevenly distributed (conductive point unevenly distributed region 124A) is also performed.

  Here, the residual solvent amount indicates the ratio of the solvent weight present in the coating liquid to be applied to the solid content (the weight of the solid content of the resin material + the weight of the conductive particles). The method for obtaining the residual solvent amount is as follows.

  For example, when the weight of the solid content of the resin material (dry weight of the resin material) and the weight of the conductive particles are known as the solid content, the total weight of the coating film before drying is accurately weighed, and the coating film The weight of the solvent contained in the total weight of is calculated. Thereafter, the total weight of the coating film after drying is accurately weighed, and the weight of the solvent disappeared from the weight of the solvent calculated before drying is subtracted as the weight of the solvent that has lost the decrease. Find the weight. From this, the weight of residual solvent / (weight of conductive particles + weight of resin solids + weight of residual solvent) is calculated, and the amount of residual solvent is obtained.

  Further, the residual solvent amount may be obtained using a heat extraction gas chromatogram mass spectrometer. An example of this measurement is shown below. For example, a sample is obtained by cutting out from about 2 mg to 3 mg from the dried coating film, and the sample is weighed and then placed in a heat extraction device (PY2020D: manufactured by Frontier Laboratories) and heated to 400 ° C. Volatile components are injected into a gas chromatogram mass spectrometer (GCMS-QP2010: manufactured by Shimadzu Corporation) through an interface at 320 ° C. and quantified. That is, using helium gas as a carrier gas, 1/51 of the amount volatilized from the sample (split ratio 50: 1) is linear velocity 153.8 cm / sec (carrier gas flow rate 1.50 ml / min at column temperature 50 ° C., pressure 50 kPa), and is injected into a column (frontier lab capillary column UA-5) having an inner diameter of 0.25 μmφ × 30 m. Subsequently, after maintaining at 50 ° C. for 3 minutes, the column was heated to 400 ° C. at a rate of 8 ° C. per minute and held at the same temperature for 10 minutes to desorb volatile components. Further, a volatile component is injected into the mass spectrometer at an interface temperature of 320 ° C., and a peak area corresponding to the solvent is obtained. The quantification was performed by preparing a calibration curve in advance with a known amount of the same solvent. The solvent weight determined from this is divided by the sample weight after drying to determine the residual solvent amount. However, the above measurement example is an example, and the measurement conditions may be changed depending on the decomposition or changing temperature of the resin used or the boiling point of the solvent.

  Next, as shown in FIG. 7 (B), an outer layer coating solution containing conductive particles 124, a resin material, and a solvent is prepared, and this is formed and dried on the cylindrical molded tube 11 to form an inner layer coating film. It is applied to 122A to form an outer layer coating film 121A of the coating solution. In the area where the outer layer coating film 121A is applied, the solvent of the outer layer coating film 121A penetrates into the dried inner layer coating film 122A, and the area under the coating surface of the inner layer coating film 122A is swollen. At this time, the solvent amount of the outer layer coating film 121A existing on the coating surface of the inner layer coating film 122A is larger than the region under the coating surface of the inner layer coating film 122A, that is, the solvent concentration becomes higher. Therefore, it is easy to elute and move to the outer layer coating film 121A existing on the coating surface of the inner layer coating film 122A.

  Then, as shown in FIG. 7C, since the conductive particles 124 do not elute into the solvent of the outer layer coating film 121A, when the resin material elutes, in the region where the resin material elutes, other regions In comparison with the above, the density of the conductive particles 124 increases as the resin material is eluted. As a result, a region where the conductive particles 124 are unevenly distributed is formed. In FIG. 7, reference numeral 124B denotes a region where the conductive particles 124 are unevenly distributed.

  The coating method of the outer layer coating liquid onto the inner layer coating film 122A formed and dried on the cylindrical tube 11 is the same as the inner layer coating liquid.

  Next, as shown in FIG. 7D, the outer layer coating film 121A applied to the surface of the inner layer coating film 122A is dried. In the main drying, for example, the residual solvent amount is preferably 10% or less. The amount of residual solvent is determined from the type of resin material used, the intended use of the resulting transfer belt, the strength and maintainability of the resulting transfer belt, and the like.

  Due to the main drying, in the region between the region where the conductive particles 124 are unevenly distributed and the outer layer coating film 121A, the resin material eluted in the solvent of the impregnated outer layer coating solution also dries the outer layer coating film 121A. Thus, the resin material is deposited, and this is formed in a layer form on the region where the conductive particles 124 are unevenly distributed. At this time, the region between the region in which the conductive particles 124 are unevenly distributed and the outer layer coating film 121A is a region that is included in a smaller amount than the other regions because the conductive particles 124 are unevenly distributed. However, since the area is thin relative to the thickness of the entire belt, a decrease in conductivity in the area can be ignored. Specifically, if the thickness of the outer layer is equal to or greater than the thickness of the inner layer, the surface resistance of the outer layer is not easily affected. The thickness of the region containing less conductive particles 124 than other regions is preferably about 1 μm to 5 μm.

Then, when the region where the conductive particles 124 are unevenly distributed is dried, a conductive point uneven region 124A where the conductive particles 124 serving as conductive points are unevenly formed is formed.
When the outer layer coating film 121A is thicker than the inner layer coating film 122A, the total energy applied to the outer layer coating film 121A is preferably larger than the total energy applied to the inner layer coating film 122A. Specifically, for example, if the drying temperature is the same, the drying time of the outer layer coating film 121A may be longer than that of the inner layer coating film 122A. Thereby, since the solvent of the inner layer coating film 122A is dried through the outer layer coating film 121A, the inner layer coating film 122A and the outer layer coating film 121A are simultaneously dried.

  Here, when a resin precursor (polyamic acid solution) typified by a polyimide resin or the like is used as the resin material, the transfer belt 120 is manufactured by performing baking after drying the elution solvent 123. In order to perform this baking, that is, to convert the polyamic acid into an imide, a high temperature treatment of 200 ° C. or more is generally used. Sufficient imide conversion cannot be obtained at 200 ° C. or lower. On the other hand, high-temperature treatment is advantageous for imide conversion, and stable characteristics can be obtained.However, since heat energy is used, the thermal efficiency is low and the cost is high, so the heat treatment temperature is set in consideration of the characteristics and productivity of the transfer belt. It is necessary to decide.

  Through the above steps, the transfer belt according to the present embodiment is manufactured.

  Hereinafter, a method for manufacturing a transfer belt according to another embodiment will be described. 9 and 10 are process diagrams showing a transfer belt manufacturing method according to another embodiment.

  In another method of manufacturing the transfer belt 120 according to the present embodiment, first, an outer layer coating solution containing conductive particles 124, a resin material, and a solvent is prepared. And as shown to FIG. 9 (A), the coating liquid for outer layers is apply | coated to the internal peripheral surface of the cylindrical forming pipe 11, and the coating film 121A for outer layers of the said coating liquid is formed.

  The method for applying the outer layer coating liquid onto the cylindrical tube 11 is not particularly limited. For example, the outer layer coating film 121 </ b> A is formed in an endless manner using a method such as spin coating on the inner peripheral surface. In forming the belt, it is preferable to perform mold release treatment.

  As a specific example of a method for applying the outer layer coating liquid onto the cylindrical tube 11, a spin coating method will be described. In the spin coating method, as shown in FIG. 11, for example, a cylindrical forming tube 11 having an inner diameter corresponding to the length of the transfer belt 120 is prepared. A nozzle 15 for discharging the coating liquid 16 onto the inner peripheral surface of the cylindrical molded tube 11 is disposed at a position along the inner peripheral surface of the cylindrical molded tube 11, and the nozzle 15 is connected to the coating liquid container 14 through the pipe. Further, the coating solution container 14 is connected to the pressurizing device 17 through a pipe. A blade 18 for leveling the discharged coating liquid 16 on the inner peripheral surface of the cylindrical tube 11 is disposed below the nozzle 15.

  The cylindrical molding tube 11 is rotated in the direction of the rotation of the cylindrical molding tube (arrow D), and the coating liquid 16 (outer layer coating liquid) is discharged from the nozzle 15 onto the inner peripheral surface of the cylindrical molding pipe 11. Leveling on the inner peripheral surface of the cylindrical molded tube 11. The nozzle 15 and the blade 18 move at a constant speed in the nozzle and blade moving direction (arrow E), and the coating liquid 16 is applied on the inner peripheral surface of the cylindrical tube 11 with a constant thickness. The coating liquid 16 is adjusted so that a predetermined amount is discharged from the nozzle 15 by the pressurizing device 17. As a result, a coating film of the coating liquid 16 is formed on the inner peripheral surface of the cylindrical tube 11.

  Next, the outer layer coating film 121 </ b> A applied to the cylindrical tube 11 is dried. In this drying, there is no restriction | limiting in particular about the residual solvent amount of the coating film 121A for outer layers, You may exceed the said residual solvent amount 25%. Note that in the case where it is better not to form a conductive point unevenly distributed region in the outer layer 121 to be formed, it is preferable to dry so that the residual solvent amount exceeds 25%.

Next, as shown in FIG. 9B, an outer layer coating solution containing conductive particles 124, a resin material, and a solvent is prepared, and this is formed and dried on the cylindrical molded tube 11. It is applied to 121A to form an inner layer coating film 122A of the coating solution.
Further, as the method for applying the inner layer coating liquid onto the cylindrical tube 11, the coating methods mentioned in the outer layer coating liquid coating method including the conductive particles 124 and the resin material are used.

  Next, the inner layer coating film 122A applied to the cylindrical tube 11 is dried. In the main drying, as described above, the residual solvent amount of the inner layer coating film 122A is preferably 50% by weight or less, particularly 25% or less, desirably 20% by weight or less, and more desirably 16% by weight. % Or less.

  Next, as shown in FIG. 9C, an elution solvent 123 for elution of the resin material is applied to the surface (inner peripheral surface) of the dried inner layer coating film 122A. In the region where the elution solvent 123 is applied, the elution solvent 123 penetrates into the dried inner layer coating film 122A, and the region under the coating surface of the inner layer coating film 122A is swollen. At this time, the solvent amount of the elution solvent 123 present on the coating surface of the inner layer coating film 122A is larger than the region under the coating surface of the inner layer coating film 122A, that is, the solvent concentration becomes higher. The elution becomes easier to move to the elution solvent 123 side present on the coating surface of the inner layer coating film 122A.

  Then, as shown in FIG. 10D, since the conductive particles 124 are not eluted into the elution solvent 123, when the resin material is eluted, the region where the resin material is eluted is compared with the other regions. As a result, the density of the conductive particles 124 increases as the resin material is eluted. As a result, a region where the conductive particles 124 are unevenly distributed is formed. In FIG. 10, reference numeral 124B denotes a region where the conductive particles 124 are unevenly distributed.

  Here, the elution solvent 123 is a solvent for eluting the resin material. For this reason, the elution solvent is selected from solvents that dissolve the resin material. Here, dissolving the resin material means that the saturation solubility of the resin material with respect to the solvent at 25 ° C. is 10 wt% or more.

  As the elution solvent, it is preferable to apply the same type of solvent as the solvent contained in the inner layer coating solution. For example, when a polyamic acid solution is used as a coating solution, a polar solvent can be used, and for example, N, N-dialkylamides are desirable. Specifically, for example, N, N-dimethyl having a low molecular weight can be used. Formamide, N, N-dimethylacetamide, N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethyl sulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine, Examples include tetramethylene sulfone and dimethyltetramethylene sulfone. These may be used singly or in combination.

Moreover, the application amount of the elution solvent 123 is, for example, 0.001 g / cm ² or more and 1 g / cm ² or less, desirably 0.01 g / cm ² or more and 1 g / cm ² or less, more desirably 0.01 g. / Cm ² or more and 0.5 g / cm ² or less.

  In addition, as a method for applying the elution solvent 123, the application method described in the method for applying the outer layer coating liquid containing the conductive particles 124 and the resin material is used.

  Next, as shown in FIG. 10E, the elution solvent 123 applied to the surface (inner peripheral surface) of the inner layer coating film 122A is dried. In the main drying, for example, the residual solvent amount is preferably 10% or less. The amount of residual solvent is determined from the type of resin material used, the intended use of the resulting transfer belt, the strength and maintainability of the resulting transfer belt, and the like.

  Since the elution solvent 123 contains the resin material eluted as described above, the resin material is precipitated by drying the elution solvent 123, and the conductive particles 124 are unevenly distributed. A layer is formed on the region. At this time, the applied elution solvent 123 is an area where the conductive particles 124 are unevenly distributed, so that the area is thinner than the other areas. However, the area is thinner than the entire belt thickness. Therefore, the decrease in conductivity in the region can be ignored.

  Here, when a resin precursor (polyamic acid solution) typified by a polyimide resin or the like is used as the resin material, the transfer belt 120 is manufactured by performing baking after drying the elution solvent 123. In order to perform this baking, that is, to convert the polyamic acid into an imide, a high temperature treatment of 200 ° C. or more is generally used. Sufficient imide conversion cannot be obtained at 200 ° C. or lower. On the other hand, high-temperature treatment is advantageous for imide conversion, and stable characteristics can be obtained.However, since heat energy is used, the thermal efficiency is low and the cost is high, so the heat treatment temperature is set in consideration of the characteristics and productivity of the transfer belt. It is necessary to decide.

  Through the above steps, another transfer belt according to this embodiment is manufactured.

(Transfer unit)
FIG. 12 is a schematic perspective view showing a transfer unit according to the present embodiment. As shown in FIG. 12, the transfer unit 130 according to the present embodiment includes the transfer belt 120 according to the embodiment, and the transfer belt 120 is tensioned by a drive roll 131 and a driven roll 132 that are arranged to face each other. It is stretched in a state (hereinafter, simply referred to as “stretch”). Although not shown, a roll for primary transfer of the toner image on the surface of the photosensitive member (image holding member) onto the transfer belt 120 and a toner image transferred onto the transfer belt 120 are further added to the recording medium. A roll for the next transfer is arranged. The number of rolls around which the transfer belt 120 is stretched is not limited, and may be arranged according to the usage mode. The transfer unit 130 having such a configuration is used by being incorporated in an image forming apparatus. During image formation, the transfer belt 120 rotates while the drive roll 131 and the driven roll 132 rotate.

(Image forming device)
FIG. 13 is a schematic configuration diagram illustrating an image forming apparatus according to the present embodiment.

  The image forming apparatus 100 according to the present embodiment is a so-called tandem system, and is a form in which the transfer belt according to the present embodiment is applied as an intermediate transfer belt.

  As shown in FIG. 13, the image forming apparatus 100 according to the present embodiment sequentially includes charging devices 102 a to 102 d, around the four image holding bodies 101 a to 101 d made of an electrophotographic photosensitive member, in the rotation direction. Exposure devices 114a to 114d, developing devices 103a to 103d, primary transfer devices (primary transfer rolls) 105a to 105d, and image carrier cleaning devices 104a to 104d are arranged. Note that a static eliminator may be provided in order to remove residual potential remaining on the surfaces of the image carriers 101a to 101d after transfer.

  Further, an intermediate transfer belt 107 is stretched around tension rolls 106a to 106d, a drive roll 111, and a backup roll 108 to constitute a transfer unit. By these tension rolls 106a to 106d, the drive roll 111, and the backup roll 108, the intermediate transfer belt 107 is in contact with the surfaces of the image carriers 101a to 101d, and the image carriers 101a to 101d and the primary transfer rolls 105a to 105a. It can move in the direction of arrow A between 105d. A portion where the primary transfer rolls 105a to 105d come into contact with the image carriers 101a to 101d via the intermediate transfer belt 107 becomes a primary transfer portion, and a contact portion between the image carriers 101a to 101d and the primary transfer rollers 105a to 105d. A primary transfer voltage is applied to.

  Further, as a secondary transfer device, a backup roll 108 and a secondary transfer roll 109 are arranged to face each other with an intermediate transfer belt 107 interposed therebetween. The transfer medium 115 such as paper moves in the direction of arrow B between the intermediate transfer belt 107 and the secondary transfer roll 109 while contacting the surface of the intermediate transfer belt 107, and then passes through the fixing device 110. A portion where the secondary transfer roll 109 comes into contact with the backup roll 108 via the intermediate transfer belt 107 becomes a secondary transfer portion, and a secondary transfer voltage is applied to a contact portion between the secondary transfer roll 109 and the backup roll 108. . Further, intermediate transfer belt cleaning devices 112 and 113 are arranged so as to come into contact with the intermediate transfer belt 107 after transfer.

  In the full-color image forming apparatus 100 having this configuration, the image carrier 101a rotates in the direction of the arrow C and the surface thereof is uniformly charged by the charging device 102a, and then the first color is applied by the exposure device 114a such as laser light. Electrostatic latent image is formed. The formed electrostatic latent image is developed (visualized) with toner by a developing device 103a containing toner corresponding to the color to form a toner image. The developing devices 103a to 103d contain toners (for example, yellow, magenta, cyan, and black) corresponding to the electrostatic latent images of the respective colors.

  The toner image formed on the image carrier 101a is electrostatically transferred (primary transfer) onto the intermediate transfer belt 107 by the primary transfer roll 105a when passing through the primary transfer portion. Thereafter, the primary transfer rollers 105b to 105d perform primary transfer so that the second color, third color, and fourth color toner images are sequentially superimposed on the intermediate transfer belt 107 that holds the first color toner image. Finally, a full color multiple toner image is obtained.

  The multiple toner images formed on the intermediate transfer belt 107 are electrostatically collectively transferred to the transfer medium 115 when passing through the secondary transfer portion. The transfer medium 115 onto which the toner image has been transferred is conveyed to the fixing device 110, subjected to a fixing process by heating and / or pressing, and then discharged outside the apparatus.

  Residual toner is removed from the image carriers 101a to 101d after the primary transfer by the image carrier cleaning devices 104a to 104d. On the other hand, the residual toner is removed from the intermediate transfer belt 107 after the secondary transfer by the intermediate transfer belt cleaning devices 112 and 113 to prepare for the next image forming process.

(Image carrier)
As the image carriers 101a to 101d, known electrophotographic photosensitive members can be widely applied. As the electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer made of an inorganic material, an organic photoreceptor having a photosensitive layer made of an organic material, or the like can be used. In the organic photoconductor, a function-separated type organic photoconductor in which a charge generation layer that generates charges upon exposure and a charge transport layer that transports charges are stacked, and a function that generates charges and a function that transports charges are the same. A single layer type organic photoreceptor fulfilled by the layer is preferably used. In addition, as the inorganic photoconductor, a photoconductive layer composed of amorphous silicon is preferably used.

  The shape of the image carrier is not particularly limited, and a known shape such as a cylindrical drum shape, a sheet shape, or a plate shape is employed.

[Charging device]
The charging devices 102a to 102d are not particularly limited, and are, for example, conductive (here, “conductive” means, for example, a volume resistivity of less than 10 ⁷ Ω · cm. In this specification, special mention is made. The same is true unless otherwise specified.) Or semiconductive (here, “semiconductive” means, for example, a volume resistivity of 10 ⁷ to 10 ¹³ Ωcm. In this specification, the same applies unless otherwise specified. .) Can be widely applied to a contact charger using a roller, brush, film, rubber blade, or the like, a scorotron charger using a corona discharge, or a corotron charger. Among these, a contact charger that generates less ozone and can perform efficient charging is preferable.

  The charging devices 102a to 102d normally apply a direct current to the image carriers 101a to 101d, but an alternating current may be further superimposed and applied.

[Exposure equipment]
The exposure devices 114a to 114d are not particularly limited, and for example, on the surfaces of the image carriers 101a to 101d, light sources such as semiconductor laser light, LED light, or liquid crystal shutter light, or from these light sources through a polygon mirror. A known exposure apparatus such as an optical system apparatus that can perform exposure in a desired image manner can be widely applied.

[Development equipment]
The developing devices 103a to 103d can be selected according to the purpose. For example, a known developing device that develops a one-component developer or a two-component developer in contact or non-contact with a brush, a roller, or the like can be used.

  The toner (developer) used in the image forming apparatus 100 of the present embodiment is not particularly limited, and includes, for example, a binder resin and a colorant.

[Primary transfer roll]
The primary transfer rolls 105a to 105d may be either a single layer or a multilayer. For example, in the case of a single layer structure, it is composed of a roll in which an appropriate amount of conductive particles such as carbon black is blended in foamed or non-foamed silicone rubber, urethane rubber, ethylene-propylene-diene rubber (EPDM), or the like. The resistance value is preferably in the range of 10 ⁵ Ω to 10 ¹⁰ Ω. A voltage of 1.0 kV to 5.5 kV is applied to the primary transfer rolls 105a to 105d, and the toner is transferred by an electric field generated between the image carriers 101a to 101d.

[Image carrier cleaning device]
The image carrier cleaning devices 104a to 104d are for removing residual toner adhering to the surfaces of the image carriers 101a to 101d after the primary transfer process. In addition to the cleaning blade, brush cleaning, roll cleaning, or the like Can be used. Among these, it is preferable to use a cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

[Secondary transfer roll]
The layer structure of the secondary transfer roll 109 is not particularly limited. For example, in the case of a three-layer structure, the layer structure includes a core layer, an intermediate layer, and a coating layer covering the surface. The core layer is a foamed material such as silicone rubber, urethane rubber or EPDM in which conductive particles are dispersed, and the intermediate layer is composed of these non-foamed materials. Examples of the material for the coating layer include tetrafluoroethylene-hexafluoropropylene copolymer and perfluoroalkoxy resin. The volume resistivity of the secondary transfer roll 109 is preferably 10 ⁷ Ωcm or less. A two-layer structure excluding the intermediate layer is also possible.

[Backup roll]
The backup roll 108 forms a counter electrode of the secondary transfer roll 109. The layer structure of the backup roll 108 may be either a single layer or a multilayer. For example, in the case of a single layer structure, it is composed of a roll in which a suitable amount of conductive particles such as carbon black is blended in silicone rubber, urethane rubber, EPDM or the like. In the case of a two-layer structure, it is composed of a roll in which the outer peripheral surface of the elastic layer composed of the rubber material as described above is covered with a high resistance layer. The surface resistivity of the backup roll 108 is preferably in the range of 10 ⁷ Ω / □ to 10 ¹¹ Ω / □.

  A voltage of 1 kV to 6 kV is normally applied between the shafts of the backup roll 108 and the secondary transfer roll 109. Further, instead of applying a voltage to the shaft of the backup roll 108, a voltage can be applied between the electrically conductive electrode member brought into contact with the backup roll 108 and the secondary transfer roll 109. Examples of the electrode member include a metal roll, a conductive rubber roll, a conductive brush, a metal plate, or a conductive resin plate.

[Fixing device]
As the fixing device 110, for example, a known fixing device such as a heat roller fixing device, a pressure roller fixing device, or a flash fixing device can be widely applied.

[Intermediate transfer belt cleaning device]
As the intermediate transfer belt cleaning devices 112 and 113, in addition to a cleaning blade, brush cleaning, roll cleaning, and the like can be used. Among these, it is preferable to use a cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

  In the above-described embodiment, a so-called tandem image forming apparatus including a plurality of image carriers has been described. However, the present invention is not limited to this. For example, one image carrier is used and intermediate transfer is performed for the number of colors. A well-known apparatus such as a so-called multi-cycle type (for example, four-cycle type) image forming apparatus in which the belt rotates and forms an image can be applied.

  Hereinafter, although an example and a comparative example are explained, the present invention is not limited to the following examples.

(Preparation of tubular body 1)
Carbon black is added to 100 parts by weight of NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (solid content ratio after imide conversion is 18 wt%). (Special Black 4: manufactured by Degussa) 80 parts by weight, and using a jet mill disperser (Geanus PY [minimum cross-sectional area of collision part 0.032 mm ² ]: manufactured by Genus) at a pressure of 200 MPa Was dispersed and mixed 5 times. An NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (with a solid content ratio after imide conversion) of the resulting dispersion 18 wt%) is added to 100 parts by weight of polyamic acid so that the amount of carbon black is 21 parts by weight, and mixed and stirred using a planetary mixer (Aiko mixer manufactured by Aikosha Seisakusho). A dispersed polyimide precursor solution was prepared.

  On the other hand, an aluminum cylindrical body having an outer diameter of 166 mm and a length of 650 mm was prepared as the cylindrical forming tube 11 shown in FIG. Such an aluminum cylinder is obtained by cutting the surface to an outer diameter of 189 mm and then roughening the surface to Ra: 1.52 μm by blasting with spherical glass particles. A silicone-based release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface of the cylindrical molded tube 11 and baked at 300 ° C. for 1 hour. Furthermore, as a spin coating process, as shown in FIG. 8, the cylindrical tube 11 was rotated at 40 rpm in the direction of arrow D with the axial direction horizontal. The blade 18 is made of SUS having a width of 20 mm and a thickness of 0.5 mm, and has elasticity. A blade 18 was pressed against the cylindrical forming tube 11, and the carbon black-dispersed polyimide precursor solution was used as the coating solution 16, and extruded from the coating solution container 14 through a nozzle 15 having a diameter of 2 mm. When the polyimide precursor solution passed through the blade 18, the blade 18 was spread and a gap was formed between the blade 18 and the cylindrical tube 11. Next, the nozzle 15 and the blade 18 were moved in the direction of arrow E at a speed of 120 mm / min. Next, the cylindrical forming tube 11 coated with the carbon black-dispersed polyimide precursor solution is kept horizontal and heated and dried at 145 ° C. for 18 minutes while rotating at 6 rpm to obtain a carbon black-dispersed polyimide precursor dry coating film for the inner layer. It was.

  In addition, the film thickness of the carbon black dispersion | distribution polyimide precursor dry coating film for inner layers adjusted the amount of extrusion liquids from the nozzle 15 at the time of application | coating so that the film thickness after the imidation shown later may become a desired value. Moreover, the residual NMP amount in the carbon black-dispersed polyimide precursor dry coating film for the inner layer was 24.9 wt%. The amount of residual NMP was calculated from the weight difference of the cylindrical molded tube 11 after drying from the weight of the cylindrical molded tube 11 after application of the inner layer coating film.

  Next, the carbon black-dispersed polyimide precursor solution for the outer layer is applied using the carbon black-dispersed polyimide precursor solution on the dried carbon black-dispersed polyimide precursor coating for the inner layer in the same manner as when the inner-layer coating film is applied. did. In applying the coating film for the outer layer, the carbon black-dispersed polyimide precursor solution for the outer layer was applied with a slight shift from the coating area for the inner layer so that a region where the inner layer and the outer layer each became a single layer was obtained. Then, it was left for 20 minutes.

  Next, while the cylindrical tube 11 coated with the carbon black-dispersed polyimide precursor solution for the outer layer is kept horizontal and rotated at 6 rpm, it is heated and dried at 145 ° C. for 18 minutes in the same manner as the inner-layer coating film. A precursor dry coating film was obtained. In addition, the film thickness of the carbon black dispersion polyimide precursor dry coating film for outer layers adjusted the amount of extrusion liquid from the nozzle 15 at the time of application | coating so that the film thickness after the imidation shown later may become a desired value.

  The cylindrical formed tube 11 obtained by laminating the carbon black-dispersed polyimide precursor dry coating film for the outer layer on the obtained carbon black-dispersed polyimide precursor dry coating film for the inner layer was heated at 200 ° C. for 30 minutes, 260 ° C. for 30 minutes, 300 A carbon black-dispersed polyimide film was formed by heating at 320 ° C. for 30 minutes and at 320 ° C. for 20 minutes. Thereafter, when the temperature of the cylindrical molded tube 11 was cooled to room temperature, the polyimide resin film was peeled from the cylindrical molded tube 11. The center part of the obtained polyimide resin film was cut | disconnected by the width | variety of 369 mm, and the tubular body 1 was obtained.

  Next, when the film thickness of the region where the inner layer and the outer layer were formed as described above was measured, the inner layer was 50.1 μm and the outer layer was 50.5 μm. For the measurement of the film thickness, both the inner layer and the outer layer were measured at 20 points in the circumferential direction to obtain an average value. Moreover, when the volume resistivity of the obtained tubular body 1 was measured, it was 12.5 LogΩ · cm. The volume resistivity was measured at an applied voltage of 500 V, and 20 points in the circumferential direction of the tubular body 1, 4 points in the direction perpendicular to the circumferential direction, and 80 points in total were measured to obtain an average value.

(Production of tubular bodies 2 to 7)
In preparation of the tubular body 1, the drying time after coating the inner layer coating film and the outer layer coating film, and the film thickness after imidization of the inner layer coating film and the outer layer coating film were set to values shown in Table 1, respectively. Produced tubular bodies 2 to 7 in the same manner as the tubular body 1. Table 1 shows the amount of residual NMP and the volume resistivity after drying the inner layer coating of the tubular bodies 2-7.

(Production of tubular body 8)
Carbon black is added to 100 parts by weight of NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (solid content ratio after imide conversion is 18 wt%). (Special Black 4: manufactured by Degussa) 80 parts by weight, and using a jet mill disperser (Geanus PY [minimum cross-sectional area of collision part 0.032 mm ² ]: manufactured by Genus) at a pressure of 200 MPa Was dispersed and mixed 5 times. An NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (with a solid content ratio after imide conversion) of the resulting dispersion 18 wt%) is added so that carbon black is 23.0 parts by weight with respect to 100 parts by weight of polyamic acid, and mixed and stirred using a planetary mixer (Aiko mixer manufactured by Aikosha Seisakusho). A carbon black-dispersed polyimide precursor solution for the inner layer was prepared.

  On the other hand, an aluminum cylindrical body having an outer diameter of 166 mm and a length of 650 mm was prepared as the cylindrical forming tube 11 shown in FIG. Such an aluminum cylinder is obtained by cutting the surface to an outer diameter of 189 mm and then roughening the surface to Ra: 1.52 μm by blasting with spherical glass particles. A silicone-based release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface of the cylindrical molded tube 11 and baked at 300 ° C. for 1 hour. Furthermore, as a spin coating process, as shown in FIG. 8, the cylindrical tube 11 was rotated at 40 rpm in the direction of arrow D with the axial direction horizontal. The blade 18 is made of SUS having a width of 20 mm and a thickness of 0.5 mm, and has elasticity. A blade 18 was pressed against the cylindrical forming tube 11, and the carbon black-dispersed polyimide precursor solution was used as the coating solution 16, and extruded from the coating solution container 14 through a nozzle 15 having a diameter of 2 mm. When the polyimide precursor solution passed through the blade 18, the blade 18 was spread and a gap was formed between the blade 18 and the cylindrical tube 11. Next, the nozzle 15 and the blade 18 were moved in the direction of arrow E at a speed of 120 mm / min. Next, the cylindrical forming tube 11 coated with the inner layer carbon black-dispersed polyimide precursor solution is heated and dried at 145 ° C. for 32 minutes while rotating at 6 rpm while being horizontal, and the inner layer carbon black-dispersed polyimide precursor dried coating film Got.

  In addition, the film thickness of the carbon black dispersion | distribution polyimide precursor dry coating film for inner layers adjusted the amount of extrusion liquids from the nozzle 15 at the time of application | coating so that the film thickness after the imidation shown later may become a desired value. Moreover, the residual NMP amount in the carbon black-dispersed polyimide precursor dry coating film for the inner layer was 11.3 wt%. The residual NMP amount was calculated from the difference in the weight of the cylindrical molded tube 11 after drying from the weight of the cylindrical molded tube 11 after application of the inner layer coating film.

  Next, an NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (solid content ratio after imide conversion) 18 wt%) is added so that carbon black is 19 parts by weight with respect to 100 parts by weight of polyamic acid, and the outer layer is mixed and stirred using a planetary mixer (Aiko mixer manufactured by Aikosha Seisakusho). A carbon black-dispersed polyimide precursor solution was prepared. The obtained carbon black-dispersed polyimide precursor solution for the outer layer was applied onto the dried carbon black-dispersed polyimide precursor coating film for the inner layer in the same manner as when the inner layer coating film was applied. In applying the coating film for the outer layer, the carbon black-dispersed polyimide precursor solution for the outer layer was applied with a slight shift from the coating area for the inner layer so that a region where the inner layer and the outer layer each became a single layer was obtained. Then, it was left for 20 minutes.

  Next, the cylindrical formed tube 11 coated with the carbon black-dispersed polyimide precursor solution for the outer layer is kept horizontal and heated and dried at 145 ° C. for 32 minutes while rotating at 6 rpm, and the carbon black-dispersed polyimide for the outer layer. A precursor dry coating film was obtained. In addition, the film thickness of the carbon black dispersion polyimide precursor dry coating film for outer layers adjusted the amount of extrusion liquid from the nozzle 15 at the time of application | coating so that the film thickness after the imidation shown later may become a desired value.

  The cylindrical formed tube 11 obtained by laminating the carbon black-dispersed polyimide precursor dry coating film for the outer layer on the obtained carbon black-dispersed polyimide precursor dry coating film for the inner layer was heated at 200 ° C. for 30 minutes, 260 ° C. for 30 minutes, 300 A carbon black-dispersed polyimide film was formed by heating at 320 ° C. for 30 minutes and at 320 ° C. for 20 minutes. Thereafter, when the temperature of the cylindrical molded tube 11 was cooled to room temperature, the polyimide resin film was peeled from the cylindrical molded tube 11. The central part of the obtained polyimide resin film was cut at a width of 369 mm, and a tubular body 8 was obtained.

  Next, when the film thickness of the region where the inner layer and the outer layer were formed as described above was measured, the inner layer was 50.8 μm and the outer layer was 50.1 μm. Further, the volume resistivity was measured and found to be 12.5 LogΩ · cm. The volume resistivity was measured at an applied voltage of 500 V, and 20 points in the circumferential direction of the annular body 8, 4 points in the direction perpendicular to the circumferential direction, and 80 points in total were measured to obtain an average value.

(Production of tubular body 9)
In preparation of the tubular body 1, the drying time after coating the inner layer coating film and the outer layer coating film, and the film thickness after imidization of the inner layer coating film and the outer layer coating film were set to values shown in Table 1, respectively. Produced a tubular body 9 in the same manner as the tubular body 1. Table 1 shows the amount of residual NMP and the volume resistivity after drying the inner layer coating film of the tubular body 9.

(Production of tubular bodies 10-11)
In preparation of the tubular body 8, the drying time after coating the inner layer coating film and the outer layer coating film, and the film thickness after imidization of the inner layer coating film and the outer layer coating film were set to values shown in Table 1, respectively. Produced tubular bodies 10 to 11 in the same manner as the tubular body 8. Table 1 shows the amount of residual NMP and the volume resistivity after drying the inner layer coating of the tubular bodies 10-11.

(Production of tubular body 12)
Carbon black is added to 100 parts by weight of NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (solid content ratio after imide conversion is 18 wt%). (Special Black 4: manufactured by Degussa) 80 parts by weight, and using a jet mill disperser (Geanus PY [minimum cross-sectional area of collision part 0.032 mm ² ]: manufactured by Genus) at a pressure of 200 MPa Was dispersed and mixed 5 times. An NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (with a solid content ratio after imide conversion) of the resulting dispersion 18 wt%) is added to 100 parts by weight of polyamic acid so that the amount of carbon black is 21 parts by weight, and mixed and stirred using a planetary mixer (Aiko mixer manufactured by Aikosha Seisakusho). A dispersed polyimide precursor solution was prepared.

  On the other hand, an aluminum cylindrical body having an inner diameter of 166 mm and a length of 650 mm was prepared as the cylindrical forming tube 11 shown in FIG. The aluminum cylinder was coated with a silicone mold release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) on the inner peripheral surface of the cylindrical tube 11 and baked at 300 ° C. for 1 hour. Furthermore, as a spin coating process, as shown in FIG. 11, the cylindrical tube 11 was rotated at 40 rpm in the direction of arrow D with the axial direction horizontal. The blade 18 is made of SUS having a width of 20 mm and a thickness of 0.5 mm, and has elasticity. A blade 18 was pressed against the inner surface of the cylindrical tube 11, and the carbon black-dispersed polyimide precursor solution was used as the coating liquid 16 and was extruded from the coating liquid container 14 through a nozzle 15 having a diameter of 2 mm. When the polyimide precursor solution passed through the blade 18, the blade 18 was spread and a gap was formed between the blade 18 and the inner surface of the cylindrical tube 11. Next, the nozzle 15 and the blade 18 were moved in the direction of arrow E at a speed of 120 mm / min. Next, the cylindrical molded tube 11 coated with the carbon black-dispersed polyimide precursor solution is kept horizontal and heated and dried at 145 ° C. for 18 minutes while rotating at 6 rpm to obtain a carbon black-dispersed polyimide precursor dry coating film for the outer layer. It was.

  In addition, the film thickness of the carbon black dispersion polyimide precursor dry coating film for outer layers adjusted the amount of extrusion liquid from the nozzle 15 at the time of application | coating so that the film thickness after the imidation shown later may become a desired value. Moreover, the residual NMP amount in the carbon black-dispersed polyimide precursor dry coating film for the outer layer was 22 wt%. The residual NMP amount was calculated from the difference in the weight of the cylindrical molded tube 11 after drying from the weight of the cylindrical molded tube 11 after application of the outer layer coating film.

  Next, the carbon black-dispersed polyimide precursor solution for the inner layer is applied using the carbon black-dispersed polyimide precursor solution on the dried carbon black-dispersed polyimide precursor coating for the outer layer in the same manner as the coating of the outer layer. did. When applying the inner layer coating film, the outer layer carbon black-dispersed polyimide precursor solution was applied with a slight shift from the inner layer coating film application region so that a region where the outer layer and the outer layer each became a single layer was obtained.

  Next, while the cylindrical tube 11 coated with the carbon black-dispersed polyimide precursor solution for the inner layer is kept horizontal and rotated at 6 rpm, it is heated and dried at 145 ° C. for 18 minutes in the same manner as the outer-layer coating film. A precursor dry coating film was obtained. In addition, the film thickness of the carbon black dispersion | distribution polyimide precursor dry coating film for inner layers adjusted the amount of extrusion liquids from the nozzle 15 at the time of application | coating so that the film thickness after the imidation shown later may become a desired value. Moreover, the residual NMP amount in the carbon black-dispersed polyimide precursor dry coating film for the inner layer was 25.0 wt%. The residual NMP amount was calculated from the difference in the weight of the cylindrical molded tube 11 after drying from the weight of the cylindrical molded tube 11 after application of the inner layer coating film.

Next, NMP was applied on the carbon black-dispersed polyimide precursor dried coating film for the inner layer in the same manner as the coating for the outer layer and the coating film for the inner layer (coating amount 0.1 g / cm ² ). Then, it was left for 20 minutes.

  Next, on the carbon black-dispersed polyimide precursor dry coating film for the inner layer, the cylindrical formed tube 11 coated with NMP is kept horizontal and heated and dried at 145 ° C. for 18 minutes while rotating at 6 rpm, A carbon black-dispersed polyimide precursor dry coating film for the inner layer was obtained.

  The cylindrical molded tube 11 obtained by laminating the carbon black-dispersed polyimide precursor dry coating film for the inner layer on the carbon black-dispersed polyimide precursor dry coating film for the outer layer was obtained at 300 ° C. for 30 minutes, 260 ° C. for 30 minutes, 300 A carbon black-dispersed polyimide film was formed by heating at 320 ° C. for 30 minutes and at 320 ° C. for 20 minutes. Thereafter, when the temperature of the cylindrical molded tube 11 was cooled to room temperature, the polyimide resin film was peeled from the cylindrical molded tube 11. The central part of the obtained polyimide resin film was cut at a width of 369 mm, and a tubular body 12 was obtained.

  Next, when the film thickness of the region where the inner layer and the outer layer were formed as described above was measured, the inner layer was 49.2 μm and the outer layer was 50.1 μm. For the measurement of the film thickness, both the inner layer and the outer layer were measured at 20 points in the circumferential direction to obtain an average value. Moreover, when the volume resistivity of the obtained tubular body 12 was measured, it was 12.3 Log Ω · cm. The volume resistivity was measured at an applied voltage of 500 V, and 20 points in the circumferential direction of the tubular body 12, 4 points in the direction perpendicular to the circumferential direction, and 80 points in total were measured to obtain an average value.

(Production of tubular bodies 13 to 18)
In the production of the tubular body 12, the coating time for the inner layer, the coating time for the outer layer, the drying time after the NMP coating, and the film thickness after imidization of the inner layer coating and the outer layer coating are shown in Table 1. Tubular bodies 13 to 18 were produced in the same manner as the tubular body 12 except that the values shown in FIG. Table 1 shows the amount of residual NMP and the volume resistivity after drying the inner layer coating of the tubular bodies 13 to 18.

(Production of tubular body 19)
Carbon black is added to 100 parts by weight of NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (solid content ratio after imide conversion is 18 wt%). (Special Black 4: manufactured by Degussa) 80 parts by weight, and using a jet mill disperser (Geanus PY [minimum cross-sectional area of collision part 0.032 mm ² ]: manufactured by Genus) at a pressure of 200 MPa Was dispersed and mixed 5 times. An NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (with a solid content ratio after imide conversion) of the resulting dispersion 18 wt%) is added so that carbon black is 19 parts by weight with respect to 100 parts by weight of polyamic acid, and mixed and stirred using a planetary mixer (Aiko mixer manufactured by Aikosha Seisakusho) for outer layer use. A carbon black-dispersed polyimide precursor solution was prepared.

  On the other hand, an aluminum cylindrical body having an inner diameter of 166 mm and a length of 650 mm was prepared as the cylindrical forming tube 11 shown in FIG. Such an aluminum cylinder was coated with a silicone release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) on the inner surface of the cylindrical tube 11 and baked at 300 ° C. for 1 hour. Furthermore, as a spin coating process, as shown in FIG. 11, the cylindrical tube 11 was rotated at 40 rpm in the direction of arrow D with the axial direction horizontal. The blade 18 is made of SUS having a width of 20 mm and a thickness of 0.5 mm, and has elasticity. The blade 18 was pressed against the inner surface of the cylindrical tube 11, and the outer layer carbon black-dispersed polyimide precursor solution was used as the coating solution 16, and extruded from the coating solution container 14 through a nozzle 15 having a diameter of 2 mm. When the polyimide precursor solution passed through the blade 18, the blade 18 was spread and a gap was formed between the blade 18 and the inner surface of the cylindrical tube 11. Next, the nozzle 15 and the blade 18 were moved in the direction of arrow E at a speed of 120 mm / min. Next, the cylindrical molded tube 11 coated with the carbon black-dispersed polyimide precursor solution is kept horizontal and heated and dried at 145 ° C. for 18 minutes while rotating at 6 rpm to obtain a carbon black-dispersed polyimide precursor dry coating film for the outer layer. It was.

  In addition, the film thickness of the carbon black dispersion polyimide precursor dry coating film for outer layers adjusted the amount of extrusion liquid from the nozzle 15 at the time of application | coating so that the film thickness after the imidation shown later may become a desired value. Moreover, the amount of residual NMP in the carbon black-dispersed polyimide precursor dry coating film for the outer layer was 22.5 wt%. The residual NMP amount was calculated from the difference in the weight of the cylindrical molded tube 11 after drying from the weight of the cylindrical molded tube 11 after application of the outer layer coating film.

  Next, NMP of polyamic acid comprising 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether is obtained with respect to the obtained dispersion. A solution (solid content ratio after imide conversion is 18 wt%) is added so that carbon black is 23.0 parts by weight with respect to 100 parts by weight of polyamic acid, and a planetary mixer (Aiko mixer manufactured by Aikosha Seisakusho) Were mixed and stirred to prepare a carbon black-dispersed polyimide precursor solution for the inner layer.

  Next, in the same manner as when the outer layer coating film is applied, the inner layer carbon black dispersed polyimide precursor solution is used on the outer layer carbon black dispersed polyimide precursor dry coating film, and the inner layer carbon black dispersed polyimide precursor solution is used. Was applied. In applying the inner layer, the carbon black-dispersed polyimide precursor solution for the outer layer was applied with a slight shift from the coating layer for the inner layer so that a region where the outer layer and the outer layer each became a single layer was obtained.

  Next, while the cylindrical tube 11 coated with the carbon black-dispersed polyimide precursor solution for the inner layer is kept horizontal and rotated at 6 rpm, it is heated and dried at 145 ° C. for 25 minutes in the same manner as the outer-layer coating film. A precursor dry coating film was obtained. In addition, the film thickness of the carbon black dispersion | distribution polyimide precursor dry coating film for inner layers adjusted the amount of extrusion liquids from the nozzle 15 at the time of application | coating so that the film thickness after the imidation shown later may become a desired value. Moreover, the amount of residual NMP in the carbon black-dispersed polyimide precursor dry coating film for the inner layer was 15.2 wt%. The residual NMP amount was calculated from the difference in the weight of the cylindrical molded tube 11 after drying from the weight of the cylindrical molded tube 11 after application of the inner layer coating film.

Next, NMP was applied on the carbon black-dispersed polyimide precursor dried coating film for the inner layer in the same manner as the coating for the outer layer and the coating film for the inner layer (coating amount 0.1 g / cm ² ). Then, it was left for 20 minutes.

  Next, on the carbon black-dispersed polyimide precursor dry coating film for the inner layer, the cylindrical formed tube 11 coated with NMP is kept horizontal and heated and dried at 145 ° C. for 18 minutes while rotating at 6 rpm, A carbon black-dispersed polyimide precursor dry coating film for the inner layer was obtained.

  The cylindrical molded tube 11 obtained by laminating the carbon black-dispersed polyimide precursor dry coating film for the inner layer on the carbon black-dispersed polyimide precursor dry coating film for the outer layer was obtained at 300 ° C. for 30 minutes, 260 ° C. for 30 minutes, 300 A carbon black-dispersed polyimide film was formed by heating at 320 ° C. for 30 minutes and at 320 ° C. for 20 minutes. Thereafter, when the temperature of the cylindrical molded tube 11 was cooled to room temperature, the polyimide resin film was peeled from the cylindrical molded tube 11. The central part of the obtained polyimide resin film was cut with a width of 369 mm, and a tubular body 19 was obtained.

  Next, when the film thickness of the region where the inner layer and the outer layer were formed as described above was measured, the inner layer was 39.8 μm and the outer layer was 59.9 μm. For the measurement of the film thickness, both the inner layer and the outer layer were measured at 20 points in the circumferential direction to obtain an average value. The volume resistivity of the obtained tubular body 19 was measured and found to be 12.4 LogΩ · cm. The volume resistivity was measured at an applied voltage of 500 V, and 20 points in the circumferential direction of the tubular body 19, 4 points in the direction perpendicular to the circumferential direction, and 80 points in total were measured to obtain an average value.

(Production of tubular body 20)
In the production of the tubular body 12, the coating time for the inner layer, the coating time for the outer layer, the drying time after the NMP coating, and the film thickness after imidization of the inner layer coating and the outer layer coating are shown in Table 1. A tubular body 20 was produced in the same manner as the tubular body 12 except that the values shown in FIG. Table 1 shows the amount of residual NMP and the volume resistivity after drying of the inner layer coating film of the tubular body 20.

(Production of tubular bodies 21 to 22)
In the production of the tubular body 19, the drying time after coating the inner layer coating, after coating the outer layer coating and after applying the NMP, and the film thickness after imidization of the inner layer coating and the outer layer coating are shown in Table 1. The tubular bodies 21 to 22 were produced in the same manner as the tubular body 19 except that the values shown in FIG. Table 1 shows the amount of residual NMP and the volume resistivity after drying the inner layer coating of the tubular bodies 21 to 22.

[Specification of conductive point uneven distribution area]
(Specification of conductive point uneven distribution region of tubular body 1)
The surface resistivity of the outer peripheral surface of the outer layer of the tubular body 1 obtained in the production of the tubular body 1 was specified. Next, the inner peripheral surface of the inner layer of the measured location was polished with a polishing film (wrapping film # 2000 [A3-9SHT]: manufactured by Sumitomo 3M), and then the polishing film (wrapping film # 10000 [C3-0.5SHT] : Finished polishing by Sumitomo 3M Co.). When the film thickness after polishing was measured, the shaved film thickness was 0.2 μm. After polishing, the surface resistivity of the outer peripheral surface of the outer layer was measured again. Thereafter, polishing from the inner peripheral surface of the inner layer and measurement of the surface resistivity of the outer peripheral surface of the outer layer were repeated. FIG. 14 shows the measurement results of the polishing amount from the inner peripheral surface of the inner layer and the surface resistivity of the outer peripheral surface of the outer layer, that is, changes in the surface resistivity of the outer peripheral surface of the outer layer with respect to the polishing amount from the inner peripheral surface of the inner layer.

  It is considered that the current that flows when measuring the surface resistivity of the outer peripheral surface of the outer layer mainly flows through the inside of the outer layer and the conductive point uneven distribution region of the inner layer. For this reason, when polishing is performed from the inner peripheral surface of the inner layer, no change in surface resistivity due to polishing is observed on the inner peripheral surface side of the inner layer from the conductive point uneven distribution region. However, when the conductive point is unevenly distributed, the surface resistivity is increased because the current value required for the surface resistivity measurement is decreased. Therefore, the boundary position 1 on the inner peripheral surface side of the inner layer of the conductive point uneven distribution region is specified by the polishing amount that causes the change in the surface resistivity of the outer peripheral surface of the outer layer with respect to the polishing amount from the inner peripheral surface of the inner layer. Can do. FIG. 14 shows the boundary position 1 specified from the change point of the surface resistivity. The change point is specified as an intersection of an approximate line in a region where the surface resistivity does not change with respect to the polishing amount from the inner peripheral surface of the inner layer and an approximate line in a region where the change occurs. In the tubular body 1, the boundary position 1 was 42.3 μm.

  Next, the boundary position 2 on the outer peripheral surface side of the outer layer was specified in the same manner as the specification of the boundary position 1 on the inner layer side of the conductive point uneven distribution region. That is, the boundary position 2 on the outer peripheral surface side of the outer layer of the conductive point uneven distribution region was specified from the change point of the surface resistivity of the inner peripheral surface of the inner layer with respect to the polishing amount from the outer peripheral surface of the outer layer. FIG. 15 shows the change in the surface resistivity of the inner peripheral surface of the inner layer with respect to the polishing amount from the outer peripheral surface of the outer layer, and the specified boundary position 2. In the tubular body 1, the boundary position 2 was 53.7 μm.

(Specification of conductive point uneven distribution region of tubular bodies 2 to 8)
The boundary position 1 and the boundary position 2 of the conductive point uneven distribution region of the tubular bodies 2 to 8 were specified in the same manner as the specification of the conductive point uneven distribution region of the tubular body 1. Table 1 shows the boundary position 1 and the boundary position 2 of the conductive point uneven distribution regions of the tubular bodies 2 to 8.

(Specification of conductive point uneven distribution region of tubular bodies 9 to 11)
Similar to the specification of the region where the conductive points are unevenly distributed in the tubular body 1, the change in the surface resistivity of the outer peripheral surface of the outer layer with respect to the polishing amount from the inner peripheral surface of the inner layer, and the inner periphery of the inner layer with respect to the polishing amount from the outer peripheral surface of the outer layer The change in the surface resistivity of the surface was examined, but in any of the tubular bodies 9 to 11, no change in the surface resistivity was observed, and it was confirmed that there was no conductive point uneven distribution region.

(Specification of tubular body 12-19 conduction point uneven distribution region)
The boundary position 1 and the boundary position 2 of the conductive point uneven distribution region of the tubular bodies 12 to 19 were specified in the same manner as the specification of the conductive point uneven distribution region of the tubular body 1. Table 1 shows the boundary position 1 and the boundary position 2 of the conductive point uneven distribution regions of the tubular bodies 12 to 19, respectively.

(Specification of conductive point uneven distribution region of tubular bodies 20 to 22)
Similar to the specification of the region where the conductive points are unevenly distributed in the tubular body 1, the change in the surface resistivity of the outer peripheral surface of the outer layer with respect to the polishing amount from the inner peripheral surface of the inner layer, and the inner periphery of the inner layer with respect to the polishing amount from the outer peripheral surface of the outer layer The change in the surface resistivity of the surface was examined, but no change in the surface resistivity was observed in any of the tubular bodies 20 to 22, and it was confirmed that there was no conductive point uneven distribution region.

[Conductive atomic force microscope observation (cAFM) image]
The maximum current value and the mean square current value obtained by conducting a conductive atomic force microscope (cAFM) image on the conductivity between the conductive point uneven region in the inner layer and other regions (inner layer region and outer layer region other than the conductive point uneven region) Examined. The results are shown in Table 2.

Example 1
The tubular body 1 was mounted on an evaluation machine obtained by remodeling a full-color printer (DocuPrint C5450: manufactured by Fuji Xerox Co., Ltd.) having the basic configuration shown in FIG.
Using this image quality evaluation machine, double-sided printing was performed on A3 paper (J paper: manufactured by Fuji Xerox Co., Ltd.). During printing, the transfer voltage applied to the secondary transfer roll was set to 4.0 kV. A halftone pattern (Cyan 70% density) was printed as an output image, and the scale-like density unevenness and white spots were graded visually. The image quality was evaluated on the back side of double-sided printing. The image output was performed in an environment of 10 ° C. and 15 RH%. The grade criteria for each image defect are as follows. Table 2 shows the results of the image quality evaluation.

<Scale uneven density>
G0: No occurrence G1: Slight occurrence (within acceptable level)
G2: Occurrence is observed (within acceptable level)
G3: Occurrence can be easily confirmed (within acceptable level)
G4: Level at which occurrence can be confirmed and becomes unacceptable G5: Generation becomes significant and greatly exceeds the allowable level G6: Level at which a clear scale shape can be confirmed

<White spot>
G0: No occurrence G1: Slight occurrence (within acceptable level)
G2: Occurrence is observed (within acceptable level)
G3: Occurrence can be easily confirmed (within acceptable level)
G4: Level at which occurrence can be confirmed and becomes unacceptable G5: Occurrence becomes significant and greatly exceeds the allowable level G6: Number of occurrences and size increases, far exceeding the allowable level

(Examples 2 to 16)
In Example 1, the image quality was evaluated in the same manner as in Example 1 except that the tubular body shown in Table 1 was used instead of the tubular body 1. The results are shown in Table 2.

(Comparative Examples 1-6)
In Example 1, the image quality was evaluated in the same manner as in Example 1 except that the tubular body shown in Table 1 was used instead of the tubular body 1. The results are shown in Table 2.

  From the above results, it can be seen that in Examples 1 to 16, white spots and scale-like density unevenness are suppressed as compared with the comparative example. On the other hand, in Comparative Examples 1 to 6, it can be seen that white spots and scale-like density unevenness occur and the output image quality is degraded.

(Example 17)
-Production of tubular body 23-
Polyimide precursor solution (trade name: U varnish, Ube Industries, solid concentration 18%, solvent is N-methylpyrrolidone) 100 parts by weight, carbon black (trade name: Special Black 4, Degussa Huls) solid content 22% by weight and 15 parts by weight of N-methylpyrrolidone are mixed and then dispersed by a counter collision type disperser (Genus PY, manufactured by Genus Co., Ltd.), and the inner layer carbon having a viscosity of about 12 Pa · s at 25 ° C. A black dispersed polyimide precursor solution was obtained.

On the other hand, a cylindrical body made of SUS304 having an outer diameter of 600 mm, a wall thickness of 8 mm, and a length of 900 mm was prepared as the cylindrical forming tube 11. This cylindrical body has a thickness of 8 mm, an outer diameter that fits into the cylindrical body, and a SUS disk-shaped holding plate provided with four 150 mm diameter ventilation holes, fitted on both ends of the cylindrical body and welded. It is. Further, the surface of the cylindrical body is roughened to Ra 0.4 μm by blasting with spherical alumina particles.
Next, a silicone mold release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface of the cylindrical tube 11 and baked at 300 ° C. for 1 hour.
A masking member (trade name: Scotch tape # 232, manufactured by Sumitomo 3M Limited, having a width of 24 mm made of a crepe paper base material and an acrylic adhesive material) was attached to both ends of the cylindrical molded tube 11 over the entire circumference.

Next, a carbon black-dispersed polyimide precursor dry coating film for the inner layer is formed on the cylindrical tube 11 by the spin coating method shown in FIG. Coating is performed by connecting a pressure device 20 (Mono pump) to a container 14 containing 10 L of a carbon black-dispersed polyimide precursor solution for inner layer as a polyimide precursor solution 16 and discharging 20 ml per minute from a nozzle 15 to form a cylinder. The tube 11 is rotated in the circumferential direction (arrow D) at 20 rpm. After the discharged polyimide precursor solution 16 adheres to the cylindrical tube 11, the blade 18 is pressed against the surface of the tube 11, and the axial direction of the cylindrical tube 11 (arrow E) ) At a speed of 210 mm / min. The blade 22, which is a smoothing means, is obtained by processing a stainless steel plate having a thickness of 0.2 mm into a width of 20 mm and a length of 50 mm. The coating width was from the position of the end 10 mm of the cylindrical molded tube 11 to the position of the other end 10 mm.
After the application, the spiral formed on the surface of the coating film disappeared by continuing to rotate the cylindrical tube 11 for 5 minutes. Thereby, the carbon black dispersion | distribution polyimide precursor coating film for inner layers whose film thickness is 160 micrometers was formed. This thickness corresponds to a finished film thickness of 33 μm.

Thereafter, the cylindrical forming tube 11 was rotated at 10 rpm and placed in a drying furnace at 180 ° C., and the carbon black-dispersed polyimide precursor coating film for the inner layer was dried for 20 minutes. After taking out from the drying furnace, a masking member (trade name: Scotch Tape # 232, manufactured by Sumitomo 3M Co., Ltd. is used to cover the edge of the dried carbon black-dispersed polyimide precursor coating film for the inner layer. A 24 mm width made of a system adhesive material) was pasted over the entire circumference.
In addition, the residual solvent amount in the dry state of the carbon black-dispersed polyimide precursor dry coating film for the inner layer was 35% by weight. The amount of the residual solvent was calculated from the difference in the weight of the cylindrical molded tube 11 after drying from the weight of the cylindrical molded tube 11 after coating the inner layer coating film.

  Next, 100 parts by weight of a polyimide precursor solution (trade name: U varnish, Ube Industries, solid concentration 18%, solvent N-methylpyrrolidone), carbon black (trade name: Special Black 4, Degussa Huls) Is mixed with an opposing collision type disperser (Geanus PY, manufactured by Genus Co., Ltd.), and a carbon black-dispersed polyimide precursor solution for an outer layer having a viscosity at 25 ° C. of about 44 Pa · s is mixed. Obtained.

Next, the carbon black-dispersed polyimide precursor solution for the outer layer was applied onto the dry coating film for the carbon black-dispersed polyimide precursor for the inner layer by the same spin coating method as described above. However, the discharge amount from the nozzle 15 was 40 ml per minute. The coating width was also from the position of the end 10 mm of the cylindrical molded tube 11 to the position of the other end 10 mm.
After the application, the spiral formed on the surface of the coating film disappeared by continuously rotating the cylindrical tube 11 for 5 minutes. Thereby, the carbon black dispersion | distribution polyimide precursor coating film for outer layers whose film thickness is 300 micrometers was formed. This thickness corresponds to a finished film thickness of 67 μm.
Thereafter, the cylindrical forming tube 11 was rotated at 10 rpm and placed in a drying furnace at 180 ° C., and the carbon black-dispersed polyimide precursor coating film for the outer layer was dried for 30 minutes. Thereby, the residual solvent amount of the carbon black-dispersed polyimide precursor dry coating combined with the inner and outer layers is 40% by weight, and a coating in a state where the coating does not sag even when the rotation of the cylindrical tube 11 is stopped can be obtained. It was.

  Next, the masking members at the ends of the inner layer carbon black-dispersed polyimide precursor dry coating film and the outer layer carbon black-dispersed polyimide precursor dried coating film were peeled off by hand. At that time, the end of the dry film was pressed with one hand to prevent the film from tearing. After this step, a gap having a width of 5 to 8 mm was formed under the edge of the carbon black-dispersed polyimide precursor dry coating film for the inner layer.

  On the obtained carbon black-dispersed polyimide precursor dry coating film for the inner layer, the cylindrical formed tube 11 in which the carbon black-dispersed polyimide precursor dry coating film for the outer layer was laminated was lowered from the turntable and placed vertically in a heating furnace. A carbon black-dispersed polyimide film was formed by heating and reacting at 30 ° C. for 30 minutes and at 300 ° C. for 30 minutes, and simultaneously drying the residual solvent and imidizing the polyimide resin.

Next, after cooling to room temperature (25 ° C.), the carbon black-dispersed polyimide film is extracted from the cylindrical forming tube 11, this center is cut, and unnecessary portions are cut from both ends, and two tubes having a width of 360 mm are obtained. Body 23 was obtained.
When the film thickness of the obtained tubular body was measured with a dial gauge, the total of the inner layer and the outer layer was 100 μm. Further, when a thin piece having a longitudinal section of about 1 μm in thickness was produced from the obtained tubular body and the section was observed with transmitted light with an optical microscope, as shown in FIG. 16, the inner layer side at the interface between the inner layer and the outer layer was shown. It was confirmed that a region where carbon black is unevenly distributed (carbon black unevenly distributed region: that is, a region where the density of carbon black is high) exists with a thickness of about 5 μm.
The obtained tubular body has an outer layer surface resistivity of 12.5 LogΩ / □, an inner layer surface resistivity (back surface resistivity) of 12.1 LogΩ / □, and a volume resistivity of 13.8 LogΩ · cm, It was a preferable value as an intermediate transfer belt.

(Comparative Example 7)
-Production of tubular body 24-
In the same manner as in Example 17, a carbon black-dispersed polyimide precursor coating film for the inner layer was formed on the cylindrical molded tube 11, and the cylindrical molded tube 11 was placed in a drying furnace at 180 ° C. while rotating at 10 rpm, and dried for 20 minutes. It was.
Next, the masking member at the end of the carbon black-dispersed polyimide precursor dry coating film for inner layer thus obtained was peeled off by hand, the cylindrical forming tube 11 was taken down from the turntable and placed in a heating furnace at 200 ° C. The reaction was heated for 30 minutes at 300 ° C. for 30 minutes, and drying of the residual solvent and imidization reaction of the polyimide resin were performed simultaneously to form a carbon black-dispersed polyimide film, which was used as the inner layer.

  Next, after cooling to room temperature (25 ° C.), a masking member (trade name: Scotch Tape # 232, manufactured by Sumitomo 3M Co., Ltd., covered with a crepe paper base material and an acrylic adhesive material so as to cover the end of the inner layer. 24 mm) was pasted all around.

Next, in the same manner as in Example 17, the carbon black-dispersed polyimide precursor coating film for the outer layer was formed on the carbon black-dispersed polyimide precursor coating film for the inner layer, and the cylindrical molded tube 11 was rotated at 10 rpm for 180. It was put in a drying oven at 0 ° C. and dried for 30 minutes.
Next, the masking member at the end of the obtained carbon black-dispersed polyimide precursor dry coating film for the outer layer was peeled off by hand, the cylindrical forming tube 11 was taken down from the turntable and placed in a heating furnace at 200 ° C. The reaction was heated for 30 minutes at 300 ° C. for 30 minutes, and the drying of the residual solvent and the imidization reaction of the polyimide resin were performed simultaneously to form a carbon black-dispersed polyimide film, which was used as the outer layer.

Thereafter, a tubular body 24 was obtained in the same manner as in Example 17.
A thin section having a longitudinal section of about 1 μm in thickness was prepared from the obtained tubular body, and the section was observed with transmitted light using an optical microscope. The area where carbon black was unevenly distributed (carbon black unevenly distributed area: that is, the density of carbon black The high region) was not formed.
The obtained tubular body had an outer layer surface resistivity of 15 LogΩ / □ or more and a volume resistivity of 15 LogΩ · cm or more, and was not preferable as an intermediate transfer belt.

(Comparative Example 8)
-Production of tubular body 25-
In Example 17, a tubular body 25 was obtained in the same manner as in Example 17 except that the drying condition of the carbon black-dispersed polyimide precursor coating film for the inner layer was changed to 180 ° C. for 8 minutes. The residual solvent of the dried carbon black-dispersed polyimide precursor dry coating film for the inner layer was 55% by weight.
A thin section having a longitudinal section of about 1 μm in thickness was prepared from the obtained tubular body, and the section was observed with transmitted light with an optical microscope. As shown in FIG. 18, a region where carbon black was unevenly distributed (carbon black unevenly distributed region) : That is, the region where the density of carbon black is high) was not formed.
The obtained tubular body had a surface resistivity of the outer layer of 14.5 LogΩ / □, a surface resistivity of the inner layer (surface resistivity of the back surface) of 14.5 LogΩ / □, and a volume resistivity of 14.1 LogΩ · cm. .

(Comparative Example 9)
-Production of tubular body 26-
In Example 17, a tubular body 26 was obtained in the same manner as in Example 17 except that the drying condition of the carbon black-dispersed polyimide precursor coating film for the inner layer was changed to 180 ° C. and 35 minutes. In addition, the residual solvent of the dried carbon black dispersion polyimide precursor dry coating film for inner layers was 19 weight%.
The obtained tubular body had bubble defects on the entire surface. Also, the resistance of the obtained tubular body could not be measured because the ring electrode touched the bubble defect and the load was not applied uniformly.

(Example 18)
-Production of tubular body 27-
In Example 17, the drying condition of the inner layer carbon black-dispersed polyimide precursor coating was changed to 190 ° C. and 25 minutes, and the drying condition of the outer layer carbon black-dispersed polyimide precursor coating was changed to 180 ° C. and 30 minutes. Except for this, a tubular body 27 was obtained in the same manner as in Example 17. In addition, the residual solvent of the dried carbon black-dispersed polyimide precursor dry coating film for the inner layer was 22% by weight, the shape of the obtained inner layer and outer layer was maintained, and no bubble defect occurred even after the outer layer was formed.
When a thin piece having a longitudinal section of about 1 μm in thickness is prepared from the obtained tubular body and the section is observed with transmitted light using an optical microscope, carbon black is formed on the inner layer side at the interface between the inner layer and the outer layer as shown in FIG. It was confirmed that a region where carbon was unevenly distributed (carbon black unevenly distributed region: that is, a region where the density of carbon black was high) was present at a thickness of about 5 μm. In addition, between the interface between the inner layer and the outer layer and the carbon black unevenly distributed region (that is, between the outer layer and the carbon black unevenly distributed region), a region containing less carbon black than other regions (carbon black low density) It was confirmed that the region) was present with a thickness of about 1 μm.
The obtained tubular body has an outer layer surface resistivity of 12.2 LogΩ / □, an inner layer surface resistivity (back surface resistivity) of 10.9 LogΩ / □, and a volume resistivity of 13.3 LogΩ · cm, The intermediate transfer belt was in a preferable range.

(Example 19)
-Production of tubular body 28-
In Example 17, the drying condition for the inner layer carbon black-dispersed polyimide precursor coating film was changed to 125 ° C. for 50 minutes, and the drying condition for the outer layer carbon black-dispersed polyimide precursor coating film was changed to 180 ° C. for 30 minutes. Except for this, a tubular body 28 was obtained in the same manner as in Example 17.
When a thin section having a longitudinal section of about 1 μm in thickness is prepared from the obtained tubular body and the section is observed with transmitted light using an optical microscope, a region in which carbon black is unevenly distributed on the inner layer side at the interface between the inner layer and the outer layer (carbon black It was confirmed that the unevenly distributed region (that is, the region where the density of carbon black is high) is present at a thickness of about 2.5 μm.
The obtained tubular body has an outer layer surface resistivity of 13.6 LogΩ / □, an inner layer surface resistivity (back surface resistivity) of 13.3 LogΩ / □, and a volume resistivity of 14.0 LogΩ · cm. It was a preferable value as a transfer belt.

  Hereafter, it lists in Table 3 about Examples 17-19 and Comparative Examples 8-9.

DESCRIPTION OF SYMBOLS 11 Cylindrical forming pipe 14 Container 15 Nozzle 16 Polyimide precursor solution 17 Pressurization apparatus 18 Blade 21 Front surface electrode 22 Guard electrode 23 Back surface electrode 24 Insulation sheet 25 DC power supply 26 Microammeter 27 Measurement sample 101a-101d Image holding body 102a-102d Charging devices 103a to 103d Developing devices 104a to 104d Image carrier cleaning devices 105, 105a to 105d Primary transfer rolls 106a to 106d Tension roll 107 Intermediate transfer belt 107b Transfer unit 108 Backup roll 109 Secondary transfer roll 110 Fixing device 111 Drive roll 112 Intermediate transfer belt cleaning blade 113 Intermediate transfer belt cleaning brushes 114a to 114d Image exposure device 115 Transfer medium 120 Transfer belt 121 Outer layer 121A For outer layer Membrane 122 lining 122A for inner coating 123 elution solvent 124 conductive particles 124A conductive point localized region 130 transfer unit 131 drive roller 132 driven roll

Claims (3)

Having at least two layers of an outer layer and an inner layer including resin and conductive particles,
The tubular body in which the inner layer has a region having higher conductivity than other regions in the thickness direction.   A transfer unit, comprising: a transfer belt that is a tubular body according to claim 1; and a plurality of rolls that hang the transfer belt in a tensioned state, and is detachable from an image forming apparatus main body. An image carrier,
Charging means for charging the surface of the image carrier;
Latent image forming means for forming a latent image on the surface of the image carrier;
Developing means for developing a latent image on the surface of the image carrier with toner to form a toner image;
An intermediate transfer member to which the toner image formed on the surface of the image carrier is transferred;
Primary transfer means for primarily transferring the toner image formed on the surface of the image carrier to the surface of the intermediate transfer member;
Secondary transfer means for secondary transfer of the toner image transferred to the surface of the intermediate transfer member to a transfer medium;
Fixing means for fixing the toner image transferred to the recording medium;
With
The image forming apparatus according to claim 1, wherein the intermediate transfer body is a tubular body.