JP2009258708A - Circular body, circular body unit, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resinous circular body preventing an occurrence of image quality defects (scale-like density unevenness and white spots) on an output image, and thereby providing a favorable output image. <P>SOLUTION: The resinous circular body satisfies following expressions (1) to (3): the expression(1) 11.6Log&Omega;/sq.&le;&rho;s&le;14.0Log&Omega;/sq., the expression (2) 10.3Log&Omega; cm&le;&rho;v &le;14.0Log&Omega; cm, and the expression (3) 9.8Log&Omega;/sq.&le;&rho;exs&le;13.4Log&Omega;/sq. In the expressions (1) to (3), &rho;s means surface resistivity of an outer peripheral surface of the circular body, &rho;v means volume resistivity of the outer peripheral surface of the circular body, and &rho;exs means creeping resistivity of an extreme surface of an inner peripheral surface of the circular body respectively. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an annular body, an annular body 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. An image forming apparatus is known in which an image is electrostatically transferred onto an intermediate transfer belt (primary transfer process) and then transferred again onto a transfer medium such as transfer paper (secondary transfer process) to form an image. Yes. 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.

In an intermediate transfer belt, in order to obtain a stable and good output image over a long period of time, electrical strength such as surface resistivity and volume resistivity as well as mechanical strength such as flexibility, folding resistance and tensile breaking strength are provided. Properties are important.
For example, a technique is disclosed in which the surface resistivity of the outer peripheral surface of the intermediate transfer belt is 8 LogΩ / □ to 12 LogΩ / □ and the surface resistivity of the inner peripheral surface is 5 LogΩ / □ to 10 LogΩ / □ (for example, Patent Documents). 1). The surface resistivity of the intermediate transfer member 10LogΩ / □ or more 14LogΩ / □ or less, the volume resistivity of not more than 13LogΩ · cm, and a surface resistivity of 10 ^X Ω / □, the volume resistivity at 10 ^Y Ω · cm A technique for expressing X ≦ Y when expressed is disclosed (for example, see Patent Document 2).

JP-A-8-30109 JP 2004-46277 A

  The object of the present invention is the case where the surface resistivity of the outer peripheral surface of the annular body, the volume resistivity of the outer peripheral surface of the annular body, and the creeping resistivity of the pole surface on the inner peripheral surface of the annular body are not considered. In comparison, an object of the present invention is to provide an annular body in which the occurrence of image quality defects (scale-like density unevenness, white spots) on an output image is prevented and a good output image can be obtained.

The above object is achieved by the present invention described below.
That is, the invention according to claim 1
It is a resin-made annular body characterized by satisfying the following formulas (1) to (3).
11.6 LogΩ / □ ≦ ρs ≦ 14.0 LogΩ / □ (1)
10.3 LogΩ · cm ≦ ρv ≦ 14.0 LogΩ · cm (2)
9.8 LogΩ / □ ≦ ρexs ≦ 13.4 LogΩ / □ (3)
(In the above formulas (1) to (3), ρs is the surface resistivity of the outer circumferential surface of the annular body, ρv is the volume resistivity of the outer circumferential surface of the annular body, and ρexs is the creeping resistance of the surface of the circumferential surface of the annular body. (The rate is expressed respectively.)

The invention according to claim 2
2. The resin-made annular body according to claim 1, comprising at least two layers of an outermost peripheral layer and an innermost peripheral layer and satisfying the following formula (4):
1.2 ≦ du / dl ≦ 4.0 (4)
(In the above formula (4), du represents the film thickness (μm) of the outermost peripheral layer, and dl represents the film thickness (μm) of the innermost peripheral layer.)

The invention according to claim 3
An annular body unit comprising: the annular body according to claim 1 or 2; and a plurality of rotating members that span the annular body in a tensioned state so as to be rotatable from an inner surface side. .

The invention according to claim 4
An image carrier, a charging unit for charging the image carrier, an exposure unit for forming an electrostatic latent image on the image carrier charged by the charging unit, and an electrostatic latent image on the image carrier. Developing means for developing a toner image, primary transfer means for transferring the toner image to an intermediate transfer belt, and secondary transfer means for transferring the toner image transferred to the intermediate transfer belt to a transfer medium; And a fixing unit that fixes the toner image on the transfer medium, and the annular transfer body according to claim 1 or 2 is used as the intermediate transfer belt.

  According to the first aspect of the present invention, the surface resistivity of the outer peripheral surface of the annular body, the volume resistivity of the outer peripheral surface of the annular body, and the creeping resistivity of the pole surface on the inner peripheral surface of the annular body are not considered. As compared with, generation of image quality defects (scale-like density unevenness, white spots) on the output image is suppressed, and a good output image can be obtained.

  According to the second aspect of the present invention, compared to the case where the present configuration is not provided, the occurrence of an image quality defect (a region where the toner image is missing on the output image), which will be described later, on the output image is suppressed, and a favorable output is achieved. An image can be obtained.

  According to the invention of claim 3, the annular body that does not take into account the surface resistivity of the outer peripheral surface of the annular body, the volume resistivity of the outer peripheral surface of the annular body, and the creeping resistivity of the pole surface on the inner peripheral surface of the annular body. Compared with the case of using, the occurrence of image quality defects (scale density unevenness, white spots) on the output image is suppressed, and a good output image can be obtained.

  According to the invention of claim 4, the annular body that does not consider the surface resistivity of the outer peripheral surface of the annular body, the volume resistivity of the outer peripheral surface of the annular body, and the creeping resistivity of the pole surface on the inner peripheral surface of the annular body. Compared with the case of using, the occurrence of image quality defects (scale density unevenness, white spots) on the output image is suppressed, and a good output image can be obtained.

1 is a schematic cross-sectional view showing a preferred embodiment of an image forming apparatus of the present embodiment. FIG. 3 is a schematic cross-sectional view showing an embodiment of a cylindrical tube-applying device used for producing the intermediate transfer belt of the present embodiment. 1 is a schematic cross-sectional view of a surface resistivity measuring device for an intermediate transfer belt according to an embodiment. 1 is a schematic cross-sectional view of a volume resistivity measuring device for an intermediate transfer belt according to an embodiment. 1 is a schematic cross-sectional view of a creeping resistivity measuring device for a pole surface of an intermediate transfer belt according to an embodiment. FIG. 3 is a schematic plan view of electrodes used in the surface resistivity and volume resistivity measuring device of the intermediate transfer belt of the present embodiment. FIG. 3 is a schematic plan view of electrodes used in a creeping resistivity measuring device on the pole surface of the intermediate transfer belt of the present embodiment. It is a figure showing the relationship between the surface resistivity and granularity generation | occurrence | production grade in the Example and comparative example of this embodiment. It is a figure showing the relationship between the volume resistivity and the white spot generation | occurrence | production grade in the Example and comparative example of this embodiment. It is a figure showing the relationship between the creeping resistivity and the white spot generation | occurrence | production grade of the inner peripheral surface pole surface in the Example and comparative example of this embodiment. It is a figure showing the relationship between the creeping resistivity of the inner peripheral surface pole surface in the Example of this embodiment, and a scale-like density nonuniformity generation | occurrence | production grade. It is a figure showing the relationship between du / dl and the white point generation | occurrence | production grade in the Example and comparative example of this embodiment. It is a figure showing the relationship between du / dl and the HT nonuniformity generation grade in the Example and comparative example of this embodiment.

Hereinafter, preferred embodiments will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram illustrating an example (one embodiment) of a configuration of an image forming apparatus according to a preferred embodiment. The image forming apparatus 100 according to the present embodiment is a so-called tandem system, and sequentially around the four image holding bodies 101a to 101d made of an electrophotographic photosensitive member along the rotation direction, the charging devices 102a to 102d, and the 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.

  An intermediate transfer belt 107 is stretched around tension rolls 106a to 106d, a drive roll 111, and a backup roll 108 to form an annular unit (intermediate transfer unit). With these tension rolls 106a to 106d, drive roll 111, and 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 rollers 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.

  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 and a secondary transfer belt 116 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 and the secondary transfer belt 116 becomes a secondary transfer portion, and a contact portion between the secondary transfer roll 109 and the backup roll 108 has a secondary contact portion. A transfer voltage is applied. 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, fixed by heating and / or pressurization, 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, 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.

  In an image forming apparatus using an intermediate transfer belt (annular body), scale-like density unevenness may occur on the output image, or an area (white point) from which the toner image is missing may occur on the output image. .

In the secondary transfer process, the present inventors have found that the phenomenon that the uneven density of scales is generated is caused by a discharge on the backup roll contacting the inner peripheral surface of the intermediate transfer belt and the back surface of the intermediate transfer belt. The inventors have found that the toner image on the outer peripheral surface of the intermediate transfer member is disturbed.
Further, in the secondary transfer step, discharge occurs in the secondary transfer roll contacting the outer peripheral surface of the intermediate transfer belt via the transfer medium and the outer peripheral surface of the intermediate transfer belt, so that the toner in the region where the discharge has occurred It has been found that a region (white point) in which a toner image is missing occurs on the output image due to the fact that the toner is charged with the opposite polarity and is not transferred to the transfer medium.

  The secondary transfer roll refers to a toner image that is transferred from the outer peripheral surface of the intermediate transfer belt to the transfer medium by applying an electric field having a polarity opposite to that of the toner to the toner image on the outer peripheral surface of the intermediate transfer belt in the secondary transfer step. It is a part for transferring.

[Formulas (1) to (4)]
On the other hand, in the present embodiment, the intermediate transfer belt 107 needs to satisfy the following formulas (1) to (3).
11.6 LogΩ / □ ≦ ρs ≦ 14.0 LogΩ / □ (1)
10.3 LogΩ · cm ≦ ρv ≦ 14.0 LogΩ · cm (2)
9.8 LogΩ / □ ≦ ρexs ≦ 13.4 LogΩ / □ (3)
(In the above formulas (1) to (3), ρs is the surface resistivity of the outer peripheral surface of the intermediate transfer belt 107, ρv is the volume resistivity of the outer peripheral surface of the intermediate transfer belt 107, and ρexs is the intermediate transfer belt. 107 represents the creeping resistivity of the pole surface on the inner peripheral surface of 107.)

In the present embodiment, it is desirable that the intermediate transfer belt 107 has at least two layers of an outermost peripheral layer and an innermost peripheral layer and satisfy the following formula (4).
1.2 ≦ du / dl ≦ 4.0 (4)
(In the above formula (4), du represents the film thickness (μm) of the outermost peripheral layer, and dl represents the film thickness (μm) of the innermost peripheral layer.)

The “ρs” is preferably 11.9 LogΩ / □ ≦ ρs ≦ 13.3 LogΩ / □, and more preferably 12.2 LogΩ / □ ≦ ρs ≦ 12.9 LogΩ / □.
When ρs <11.6 LogΩ / □, the transfer electric field applied from the secondary transfer roll 109 wraps around the toner on the intermediate transfer belt 107 in the secondary transfer step, so that the toner scatters around the transfer transfer medium. The toner image is transferred in a blurred state on 115 and the graininess is deteriorated, so that a good output image cannot be obtained. In addition, when 14.0 LogΩ / □ <ρs, the amount of charge induced on the outer peripheral surface of the intermediate transfer belt 107 is increased by the toner electrostatically adsorbed on the outer peripheral surface of the intermediate transfer belt 107. Thus, the discharge occurs in the lateral direction (the creeping direction) along the surface on the outer peripheral surface, so that the toner image is blurred and the granularity is deteriorated, and a good output image cannot be obtained.

The “ρv” is preferably 11.0 LogΩ · cm ≦ ρv ≦ 13.5 LogΩ · cm, more preferably 11.6 LogΩ · cm ≦ ρv ≦ 13.1 LogΩ · cm, more preferably 11.9 LogΩ · cm. More preferably, cm ≦ ρv ≦ 12.9 LogΩ · cm.
When ρv <10.3 LogΩ · cm, in the secondary transfer process, a discharge occurs between the outer peripheral surface of the secondary transfer roll 109 and the intermediate transfer belt 107, and the toner in the discharge area is charged to a reverse polarity and transferred. By not being transferred to the medium 115, a region (white point) where the toner image is missing occurs on the output image, and the quality of the output image is impaired. Further, when 14.0 LogΩ · cm <ρv, the secondary transfer roll 109 repeatedly applies a voltage to the intermediate transfer belt 107, whereby the charging potential of the outer peripheral surface of the intermediate transfer belt 107 is increased, and the image holding member. Discharge occurs between other members in contact with the outer peripheral surface of the intermediate transfer belt 107, etc., and the toner in the discharge area is charged with a reverse polarity and is not transferred to the transfer medium 115, so that a toner image is formed on the output image. An area (white point) in which the image is missing occurs, and the quality of the output image is impaired.

Furthermore, the “ρexs” is preferably 10.6 LogΩ / □ ≦ ρexs ≦ 13.0 LogΩ / □, more preferably 11.0 LogΩ / □ ≦ ρexs ≦ 12.6 LogΩ / □, and 11.3 LogΩ / □. More preferably, □ ≦ ρexs ≦ 12.4 LogΩ / □.
When ρexs <9.8 LogΩ / □, in the secondary transfer process, a discharge occurs between the outer peripheral surface of the secondary transfer roll 109 and the intermediate transfer belt 107, and the toner in the discharge area is charged to a reverse polarity, so that the transferred image is transferred. By not being transferred to the medium 115, a region (white point) where the toner image is missing occurs on the output image, and the quality of the output image is impaired. Further, when 13.4 LogΩ / □ <ρexs, discharge occurs between the backup roll 108 contacting the inner peripheral surface of the intermediate transfer belt 107 and the back surface of the intermediate transfer belt 107 in the secondary transfer step. Further, the toner image on the outer peripheral surface of the intermediate transfer belt 107 is disturbed, and scale-like density unevenness occurs on the output image, thereby deteriorating the quality of the output image.

The “du / dl” preferably satisfies 1.5 ≦ du / dl ≦ 3.0, and more preferably 1.6 ≦ du / dl ≦ 2.7.
Here, in the secondary transfer process, the charge flowing from the backup roll 108 that contacts the inner peripheral surface of the intermediate transfer belt 107 is accumulated between the outermost and innermost layers of the intermediate transfer belt. A local electric field is generated. When the electric field strength of the local electric field exceeds a threshold value, electric charges flow into the outermost peripheral layer at once, and discharge occurs between the secondary transfer roll 109. The inventors of the present invention have found that a toner image missing region (HT unevenness) is generated on the output image because the toner in the region where the discharge is generated is charged with a reverse polarity and is not transferred to the transfer medium. .
When 1.2 ≦ du / dl, it is possible to suppress the occurrence of discharge between the secondary transfer roll 109 and the outer peripheral surface of the intermediate transfer belt 107 in the secondary transfer process, and to prevent the toner from having a reverse polarity. As a result, a region where the toner image is missing (white point) does not occur, and a good output image is obtained. Further, when du / dl ≦ 4.0, the charge flowing from the backup roll 108 is not accumulated between the outermost and innermost layers of the intermediate transfer belt 107, and therefore, between the secondary transfer roll 109 and the intermediate transfer belt 107. Since no discharge is generated and the toner is prevented from having a reverse polarity, a region (HT unevenness) in which the toner image is missing does not occur and a good output image is obtained.

[Intermediate transfer belt]
Further, the intermediate transfer belt 107 in this embodiment desirably has a total film thickness of 50 μm or more and 130 μm or less. If the total film thickness is 50 μm or more, sufficient mechanical strength can be maintained, and a better output image can be obtained even in long-term use in the image forming apparatus. In addition, if the total film thickness is 130 μm or less, sufficient flexibility can be maintained, and even if the film is stretched for a long time in the image forming apparatus, the intermediate transfer belt can be traced. Therefore, a better output image can be obtained.

  Examples of the material of the intermediate transfer belt 107 include polycarbonate resin, polyvinylidene fluoride resin, polyalkylene phthalate resin, polycarbonate / polyalkylene phthalate blend material, thermoplastic resin such as ethylene tetrafluoroethylene copolymer, polyimide, polyimide, and the like. A material obtained by dissolving or dispersing a conductive agent in a thermosetting resin such as a copolymer of polyamide and polyamide (polyamideimide) is used.

  Examples of the conductive agent include conductive particles such as carbon black, graphite, aluminum, nickel, copper, tin oxide, zinc oxide, titanium oxide, or potassium titanate, and organic conductive substances such as polyaniline and polythiophene. It is done. Among these, the intermediate transfer belt 107 in which polyimide resin is the main component (the main component indicates that the polyimide resin content in the intermediate transfer belt exceeds 50 mass%) and conductive particles such as carbon black are dispersed. However, it is particularly preferably used because of its excellent mechanical strength, high elastic modulus, and excellent creep resistance (a property that resists the phenomenon that strain increases with time when a continuous stress acts on an object).

The method for manufacturing the intermediate transfer belt 107 according to the present embodiment is not particularly limited, but for example, it can be suitably manufactured by a spin coating method as shown in FIG. 2 using a polyimide precursor solution.
In this method, a cylindrical tube 11 having an outer diameter corresponding to the length of the intermediate transfer belt 107 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), the coating liquid 16 is discharged from the nozzle 15 onto the outer circumferential surface of the cylindrical molding tube 11, and the outer circumferential surface of the cylindrical molding tube 11 by the blade 18. Level up. 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. Thereby, a coating film of the coating liquid 16 is formed on the outer peripheral surface of the cylindrical tube 11.
The obtained coating liquid 16 is dried by heating, and after cooling, is peeled off from the cylindrical tube 11 and cut at a predetermined width to obtain the intermediate transfer belt 107. In addition, when using a polyimide precursor as a resin material of the coating liquid 16, after forming the coating liquid 16 coating film on the outer peripheral surface of the cylindrical tube 11, the solvent is removed by drying at 80 ° C. or more and 170 ° C. or less. The polyimide resin film is formed by removing (drying process) and further imide conversion (baking process) by heating to 250 ° C. or more and 350 ° C. or less. After cooling, the obtained polyimide resin film is peeled off from the cylindrical tube 11 and cut at a predetermined width, whereby the intermediate transfer belt 107 can be obtained.

  The solid content concentration of the coating liquid 16 can be, for example, 10 mass% or more and 40 mass% or less, and the viscosity can be 1 Pa · s or more and 100 Pa · s or less. In addition, a predetermined amount of conductive particles such as carbon black is dispersed in the coating liquid 16 in accordance with the required surface resistivity of the intermediate transfer belt. As a dispersion method, a known method such as a jet mill, a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, or a paint shaker can be used.

The present inventors have found a method for independently controlling the “ρs”, “ρv”, and “ρexs” in the method of manufacturing the intermediate transfer belt 107, and have completed the present invention.
That is, when the intermediate transfer belt 107 is configured to have at least two layers of the outermost peripheral layer and the innermost peripheral layer, ρv is increased in the innermost peripheral layer depending on the amount of the conductive material contained in the outermost peripheral layer. Ρexs is adjusted by the amount of the conductive material contained. Further, when the coating liquid 16 formed on the outer peripheral surface of the cylindrical tube 11 is dried, ρs is controlled independently of ρv and ρexs by setting the coating liquid 16 to a predetermined temperature. More specifically, when the drying temperature is increased, ρs is increased, and when the drying temperature is decreased, ρs is decreased. The independent control of ρs, ρv and ρexs is more preferably used when a polyimide precursor is used as the coating liquid 16 resin material and carbon black is used as the conductive material. In the case of using a polyimide precursor and carbon black, ρs is controlled independently of ρv and ρexs by adjusting the temperature in the drying step while keeping the amount of residual solvent after the drying step constant.

  In the method of manufacturing the intermediate transfer belt 107, it is desirable that the drying temperature is 100 ° C. or higher and 170 ° C. or lower. If the drying temperature is too low in the drying step, the solvent in the polyimide precursor does not dry, and even if the drying time is extended, it is difficult to reach a predetermined residual solvent amount. Also, if the drying temperature is too high, a dry film may be formed on the surface of the polyimide precursor at the very beginning of the drying process, and the solvent inside the polyimide precursor may not be sufficiently dried, or the polyimide precursor film after the drying process. The surface of the film is pulled, and wrinkle-like defects are easily generated on the surface of the coating film. By setting the drying temperature to 100 ° C. or more and 170 ° C. or less, a polyimide precursor film having a predetermined residual solvent amount and a better coating film is obtained.

The intermediate transfer belt 107 preferably has at least two layers, and the materials used are the same as those described above even in the case of three layers or more. In addition, the multilayer structure film of two or more layers is formed by forming the coating liquid 16 coating on the outer peripheral surface of the cylindrical tube 11 and drying it to form the innermost peripheral layer, and then repeating the coating and drying process. A desired constituent film is obtained. When a polyimide precursor containing carbon black is used as the coating solution 16, the coating / drying process is repeated, and after the desired configuration is obtained, the desired constituent film is obtained through the firing step.
When a resin other than a polyimide resin is applied as the resin used for the intermediate transfer belt 107, conditions such as the coating film thickness, drying temperature and time are appropriately adjusted, and the coating and coating are performed as described above. A constituent film required by repeating the drying step is obtained.

  The thickness of the intermediate transfer belt 107 is adjusted by the discharge amount of the coating liquid 16, the moving speed of the nozzle 15 and the blade 18, and the solid content concentration of the coating liquid 16. The thickness of the intermediate transfer belt 107 is preferably not less than 50 μm and not more than 130 μm from the viewpoint of maintaining dimensional accuracy even in repeated image output.

(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. Unless otherwise specified, the term “semiconductive” refers to, for example, a volume resistivity of 10 ⁷ to 10 ¹³ Ωcm. .)) Can be widely used, such as a contact-type 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. For example, the light sources such as semiconductor laser light, LED light, or liquid crystal shutter light on the surfaces of the image carriers 101a to 101d, 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.

  Examples of the binder resin include homopolymers or copolymers such as styrenes, monoolefins, vinyl esters, α-methylene aliphatic monocarboxylic acid esters, vinyl ethers, and vinyl ketones. Typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include coalescence, polyethylene, and polypropylene. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax, and the like can be given.

  Colorants include magnetic powders such as magnetite and ferrite, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black. Rose Bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment blue 15: 1 or C.I. I. Pigment Blue 15: 3 is a typical example.

  The toner may be internally added or externally added with known additives such as a charge control agent, a release agent, and other inorganic particles.

  Typical examples of the release agent include low molecular polyethylene, low molecular polypropylene, Fischer-Tropsch wax, montan wax, carnauba wax, rice wax, and candelilla wax.

  Known charge control agents can be used, but charge control agents such as azo-based metal complex compounds, metal complex compounds of salicylic acid, and resin types containing polar groups can be used.

As other inorganic particles, small-diameter inorganic particles having an average primary particle size of 40 nm or less are used for the purpose of powder flowability, charge control, etc., and if necessary, larger diameters are used to reduce adhesion. These inorganic or organic particles may be used in combination. As these other inorganic particles, known ones are used.
In addition, the surface treatment of the small-diameter inorganic particles is effective because the dispersibility becomes high and the effect of increasing the powder fluidity increases.

  As a method for producing the toner, a polymerization method such as an emulsion polymerization aggregation method or a dissolution suspension method is preferably used because high shape controllability can be obtained. In addition, a manufacturing method may be performed in which the toner obtained by these methods is used as a core, and agglomerated particles are further adhered and heat-fused to have a core-shell structure.

  In addition, when adding an external additive, it can manufacture by mixing a toner and an external additive with a Henschel mixer or a V blender. In addition, when the toner is manufactured by a wet method, external addition may be performed by a wet method.

[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, etc. 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 an appropriate 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 embodiments, a so-called tandem image forming apparatus including a plurality of image carriers has been described. However, the intermediate transfer belt rotates and forms an image by one image carrier and the number of colors. The image forming apparatus may be a so-called multi-cycle method (for example, a 4-cycle method) that performs the process.

EXAMPLES Examples and comparative examples will be described below, but the present invention is not limited to the following examples.
(Preparation of intermediate transfer belt 1)
Preparation of carbon black-dispersed polyimide precursor solution for inner peripheral layer N-methyl-2-polyamic acid consisting of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether In a pyrrolidone (NMP) solution (solid content ratio after imide conversion is 18% by mass), carbon black (Special Black 4: manufactured by Degussa) is 80 parts by mass with respect to 100 parts by mass of the solid content of polyamic acid. And using a jet mill disperser (Geanus PY [minimum cross-sectional area of collision part 0.032 mm ² ]: manufactured by Genus Co., Ltd.), the dispersion unit is passed 5 times at a pressure of 200 MPa, and dispersed and mixed. A liquid (A) was obtained.
An NMP solution of polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether (solid after imide conversion) was added to the resulting dispersion (A). 18 mass%) is added so that the carbon black is 21.6 parts by mass with respect to 100 parts by mass of the solid content of the polyamic acid, and a planetary mixer (Aiko mixer: manufactured by Aikosha Seisakusho) is used. By mixing and stirring, a carbon black-dispersed polyimide precursor solution for the inner peripheral layer was prepared.

-Formation of inner peripheral layer carbon black-dispersed polyimide precursor dry film On the other hand, an aluminum cylindrical body having an outer diameter of 366 mm, a length of 600 mm, and a thickness of 6 mm was prepared as the cylindrical molded tube 11 shown in FIG. Such an aluminum cylinder is roughened to a surface roughness Ra of 0.40 μm by blasting with spherical glass particles. A silicone 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 to produce an aluminum cylindrical body.
Furthermore, as a spin coating process, as shown in FIG. 2, the cylindrical tube 11 was rotated at 50 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 cylindrical molding tube 11 and the carbon black-dispersed polyimide precursor solution for the inner peripheral layer was used as the coating solution 16 and extruded from the container 14 through the nozzle 15 having a diameter of 2 mm. When the coating liquid 16 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. In addition, at the time of application | coating, the non-application area | region of 20 mm was provided in the both ends of the cylindrical forming pipe 11. Next, the inner peripheral layer carbon black-dispersed polyimide precursor is heated and dried at 125 ° C. for 40 minutes while rotating the cylindrical tube 11 coated with the inner peripheral layer carbon black-dispersed polyimide precursor solution at 6 rpm. A dry film was obtained. In addition, the film thickness of the inner peripheral layer carbon black dispersion polyimide precursor dry film 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 amount of residual NMP in the inner peripheral layer carbon black-dispersed polyimide precursor dry film was 24.0% by mass. 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 peripheral layer.

-Preparation of carbon black-dispersed polyimide precursor solution for outer peripheral layer Next, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 4,4'-diamino were added to the dispersion (A). An NMP solution of polyamic acid composed of diphenyl ether (solid content ratio after imide conversion is 18% by mass) is added so that carbon black is 19.5 parts by mass with respect to 100 parts by mass of polyamic acid, and planetary A carbon black-dispersed polyimide precursor solution for the outer peripheral layer was prepared by mixing and stirring using a mixer (Aiko mixer manufactured by Aikosha Seisakusho).

-Formation of outer peripheral layer carbon black-dispersed polyimide precursor dry film Using the obtained carbon black-dispersed polyimide precursor solution for outer peripheral layer, the rotational speed of cylindrical forming tube 11 is 40 rpm, and the moving speed of nozzle 15 is 90 mm / min. The carbon black-dispersed polyimide precursor solution for the outer peripheral layer was applied to the surface of the inner peripheral layer carbon black-dispersed polyimide precursor dry film by the method at the time of applying the inner peripheral layer.
Next, the cylindrical tube 11 coated with the carbon black-dispersed polyimide precursor solution for the outer peripheral layer is horizontally dried while being rotated at 6 rpm for 40 minutes at 120 ° C., and the outer peripheral layer carbon black-dispersed polyimide precursor dried film Got. In addition, as for the film thickness of the outer peripheral layer carbon black-dispersed polyimide precursor dry film, the amount of the extrusion liquid from the nozzle 15 at the time of application was adjusted so that the film thickness after imidization described later has a desired value. The amount of residual NMP after drying was 35.2% by mass. In addition, since this residual NMP amount is measured after the outer peripheral layer is dried, it is the residual NMP amount that combines the inner peripheral layer and the outer peripheral layer.

-Preparation of intermediate transfer belt A cylindrical molded tube 11 obtained by laminating an outer peripheral layer carbon black-dispersed polyimide precursor dry film on an inner peripheral layer carbon black-dispersed polyimide precursor dry film obtained as described above was placed at 200 ° C. For 30 minutes, 260 ° C. for 30 minutes, 300 ° C. for 30 minutes, and 320 ° C. for 20 minutes to form a carbon black-dispersed polyimide film. Thereafter, when the temperature of the cylindrical molded tube 11 was cooled to room temperature (25 ° C.), the polyimide film was peeled from the cylindrical molded tube 11. The obtained polyimide film was cut to a width of 362 mm to obtain an intermediate transfer belt A. Two intermediate transfer belts A thus obtained were joined to obtain an intermediate transfer belt 1 having a circumference of 2111 mm.

  Further, when the film thicknesses of the outer peripheral layer and the inner peripheral layer were measured using the remaining cut ends of the intermediate transfer belt A, they were 31.2 μm and 64.9 μm, respectively. Further, when ρs, ρv, and ρexs were measured, they were 12.42 LogΩ / □, 12.41 LogΩ · cm, and 13.38 LogΩ / □, respectively. The results are shown in Table 1.

(Preparation of intermediate transfer belts 2 to 57)
When forming the intermediate transfer belt 1, the amount of carbon black (CB) contained in the inner peripheral layer, the amount of carbon black (CB) contained in the outer peripheral layer, and the inner layer carbon black-dispersed polyimide precursor dry film Intermediate transfer belts 2 to 57 were produced in the same manner as the intermediate transfer belt 1 except that the drying temperature and time after coating were changed to the values shown in Tables 1 to 3, respectively. In the intermediate transfer belts 2 to 57, the inner layer and the outer layer have the same drying conditions, which are shown in Tables 1 to 3, respectively. When the outer peripheral layer thickness, the inner peripheral layer thickness, ρs, ρv, and ρexs were measured, the values shown in Tables 1 to 3 were obtained.

(Preparation of intermediate transfer belt 58)
-Preparation of carbon black-dispersed polyamideimide solution for inner circumference layer To N-methyl-2-pyrrolidone (NMP) solution (solid content is 18% by mass) of polyamideimide resin (Viromax HR-20NN manufactured by Toyobo Co., Ltd.) Carbon black (Special Black 4: manufactured by Degussa) was added to 90 parts by mass with respect to 100 parts by mass of the solid content, and a jet mill disperser (Geanus PY [minimum cross-sectional area of collision part 0.032 mm ² ]). The product was dispersed and mixed by passing the dispersion unit part 5 times at a pressure of 200 MPa, and a dispersion (B) was obtained.
An N-methyl-2-pyrrolidone (NMP) solution (solid content: 17% by mass) of polyamideimide resin (Viromax HR-40NN manufactured by Toyobo Co., Ltd.) is added to the obtained dispersion liquid (B). Carbon black is added to 38.2 parts by mass with respect to 100 parts by mass of the total solid content of Max HR-20NN and Viromax HR-40NN, and a planetary mixer (Aiko mixer manufactured by Aikosha Seisakusho) is used. By mixing and stirring, a carbon black-dispersed polyamideimide solution for the inner peripheral layer was prepared.

-Formation of inner peripheral layer carbon black-dispersed polyamideimide dry film On the other hand, the cylindrical molded tube 11 shown in FIG. 2 has an outer diameter of 366 mm, a length of 600 mm, and a thickness of 6 m.
m aluminum cylinders were prepared. Such an aluminum cylinder is roughened to a surface roughness Ra of 0.40 μm by blasting with spherical glass particles. A silicone 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 to produce an aluminum cylindrical body.
Furthermore, as a spin coating process, as shown in FIG. 2, the cylindrical tube 11 was rotated at 50 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 cylindrical molding tube 11, and the carbon black-dispersed polyamideimide solution for inner peripheral layer was used as the coating solution 16, and extruded from the container 14 through the nozzle 15 having a diameter of 2 mm. When the coating liquid 16 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. In addition, at the time of application | coating, the non-application area | region of 20 mm was provided in the both ends of the cylindrical forming pipe 11. Next, the cylindrical molded tube 11 coated with the carbon black-dispersed polyamideimide solution for the inner peripheral layer is kept horizontal and heated and dried at 110 ° C. for 25 minutes while rotating at 6 rpm, and the inner peripheral layer carbon black-dispersed polyamideimide is dried. Got. In addition, as for the film thickness of the inner peripheral layer carbon black-dispersed polyamideimide dry film, the amount of the extrusion liquid from the nozzle 15 at the time of coating was adjusted so that the film thickness after drying described later has a desired value. Moreover, the amount of residual NMP in the inner peripheral layer carbon black-dispersed polyamideimide dry film was 24.1% by mass. 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 peripheral layer.

-Preparation of carbon black-dispersed polyamideimide solution for outer peripheral layer Next, N-methyl-2-pyrrolidone (NMP) of polyamideimide resin (Vilomax HR-40NN manufactured by Toyobo Co., Ltd.) is used for the dispersion (B). The solution (solid content rate is 17% by mass) is added so that the carbon black is 37.2 parts by mass with respect to 100 parts by mass of the total solid content of Viromax HR-20NN and Viromax HR-40NN, and the planetary type A carbon black-dispersed polyamideimide solution for the outer peripheral layer was prepared by mixing and stirring using a mixer (Aiko mixer manufactured by Aikosha Seisakusho).

-Formation of outer peripheral layer carbon black-dispersed polyamideimide dry film Using the obtained carbon black-dispersed polyamideimide solution for outer peripheral layer, the rotational speed of the cylindrical molded tube 11 was 40 rpm, and the moving speed of the nozzle 15 was 90 mm / min. The carbon black-dispersed polyamideimide solution for the outer peripheral layer was applied to the surface of the inner peripheral layer carbon black-dispersed polyamideimide dry film by the method at the time of applying the inner peripheral layer.
Next, the cylindrical molded tube 11 coated with the carbon black-dispersed polyamideimide solution for the outer peripheral layer is kept horizontal and heated and dried at 110 ° C. for 25 minutes while rotating at 6 rpm to obtain a carbon black-dispersed polyamideimide dried film of the outer peripheral layer. It was. In addition, as for the film thickness of the outer peripheral layer carbon black-dispersed polyamideimide dry film, the amount of the extrusion liquid from the nozzle 15 at the time of coating was adjusted so that the film thickness after drying described later has a desired value. The amount of residual NMP after drying was 34.9% by mass. In addition, since this residual NMP amount is measured after the outer peripheral layer is dried, it is the residual NMP amount that combines the inner peripheral layer and the outer peripheral layer.

-Preparation of intermediate transfer belt A cylindrical molded tube 11 in which an outer peripheral layer carbon black-dispersed polyamideimide dry film was laminated on the inner peripheral layer carbon black-dispersed polyamideimide dry film obtained as described above was formed at 20 ° C at 175 ° C. This was heated at 210 ° C. for 40 minutes and at 250 ° C. for 20 minutes to form a carbon black-dispersed polyamideimide film. Thereafter, when the temperature of the cylindrical molded tube 11 was cooled to room temperature (25 ° C.), the polyamideimide film was peeled from the cylindrical molded tube 11. The obtained polyamideimide film was cut to a width of 362 mm to obtain an intermediate transfer belt B. Two intermediate transfer belts B were joined to obtain an intermediate transfer belt 58 having a circumference of 2111 mm.

  Further, when the film thicknesses of the outer peripheral layer and the inner peripheral layer were measured using the remaining cut ends of the intermediate transfer belt B, they were 32.3 μm and 64.8 μm, respectively. Further, when ρs, ρv, and ρexs were measured, they were 12.43 LogΩ / □, 12.09 LogΩ · cm, and 11.31 LogΩ / □, respectively. The results are shown in Table 3.

(Preparation of intermediate transfer belts 59 to 63)
In the production of the intermediate transfer belt 58, the amount of carbon black (CB) contained in the inner peripheral layer, the amount of carbon black (CB) contained in the outer peripheral layer, and the inner layer carbon black-dispersed polyamideimide dry film are formed. Intermediate transfer belts 59 to 63 were produced in the same manner as the intermediate transfer belt 58 except that the drying temperature and time after application were changed to the values shown in Table 3, respectively. In the intermediate transfer belts 59 to 63, the drying conditions of the inner peripheral layer and the outer peripheral layer are the same, and are the drying conditions shown in Table 3, respectively. When the outer peripheral layer thickness, inner peripheral layer thickness, ρs, ρv, and ρexs were measured, the values shown in Table 3 were obtained.

(Measurement of surface resistivity ρs)
FIG. 3 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 (5).
ρs = [π (d2 + d1) / (d2−d1)] × (V / I) (5)
(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%. )

(Measurement of volume resistivity ρv)
FIG. 4 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 (6).
ρv = [(π × d1 ² ) / 4] × (V / I) × (1 / t) (6)
(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%.)

(Measurement of creepage resistivity ρexs on the pole surface)
FIG. 5 is a schematic cross-sectional view of a creeping resistivity measuring device on the pole surface. A measurement sample 27 is disposed on the back electrode 23 connected to the GND. The voltage application electrode 28 and the current measurement electrode 29 are arranged on the measurement sample 27, and the measurement sample 27 is sandwiched between the back electrode 23, the voltage application electrode 28, and the current measurement electrode 29. A direct current voltage is applied by a direct current power source 25 connected to the voltage application electrode 28, a current amount flowing by a microammeter 26 connected to the current measurement electrode 29 is measured, and a creeping resistivity on the pole surface is calculated.

FIG. 7 shows a schematic plan view of electrodes used in a creeping resistivity measuring device for the pole surface. A current measuring electrode 29 is arranged around the voltage applying electrode 28 and parallel to the voltage applying electrode 28 on both sides thereof. Here, d4 to d6 represent the width of the voltage application electrode 28 and the current measurement electrode 29, the length of the voltage application electrode 28 and the current measurement electrode 29, and the distance between the voltage application electrode 28 and the current application electrode 29, respectively. These values can be arbitrarily set according to the size and shape of the measurement sample. In the measurement of the creeping resistivity on the pole surface in this example, d4 to d6 were set to the following values, respectively.
d4 = 10mm
d5 = 50mm
d6 = 10mm
The creeping resistivity ρexs on the pole surface was calculated by the following formula (7).
ρexs = V / (I / 2) × (d5 / d6)
= 2 × (V / I) × (d5 / d6) (7)
(Here, V represents the voltage value (V) applied to the voltage application electrode 28, and I represents the current value (A) detected by the microammeter 26. The creeping resistivity of the pole surface in the present example. In the measurement, the voltage applied to the voltage application electrode 28 was set to 500 V. Further, the current value I was set to a value 15 seconds after the voltage V was applied. (Performed in an environment with a humidity of 40%.)
Incidentally, the creeping resistivity of the pole surface is different from the so-called surface resistivity that has been measured in the past by setting the electrode shape and the measurement conditions as described above. ) To measure resistivity.

(Example 1)
An image quality evaluation machine (secondary transfer roll is disconnected from the power supply built in the evaluation machine main body) by modifying a full-color multifunction peripheral (DocuColor 8000 Digital Press: manufactured by Fuji Xerox) having the basic configuration shown in FIG. The intermediate transfer belt 1 was mounted on the model 610D) and modified so that a voltage could be directly applied to the secondary transfer roll from the outside.
Double-sided printing was performed on A3 paper (Fuji Xerox J paper) using this image quality evaluation machine. During printing, the transfer voltage applied to the secondary transfer roll was set to 4.0 kV. As output images, halftone pattern 1 (Cyan 70% density) and halftone pattern 2 (Black 20% density) images were printed. The halftone pattern 1 was visually evaluated for scale unevenness, white spots, and graininess, and the halftone pattern 2 was used to visually evaluate the region where the toner image was missing (HT unevenness). 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.

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

<Deterioration of graininess>
G0: No dot blurring G1: Some dot blurring (within acceptable level)
G2: Dot blur is observed (within acceptable level)
G3: The blurring of dots can be easily confirmed (within acceptable level).
G4: The level at which dot blurring can be confirmed and becomes unacceptable G5: The dot blurring becomes noticeable and greatly exceeds the allowable level G6: The dot shape cannot be confirmed due to blurring

<Area where toner image is missing on output image (HT unevenness)>
G0: No occurrence G1: Slight occurrence (within acceptable level)
G2: Occurrence is observed (within acceptable level)
G3: Generation 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 and far exceeds the allowable level Image quality evaluation results are shown in Tables 4 to 6 and FIG. As shown in FIG.

(Examples 2-47)
In Example 1, the image quality was evaluated in the same manner as in Example 1 except that the intermediate transfer belt shown in Tables 4 to 6 was used instead of the intermediate transfer belt 1. The results are shown in Tables 4 to 6 and FIGS.

(Comparative Examples 1-16)
In Example 1, the image quality was evaluated in the same manner as in Example 1 except that the intermediate transfer belt shown in Tables 4 to 6 was used instead of the intermediate transfer belt 1. The results are shown in Tables 4 to 6 and FIGS.

From FIG. 8, good granularity is obtained when 11.6 LogΩ / □ ≦ ρs ≦ 14.0 LogΩ / □, whereas ρs <11.6 LogΩ / □ and 14.0 LogΩ / □ <ρs. In this case, it can be seen that the graininess is significantly deteriorated.
In addition, even if 11.6 LogΩ / □ ≦ ρs ≦ 14.0 LogΩ / □, white spots and scales with uneven density in scales are included.

  From FIG. 9, the white spot generation grade is well suppressed when 10.3 LogΩ · cm ≦ ρv ≦ 14.0 LogΩ · cm, whereas ρv <10.3 LogΩ · cm and 14.0 LogΩ · cm < In the case of ρv, it can be seen that the white spot generation grade is significantly deteriorated. Even if 10.3 Log Ω · cm ≦ ρv ≦ 14.0 Log Ω · cm, there is a white spot generation grade (enclosed line portion), but this is not in the range of 9.8 LogΩ / □ ≦ ρexs. It is due to that.

From FIG. 10, the white spot generation grade is satisfactorily suppressed when 9.8 LogΩ / □ ≦ ρexs, whereas the white spot generation grade is significantly deteriorated when ρexs <9.8 LogΩ / □. I understand. In addition, even if 9.8 LogΩ / □ ≦ ρexs, there is a bad white spot generation grade (enclosed line part), but this is not in the range of ρv 10.3 LogΩ · cm ≦ ρv ≦ 14.0 LogΩ · cm. It is due to that.
From FIG. 11, the scale-like density unevenness generation grade is satisfactorily suppressed when ρexs ≦ 13.4 LogΩ / □, whereas the scale-like density unevenness generation grade is remarkable when 13.4 LogΩ / □ <ρexs. You can see that it is getting worse.

From FIG. 12, it can be seen that the white spot generation grade is satisfactorily suppressed when 1.2 ≦ du / dl, whereas the white spot generation grade tends to deteriorate when du / dl <1.2. It is done. In addition, even if 1.2 ≦ du / dl, there is a white point grade that is bad (boxed line part). This is because ρexs is not in the range of 9.8 LogΩ / □ ≦ ρexs, or ρv is 10 This is caused by not being in the range of 3 LogΩ · cm ≦ ρv ≦ 14.0 LogΩ · cm.
From FIG. 13, when du / dl ≦ 4.0, the HT unevenness generation grade is suppressed well, whereas when 4.0 <du / dl, the HT unevenness generation grade is significantly deteriorated. I can see that

DESCRIPTION OF SYMBOLS 11 Cylindrical forming pipe 14 Container 15 Nozzle 16 Coating liquid 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 28 Voltage application electrode 29 Current measurement electrodes 101a to 101d Image carrier 102a to 102d Charging device 103a to 103d Developing device 104a to 104d Image carrier cleaning device 105a to 105d Primary transfer roll 106a to 106d Tension roll 107 Intermediate transfer belt 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 116 Secondary Transfer Belt

Claims (4)

A resinous annular body satisfying the following formulas (1) to (3).
11.6 LogΩ / □ ≦ ρs ≦ 14.0 LogΩ / □ (1)
10.3 LogΩ · cm ≦ ρv ≦ 14.0 LogΩ · cm (2)
9.8 LogΩ / □ ≦ ρexs ≦ 13.4 LogΩ / □ (3)
(In the above formulas (1) to (3), ρs is the surface resistivity of the outer circumferential surface of the annular body, ρv is the volume resistivity of the outer circumferential surface of the annular body, and ρexs is the creeping resistance of the surface of the circumferential surface of the annular body. (The rate is expressed respectively.) The resin-made annular body according to claim 1, comprising at least two layers of an outermost peripheral layer and an innermost peripheral layer, and satisfying the following formula (4).
1.2 ≦ du / dl ≦ 4.0 (4)
(In the above formula (4), du represents the film thickness (μm) of the outermost peripheral layer, and dl represents the film thickness (μm) of the innermost peripheral layer.)   An annular body unit comprising: the annular body according to claim 1 or 2; and a plurality of rotating members that span the annular body in a tensioned state so as to be rotatable from an inner surface side. An image carrier, a charging unit for charging the image carrier, an exposure unit for forming an electrostatic latent image on the image carrier charged by the charging unit, and an electrostatic latent image on the image carrier. Developing means for developing a toner image, primary transfer means for transferring the toner image to an intermediate transfer belt, and secondary transfer means for transferring the toner image transferred to the intermediate transfer belt to a transfer medium; Fixing means for fixing the toner image on the transfer medium,
An image forming apparatus using the annular body according to claim 1 or 2 as the intermediate transfer belt.