JP5102058B2 - A method for measuring an electrical resistance distribution in a film thickness direction of a conductive polymer sheet, and an intermediate transfer medium and an intermediate transfer medium made of the conductive polymer sheet. - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intermediate transfer medium capable of reducing and improving the unevenness when carrying and transferring a toner image, excellent in a mechanical characteristic and durability, and capable of providing an image of high quality stably over a long period, as a result thereof, and an image forming device using the same, together with a novel measuring-evaluating means for the intermediate transfer medium. <P>SOLUTION: A thickness-directional electric resistance distribution of the image-forming intermediate transfer medium comprising a conductive material dispersed in a polymer is measured by a novel measuring method for a conductive polymer sheet, that is an application technique of a surface potential microscope (SPoM), and the distribution is same along a face direction of the medium, and a ratio Rmax/Rmin of the maximum value Rmax to the minimum value Rmin is 3-10 in the distribution. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  In the present invention, first, an electrophotographic intermediate transfer medium (hereinafter sometimes simply referred to as “intermediate transfer medium”) in an electrophotographic image forming apparatus is typically used. The present invention relates to a method for measuring the electrical resistance distribution in the film thickness direction. Further, a charging unit, an image writing unit, and a developing unit are arranged around the image carrier, and the toner image formed on the image carrier is temporarily transferred to the intermediate transfer medium. The present invention relates to an intermediate transfer medium evaluated by the above-described measurement method in an electrophotographic image forming apparatus such as a copying machine, a printer, or a fax machine that transfers the image to a sheet-like medium (recording medium).

  In recent years, electrophotographic image forming apparatuses capable of copying and printing full-color images have been put into practical use. As a transfer method of a full-color image to a transfer material, a plurality of (usually yellow, magenta, cyan, and black) color images formed on an image carrier such as a photoconductor are sequentially superimposed and transferred onto an intermediate transfer member. However, the intermediate transfer body double transfer system (also referred to simply as the intermediate transfer system) that transfers the transferred full-color toner image to the transfer material at a time is advantageous and widely available in terms of paper-free properties and full-surface copying. It has been put into practical use. In such an image forming apparatus, the intermediate transfer medium is positioned as one of key parts that influence the image quality.

  An image forming apparatus using an electrophotographic method has only one image carrier, and a revolver method that forms an image for each color with the image carrier, and a tandem method that uses one image carrier for each color. is there. The revolver method is relatively inexpensive, and the tandem method is expensive, but high-speed printing can be performed. The current mainstream is the tandem method that enables high-speed printing. The image forming apparatus referred to in the present invention means a printer, a copier, a facsimile machine or a printing machine, and an image forming apparatus targeted for a configuration in which these functions are combined.

An image forming apparatus used in the present invention will be described with an example.
FIG. 1 shows an example of an image forming apparatus that employs an intermediate transfer method, in which a drum-shaped intermediate transfer medium is used.
First, the primary transfer operation will be described.
The toner 27 developed on the belt photoreceptor 18 serving as an image carrier by a developing device (not shown) comes into contact with the intermediate transfer body 11 that rotates in synchronization with the belt photoreceptor 18 in the primary transfer portion A, and applies a predetermined bias potential. And transferred to the intermediate transfer member 11. The toner images developed in black, yellow, magenta, and cyan are transferred from the belt photoreceptor 18 to the intermediate transfer drum 11, and the color toner images are superimposed on the intermediate transfer body 11.

Next, the operation of secondary transfer will be described.
The secondary transfer roller 23 is usually separated from the intermediate transfer body 11, but is in close contact with the intermediate transfer body 11 during the secondary transfer. The transfer material 15 is conveyed in synchronization with the intermediate transfer member 11 and passes between the intermediate transfer member 11 and the secondary transfer roller 23. At this time, a bias voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 23, and the toner 27 is secondarily transferred to the transfer material 15. Thereafter, the transfer material 15 is given a predetermined charge by the sheet neutralizing device 28, and the staying charge is removed, so that the transfer material 15 is easily peeled off from the intermediate transfer body 11.
Thereafter, the transfer material 15 moves to the fixing step. The toner 27 remaining on the intermediate transfer body 11 is removed and initialized by a predetermined intermediate transfer cleaning device 13 in contact with the intermediate transfer body 11. Examples of the intermediate transfer cleaning device 13 include a brush and a roller.

Next, an example of a so-called tandem method using a seamless belt as an intermediate transfer medium will be described.
In FIG. 2, the printer main body 10 includes an image writing unit 12, an image forming unit 13, and a paper feeding unit 14 for performing color image formation by electrophotography. Based on the image signal, the image processing unit converts the image into black (BK), magenta (M), yellow (Y), and cyan (C) color signals for image formation and transmits them to the image writing unit 12. To do. The image writing unit 12 is a laser scanning optical system including, for example, a laser light source, a deflector such as a rotating polygon mirror, a scanning imaging optical system, and a mirror group, and includes four writings corresponding to the color signals described above. Image writing corresponding to each color signal is performed on image carriers (photoconductors) 21BK, 21M, 21Y, and 21C that have an optical path and are provided for each color of the image forming unit 13. This apparatus corresponds to an intermediate transfer type image forming apparatus having a four-tandem configuration.

  The image forming unit 13 includes photoconductors 21BK, 21M, 21Y, and 21C that are image carriers for black (BK), magenta (M), yellow (Y), and cyan (C). . As each photoconductor for each color, an OPC photoconductor is usually used. Around the photoreceptors 21BK, 21M, 21Y, and 21C, there are a charging device, an exposure unit for laser light from the writing unit 12, and developing devices 20BK, 20M, 20Y for black, magenta, yellow, and cyan, respectively. 20C, primary transfer bias rollers 23BK, 23M, 23Y, and 23C as a primary transfer unit, a cleaning device (not shown), and a photosensitive member discharging device (not shown) are disposed. The developing devices 20BK, 20M, 20Y, and 20C use a two-component magnetic brush developing system. The intermediate transfer belt 22, which is a belt component, is interposed between the photosensitive members 21BK, 21M, 21Y, and 21C and the primary transfer bias rollers 23BK, 23M, 23Y, and 23C, and is formed on the photosensitive members. The toner images of each color are sequentially superimposed and transferred.

  On the other hand, the transfer paper (recording medium) P is fed from the paper feeding unit 14 and then carried by the transfer conveyance belt 50 which is a belt constituting unit via the registration roller 16. When the intermediate transfer belt 22 and the transfer conveyance belt 50 come into contact with each other, the toner image transferred onto the intermediate transfer belt 22 is subjected to secondary transfer (collective transfer) by a secondary transfer bias roller 60 as a secondary transfer unit. ) As a result, a color image is formed on the transfer paper P. The transfer paper P on which the color image is formed is conveyed to the fixing device 15 by the transfer conveying belt 50, and after the image transferred by the fixing device 15 is fixed, it is discharged out of the printer main body.

  The intermediate transfer medium is made by an extrusion molding method, a centrifugal molding method, a roll coating method (mold coating method), a dip coating, or a combination thereof. The extrusion method is suitable for mass production, but generally has a large variation in electric resistance, and it is difficult to ensure dimensional accuracy. Centrifugal molding and roll coating methods become more difficult to dry uniformly as the desired thickness increases, and in related, the individual deviation of the electrical characteristics as determined by the distribution (dispersibility) of the dispersed conductive material (filler) There is a fault that tends to occur.

  The intermediate transfer medium is either (1) formed of a dielectric or at least the surface of the intermediate transfer medium to which toner is transferred is formed of a dielectric, or (2) is the intermediate transfer medium formed of a medium resistance material. The above-mentioned extrusion molding method, centrifugal molding method, and roll coating method are suitable as a method for producing the intermediate resistance type intermediate transfer medium (2). On the other hand, in many cases, a core layer material is used. Is prepared by dip coating, spray coating or laminating, and is suitable for the dielectric type intermediate transfer medium manufacturing method (1).

  In the dielectric type intermediate transfer medium, the charge derived from the transfer bias and the triboelectric charge affects the transfer process, which is the next process, and requires a special static eliminating device for removing the charge, which increases the cost. For this reason, recently, intermediate resistance type intermediate transfer media are increasingly used. However, it is not always possible to distinguish between a dielectric type and a medium resistance type, and an actual intermediate transfer medium has more or less the properties of both.

  Judging from the experience of the present inventors, in an electrophotographic image forming process involving transfer, a medium resistance type intermediate transfer medium is most preferable, and the core of the structure is a conductive material dispersed in a polymer. It is preferable to make it a layer. Examples of such an intermediate transfer medium are disclosed in Patent Documents 1 to 3, for example.

  By the way, the characteristics of the intermediate transfer medium include electrical characteristics such as surface resistance and volume resistance, and mechanical characteristics such as film thickness, hardness, elastic modulus, elongation, surface friction, and flexibility. A typical measurement example is as follows. The surface resistance and volume resistance can be measured based on “JIS K6911 5.13.1”. The surface micro hardness can be measured by a micro rubber hardness meter (for example, MD-1 manufactured by Kobunshi Keiki Co., Ltd.). The tensile strength and breaking strength can be measured based on “JIS K7113”. Flexibility can be measured based on “JIS P8115” as the number of bending resistances. The surface roughness Rz can be measured based on “JIS B0601-2001”, and a stylus type surface roughness measuring instrument (for example, Surfcom manufactured by Tokyo Seimitsu Co., Ltd.) can be used. The coefficient of static friction can be measured, for example, by the Euler belt type (edited by the Japan Society of Mechanical Engineers, “Basics of Mechanical Engineering, A3 Mechanics / Mechanical Mechanics” P35 (published in 1986)). The measurement of these characteristics may employ standard measurement methods from industry and academic societies, and it goes without saying that it can be developed independently as long as it has good reproducibility.

  However, the conventional characteristic measurement of the intermediate transfer medium has a very fundamental and essential problem that three-dimensional information that directly reflects the material actual condition inside the intermediate transfer medium cannot be obtained. In particular, in a medium resistance type intermediate transfer medium in which a conductive material is dispersed in a solution, and the solution is formed into a film, the three-dimensional state of the conductive material dispersion determines the basic characteristics. This confirmation means has not existed in the past.

  In other words, the material evaluation of the sheet-like member has been limited to the range of evaluation in which it is regarded as a two-dimensional body in many cases. Regarding the thickness direction of the film, even though the material structure and the layer structure are considered as design issues, little consideration has been given to the distribution of microscopic characteristics. Therefore, even if the macro and micro two-dimensional characteristic values along the surface are within the range of characteristics desired from the process, there is a clear superiority or inferiority in the durability of the image forming process and the quality of the image. It was.

  One of the main reasons why the micro-characteristic distribution is not taken into account is that it is difficult to confirm with the prior art. The state of the cross section of the film can be easily observed with SEM (scanning electron microscope) or TEM (transmission electron microscope), but these are secondary electrons from the sample, reflected electrons, or electron density of the sample. For example, in a material in which carbon particles are dispersed in a polymer, the carbon distribution that determines the distribution of electrical characteristics (mainly electrical resistance in this case) is confirmed with sufficient accuracy. I couldn't. Even with detection methods that target elements, molecular structures and bonding groups, it is almost impossible.

  In the end, it is difficult to achieve an intermediate transfer medium that is highly superior in performance and durability only within the design range related to the material structure and layer structure. It can be achieved for the first time by establishing and preferably defining it.

JP 2007-25096 A JP-A-5-345368 JP 2004-32834 A

  The present invention has been made in view of the above-described problems of the prior art, and its purpose is to reduce and improve toner image holding and transfer unevenness, and to provide uniform and isotropic mechanical characteristics. And, as a result, an intermediate transfer medium capable of stably obtaining a high-quality toner image over a long period of time is provided together with the measurement / evaluation means, and a novel image forming apparatus including the intermediate transfer medium is also provided. There is.

  The present inventors have intensively studied to solve the above-mentioned conventional problems, and the present inventors have disclosed “Japan Hardcopy 2003 Papers; p. 301”, “The Journal of the Imaging Society of Japan, 42 (4), p. 39 ( 2003) ”,“ Ricoh Technical Report, 30, p. 27 (2004) ”, etc., the Cross-sectional SPoM (SPoM; Surface Potential Microscopy) originally developed as a means for analyzing the internal structure of the toner, We have developed a technology that can be applied to the measurement method for conductive polymer sheets used in intermediate transfer media, and designed a suitable intermediate transfer medium for an electrophotographic image forming apparatus only by relying on such measurement and evaluation methods. The present invention has been found and the present invention has been completed.

  More specifically, the intermediate transfer medium has a conductive material dispersed in a polymer, and when observed with Cross-section SPoM, the electrical resistance distribution in the thickness direction is substantially the same in the plane direction of the medium. It has been found that the above object can be achieved with an intermediate transfer medium in which the ratio Rmax / Rmin between the maximum value (Rmax) and the minimum value (Rmin) of the distribution is 3 to 10. The present invention has been made based on such knowledge.

  That is, the above object is achieved by the following inventions (1) to (8).

(1) A conductive polymer sheet having a uniform thickness is cut to a thickness of 0.1 to 1.0 μm on a surface perpendicular to the front and back surfaces to obtain a section, and the section is formed into a substantially conductive plate. Attaching the cut surface to the front, charging the exposed cut surface to a certain polarity with a charger, observing the charged surface with a surface potential microscope, and observing the potential distribution in the film thickness direction of the polymer sheet A method for measuring an electrical resistance distribution of a conductive polymer sheet.

(2) An electrophotographic intermediate transfer medium for developing an electrostatic latent image formed on an image carrier with toner and transferring the obtained toner image to a recording medium, wherein the electrophotographic intermediate transfer medium comprises: An electrical resistance distribution measured by the electrical resistance measurement method according to claim 1 is substantially the same in the surface direction of the intermediate transfer medium. An electrophotographic intermediate transfer medium, wherein the ratio Rmax / Rmin of the maximum value (Rmax) and the minimum value (Rmin) of the electrical resistance distribution is 3 to 10.

(3) The electrophotographic intermediate transfer medium according to claim 2, wherein the volume resistance is 10 ⁸ to 10 ¹² Ω · cm.

(4) The electrophotographic intermediate transfer medium according to (2) or (3), wherein the polymer is a polyimide resin, and the conductive particles are carbon black.

(5) The electrophotographic intermediate transfer medium according to any one of claims 2 to 4, wherein the electrophotographic intermediate transfer medium has a seamless belt shape.
(6) The electrophotographic intermediate transfer medium according to (5), wherein the electrophotographic intermediate transfer medium having a seamless belt shape is formed by a roll coating method.

(7) An image carrier on which an electrostatic latent image is formed and capable of carrying a toner image, a developing means for developing the electrostatic latent image formed on the image carrier with toner, and developed by the developing means An intermediate transfer medium on which the toner image is primarily transferred; and transfer means for secondary transfer of the toner image carried on the intermediate transfer medium to a recording medium. An image forming apparatus, which is the intermediate transfer medium according to claim 6.

(8) The image forming apparatus is an image forming apparatus that forms a full-color image by superimposing a plurality of colors of toner, and includes a plurality of latent image carriers corresponding to the developing units of the respective colors arranged in series. The image forming apparatus according to claim 7.

(1) According to the invention described in claim 1, a conductive polymer sheet having a uniform thickness is cut to a thickness of 0.1 to 1.0 μm on a surface perpendicular to the front and back surfaces to obtain a section, The section was attached to a substantially conductive plate with the cut surface facing up, and the exposed cut surface was charged to a certain polarity with a charger, and the charged surface was observed with a surface potential microscope. By observing the potential distribution in the film thickness direction of the conductive polymer sheet, the conductive filler distribution that uniquely determines the electrical and mechanical properties of the conductive polymer sheet can be observed three-dimensionally as a resistance distribution. effective.

(2) According to the invention described in claim 2, the intermediate transfer medium is a conductive polymer in which conductive particles are dispersed, and the electrical resistance measurement method according to claim 1 is used. The measured electric resistance distribution is substantially the same in the surface direction of the intermediate transfer medium, and the ratio Rmax / Rmin between the maximum value (Rmax) and the minimum value (Rmin) of the electric resistance distribution is 3 to 10. Thus, according to such an embodiment, the resistance component becomes isotropic, and there is an effect that unevenness of toner image holding and transfer can be reduced or improved. At the same time, the mechanical properties of the intermediate transfer medium are uniform and isotropic, and partial expansion and contraction and distortion are reduced, so that the durability of the member can be increased.

(3) According to the invention described in claim 3, in the layer formed by dispersing the conductive material in the polymer of claim 2, the volume resistance range is 10 ⁸ to 10 ¹² Ω · cm. This has the effect of achieving stable transfer characteristics.

(4) According to the invention described in claim 4, in the layer formed by dispersing the conductive material in the polymer of claim 2 or 3, the polymer is a polyimide resin, and the conductive material is carbon. As a result, the productivity of the intermediate transfer medium is high, the quality can be easily controlled, and a high-quality intermediate transfer medium can be obtained at low cost.

(5) According to the invention described in claim 5, by making the intermediate transfer medium of any one of claims 2 to 4 into a seamless belt shape, the degree of freedom of configuration of the electrophotographic system is increased, and end detection is performed. By making it unnecessary, there is an effect that the apparatus can be reduced in size and simplified.

(6) According to the invention described in claim 6, by forming the intermediate transfer medium having the seamless belt shape of claim 5 by a roll coating method, the orientation of polyimide during coating is small, and the circumferential direction There is an effect that a difference in physical properties in the axial direction is unlikely to occur and a stable belt running property can be obtained.

(7) According to the invention described in claim 7, an image carrier on which an electrostatic latent image is formed and capable of carrying a toner image, and the electrostatic latent image formed on the image carrier are developed with toner. Developing means, an intermediate transfer medium on which the toner image developed by the developing means is primarily transferred, and a transfer means for secondary transfer of the toner image carried on the intermediate transfer medium to a recording medium. Thus, since the intermediate transfer medium is the intermediate transfer medium according to any one of claims 2 to 6, there is an effect that an image having excellent image quality can be obtained.

(8) According to the invention described in claim 8, the image forming apparatus forms a full color image by superimposing a plurality of colors of toner, and a plurality of latent images corresponding to the developing means of each color. By arranging the carriers in series, there is an effect that an image forming excellent in driving stability, image forming speed and image quality can be obtained.

  An object of the present invention is to provide a method for measuring the electrical resistance distribution of a conductive polymer sheet, and a novel electrophotographic image forming intermediate transfer medium optimized by such a measuring method. The best mode for carrying out the invention will be described in detail. However, it goes without saying that the present invention is not limited to this.

First, an explanation regarding the intermediate transfer medium will be given. The intermediate transfer medium for image formation of the present invention has a configuration in which a conductive material is dispersed in a polymer.
The polymer as a basic material for the intermediate transfer medium will be described as follows.
The polymer is first selected in consideration of releasability with respect to toner and original mechanical properties.

As a polymer for an intermediate transfer medium having good releasability, silicone resins and elastomers, polyolefin materials, fluorine resins and elastomers are known.
Silicone resins and elastomers include, for example, JP-A-5-46035, JP-A-8-30117, JP-A-9-269676, JP-A-10-20538, JP-A-11-231678, and the like. There is a disclosure.
Polyolefin-based materials are disclosed in, for example, JP-A-5-31116, JP-A-7-24912, and the like.
Examples of fluorine-based resins and elastomers include JP-A-5-40417, JP-A-6-234903, JP-A-7-92825, JP-A-8-267605, and JP-A-10-166508. There is a disclosure.

As polymers for intermediate transfer media having excellent mechanical properties, polycarbonate materials, polyester materials, polyurethane materials, polyimide materials, materials in which fluorine resin fine particles or fluorine organic compounds are dispersed in polyimide are known. .
Polycarbonate materials are disclosed in, for example, JP-A-6-93175, JP-A-6-149081, JP-A-6-149083, JP-A-10-10880, JP-A-13-31849, and the like. is there.
Polyester materials are disclosed in, for example, JP-A Nos. 13-13801 and 13-18284.
Polyurethane materials are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 10-319727 and 11-30915.
Polyimide-based materials are disclosed in, for example, JP-A-7-156287, JP-A-8-176319, JP-A-11-24427, JP-A-11-170389, JP-A-12-172085, and the like. is there.
Materials in which fluorine resin fine particles or fluorine organic compounds are dispersed in polyimide are disclosed in, for example, JP-A-11-156971, JP-A-11-119560, JP-A-7-156287, and the like.

  Any of the resins listed above can be used in the present invention, but considering various physical and chemical hazard conditions in actual use, according to the knowledge of the present inventors, intermediate As the transfer medium polymer, a polyimide resin is most preferably used among the above.

  Polyimide resins are excellent in heat resistance, mechanical properties, chemical resistance, radiation resistance, etc., so various molding materials such as films and sheets, paints such as enamels for electric wires, electronic materials, flexible printed boards It is a fact well known to engineers and researchers in the field that it is widely used for applications such as heat-resistant substrates, semiconductor sealing materials, adhesives, and organic-inorganic inorganic composites.

  Attempts have been made to improve physical properties by adding insulating fine particles to this polyimide resin. For example, Japanese Patent Application Laid-Open No. 63-172741 discloses that heat resistance is improved and the coefficient of thermal expansion is reduced. In addition, it is disclosed in Japanese Patent Application Laid-Open Nos. 6-145378 and 11-109761 to improve the slipperiness and running durability. In addition, since carbon black dispersed in a polyimide resin can provide light-shielding properties and conductivity, it can be used as a black matrix for color filters of liquid crystal display devices using light-shielding properties. It is used as an electromagnetic wave absorbing sheet as a coating material, as a planar heating element.

  These cases, especially when used as film-like or sheet-like members, show that polyimide-based resins are engineering plastics with outstanding performance and ease of use. Can be used effectively.

  The polyimide here is generally obtained by a condensation reaction between an aromatic polycarboxylic acid anhydride or a derivative thereof and an aromatic diamine. However, because it has insoluble and infusible properties due to its rigid main chain structure, a polyamic acid (or polyamic acid to polyimide precursor) soluble in an organic solvent is first synthesized from an acid anhydride and an aromatic diamine. Molding is performed by various methods at a stage, and then polyimide is obtained by dehydration cyclization (imidization) by heating or a chemical method (see Chemical Formula 1).

(In the formula, Ar ¹ represents a tetravalent aromatic residue containing at least one carbon 6-membered ring, and Ar ² represents a divalent aromatic residue containing at least one carbon 6-membered ring.)

Specific examples of the aromatic polyvalent carboxylic acid anhydride are given below.
For example, ethylenetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,2 ′, 3 , 3′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 2, 2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1 -Bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2, -Bis (3,4-dicarboxylphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4 , 5,8-Naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9 , 10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, and the like. These may be used alone or in combination of two or more.

Specific examples of aromatic diamines that can be used in combination are given below.
For example, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 3,4′- Diaminodiphenyl ether, bis (3-aminophenyl) sulfide, (3-aminophenyl) (4-aminophenyl) sulfide, bis (4-aminophenyl) sulfide, bis (3-aminophenyl) sulfide, (3-aminophenyl) (4-aminophenyl) sulfoxide, bis (3-aminophenyl) sulfone, (3-aminophenyl) (4-aminophenyl) sulfone, bis (4-aminophenyl) sulfone, 3,3′-diaminobenzophenone, 3, 4′-diaminobenzophenone, 4, '-Diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (4- Aminophenoxy) phenyl] methane, 1,1-bis [4- (3-aminophenoxy) phenyl] ethane, 1,1-bis [4- (4-aminophenoxy) phenyl] -ethane, 1,2-bis [ 4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2, 2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] butane, 2, -Bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1 , 1,3,3,3-hexafluoropropane, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) Benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (3- Aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophen Xy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfoxide, bis [4- (4-aminophenoxy) phenyl] sulfoxide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [ 4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,4-bis [4- (3 -Aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 4,4'-bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4'- Bis [3- (3-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [4- (4-a No-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, bis [4- {4- (4-amino Phenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4- (4-aminophenoxy) phenoxy] -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α , Α-dimethylbenzyl] benzene and the like. These are used individually or in mixture of 2 or more types.

  A polyimide precursor (polyamic acid) can be obtained by polymerizing the aromatic polyvalent carboxylic acid anhydride component and the diamine component in a substantially equimolar organic polar solvent.

A method for producing a polyamic acid will be specifically described.
Examples of the organic polar solvent used in the polymerization reaction of polyamic acid include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, and N, N. -Acetamide solvents such as dimethylacetamide, N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, phenol, o-, m- or p-cresol, xylenol , Phenolic solvents such as halogenated phenol and catechol, ether solvents such as tetrahydrofuran, dioxane and dioxolane, alcohol solvents such as methanol, ethanol and butanol, cellosolve such as butyl cellosolve or hexamethyl Suhoruamido, .gamma.-butyrolactone, etc. can be mentioned, it is desirable to use these as the sole or mixed solvent. The solvent is not particularly limited as long as it dissolves polyamic acid, but N, N-dimethylacetamide and N-methyl-2-pyrrolidone are particularly preferable.

  First, one or a plurality of diamines are dissolved in the above organic solvent or diffused in a slurry state in an inert gas atmosphere such as argon or nitrogen. When the above-described at least one aromatic polycarboxylic acid anhydride or derivative thereof is added to this solution in a solid state, an organic solvent solution state or a slurry state, a ring-opening polyaddition reaction occurs with heat generation. Occurs, the viscosity of the polymerization solution increases rapidly, and a high molecular weight polyamic acid solution is obtained. The reaction temperature at this time is −20 ° C. to 100 ° C., preferably 60 ° C. or less. The reaction time is 30 minutes to 12 hours.

  In this reaction, contrary to the addition procedure, first, the aromatic polycarboxylic anhydride or derivative thereof is first dissolved or diffused in an organic solvent, and the solution or slurry of the diamine solid or organic solvent in this solution. May be added. Moreover, you may make it react simultaneously, and the mixing order of an acid dianhydride component and a diamine component is not limited.

  The above aromatic polycarboxylic acid anhydride or derivative thereof and the aromatic diamine component are weighed approximately equimolarly and dissolved in the organic polar solvent. In the present invention, the order of adding the aromatic tetracarboxylic dianhydride and the aromatic diamine is not limited. You may add simultaneously. Moreover, you may mix the organic polar solvent which melt | dissolved each.

  As described above, the polyamic acid composition according to the present invention is obtained by subjecting an aromatic polycarboxylic acid anhydride or derivative thereof and an aromatic diamine component to approximately equimolar amounts by polymerization reaction in an organic polar solvent. A polyamic acid solution in which the product is uniformly dissolved in the organic polar solvent is obtained.

Although these polyamic acid compositions can be easily synthesized as described above, it is easy to obtain a commercially available polyimide varnish in which the polyamic acid composition is dissolved in an organic solvent. Is possible.
These include, for example, Torenice (manufactured by Toray Industries, Inc.), U-Varnish (manufactured by Ube Industries, Ltd.), Rika Coat (manufactured by Nippon Nippon Chemical Co., Ltd.), Optmer (manufactured by JSR), SE812 (manufactured by Nissan Chemical Industries), CRC8000 (manufactured by Sumitomo Bakelite) ) And the like.

  Various additives can be added to the polyamic acid composition as necessary in order to improve various properties. Specific examples of various additives will be given.

  Various surface tension modifiers can be added for the purpose of improving surface flatness and leveling. These additives are generally known as leveling agents, antifoaming agents, and coating film defect improving agents. Of these, a particularly preferred additive is a silicone-based additive. Also, non-silicone additives are preferably used, for example, glycerin higher fatty acid esters, higher alcohol borate esters, fluorine-containing surfactants and the like. These addition amounts are 0.001 to 1% (composition weight).

  As the reinforcing agent, for example, one or more glass fibers, carbon fibers, aromatic polyamide fibers, silicon carbide fibers, potassium titanate fibers, and glass beads can be added. Further, for the purpose of improving slipperiness, one or more solid lubricants such as molybdenum disulfide, graphite, boron nitride, lead monoxide, lead powder and the like can be added.

  In addition, one or more usual additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, a lubricant, and a colorant can be added within a range not detracting from the object of the present invention.

  Among the resistance control agents for adjusting the electrical resistance value of the polyimide of the present invention, examples of the electronic conductive resistance control agent include carbon black, graphite, or metals such as copper, tin, aluminum, indium, tin oxide, Examples thereof include metal oxide fine powders such as zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, tin oxide doped with antimony, and indium oxide doped with tin. Examples of the ion conductive resistance control agent include tetraalkyl ammonium salt, trialkyl benzyl ammonium salt, alkyl sulfonate, alkyl benzene sulfonate, alkyl sulfate, glycerol fatty acid ester, sorbitan fatty acid ester, polyoxyethylene alkyl amine, poly Examples thereof include oxyethylene fatty alcohol ester, alkyl betaine, and lithium perchlorate. However, the present invention is not limited to these exemplary compounds.

  Of these resistance control agents, carbon black can be preferably used for polyimide. However, carbon black has a high cohesion between particles, and its affinity with other resins and solvents is weaker than that, so it is also difficult to uniformly mix or disperse. Therefore, in order to solve this problem, carbon black is uniformly mixed or dispersed by coating the surface of carbon black with various surfactants and resins to enhance the affinity with a solid or liquid base. Many technologies have been studied.

  As a method for improving the dispersibility of carbon black, a method of treating carbon black with a coupling agent has been studied (Japanese Patent Laid-Open No. 63-175869, Japanese Patent Laid-Open No. 63-158656, British Patent No. 1583564). And British Patent No. 1583411). These have the problem that the dispersion of the treated carbon black into the polymerizable monomer is still incomplete and the cost is high. In addition, a method using a monomer component in the presence of carbon black has also been proposed (Japanese Patent Laid-Open No. 64-6965, West German Patent No. 3102823, etc.). Since this method has poor grafting efficiency, carbon black after grafting was not sufficiently dispersed in the polymerizable monomer. Further, a method of treating carbon black by reacting with an organic compound by a polymer reaction using a surface functional group of carbon black has been studied (Japanese Patent Laid-Open Nos. 1-284564 and 5-241378). etc).

  Examples of organic compounds that can be used in the present invention include vinyl acetate, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, p-methoxystyrene, p-bromostyrene, and p-chlorostyrene. , Styrene compounds such as sodium p-styrenesulfonate, acrylic acid ester compounds such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, methacryl Methacrylic acid ester compounds such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, acrylonitrile, acrylamide, N-isopropylacrylamide, N-piperylacrylamide Of N- substituted acrylamide compounds, divinyl benzene, methylene bisacrylamide, 1,3-butane diol but dimethacrylate crosslinking monomer, etc. and the like, but is not limited thereto.

  The polyamic acid thus obtained can be imidized by (i) a method of heating or (ii) a chemical method. (I) is a method of converting to polyimide by heating to 200 to 350 ° C., and a polyimide resin can be obtained simply and practically. (Ii) is a polyamic acid that is formed from a carboxylic acid anhydride and a tertiary amine. The method of (i) is frequently used because it is a method of complete imidization by heating after a reaction reaction with a dehydrating cyclization reagent such as a mixture, and is a complicated and costly method compared to (i). .

  In order to complete imidization by heating, the intrinsic performance of the polyimide cannot be exhibited unless it is heated above the glass transition temperature of the polyimide used essentially. In order to evaluate the degree of imidization, the imidation rate is usually measured.

  Various methods for measuring the imidization rate are known, and nuclear magnetic resonance spectroscopy is calculated from the integral ratio of 1H attributed to an amide group in the vicinity of 9 to 11 ppm and 1H attributed to an aromatic ring in the vicinity of 6 to 9 ppm. (NMR method), Fourier transform infrared spectroscopy (FT-IR method), a method for quantifying moisture accompanying imide ring closure, and carboxylic acid neutralization titration method, but most commonly, Fourier transform red External spectroscopy (FT-IR method) is used.

In the Fourier transform infrared spectroscopy (FT-IR method), the imidization rate can be defined as follows.
Imidation ratio = (number of moles of imide group in the firing stage) / (number of moles of imide group when theoretically imidized at 100%) × 100

This can be determined from the absorbance ratio of the characteristic absorption of the imide group of IR. Typical examples are:
(1) Absorbance ratio between 725 cm ⁻¹ (immobilization vibration band of imide ring C═O group) which is one of characteristic absorptions of imide and benzene ring characteristic absorption 1,015 cm ⁻¹ (2) Characteristic absorption of imide Absorbance ratio between 1,380 cm ⁻¹ (inflection vibration band of imide ring C—N group) which is one of the above and 1,500 cm ⁻¹ characteristic absorption of benzene ring (3) One of characteristic absorption of imide Absorbance ratio between 1,720 cm ⁻¹ (inflection band of imide ring C═O group) and characteristic absorption of 1,500 cm ^{−1 of} benzene ring (4) 1,720 cm ⁻¹ which is one of characteristic absorption of imide The imidation ratio can be evaluated by using the absorbance ratio of amide group characteristic absorption 1,670 cm ⁻¹ (interaction between amide group N—H bending vibration and C—N stretching vibration).
Moreover, if it confirms that the multiple absorption band derived from an amide group over 3000-3300cm < ^-1 > has lose | disappeared, the reliability of imidation completion will increase further.

  The resistance control agent carbon black that can be most suitably used in the intermediate transfer medium of the present invention will be described.

  Carbon black is defined as an aggregate of fine spherical particles obtained by incomplete combustion of various hydrocarbons or carbon-containing compounds, and is a generic name for carbon materials that are nearly pure and have a chemical composition of 98% or more. It is. The type is generally classified by the production method, and is roughly classified into either pyrolysis of raw material hydrocarbons or incomplete combustion, and further subdivided according to the type of raw material. The contact method is a manufacturing method in which a flame is brought into contact with iron or stone, and includes a channel method and a gas black method (roller method) which is an improved method thereof. Channel black is a representative product of the contact method, and is collected by bringing a flame into contact with the bottom surface of channel steel.

  The furnace method is a method of generating carbon black by continuously pyrolyzing raw material hydrocarbons by combustion heat of fuel air, and is classified into a gas furnace method and an oil furnace method. The thermal method is a special production method in which natural gas is used as a raw material carbon source and combustion and thermal decomposition are repeated periodically. The feature is that carbon black having a large particle size can be obtained.

  Acetylene black is a kind of thermal process that uses acetylene as a raw material. However, the thermal decomposition of acetylene is an exothermic reaction while other raw materials are endothermic, so it is possible to omit the combustion cycle in the thermal process. Continuous operation is possible. The characteristics of acetylene black are that it develops crystallinity compared to ordinary carbon black and has a high structure, so it has excellent conductivity, and is used as a conductivity-imparting agent for dry batteries and various rubbers and plastics. Yes.

  The basic characteristics of carbon black will be described.

<I> Basic characteristics of carbon Carbon black is blended and dispersed in rubber, resin, paint and ink vehicles, and the important factors for imparting functions such as reinforcement, blackness, and conductivity are particle size and structure. In addition, it is the physicochemical properties of the particle surface, which is usually called the three major characteristics of carbon black, and various carbon blacks are produced by combining these.

(The three basic characteristics of carbon black)
(1) Particle size: Particle size and surface area (2) Structure: DBP oil supply (ml / 100g) and structure index (3) Surface chemical properties: Volatile content (%) and pH

<II> Physical Properties of Carbon Black (1) Particle Structure The minimum unit of carbon black is a combination of 30 to 40 carbon six-membered rings, and this network plane has 3 to 5 layers Van.
Crystallites stacked at almost equal intervals (3.5 to 3.9 mm) by the der Waals force are arranged concentrically and densely near the particle surface, but the arrangement becomes irregular as it goes inside. Yes. Such a feature is more prominent with fine particles, and thermal black with large particles is in a regular orientation state almost to the center. A structure in which 1000 to 2000 crystallites are aggregated to form one primary particle and these particles are chemically and physically bonded is called a structure.

(2) Particle size and its distribution Carbon black particles are in a state where the particles are fused together like a dumpling stabbed into a skewer, and each spherical particle characterizes a mountain and a valley of dumplings and dumplings. However, the particle diameter in which this is regarded as a single particle is closely related to performance in various applications, such as reinforcement and blackness.

(3) Aggregates and their distribution The carbon black particles form aggregates that are described in skewered dumplings or grapes, which are called structures. Depending on the degree of agglomeration, it is classified into a high (high), normal (medium), and low (low) structure. When blended with rubber, tensile stress and extrusion characteristics, when blended with ink and paint vehicles and resins. It is an important factor having a great influence on dispersibility, blackness, viscosity, conductivity, and the like. In the structure, condensed polycyclic aromatic hydrocarbons produced through complex chemical reactions in a production furnace at 1400 ° C. or higher are condensed into fine droplets, forming precursors as nuclei, and melted through mutual collisions. It is believed to have solidified and formed. The structure can be controlled by selecting the shape of the furnace and the dynamic thermodynamic conditions in the furnace. For example, a technique of adding a trace amount of an alkali metal salt is effective.

  The structure is measured by the amount of oil supply, compression porosity, bulk density, morphological analysis of the electron microscope image, etc., but the most commonly used oil supply amount is more entangled with each other, that is, the higher the high structure carbon black. This is an application of the phenomenon of absorbing oil of oil, and was once obtained by the hand kneading method using linseed oil, but now it is measured by a DBP (Dibutyl Phthalate) abstract meter that mechanizes the same principle. Mainstream.

(4) Specific surface area and non-porous specific surface area The specific surface area of carbon black is substantially determined by the size of a single particle. It is one of the most important properties because it has interactions with other substances on its surface as well as other solids. It is considered that pores are generally present on the surface of carbon black, and fine voids are present in the fusion part between the particles, and when the specific surface area is measured, the value obtained depends on the measurement principle. It is necessary to clearly distinguish whether or not it includes the surface area in the pores. Those including the surface area in the pores are referred to as the total specific surface area, and those excluding the surface area in the pores are referred to as the non-porous specific surface area. In general, the specific surface area is measured by a low temperature nitrogen adsorption method or iodine adsorption method using the BET equation, and the non-porous specific surface area is a CTAB adsorption method, an electron microscope, a “t” method or the like.

<III> Chemical characteristics of carbon black (1) Elemental composition and impurities Carbon black also contains oxygen, hydrogen, sulfur, ash and the like. Hydrogen is derived from the dehydrogenation reaction residue in the carbonization process of the raw material hydrocarbon, sulfur is derived from the raw material oil and fuel oil, and ash is derived from the raw material oil and water for cooling. On the other hand, oxygen includes basic oxides that are bonded by contact with air after the formation of carbon black particles, and acidic oxides that are secondarily generated by reaction with nitrogen dioxide, ozone, nitric acid, etc. It is thought that exists. Sulfur exists in both chemically bound and free forms, and free sulfur can be extracted with a solvent or an aqueous alkali sulfide solution, but bound sulfur is completely desorbed even at a high temperature of 1000 ° C. It is said not to release. The composition of ash is sodium, magnesium chloride and sulfate, calcium carbonate, iron oxide, silica and the like, and the compound tends to be more in furnace black than in channel black.

(2) Surface functional groups Most of the chemical reactivity of carbon black is derived from chemical functional groups known as surface oxides and active hydrogen. It is generally said that the functional group of the acidic oxide is a carboxyl group, a hydroxyl group, a quinone group, or a lactone group, and these are often represented by volatile composition, volatile content, pH, and the like.

  Any of the above-mentioned types can be used as the carbon black used in the carbon black dispersion of the present invention.

A method for surface treatment of carbon black will be described.
The surface of carbon black particles has a condensed aromatic ring and can be subjected to various surface treatments described below.

(1) Surface oxidation treatment When carbon black is treated with an oxidizing agent, a carboxyl group or a phenolic hydroxyl group is introduced into the condensed aromatic ring on the particle surface. Furthermore, the condensed aromatic ring on the surface of carbon black reacts with the following various reagents, and various functional groups can be introduced onto the particle surface.

Φ-H + HNO3 → Φ-COOH andΦ-OH

Φ-H + H2O2 → Φ-OH

Φ-H + HNO3 / H3SO4 → Φ-NO2 (reduction) → Φ-NH2

Φ-H + CH2O / OH- → Φ-CH2OH

Φ-H + R-Cl / AlCl3 → Φ-R

Φ-H + HOOC-RN ＝ NR-COOH → Φ-R-COOH

Φ-H + X-Φ-COOCOO-Φ-X → Φ-OCO-Φ-X

Φ-H + BuLi / TMEDA → Φ-Li

Φ-H + NaNH2 → Φ-Na

(2) Surfactant dispersion Carbon black can be dispersed with a normal anionic surfactant, nonionic surfactant, cationic surfactant, amphoteric surfactant, and the like.
Preferred surfactants include interfacial polyoxyethylene alkyl ether acetates, dialkyl sulfosuccinates, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polyoxypropylene block copolymers, and acetylene glycol-based interfaces. An activator is mentioned.

(3) Polymer (resin) dispersion Carbon black can be dispersed by steric hindrance repulsion of the polymer dispersant.
Examples of the polymer dispersant include poly (N-vinyl-2-pyrrolidone), poly (N, N′-diethylacrylazide), poly (N-vinylformamide), poly (N-vinylacetamide), poly (N— Vinylphthalamide), poly (N-vinylsuccinamide), poly (N-vinylurea), poly (N-vinylpiperidone), poly (N-vinylcaprolactam), poly (N-vinyloxazoline) and the like. A single or a plurality of polymer dispersants can be added. In addition to this, within the scope of the object of the present invention, a polymer material, a surfactant, and a dispersion stabilizer for inorganic salt damage can be used.

(4) Encapsulation treatment Carbon black is coated with a resin and dispersed in a solvent, or the resin is impregnated with carbon black, that is, carbon black is present in the surface layer or inside or the whole. Its characteristics can improve properties such as dispersion stability, surface wettability, rheological properties and electrical properties. In particular, with regard to dispersion stability, the dispersibility of the graft chain in a good solvent (easily dispersible in the dispersion medium and stability after dispersion) is remarkably improved, and in terms of electrical properties, the carbon black particles are polymer matrix. Since it is easily and uniformly dispersed in the inside, there is a feature that a constant resistance value can be obtained over a wide area.

(5) Grafting treatment The carbon black grafting treatment can be classified as follows based on the grafting mechanism.
(A) Graft polymerization on the surface of carbon black A method in which a vinyl monomer is polymerized using a polymerization initiator in the presence of carbon black, and the growing polymer chain generated in the system is captured on the particle surface.
(B) Graft polymerization from carbon black surface A method of growing a graft chain from a polymerization initiating group introduced to the carbon black surface.
(C) Grafting reaction between carbon black surface and polymer A method by a reaction between a functional group on the carbon black surface and a reactive polymer.

  Among these, the method a can be most easily performed, but since a non-grafted polymer is predominantly produced, a product having a large graft ratio cannot be obtained. On the other hand, the method (b) is characterized in that a polymer (graft chain) grows outward from the carbon black surface, so that a polymer having a high graft rate can be obtained. Furthermore, according to the method c, there is a great feature that the molecular weight and the number of graft chains can be controlled, and a graft ratio can be relatively large.

(6) Gas Phase Oxidation Method This is an oxidation treatment method of the carbon black surface by ozone treatment or plasma treatment. By irradiating the carbon black with plasma, a hydroxyl group or a carboxyl group can be attached to the carbon black surface by high energy of plasma.

  As the surface treatment method of carbon black, the method of (3) above is the simplest possible surface treatment. According to the study by the present inventors, carbon black whose surface is treated with silicone-modified polyimide and a dispersion medium are used. Desired particle size distribution and particle size are easily obtained.

A typical carbon black dispersion and film forming solution manufacturing process will be described below.

Step A: Pigment + vehicle + solvent → premix (1) → main dispersion (kneading dispersion) (2) → carbon black dispersion step B; carbon black dispersion + dilution adjustment (3) → film formation solution

a. Pre-mixing process (premixing)
In the process of producing a paste with the optimum mixing composition and optimum flow state for the main disperser in the next process, the vehicle is infiltrated into the carbon black particle aggregate to completely wet the surface, and the coarse particle aggregate is crushed. There is to do.

b. Main dispersion process (grinding dispersion)
Dispersing the particle aggregate wetted by the vehicle to the particle size required for the film forming solution by impact or shear energy, dispersing the carbon black until it is close to the aggregate (aggregate), and then the vehicle on the surface of the carbon black It is to adsorb the resin component inside.

c. Dilution adjustment process (let down)
Add the required amount of resin, solvent, and additives to the high pigment concentration paste, adjust the dilution until the desired viscosity and composition are achieved, and add various resin solutions and solvents to the high pigment concentration paste. The pigment is diluted so as not to cause re-aggregation by adjusting the addition rate, order, temperature, stirring conditions and the like.

<Dispersion device>
Various dispersers are used for reasons such as the viscosity of the dispersion, the evaporation of the solvent, the production system or the final dispersed particle size.
The main ones include the following a to d.
a. Kneading type: kneader, planetary mixer, etc .: The greater the viscosity of the raw material, the greater the shear stress generated, so it is widely used for kneading hard pastes.
b. Compressive shear type: 3-roll mill, 2-roll mill: Disperser that applies a large shear stress while applying pressure to the gap between rollers, and is used for high viscosity (up to about 1000 Pa · s) and high adhesive strength .
c. Stir mixing type: colloid mill, Kady Mill, etc .: Impeller rotating at high peripheral speed (300-1200 m / min) gives high shear rate.
d.
Grinding shear type: bead mill, ball mill, etc .: A dispersing machine that disperses by impact and shear stress of a ball or bead. A shear stress of about 102 to 103 Pa is applied by a ball mill and about 104 to 105 Pa is applied by a bead mill. Both bead mills and ball mills are used to disperse volatile low-viscosity materials (possible up to several Pa · s).

  In the present invention, a grinding and shearing type dispersion apparatus is preferably used, and the dispersion time is preferably 10 hours or more and 80 hours or less. When the dispersion time is less than 10 hours, the coarse particle aggregate remains without being sufficiently crushed, and when it exceeds 80 hours, it falls into an overdispersed state, and none of the particle size distribution and particle size desired by us can be obtained. .

  In general, the primary particle diameter of carbon black is 10 nm to 1 μm. However, when mixed into a dispersion or resin, aggregation may occur when carbon black is dispersed. In this invention, it is preferable that the particle diameter of the carbon black currently disperse | distributed in a polyimide resin as a semiconductive belt is 10-300 nm. When the thickness exceeds 300 nm, carbon black having a large particle size present in the surface layer during the manufacturing process of the semiconductive belt becomes a protrusion on the surface of the belt, resulting in deterioration of surface accuracy, non-uniform resistance, May cause a decrease in resistance due to mechanical loading. On the other hand, if the thickness is less than 10 nm, the amount added is too large to obtain a desired resistance value, and the mechanical properties of the intermediate transfer member deteriorate.

  To summarize the composition of the material of the intermediate transfer medium according to the present invention, the intermediate transfer medium according to the present invention has a structure in which conductive particles are dispersed in a polymer. The polymer has mechanical characteristics and stability against hazards. In addition to the reliability supported by various achievements as engineering plastics, polyimide resin is most preferably used. In addition to the stability and low price, conductive particles are fundamental as described above. Carbon is most preferably used because of the fact that a great deal of knowledge including known techniques has been obtained with respect to properties, control, modification and the like.

The volume resistance of the intermediate transfer medium is most preferably in the range of 10 ⁸ to 10 ¹² Ω · cm. If the volume resistance is too high, when a plurality of colors are transferred, different charges remain for each color pattern, and uneven color tends to occur. On the other hand, if it is too low, white spots are likely to occur due to local charge leakage during transfer, which is not preferable. The amount of carbon black added to obtain a volume resistance in this range is preferably about 13 to 50% by weight, more preferably 15 to 35% by weight, based on the solid content of the polyimide resin. If it is less than 13% by weight, it is necessary to use highly conductive carbon black in order to develop the resistance region. If such highly conductive carbon black is added in a low addition amount, stable resistance can be produced with good reproducibility. May be difficult to do. On the other hand, if it exceeds 50% by weight, the inherent high mechanical properties of the polyimide resin are impaired, brittleness is developed, and the belt end surface may be cracked when the belt is driven by a plurality of drive rollers or the like.

  Next, a method for producing a seamless belt will be described.

  When manufacturing a seamless belt using the coating liquid containing a polyimide precursor, the following process can be achieved as a basic process. That is, (1) a step of applying and casting the coating liquid on a support (molding mold), (2) a step of removing the solvent in the coating film applied and cast on the support by heating, (3) Manufacturing by heating and heating to promote imidation of the precursor contained in the coating, and (4) releasing the formed thin film from the support to form a seamless belt. it can.

  Here, first, a description will be given of an example of centrifugal molding, which is one of the most typical manufacturing methods for polyimide belts. The following description is an example, and the conditions are not limited to this.

FIG. 3 shows a representative example of the centrifugal molding method.
Centrifugal molding is composed of a cylindrical rotating body. While slowly rotating this cylindrical rotating body, the coating liquid is uniformly applied to the entire inner surface of the cylinder by, for example, a coating device such as a dispenser. Apply and cast (form a coating). Thereafter, the rotation speed is increased to a predetermined speed, and when the predetermined speed is reached, the rotation speed is maintained at a constant speed. And the solvent in a coating film is evaporated at the temperature of about 80-150 degreeC, heating up gradually by the heating means which is not shown in figure, rotating. In this process, it is preferable to efficiently circulate and remove atmospheric vapor (such as a volatilized solvent). When a self-supporting film is obtained, it is then transferred to a heating furnace (baking furnace) capable of high-temperature treatment, and finally heated at a high temperature of about 250 ° C. to 450 ° C. while gradually raising the temperature. Treatment (firing) is performed, and the polyimide precursor or polyamideimide precursor is sufficiently imidized or polyamideimidized. After completion of imidization and the like, the thin film is peeled off from the mold by slow cooling. A seamless belt is thus formed. (One mold method)

  There is another method (two-type method) that removes the self-supporting film from the rotating body before high temperature treatment and attaches it to the outside of another cylindrical mold, and then performs the same treatment as above. The one-type construction method is preferable because of the small number of molds, but it is necessary to previously form a release agent or a release layer in the rotating body so as to be easily peeled off. By this molding method, it is possible to produce a relatively thin film which is difficult by extrusion molding or the like.

  In the case of centrifugal molding, since the mold rotates at a high speed, the degree of orientation of polyimide increases, and there is a drawback that physical properties in the circumferential direction and the axial direction tend to be different. A roll coat method is mentioned as a manufacturing method of the polyimide seamless endless belt which eliminated this fault.

The roll coat method will be described with reference to FIG.
A polyamic acid paint that has been sufficiently defoamed in advance is poured into a paint pan. The lower part of the metal roller is dipped in the paint, and pumped up while adhering the paint to the surface of the metal roller at a very slow speed of, for example, 40 mm / sec. Thereafter, the paint thickness on the metal roller is adjusted by an eccentric roller that is installed on the metal roller and can adjust an arbitrary gap with the metal roller. Next, the clearance from the metal roller is adjusted to, for example, 0.4 mm, and the paint is transferred from the mold roller onto the work (mold) that rotates in the opposite direction to the metal roller, and the paint having a predetermined film thickness is formed on the mold. Is attached.

  The subsequent steps are the same as in the centrifugal molding method described above, the step (2) of removing the solvent in the coating film coated and cast on the support by heating, and the precursor contained in the coating film by heating at elevated temperature. It can be produced by the step (3) for promoting imidization of the body and the step (4) for releasing the formed thin film from the support to form a seamless belt.

  Moreover, when manufacturing a thick film belt and a multilayer belt, it can return to the post-coating apparatus of a process (2), and can apply the coating material, and can manufacture the belt which has arbitrary film thicknesses and layer structures.

  The roll coat method has a much slower mold rotation speed than the centrifugal molding method, so the orientation of the polyimide is less, and the difference in physical properties between the circumferential direction and the axial direction is less likely to occur. The difference in the coefficient of linear expansion of moisture can be eliminated. By measuring the hygroscopic linear expansion coefficient, it is possible to evaluate the running property and end warp of the belt.

  In addition, the coating liquid adhering surface of the mold used in both methods can be applied uniformly without repelling the coating liquid, and the mold can be easily released from the mold after drying. The contradictory property of gender is necessary. For that purpose, it is also possible to treat the coating liquid adhering surface of the mold. An example of the treatment method is a chrome plating treatment in which fluorine resin particles and the like are uniformly dispersed. It is also possible to provide a high release resin film such as silicone resin or fluorine resin.

  In both the roll coating method and the centrifugal molding method described so far, in the process of coating and casting the coating liquid, by giving discontinuity to any of the flow rate, coating timing, temperature, rotational speed, etc. A constant composition density distribution can be provided in the film thickness direction, and such means is employed in the present invention.

  At the end of the description of the embodiment, Cross-sectional SPoM, a method for evaluating a conductive polymer, which is one of the basis of the present invention, will be described in accordance with the present invention. However, the scanning probe microscope (SPM) and atomic force microscope (AFM), which are the superordinate technologies, are techniques known to related academic societies, industries, researchers, and engineers. There is no explanation. The review of SPM is detailed in, for example, edited by Seizo Morita: Scanning Probe Microscope Basics and Future Prediction, Maruzen (2003). Regarding SPoM itself, for example, the application notes AN27 and 10/99 of Veeco explain the principles and examples. As described above, the present technology uses a cross-section SPoM (SPoM; Surface Potential Microscopy) originally developed by the inventors as a means for analyzing the internal structure of a toner, and a conductive polymer sheet used for an intermediate transfer medium. This is a new technology applied to the measurement and evaluation method.

The method for preparing the observation sample is shown in FIG.
Reference numeral 301 denotes an intermediate transfer medium, from which a section 302 having a thickness of 100 to 1000 nm with a diamond microtome is cut in a plane perpendicular to the front and back of the medium. The thickness of the slice is most preferably 200 nm. The length of the section may be in the range of about 0.2 to 2 mm (the width corresponds to the film thickness). In many cases, in an intermediate transfer medium, embedding of a sample with a resin during cutting can be omitted, but an embedding process may be employed if necessary. The cut section 302 is affixed to a sheet 303 of sufficiently smooth and substantially conductive material. This thin plate may be a metal, or may be a non-metal as long as the resistance is sufficient to leak electrostatic charges. For example, an ultrathin silicon mount 0.5 mm thickness and 5 × 5 mm sold by EM Japan can be suitably used. It may be a clean silicon wafer piece. Here, for the convenience of fixing magnetic force at the time of measurement, it is further affixed to a soft iron disk 305 via a conductive carbon tape 304. Note that cutting with a diamond microtome is usually performed in a wet state, but this condition is not excluded in this measurement. The sliced piece can be attached to the substrate without an adhesive by intermolecular force. It is desirable to measure the sample after sticking after storage for 8 hours or more in a dry desiccator.

  The attached thin piece sample is set in the SPM, and is charged positively or negatively in an electrostatic non-contact manner prior to observation with the stage removed from the observation position. For charging, a so-called high-voltage charging device such as corotron or scorotron may be used, but Milton's ZEROSTAT using a piezoelectric element can be preferably used. In ZEROSTAT, positive ions are released from the tip when the trigger is pulled and negative ions are released when the trigger is released. Discharge from a distance of 5-20 cm above the sample is preferred. The slight increase or decrease in the charging potential is not a problem for the technology of the present invention in which the distribution is significant rather than the absolute value. The interpretation of the potential data and the optimum range of resistance measured therefrom will be mentioned in the description of the embodiments.

  After charging, the surface of the sample has a potential distribution that reflects the distribution of its electrical properties. Immediately after charging, the potential rapidly decays, but the potential to be measured is a stable or polarized potential, and fluctuations can be ignored in several tens of minutes of measurement. The sample is moved to the observation position, and the potential distribution is observed in the surface potential microscope mode SPoM, which is one of SPM applications. This Cross-section SPoM image directly reflects the distribution of the conductive material in the film thickness direction inside the intermediate transfer medium, and provides information that cannot be known at all by conventional techniques.

  Examples 1 to 4 and Comparative Examples 1 to 3 are given below to specifically explain the present invention.

  The coating liquid is common, seamless belts A and B are examples, and seamless belts C to E are comparative examples. The present invention is not limited to these examples. For example, in the present embodiment, a photosensitive drum is used as the image carrier. However, the present invention is not limited to this and can be applied to all image carriers such as a photosensitive belt. In the present embodiment, a so-called quadruple tandem type full-color image forming system using a dedicated photoconductor drum for each of black, yellow, cyan, and magenta is used. The present invention can also be applied to a so-called revolver method in which an image is formed for each color with a carrier. In this embodiment, the transfer roller is used as the primary transfer unit, but a contact transfer system such as a transfer brush, a transfer blade, and a transfer plate is used as well as a rotary contact transfer system such as a rotary transfer brush. The present invention is applicable to any image forming apparatus.

[Preparation of coating solution]
Each equimolar amount of biphenyl-3,4,3 ′, 4′-tetracarboxylic anhydride and 4,4′-diaminodiphenyl ether was polymerized in an N-methylpyrrolidone solvent to obtain a polyamic acid solution. To this, carbon black (manufactured by Cabot, BP-L) dispersed in N-methyl-2-pyrrolidone in advance by a bead mill is used so that the carbon content is 16% by weight of the polyamic acid solid content. A coating solution was prepared by mixing and mixing well.

[Example 1: Production of seamless belt A]
A metal cylinder having an inner diameter of 100 mm and a length of 300 mm and having a mirror finish on the inner surface is used as a mold, and this cylinder mold is rotated at 50 rpm (times / minute) in an atmosphere of 25 ° C. 5 was applied to the inner surface of the cylinder so as to be cast uniformly. When the first coating film spread evenly, the rotation speed was lowered to 30 rpm and the rotation state was continued for 8 minutes. Next, raise the ambient temperature to 50 ° C, apply the remaining amount in the same manner as before, and when the coating film due to the remaining amount has spread evenly, put it into a hot air circulating dryer and gradually raise the temperature to 120 ° C And heated for 30 minutes. Thereafter, the rotation was stopped, the mixture was put into a heating furnace (baking furnace) capable of high temperature treatment, heated to 350 ° C., and subjected to heat treatment (baking) for 30 minutes. After stopping the heating by treating for a predetermined time, the mold was taken out after gradually cooling to room temperature, and the formed film was peeled off from the inner surface of the cylinder to obtain [Polyimide seamless belt A] having a film thickness of 78 μm.

[Example 2: Production of seamless belt B]
A metal cylinder having an outer diameter of 100 mm and a length of 300 mm with a mirror finish on the outer surface was attached as a work of the roll coat coating apparatus of FIG. The same coating liquid as that for the production of seamless belt A was poured into the pan, the paint was pumped at a metal roller rotation speed of 35 mm / sec in an environment of 25 ° C., and the thickness of the paint on the metal roller was controlled with an eccentric roller gap of 0.3 mm. The mold work was controlled to 35 mm / sec, and the paint was uniformly applied on the mold with a metal roller gap of 0.2 mm, then charged into a hot air circulating dryer and gradually heated to 60 ° C. to 30 Heated for minutes. Thereafter, the mold was taken out, cooled to room temperature, coated again in the same manner as described above, put into a hot air circulating dryer, gradually heated to 130 ° C. and heated for 40 minutes. Then, it put into the heating furnace (baking furnace) in which high temperature processing is possible, heated up to 350 degreeC, and heat-processed (baking) for 30 minutes. The formed film was peeled from the outer surface of the cylinder to obtain [Polyimide seamless belt B] having a film thickness of 80 μm.

[Comparative Example 1: Production of seamless belt C]
A metal cylinder having an inner diameter of 100 mm and a length of 300 mm and having a mirror finish on the inner surface is used as a mold, and the coating liquid is uniformly cast on the inner surface of the cylinder while rotating the cylinder at 50 rpm (times / minute). Flowed and applied. When the predetermined amount was completely poured and the coating film spread evenly, the number of revolutions was increased to 150 rpm, the hot air circulating dryer was introduced, and the temperature was gradually raised to 120 ° C. and heated for 30 minutes. Thereafter, the rotation was stopped, the mixture was put into a heating furnace (baking furnace) capable of high temperature treatment, heated to 350 ° C., and subjected to heat treatment (baking) for 30 minutes. After stopping the heating by treating for a predetermined time, the mold was taken out after gradually cooling to room temperature, and the formed film was peeled off from the inner surface of the cylinder to obtain [Polyimide seamless belt C] having a film thickness of 81 μm.

[Comparative Examples 2 and 3: Production of seamless belts D and E]
[Seamless belts D and E] were obtained in the same manner as the production of the seamless belt C, except that the rotation speed was 50 rpm (D) and 100 rpm (E).

  Next, evaluation methods related to the examples and comparative examples will be described.

[Image quality evaluation method]
The above-mentioned intermediate transfer belt was mounted using a Ricoh color copier Imagio Neo C600 remodeling machine, and the image on the transfer belt was evaluated. The Imagio Neo C600 remodeling machine uses a two-component development system for development and an intermediate transfer belt system for transfer, and the image forming operation can be stopped halfway at an arbitrary timing by an external signal. Write a plurality of solid images and latent images of fine line images on the photosensitive drum, stop the image forming process during the primary transfer, take out the photosensitive drum unit and the transfer belt unit from the copying machine, and print a solid image portion on the photosensitive drum. The pile height was measured, and the image of the fine line portion on the transfer belt was evaluated. The toner weight M / A per unit area was set to about 0.7 mg / cm ² . The surface linear velocity of each member including the transfer belt and the photosensitive member of the modified machine was 250 mm / sec.

[Uneven density, white-out images]
A 2 × 2 dot pattern was imaged using the intermediate transfer body of the Imagio Neo C600 modified machine, and the image state on the intermediate transfer belt was observed with an ultra-deep shape measuring microscope (VK8500; manufactured by Keyence Corporation). After this image is edited into a binarized image using image analysis software (MediaCybernetics, ImagePro), the area of the solid pattern where the toner is removed and the white area is quantified, and the white area image in the entire area is quantified. Was evaluated as follows.
<< Evaluation of uneven density and white spots >>
◎ Density unevenness and white spots do not occur on the output image.
○ There is no problem in image quality even though the output image has slightly uneven density and white spots.
× Density unevenness or white spots occur on the output image, causing problems in image quality.

[Durability of belt]
The belt sample was used as an intermediate transfer belt of the Ricoh color copier Imagio Neo C600 remodeling machine, and the state of the transfer belt after the continuous output of 500,000 sheets was visually evaluated. The evaluation criteria at that time are shown below.
<Evaluation of belt durability>
○ The transfer belt does not break.
X Breakage occurs on the transfer belt.

[Position / color misalignment]
When the belt sample was used as an intermediate transfer belt of the Ricoh color copier Imagio Neo C600), the output image was visually evaluated. The evaluation criteria at that time are shown below.
《Evaluation of positional and color shifts》
○ No positional deviation or color deviation occurs on the output image.
× There is a problem in image quality due to positional and color shifts on the output image.

  Next, measurement of each characteristic of the belt will be described.

[Measurement of belt volume resistance fluctuation range]
The volume resistivity of a belt in a low temperature and low humidity environment (L / L environment) of 10 ° C. and 15% RH is taken, and the volume resistivity in a high temperature and high humidity environment (H / H environment) of 30 ° C. and 85% RH is taken. Then, the absolute value of the difference between the common logarithm and the value was taken as the environmental fluctuation range of the volume resistance of the belt. The volume resistivity of the belt was measured as follows.

[Measurement of belt volume resistivity]
The volume resistivity of the belt was obtained from the current value after 30 seconds of application of 500 V using a Hiresta MCP-HT450 type (probe: HR-100) manufactured by Mitsubishi Chemical Corporation according to JIS K6911.

[Measurement of tensile strength and Young's modulus of belt]
The tensile strength and Young's modulus of the belt were measured by a tensile test method according to JIS K7127.

[Measurement of Rmax / Rmin]
Measurement was performed with a newly developed Cross-section SPoM. The measurement method will be described below.

  The seamless belt was cut with a microtome using a diamond knife on a surface perpendicular to the front and back surfaces to obtain a thin piece having a thickness of 200 nm. This thin piece was attached to an ultrathin silicon mount 0.5 mm thickness and 5 × 5 mm sold by EM Japan. Further, the silicon mount to which the sample flakes were attached was attached to a soft iron disk having a thickness of 0.5 mm via a conductive carbon tape. It was observed after storage for 10 hours in a desiccator at 20 ° C./35% RH.

FIG. 6 shows the state of the observation sample viewed with an optical microscope attached to the SPM.
401 is a thin piece of the sample viewed from above, and the left and right edges of the image correspond to the front and back of the sheet member. Lateral thick streaks are cracks at the time of cutting. A rectangle 402 is an SPM observation area.

  The sample was fixed to a measurement stage of a scanning probe microscope Dimension 3100 (controller NanoScope IIIa) of Digital Instruments (currently Veeco) using a magnet holder.

  The sample was once pulled out and positively charged from above 10 cm of the sample by ZEROSTATO, and then the sample was returned to the measurement position.

  Observation was made in SPoM mode using EFM-16 from NANOSENSORS as a probe. First, the position of the 50 μm × 50 μm region was shifted, and the surface potential image of the full thickness was observed multiple times. Thereafter, through zooming, a surface potential image of a 15 μm × 15 μm region near the center of the film to be noted was observed.

  FIG. 7 is an observation example of the seamless belt A. (A) is a potential image obtained by a surface potential microscope. A relatively high potential portion is expressed as a bright portion, and a low portion is expressed as a dark portion. The potentials were averaged in the vertical direction and approximated by a smooth curve, as shown in FIG. However, in FIG. 7A, it is clear that the potential distribution is almost uniform in the vertical direction, that is, the surface direction as the intermediate transfer medium. In such a case, the averaging process is not essential, and there is no great difference even if it is represented by a distribution along an arbitrary horizontal line. One of the major features of the technology provided by the present invention is that the distribution in the surface direction can be determined at a glance by representing the resistance profile as a potential image. The distribution curve was also displayed superimposed on the potential image of (a). Since the signal for each potential scanning line is an AC signal with an average value of 0 and the absolute value of the potential is unknown, it is calibrated with a reference voltage and the value is displayed as a potential value in (b). Yes. In this observation, a negatively charged portion cannot exist in the first place due to the condition of positive charging.

  A portion having a relatively high potential, that is, a bright portion is a portion having a high resistance, and is actually a portion having a low carbon density of the conductive material. In the produced seamless belt A, the low-density region of carbon exists as a boundary layer. If the upper and lower sides of the potential distribution curve of (b) are reversed, it can be regarded as a relative density distribution of carbon with a good approximation.

Looking at the potential distribution of (b), the highest potential and the lowest potential are in a ratio relationship of approximately 10: 1. This ratio does not change even if the average charging potential slightly increases or decreases under charging operation or other conditions. This potential distribution is substantially equivalent to the resistance distribution in the film thickness direction. After all, the potential ratio is also the internal resistance ratio Rmax / Rmin. In general, it can be considered that the volume resistance is internally divided in the film thickness direction at this ratio. However, the macroscopic volume resistance of the conductive polymer sheet cannot be predicted by the series resistance model even if it has a boundary layer. This is probably because the fine matrix functions as a charge path. According to the study by the present inventors, the maximum and minimum internal resistances in terms of potential (respectively, if the prescription conditions fall within the range of 10 ⁸ to 10 ¹² Ω · cm under conditions where the carbon density is uniform, respectively. When the ratio of extreme values is in the range of 3 to 10, the influence on the macroscopic volume resistance of the intermediate transfer medium can be ignored. However, by providing the resistance distribution in the film thickness direction with an extreme value within the above range, an intermediate transfer medium having excellent image characteristics, mechanical characteristics, and durability can be obtained.

  FIG. 8 is an electric potential image by Cross-section SPoM of the seamless belt C which is the first comparative example. The measurement procedure and conditions are exactly the same as those of the seamless belt A described above, but in order to supplementarily explain the physical meaning of the Cross-section SPoM according to the present invention, a potential image in a negative charge in addition to a positive charge is used. Also put.

  In FIG. 8A, an island-like bright portion exists near the center of the film. The bright portion is a relatively high resistance portion, that is, a relative low density portion of carbon, as in FIG. The macroscopic volume resistance of the seamless belt C is not much different from A, but unlike FIG. 7A, the distribution of resistance when viewed in the film thickness direction is not deterministic. In other words, the seamless belt C has a resistance profile in a different film thickness direction for each different part of the surface.

  By the way, FIG. 8B is an electric potential image observed by negatively charging substantially the same portion of the same sample as in FIG. In (a) and (b), the bright part and the dark part are inverted. From the comparison between (a) and (b), it can be confirmed that the potential image is an independent mapping of electrical characteristics that is not subjected to mixing of shape (unevenness) information. In general, conductive polymer sheets do not make a difference with respect to the movement of positive and negative charges. FIGS. 8A and 8B are cross-section SPoM according to the present invention, and only one polarity may be measured with a positive charge unless otherwise specified.

  9A shows a potential image of the seamless belt B according to the second embodiment, and FIG. 9B shows a potential distribution along a cross section near the center indicated by a white line in the potential image. In Example 2, Rmax / Rmin is 4.3. Except for Rmax / Rmin being smaller than the first embodiment, it has the same characteristics as the first embodiment.

  10A shows the potential image of the seamless belt D as the second comparative example, and FIG. 10B shows the potential distribution along the cross section near the center indicated by the white line in the potential image. In Comparative Example 1, Rmax / Rmin is approximately 3. In this comparative example, carbon is uniformly dispersed in the film, but the distribution in the plane direction is not uniform.

  11A shows a potential image of the seamless belt E as a third comparative example, and FIG. 11B shows a potential distribution along a cross section near the center indicated by a white line in the potential image. In Comparative Example 1, Rmax / Rmin is approximately 2. In this comparative example, carbon is slightly coarsely dispersed in the film than the second comparative example, but the distribution in the plane direction is not uniform, and is common to the first and second comparative examples. .

  The characteristics and quality of the seamless belts of Examples 1 and 2 and Comparative Examples 1 to 3 are as shown in Table 1 below.

  The reason why the distribution state of the conductive filler changes depending on the production conditions has not been fully elucidated. The main factor is that the viscosity of the coating liquid that varies depending on the temperature and prescription conditions is related to the flow of the filler. Needless to say, the centrifugal force generated by the rotation of the coating roller causes migration in the film thickness direction of the filler, and in the pan of the coating liquid, density gradient of the filler in the gravity direction occurs due to convection. Furthermore, the present inventors have confirmed that a fine natural vibration unique to the apparatus during driving of the coating apparatus generates a standing wave in the wet coating film and causes fluctuations in the filler density.

  Next, Example 3 (seamless belt F) and Example 4 (seamless belt G) will be described.

-Preparation of carbon black dispersion-
In N-methyl-2-pyrrolidone solvent, a polyether-modified silicone (FZ2208, manufactured by Toray Dow Corning Co., Ltd.) is dissolved as a smoothing agent, and then carbon black (Special Black 4 manufactured by Degussa) is mixed. To prepare a carbon black dispersion. The polyether-modified silicone (FZ2208 manufactured by Toray Dow Corning Co., Ltd.) has ethylene oxide and propylene oxide as hydrophilic groups.
[Distribution conditions]
・ Disperser: Sand Grainter (Igarashi Machine Co., Ltd.)
・ Crushing media: 1 mm diameter of zirconium beads ・ Filling rate of grinding media: 50% (volume)
・ Crushing time: 3 hours
The composition of the obtained carbon black dispersion was 12.0% by mass of carbon black, 1.2% by mass of silicone surfactant, and 86.8% by mass of N-methyl-2-pyrrolidone.

-Preparation of seamless belt coating solution-
U varnish S (Ube Industries, Ltd .: solid content 18 wt%) and U varnish A (Ube Industries, Ltd .: solid content 18 wt%) were used as the polyamic acid solution. To the 1/1 solution of the varnish, the carbon black dispersion was prepared such that the carbon black was 17% by mass of the solid content of the polyamic acid, and the mixture was well stirred and mixed to obtain a mixed solution. This mixed solution was stirred (1000 rpm / 2 min) and defoamed (1000 rpm / 30 sec) using a stirring defoamer (AR500: manufactured by Sinky Corporation) to prepare a seamless belt coating solution.
The volume average particle diameter of carbon black was 0.219 μm.

[Example 3: Production of seamless belt F]
In the same manner as in Example 2, the seamless belt coating solution was poured into the coating solution pan shown in FIG.
The same metal cylindrical surface as that of Example 2 with PTFE-containing electroless nickel phosphorus alloy plating was used as the coating mold. (Plating layer thickness: 7 μm) Thereafter, a seamless belt was produced in the same manner as in Example 2 to obtain a seamless belt F (film thickness 78 μm).

[Example 4: Production of seamless belt G]
A seamless belt coating solution was prepared in the same manner except that MA100: manufactured by Mitsubishi Chemical Corporation was used instead of the carbon black used in Example 3. The volume average particle diameter of carbon black was 0.235 μm. Next, a seamless belt was produced in the same manner as in Example 3 to obtain a seamless belt G (film thickness 80 μm).

  The characteristics and quality of the seamless belts of Examples 3 and 4 are as shown in Table 2 below.

  As described above, according to the present embodiment, in the intermediate transfer medium of the image forming apparatus, the ratio between the maximum value and the minimum value of the film thickness direction distribution of the internal resistance measured from the potential distribution by Cross-section SPoM is in the range of 3 to 20. By doing so, stability of electrical characteristics and mechanical characteristics and excellent image quality can be achieved. The reason for this is not always clear, but probably because the distribution of the conductive filler in the film thickness direction is well-ordered, the unevenness of the electrical characteristics in the surface direction can be suppressed, and at the same time the micro internal mechanical working during driving It is presumed that the effect of dispersing the strain in layers is working. When the ratio is smaller than 3, the effect of giving an extreme value to the resistance distribution does not appear. When the ratio is increased by one digit or more, the macro substantial resistance value increases, and unnecessary capacitance components appear. As an intermediate transfer medium, transfer becomes unstable. Considering that the dispersion state of the filler fundamentally determines both electrical and mechanical properties, the micro-distributed distribution improves the image quality at a fine level, and at the same time, an intermediate transfer medium that accompanies driving It can be reasonably convinced to reduce microscopic stretching, distortion, vibration, and the like.

  The present invention is a technique that actively uses a conductive sheet member having uniformity in the surface direction and having a constant resistance distribution in the film thickness direction as an intermediate transfer member. The characteristics are greatly different from those of the multilayer intermediate transfer member. Needless to say, the distinct boundary surface is a discontinuous surface both electrically and mechanically, and its control is much more difficult than the present invention in a combination of conditions. However, when the characteristics of the surface of the laminated member are functionally separated and a conductive belt is used in the intermediate portion, it is natural that the technique of the present invention can be used as it is. As expected, this is a category of technology.

1 is a schematic configuration diagram of an image forming apparatus using an intermediate transfer drum. 1 is a schematic configuration diagram of a tandem image forming apparatus using a seamless belt. It is a schematic block diagram of the centrifugal molding method. It is a schematic block diagram of a roll coat method. It is a figure for demonstrating the preparation method of the observation sample of an intermediate transfer medium. It is the figure which looked at the observation sample of the present invention with the optical microscope attached to SPM. (A) is a figure which shows the surface potential image in the positive charge of the seamless belt A which is this invention, (b) is a figure which shows the distribution of the electric potential which averaged the electric potential in the vertical direction. However, the potential distribution curve of (b) is superimposed on the surface potential image of (a). (A) is a figure which shows the surface potential image on the positive charging conditions of the seamless belt C which is a comparative example of this invention, (b) is a figure which shows the surface potential image on the negative charging conditions. (A) is a figure which shows the surface potential image on the positive charging conditions of the seamless belt B which is this invention, (b) is a figure which shows the electric potential distribution along the white line of electric potential image (a). (A) is a figure which shows the surface potential image on the positive charging conditions of the seamless belt D which is a comparative example of this invention, (b) is a figure which shows the electric potential distribution along the white line of an electric potential image (a). (A) is a figure which shows the surface potential image on the positive charging conditions of the seamless belt E which is a comparative example of this invention, (b) is a figure which shows the electric potential distribution along the white line of electric potential image (a).

Explanation of symbols

301 Intermediate transfer medium 303 Cut-out flake 303 Conductive plate 304 Carbon tape 305 Soft iron disc 401 Observation specimen flake 402 SPM observation area

Claims (8)

  A conductive polymer sheet having a uniform thickness is cut to a thickness of 0.1 to 1.0 μm on a surface perpendicular to the front and back surfaces to obtain a section, and this section is cut into a substantially conductive plate. It is characterized in that it is attached in a table, the exposed cutting surface is charged to a certain polarity by a charger, the charged surface is observed with a surface potential microscope, and the potential distribution in the film thickness direction of the polymer sheet is observed. Method for measuring electrical resistance distribution of conductive polymer sheet.   An electrophotographic intermediate transfer medium for developing an electrostatic latent image formed on an image carrier with toner and transferring the obtained toner image to a recording medium, wherein the electrophotographic intermediate transfer medium is a conductive particle. The electrical resistance distribution measured by the method for measuring electrical resistance distribution according to claim 1 is substantially equal in the surface direction of the electrophotographic intermediate transfer medium. An electrophotographic intermediate transfer medium, which is the same and has a ratio Rmax / Rmin of a maximum value (Rmax) and a minimum value (Rmin) of electrical resistance distribution of 3 to 10. 3. The electrophotographic intermediate transfer medium according to claim 2, wherein the volume resistance is 10 ⁸ to 10 ¹² Ω · cm.   The electrophotographic intermediate transfer medium according to claim 2 or 3, wherein the polymer is a polyimide resin and the conductive particles are carbon black.   5. The electrophotographic intermediate transfer medium according to claim 2, wherein the electrophotographic intermediate transfer medium has a seamless belt shape.   6. The electrophotographic intermediate transfer medium according to claim 5, wherein the electrophotographic intermediate transfer medium having a seamless belt shape is formed by a roll coating method.   An image carrier on which an electrostatic latent image is formed and capable of carrying a toner image, a developing unit for developing the electrostatic latent image formed on the image carrier with toner, and a toner image developed by the developing unit An electrophotographic intermediate transfer medium on which the toner image is primarily transferred, and a transfer means for secondary transfer of a toner image carried on the electrophotographic intermediate transfer medium to a recording medium. An image forming apparatus, wherein the medium is the intermediate transfer medium according to claim 2.   The image forming apparatus is an image forming apparatus that forms a full-color image by superimposing a plurality of color toners, wherein a plurality of image carriers corresponding to each color developing means are arranged in series. Item 8. The image forming apparatus according to Item 7.