JP2008116838A - Endless belt made of polyimide resin and image forming apparatus equipped with the same, and method for manufacturing endless belt made of polyimide resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an endless belt made of polyimide resin, which improves electric field dependency of resistance by further improving dispersibility of carbon black as a conductive agent, while using a polyimide resin having a high modulus of elasticity, and which also improves balance between the electric field dependency and flexibility, an image forming apparatus equipped with the same, and a method for manufacturing the endless belt made of polyimide resin. <P>SOLUTION: The endless belt made of polyimide resin comprises a first polyimide resin obtained by imide linkage of a tetracarboxylic acid dianhydride having a wholly aromatic skeleton with a diamine having a diphenyl ether skeleton, a second polyimide resin obtained by imide linkage of a tetracarboxylic acid dianhydride having a wholly aromatic skeleton with a diamine having a p-phenylene skeleton, and a conductive agent, wherein the first polyimide resin occupies 25-70 mol% of all the polyimide resins and the difference between the common logarithms of surface resistivities at the time of applying voltages of 100 V and 1,000 V under the conditions of 22°C and 55% RH is ≤0.3 (logΩ/sq.). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polyimide resin endless belt, an image forming apparatus including the same, and a method for manufacturing a polyimide resin endless belt.

  Conventionally, as an electrophotographic recording apparatus, a copying machine, a laser printer, a video printer, a facsimile, a composite machine thereof, and the like are known. In this type of device, for the purpose of improving the life of the device, there are some intermediate transfer systems that temporarily transfer the image on the image carrier such as a photosensitive drum to the intermediate transfer belt, and transfer and fix it on the print sheet. It has been adopted. Further, for the purpose of reducing the size of the apparatus, a method of performing transfer while transporting a print sheet with a transport belt is also employed.

  As a semiconductive belt that can be used for such an intermediate transfer belt or a transfer conveyance belt, for example, Patent Document 1 and Patent Document 2 include a conductive filler dispersed in a polyimide resin having excellent mechanical properties and heat resistance. Semiconductive belts have been proposed.

A carbon black-dispersed polyimide resin belt in which the relationship between the volume resistivity ρv1 at an applied voltage of 10 V and the volume resistivity ρv2 at an applied voltage of 100 V is log (ρv1 / ρv2) ≦ 2 has also been proposed (for example, a patent) Reference 3). Furthermore, it comprises a polyimide resin containing carbon black and includes a step of polymerizing polyamic acid in a carbon black dispersion solvent, thereby improving the dispersibility of carbon black, and surface resistivity of applied voltage 100V and applied voltage 1000V. An intermediate with improved electric field dependency, in which the difference between the common logarithmic values is 1.5 (logΩ / □) or less has been proposed (for example, Patent Document 4). Furthermore, in order to improve the charge dependency, 20 to 190 parts by weight of acicular and / or plate-like titanium oxide is contained with respect to 100 parts by weight of the polyimide resin, and the volume resistance value is 1 × 10 ⁹ to 1 ×. A polyimide tubular material in the range of 10 ¹⁴ Ω · cm has been proposed (Patent Document 5).

  On the other hand, an intermediate transfer belt having an improved balance between flexibility and rigidity has been proposed. For example, Patent Document 6 discloses a component A formed by imide bonding of a wholly aromatic skeleton that is a tetracarboxylic acid residue and a p-phenylene skeleton that is a diamine residue, and a wholly aromatic that is a tetracarboxylic acid residue. It has been proposed to produce a semiconductor belt by polymerizing a polyamic acid obtained by dispersing carbon black in a blend with a B component formed by imide bonding of a skeleton and a diphenyl ether skeleton that is a diamine residue. Furthermore, Patent Document 7 discloses a component A in which a wholly aromatic skeleton that is a tetracarboxylic acid residue and a p-phenylene skeleton that is a diamine residue are imide-bonded, and a wholly aromatic that is a tetracarboxylic acid residue. It has been proposed to produce a semiconductor belt by polymerizing polyamic acid obtained by dispersing oxidized carbon black in a blend with B component formed by imide bond of skeleton and diamine residue diphenyl ether skeleton. ing.

JP-A-5-77252 Japanese Patent Laid-Open No. 10-63115 Japanese Patent Laid-Open No. 2000-231272 JP 2002-148951 A JP 2003-55473 A JP 2001-142313 A JP 2002-341673 A

  The above-described intermediate transfer belt has mechanical characteristics (specifically, high elastic modulus and high strength) and electrical characteristics (specifically, electric field of resistance) required from recent high-speed and high-quality electrophotographic image forming apparatuses. Dependency) was not enough. That is, as a polyimide resin having a tensile elastic modulus of 4.0 GMpa or more in which carbon black is dispersed, the electric field dependency is about 0.6 in the conventional technique.

  Therefore, the present invention improves the electric field dependency of resistance by improving the dispersibility of carbon black, which is a conductive agent, while also using a high elastic modulus polyimide resin, and also improves the balance with flexibility. Another object of the present invention is to provide a polyimide resin endless belt, an image forming apparatus including the same, and a method for manufacturing a polyimide resin endless belt.

  The present invention has the following features.

  (1) A first polyimide resin formed by imide bonding of a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton, a tetracarboxylic dianhydride having a wholly aromatic skeleton, and p- A second polyimide resin formed by imide bonding with a diamine having a phenylene skeleton and a conductive agent are contained, and the first polyimide resin is 25 mol% or more and 70 mol% or less of the total polyimide resin. An endless belt made of polyimide resin, characterized in that the difference in common logarithm of surface resistivity when a voltage of 100 V and 1000 V is applied under the condition of 22 ° C. and 55 RH% is 0.3 (log Ω / □) or less .

  (2) An image carrier, a charging unit for charging the surface of the image carrier, a latent image forming unit for forming a latent image on the surface of the image carrier, and developing the latent image with toner to form a toner image. Developing means, transfer means for transferring the toner image to a recording medium, and fixing means for heat-fixing the toner image on the recording medium. The transfer means includes a tetracarboxylic acid diester having a wholly aromatic skeleton. A first polyimide resin formed by imide bonding of an anhydride and a diamine having a diphenyl ether skeleton, a tetracarboxylic dianhydride having a wholly aromatic skeleton, and a diamine having a p-phenylene skeleton. A second polyimide resin and a conductive agent, wherein the first polyimide resin is 25 mol% or more and 70 mol% or less of the total polyimide resin, and 22 ° C. and 55 RH%. Image forming apparatus difference common logarithm value of surface resistivity when applying a voltage of 100V and 1000V is characterized in that it comprises a polyimide resin endless belt is 0.3 (logΩ / □) or less at conditions.

(3) A method for producing an endless belt made of polyimide resin, comprising at least the following steps (a) to (c).
(A) A polyamic acid solution (i) containing a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton is mixed with carbon black to prepare a carbon black-dispersed polyamic acid solution (A). Process.
(B) The carbon black-dispersed polyamic acid solution (A) is mixed with a polyamic acid solution (ii) containing a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a p-phenylene skeleton, A step of preparing a black dispersed polyamic acid solution (B).
(C) A step of forming an endless belt by heating the carbon black-dispersed polyamic acid solution (B) and performing an imidization reaction after the steps (a) and (b).

  According to the present invention, since the first polyimide resin having a low elastic modulus and the second polyimide resin having a high elastic modulus are contained, the balance between the elastic modulus and flexibility is good, and the conductive agent is dispersed. Due to its high property, it is possible to obtain an endless belt made of polyimide resin having a small electric field dependency in resistance. Further, it is possible to provide an image forming apparatus capable of stably obtaining a high quality image.

  Embodiments of the present invention will be described below.

  The polyimide resin endless belt of the present embodiment has a first polyimide resin formed by imide bonding of a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton, and a wholly aromatic skeleton. A second polyimide resin formed by imide bonding of tetracarboxylic dianhydride and a diamine having a p-phenylene skeleton, and a conductive agent are contained, and the first polyimide resin is 25% of all polyimide resins. The difference between the common logarithmic values of the surface resistivity when a voltage of 100 V and 1000 V is applied under the condition of 22 mol% to 70 mol% and 22 ° C. and 55 RH% is 0.3 (logΩ / □) or less.

  The polyimide resin can be obtained by imidization reaction (dehydration ring closure reaction) of a polyamic acid described later. In addition, the endless belt made of polyimide resin is coated with a polyamic acid solution in which a polyamic acid, which is a polyimide precursor, is dissolved in an organic polar solvent, as described later. Is removed as appropriate, and then a baking treatment is performed to perform an imidization reaction (dehydration ring-closing reaction) of polyamic acid.

-Polyamic acid solution-
The polyamic acid solution of the present embodiment contains at least a polyamic acid, an organic polar solvent, and a conductive agent. Hereinafter, each component etc. are demonstrated in detail.

(Polyamic acid)
As the polyamic acid, a polyamic acid represented by the following general formula (1) (hereinafter sometimes referred to as “polyamic acid”) can be used. The polyamic acid is obtained by polymerizing a tetracarboxylic dianhydride and a diamine compound in a substantially equimolar amount in an organic polar solvent. From the viewpoint of the strength of the molded body, those composed of an aromatic tetracarboxylic dianhydride and an aromatic diamine are preferred.

  In addition, “R1” in the following general formula (1) is a tetravalent organic group. Specifically, a residue obtained by removing four carboxyl groups from a tetracarboxylic acid (dianhydride) exemplified later. Groups. Moreover, “R2” in the following general formula (1) is a divalent organic group, and specific examples thereof include a residue obtained by removing two amino groups from a diamine compound exemplified later. In addition, “R3” and “R4” in the general formula (2) described later are also the same as “R1” and “R2”, respectively.

(Polyamic acid polymerization temperature)
As reaction temperature at the time of polyamic acid polymerization, it is carried out in the range of 0 ° C to 80 ° C. This is because when the reaction temperature is 0 ° C. or lower, the viscosity of the solution increases and the reaction system cannot be sufficiently stirred. Moreover, when reaction temperature becomes higher than 80 degreeC, since imidation reaction occurs partially in parallel with the polymerization of polyamic acid, there is a problem in terms of reaction control.

(Tetracarboxylic dianhydride having a wholly aromatic skeleton)
Examples of the tetracarboxylic dianhydride having a wholly aromatic skeleton include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4. '-Biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8- Examples thereof include naphthalenetetracarboxylic dianhydride or compounds obtained by substituting these aromatic rings with lower alkyl groups. Of these, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is particularly preferable.

(Diamine compound)
Examples of the diamine having a diphenyl ether skeleton that forms the first polyimide resin include 4,4′-diaminodiphenyl ether and 3,3′-diaminodiphenyl ether, and 4,4′-diaminodiphenyl ether is more preferable. Moreover, p-phenylenediamine is mentioned as diamine which has the p-phenylene skeleton which forms a 2nd polyimide resin.

(Organic polar solvent)
Examples of the organic polar solvent used in the polyamic acid solution include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide; N, N-dimethyl Acetamide solvents such as acetamide and N, N-diethylacetamide; pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; phenol, o-, m-, or p-cresol, xylenol, Phenolic solvents such as halogenated phenols and catechols; Ether solvents such as tetrahydrofuran, dioxane and dioxolane; or hexamethylphosphoramide and γ-butyrolactone; and the like can be used alone or as a mixture. It is preferable, further xylene, aromatic hydrocarbons such as toluene can be used. The solvent is not particularly limited as long as it dissolves polyamic acid and polyamic acid-polyimide copolymer.

(Solid content concentration of polyamic acid)
The solid content concentration of the polyamic acid solution is not particularly defined, but is preferably 5 to 50% by mass. Furthermore, 10 to 30% by mass is particularly suitable. When the solid content concentration is less than 5% by mass, the degree of polymerization of the polyamic acid is low, and the strength of the molded product finally obtained is lowered. Moreover, when the solid content concentration at the time of polymerization is higher than 50% by mass, an insoluble part of the raw material monomer is generated and the reaction does not proceed.

  Moreover, the range which expresses a suitable viscosity is selected from the ease of the coating at the time of polyimide resin endless belt manufacture. In general, the viscosity range optimum for coating is preferably 1 to 100 Pas, and the solid content concentration described above is desirable as the solid content concentration for achieving the viscosity.

(Conductive agent)
As the conductive agent, carbon black having conductivity is preferable. From the viewpoint of improving dispersibility, it is more preferable to use acidic carbon black. The endless belt made of polyimide resin of the present embodiment is manufactured by dispersing carbon black as a conductive agent in the polyimide resin. The compounding amount of the carbon black is 15 to 35 parts by mass, preferably 20 to 30 parts by mass with respect to 100 parts by mass of the total amount of the polyamic acid. Unless carbon black is uniformly and finely dispersed, carbon black having excellent desired resistance characteristics (particularly, in-plane uniformity of resistance, electric field dependency, and maintainability of surface resistivity) cannot be obtained.

  When the content of carbon black is less than 15 parts by mass with respect to 100 parts by mass of the total amount of polyamic acid, the resistance becomes high when an endless belt made of polyimide resin is used. For example, when used as a transfer member, toner cannot be transferred. . On the other hand, when it exceeds 35 parts by mass, the resistance becomes too low when the polyimide resin endless belt is formed, and the film becomes brittle and the flexibility is lowered.

  Also, a carbon black of a different type from the above-described carbon black, or other conductive or semiconductive material can be used. Examples of the carbon black include ketjen black and acetylene black. Other conductive or semiconductive materials are not particularly limited, and examples thereof include metals such as aluminum and nickel, metal oxide compounds such as yttrium oxide and tin oxide, and potassium titanate. Further, an ion conductive material such as LiCl, or a conductive polymer material such as polyaniline, polypyrrole, polysulfone, or polyacetylene can be added. These may be used alone or in combination.

  In the present invention, good dispersion stability is obtained because of good dispersibility in the resin, resistance variation of the endless belt made of polyimide resin can be reduced, electric field dependency is also reduced, and electric field concentration due to transfer voltage is reduced. It is preferable to add acidic carbon black having a pH of 5 or less and a volatile content of 3.5% or more from the stability of the electric resistance over time.

-Endless belt made of polyimide resin-
The endless belt made of polyimide resin of the present embodiment is prepared by applying the above-described polyamic acid solution to the mold surface, and then removing the solvent appropriately by drying treatment, followed by firing treatment to obtain an imide of polyamic acid. The reaction can be carried out (dehydration ring closure reaction).

  The polyimide resin endless belt of the present embodiment has a first polyimide resin formed by imide bonding of a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton, and a wholly aromatic skeleton. A second polyimide resin formed by imide bonding of tetracarboxylic dianhydride and a diamine having a p-phenylene skeleton is contained.

More preferably, the first polyimide resin contains a structure (I) in which a 3,3 ′, 4,4′-biphenyltetracarboxylic acid skeleton and a 4,4′-diaminodiphenyl ether skeleton are imide-bonded. The second polyimide resin contains a structure (II) formed by imide bonding of a 3,3 ′, 4,4′-biphenyltetracarboxylic acid skeleton and a p-phenylene skeleton.

  At this time, it is preferable that said 1st polyimide resin is 25 mol% or more and 70 mol% or less of all the polyimide resins. If it is less than 25 mol%, it becomes difficult to obtain high dispersibility of the conductive agent, and the electric field dependency of the resistance of the endless belt made of polyimide resin cannot reach the target level. On the other hand, when it exceeds 70 mol%, the elastic modulus and strength of the endless belt made of polyimide resin are lowered. For example, when used as a transfer belt of an image forming apparatus, the high-speed aptitude deterioration of a color registration or the life is shortened. There is a case. In addition, the ratio of the 1st polyimide resin with respect to all the polyimide resins is the same as the ratio of the polyamic acid which is the precursor of the 1st polyimide resin with respect to all the polyamic acids, and before and after imidation reaction (dehydration ring closure reaction) The ratio does not change.

(Surface resistivity)
The endless belt made of polyimide resin of the present embodiment has a common logarithmic value of surface resistivity of 8 to 13 (log Ω / □) when a voltage of 100 V is applied under the condition of 22 ° C. and 55 RH%, preferably 9-12. If the surface resistivity is too low, the transferred image may be distorted due to the spread or lateral flow of the transfer current. On the other hand, if the surface resistivity is too high, a surface potential neutralization mechanism may be required to prevent contamination. .

(Electric field dependence of surface resistivity)
In addition, the endless belt made of polyimide resin of the present embodiment has a common logarithmic difference in surface resistivity of 0.3 (logΩ / □) when voltages of 100 V and 1000 V are applied under the conditions of 22 ° C. and 55 RH%. )

  By containing carbon black uniformly and finely in the resin, the amount of change in the surface resistivity of the endless belt made of polyimide resin with respect to the applied voltage (the electric field dependence of the surface resistivity) can be reduced. For example, in an image forming apparatus, a good image is normally stably formed by changing the transfer electric field according to the use environment and the type of paper. However, if the resistance of the transfer belt changes due to a change in the transfer electric field, it becomes difficult to obtain a stable transfer image, and it becomes difficult to design transfer parameters. In order to reduce the effect of transfer belt resistance fluctuations caused by such transfer electric field, the transfer belt is designed with a smaller transfer belt resistance specification or in combination with a resistor (eg, backup roll) that has a small electric field dependency. However, both lead to cost increase. When the endless belt made of the polyimide resin of the present invention is used as a transfer belt of an image forming apparatus, a good image can be formed more stably, and the transfer system as a whole can be designed at low cost.

  Further, by containing carbon black uniformly and finely in the resin, the amount of change in the surface resistivity of the polyimide resin endless belt before and after repeated use is small, and the surface resistivity is excellently maintained.

  The amount of change in surface resistivity is a value obtained when the surface resistivity value is expressed in common logarithm, and the surface resistivity value before use is subtracted from the surface resistivity value after use. For example, when a polyimide resin endless belt is used as a transfer belt and its surface resistivity is poorly maintained, for example, if paper is repeatedly transferred to a postcard size, the resistance of the transfer belt in the width direction is the same as the postcard size. The rate changes and there is a difference in resistivity with the transfer belt area where the postcard did not contact. In this state, for example, when transfer is performed on the entire surface of the A3 sheet, the transfer image area includes areas having different resistivity of the transfer belt. Therefore, transfer efficiency is different, resulting in image density unevenness in the A3 sheet. . The smaller the amount of change in the surface resistivity, the better. However, if it exceeds ± 0.3, it is often detected as density unevenness during transfer.

(Environmental dependence of surface resistivity)
Further, the endless belt made of polyimide resin of the present embodiment has a surface resistivity when a voltage of 100 V at 10 ° C. and 15 RH% is applied, and a surface resistivity when a voltage of 100 V at 28 ° C. and 80 RH% is applied. The difference in common logarithm is preferably 0.3 (logΩ / □) or less, more preferably 0.2 or less. When the difference in the common logarithm of the surface resistivity is 0.3 or less, a wide range of transfer latitude with respect to the environment is obtained. Therefore, a mechanism for controlling the transfer current and electric field depending on the use environment is unnecessary, and an inexpensive transfer system can be provided.

  As for the surface resistivity, a circular electrode shown in FIG. 1 (for example, HR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.) is used, and a voltage of 100 V is applied unless otherwise specified according to JIS K6911 (1995). The value obtained from the current value after 10 seconds. FIG. 1 is a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of a circular electrode. The circular electrode includes a first voltage application electrode A and a plate-like insulator B. The first voltage application electrode A has a columnar electrode portion C and a cylindrical ring electrode having an inner diameter larger than the outer diameter of the columnar electrode portion C and surrounding the columnar electrode portion C at regular intervals. Part D is provided. A test piece T is sandwiched between the cylindrical electrode part C and the ring-shaped electrode part D and the plate-like insulator B in the first voltage application electrode A, and the cylindrical electrode part C and the ring shape in the first voltage application electrode A. The current I (A) flowing when the voltage V (V) is applied between the electrode part D is measured, and the surface resistivity ρs (Ω / □) can be calculated by the following formula (1). Here, in the following formula (1), d (mm) indicates the outer diameter of the cylindrical electrode portion C, and D (mm) indicates the inner diameter of the ring-shaped electrode portion D.

    Formula (1) ρs = π × (D + d) / (D−d) × (V / I)

(Tensile modulus)
Further, the endless belt made of polyimide resin of the present embodiment has a tensile elastic modulus defined by JIS K7127 (1999) of 4.0 GPa or more. When the tensile elastic modulus is 4.0 GPa or more, even when a strong tension is applied and the belt is rotated at a high speed, the peripheral length of the belt does not increase. Therefore, for example, when used as a transfer belt of an image forming apparatus, it can contribute to obtaining a high-quality image with a small color registration. The tensile elastic modulus is obtained by performing a tensile test according to JIS K 7127 (1999), drawing a tangent line to the curve in the initial strain region of the obtained stress / strain curve, and obtaining the slope.

(Number of folding times)
In addition, the polyimide resin endless belt of the present embodiment has a folding endurance of 1000 or more according to the MIT test method applied with a load of 9.8 N. Since the folding resistance is 1000 times or more, the flexibility and followability are excellent. The folding endurance measurement by the MIT test method is based on JIS P8115 (2001) (“paper and paperboard” in JIS P8115 (2001) is replaced with “polyimide resin endless belt”), and FIG. Measured using the MIT test machine shown in FIG. FIG. 2 is a schematic configuration diagram for explaining the MIT testing machine. The MIT testing machine shown in FIG. 2 has a bending device 6 attached to the bending device mounting surface 4 and having a radius of curvature of 0.38 mm for sandwiching the test piece 9 and a load attached to the plunger 8. It consists of a gripping tool 10 for hanging. The procedure for measuring the folding endurance by the MIT test method is as follows. One of the test pieces 9 is sandwiched by the bending device 6. Further, the other one of the test pieces 9 is sandwiched by the gripping tool 10 and a load of 9.8 N (1 kgf) is applied to the test piece 9. Next, the bending device 6 is rotated at an angle of 135 ± 2 ° at a speed of 175 ± 10 times per minute, and the test piece 2 to which a load is applied is repeatedly bent at the curvature surface of the bending device 6 and stress is applied. To break.

As the number of folding times N, the number of folding times N until the breakage is used. Further, the bending strength FE is obtained from N according to the following formula (4).
FE = log ₁₀ N (4)

-Manufacturing method of endless belt made of polyimide resin-
The method for producing an endless belt made of polyimide resin according to the present embodiment is a method for producing an endless belt made of polyimide resin, characterized by having at least the following steps (a) to (c).
(A) A polyamic acid solution (i) containing a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton is mixed with carbon black to prepare a carbon black-dispersed polyamic acid solution (A). Process.
(B) The carbon black-dispersed polyamic acid solution (A) is mixed with a polyamic acid solution (ii) containing a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a p-phenylene skeleton, A step of preparing a black dispersed polyamic acid solution (B).
(C) A step of forming an endless belt by heating the carbon black-dispersed polyamic acid solution (B) and performing an imidization reaction after the steps (a) and (b).

Further, the polyamic acid (i) is a polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether, and the polyamic acid (ii) is 3, A polyamic acid composed of 3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine is preferred.

(Carbon black dispersion process)
Hereinafter, an example of the step of uniformly and finely dispersing carbon black will be described.

  First, when a carbon black is dispersed in a polyamic acid solution (i) containing a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton, a collision type disperser that does not use media is used. Is preferred. The collision type disperser is a machine that collides and disperses two or more divided solutions, and the pressure at the time of the collision is preferably 150 MPa or more.

  For dispersion, first, carbon black is mixed in a polyamic acid solution (i) containing a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton, and preliminary dispersion is performed. Pre-dispersion is to stir the carbon black mixture well with a stirrer to loosen the carbon black mass finely. Next, the preliminarily dispersed solution is passed through a collision type disperser.

  FIG. 3 is an explanatory diagram of a collision type disperser. Two first flow path pipes 50 connected at one point from upstream to downstream, a connection pipe 52 constituting a connection portion, and one end of the connection pipe 52. The liquid is dispersed by flowing the solution through a flow path constituted by a second flow path pipe 54 branched into two or more.

  In the operation, first, the solutions are caused to flow through the two first flow path tubes 50 respectively. This flow pressure is set to 150 MPa or more, and the solutions collide with each other at 150 MPa or more in the vicinity of one end 52a of the connecting pipe 52 constituting the connecting portion. The collided liquid mixture passes through the connecting pipe 52 and flows into the second flow path pipe 54 branched into two or more, and is divided into two again. The mixed solution divided into two again can be further flowed into the first flow path pipe 50, and the mixing and division can be repeated two or more times. Thus, by making it collide and mix at 150 MPa or more, it becomes possible to add a collision force with a strong pressure to the solution together with a shearing force, and carbon black can be uniformly and finely dispersed at a high concentration.

  The pressure needs to be 150 MPa or more, preferably 150 to 250 MPa, more preferably 180 to 220 MPa. If the pressure is less than 150 MPa, carbon black may not be finely dispersed.

The mixed liquid that has collided passes through the connecting pipe 52, but the connecting part of the two first flow path pipes 50 (in the vicinity of one end 52a of the connecting pipe 52 in the figure), that is, the collision part where the two solutions collide. the minimum cross-sectional area of 0.07 mm ² or less (preferably 0.007～0.05Mm ² or less, more preferably 0.015~0.04mm ²⁾ preferably with. This is because the pressure can be efficiently applied to the solution by reducing the area where the solution collides. Here, the minimum cross-sectional area of the collision portion where the two solutions collide corresponds to the cross-sectional area of the flow channel pipe 50 in the vicinity of the inlet of the connecting pipe 52 in the drawing.

  In order to improve the dispersibility of the carbon black, for example, this path is passed five times in total. In the present invention, the temperature of the dispersion liquid path including the first flow path pipe 50 to the second flow path pipe 54 is further increased. A mechanism for circulating the controlled cooling medium is provided, and the liquid temperature of the dispersion is controlled so as not to exceed 120 ° C. When the liquid temperature of the dispersion exceeds 120 ° C., the carbon black once dispersed may aggregate again and the dispersibility may deteriorate. Further, if the dispersion is continued in a state where the liquid temperature exceeds 120 ° C., the polyamic acid may be hydrolyzed.

  As described above, in the dispersion step, since the resin material is processed at a high temperature and a high pressure during dispersion, the resin may be deteriorated and the mechanical characteristics may be deteriorated. At the time of dispersion, it is preferable to reduce the amount of resin to be processed by carrying out carbon black at as high a concentration as possible, add a resin solution that has not undergone the dispersion treatment after dispersion, and increase the amount to prepare a predetermined carbon black content. Therefore, the amount of carbon black mixed at the time of dispersion is preferably 80 to 100 parts by mass with respect to 100 parts by mass of the film-forming resin.

  The average particle size of carbon black after dispersion is preferably 500 nm or less. If the particle size of the carbon black is too large, the electric field dependency of the resistance cannot be obtained, the mechanical strength may be lowered, and the maintainability of the surface resistivity may be deteriorated. In addition, the average particle diameter of carbon black can be measured using, for example, a dynamic light scattering type measuring device PAR-III manufactured by Otsuka Electronics. The measurement conditions are: clock rate: 100 μs, accumulate time: 10 times, correlate ch: 128, temperature: 20 ° C., solvent: NMP.

  When impurities are mixed or carbon black aggregates are present during dispersion, it is possible to remove coarse particles by passing the solution through, for example, a filter having an aperture of 25 μm or less to obtain a uniformly dispersed solution. .

  Next, the temperature of the solution is controlled to 20 to 60 ° C. after the dispersion step and before the mixing step described later. One reason for lowering the temperature is that the solvent in the polyamic acid solution (ii) containing a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a p-phenylene skeleton to be added later is rapidly evaporated. It is for suppressing doing.

(Mixing process)
A polyamic acid solution (i) containing a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton are mixed with carbon black, and the carbon black-dispersed polyamic acid solution (A) is completely mixed. A polyamic acid (ii) containing a tetracarboxylic dianhydride having an aromatic skeleton and a diamine having a p-phenylene skeleton is mixed to prepare a carbon black-dispersed polyamic acid solution (B).

  In the mixing step, the above-described collision type disperser shown in FIG. 2 may be used, or mixing may be performed using a ball mill, a sand mill, a basket mill, ultrasonic dispersion, or the like.

  A polyamic acid solution (i) containing the tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton, and a tetracarboxylic dianhydride having a wholly aromatic skeleton and a p-phenylene skeleton Although the density | concentration of the polyamic acid solution (ii) containing diamine is selected suitably, the solid content concentration of a preferable solution is 10-40 mass%. Examples of these solvents include amide solvents such as dimethylacetamide and N-methyl-2-pyrrolidone (NMP). The viscosity of the solution is adjusted by the molecular weight at the time of synthesis. At this time, the polyamic acid containing the tetracarboxylic dianhydride having a wholly aromatic skeleton and the diamine having a diphenyl ether skeleton is preferably 25 mol% or more and 70 mol% or less of the total polyamic acid. If it is less than 25 mol%, it becomes difficult to obtain high dispersibility of the conductive agent, and if it exceeds 70 mol%, the elastic modulus and strength after imidation are lowered. There is a case where the high-speed aptitude of the cash register is deteriorated or the life is shortened.

  As described above, carbon black having a pH of 5 or less and a volatile content of 3.5% or more can be preferably used. Examples of carbon black include general carbon black such as oil furnace black and channel black. From the viewpoint of properties, acidic carbon black is preferable. Moreover, it is also possible to mix | blend multiple types instead of one type.

(Film formation method)
In the present invention, the film forming method is not particularly required, and a general centrifugal molding method, a dip coating method or an annular coating method can be used.

  The core used for the mold for centrifugal molding, the dip coating method and the annular coating method is preferably a cylinder made of metal such as aluminum, stainless steel or nickel. The length of the cylinder needs to be equal to or longer than the target endless belt, and when a plurality of endless belts are manufactured at the same time, a length equal to or more than the number of the endless belts is required. Further, in order to secure a margin for the invalid area generated at the end, it is desirable that the length is about 10 to 40% longer than the target length.

  The inner diameter of the cylindrical mold used in the centrifugal molding method and the outer diameter of the cylindrical core used in the dip coating method and the annular coating method are set to match the diameter of the endless belt made of polyimide resin, and the thickness should be such that the strength can be maintained. To do. In order to prevent the formed film from adhering to the inner surface of the cylindrical mold and the outer surface of the cylindrical core body, the mold inner surface and the outer surface of the core body are given releasability. There are methods of covering the corresponding surface with a fluorine resin or a silicone resin, or applying a release agent.

  In the imidization reaction (dehydration cyclization reaction) of polyamic acid, the solvent after the reaction or evaporation of water generated during the dehydration reaction may cause partial swelling of the film after the reaction. Swelling of the film often occurs especially when the film thickness exceeds 50 μm. In order to prevent this swelling, it is preferable to roughen the core surface as disclosed in JP-A-2002-160239. As the method, there are methods such as blasting, cutting, sandpaper peeling, etc., and the surface roughness is preferably about Ra 0.2 to 2 μm. Thereby, the gas generated from the film can go out through a slight gap formed between the core and the film, and does not swell.

  Next, an example of an annular coating method using an annular body will be described. FIG. 4 is a schematic cross-sectional view of the coating apparatus during coating. However, only the main part of the coating is shown, and the peripheral parts such as the lifting and lowering means for the core body are omitted. In the present specification, “applying onto the core” means applying a coating liquid onto the surface of the core. Further, “raising the core” is a relative relationship with the liquid level, and includes the case of “stopping the core and lowering the coating liquid level”.

  In FIG. 4, when the solution 12 is put into the annular coating tank 7 and the core body 11 is passed from the lower part to the upper part, the coating film 14 is formed and coating is performed. Another core body 11 ′ is stacked under the core body 11. A sealing material 18 is attached to the bottom of the annular coating tank 17 so that the solution does not leak. The sealing material is made of a flexible plate material such as polyethylene, silicone rubber, or fluorine resin. An annular body 15 provided with a circular hole 16 larger than the outer peripheral outer diameter of the cross section of the core body 11 is installed on the coating liquid 12 in a freely movable state. The annular body floats on the solution during application, but if the buoyancy is insufficient when stationary, legs or arms that support the annular body may be provided on the outer peripheral surface of the annular body 15 or the application tank to prevent sinking. .

  At the time of application, the film thickness of the coating film 14 is adjusted by the gap between the core body 11 and the circular hole 16, and therefore the gap is adjusted in view of the desired coating film thickness. The rising speed of the core body is preferably about 0.1 to 10.0 m / min. When the core body 11 is lifted through the circular hole 16, the gap between the core body 11 and the annular body 15 is interposed by the solution 2. A frictional resistance is generated at, and the annular body 15 is lifted. When the annular body 15 is lifted in this way, the annular body 15 moves in the horizontal direction so that the frictional resistance with the core body 11 is constant in the circumferential direction, and the gap is constant in the circumferential direction. Therefore, the annular body 15 does not come into contact with the core body 1, and a constant gap is always maintained.

(Endless belt production method)
After application to the core, the solvent is removed until the coating film is dried to form a self-supporting film. The drying conditions are preferably set so that the solvent contained in the coated film after drying is about 30 to 50% by weight, the temperature is preferably 100 to 200 ° C., and the time is preferably about 10 to 60 minutes. In order to accelerate the drying of the solvent, hot air may be blown onto the surface of the coating film. When drying, it is preferable that the axis direction of the core is horizontal and rotated at 2 to 20 rpm so that the coating film does not hang downward.

  Next, the core is heated to form a film. The heating temperature is generally about 250 to 400 ° C, preferably about 300 to 350 ° C. Since the imidization reaction is difficult to complete unless the temperature is 250 ° C. or higher, the imidation reaction is preferably performed at a temperature of 250 ° C. or higher, preferably 300 ° C. or higher for 30 minutes or longer.

  After cooling, the core is taken out and the formed film is peeled off from the core to obtain an endless belt. At that time, it is preferable to blow air between the core and the film from the viewpoint of easy peeling. The endless belt is cut to a predetermined length by cutting an unnecessary portion at the end. Furthermore, you may give a drilling process, a rib attachment process, etc. as needed.

-Image forming device-
The image forming apparatus according to the present embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, a latent image forming unit that forms a latent image on the surface of the image carrier, and the latent image using toner. Development means for developing and forming a toner image; transfer means for transferring the toner image onto a recording medium; and fixing means for heating and fixing the toner image onto the recording medium. A resin endless belt is provided.

  The image forming apparatus of the present invention is not particularly limited as long as it is an image forming apparatus having the above-described configuration. For example, a normal monocolor image forming apparatus that contains only a single color toner in the developing device, A color image forming apparatus that sequentially repeats primary transfer of a toner image carried on an image carrier onto an intermediate transfer belt, and a tandem type in which a plurality of image carriers equipped with developing units for respective colors are arranged in series on the intermediate transfer belt Examples thereof include a color image forming apparatus.

  Further, the image forming apparatus of the present invention includes a first transfer unit that primarily transfers a toner image formed on an image carrier to an intermediate transfer belt, and a toner image transferred to the intermediate transfer belt to a transfer target. An image forming apparatus including at least a second transfer unit for transferring, wherein the intermediate transfer belt may be the polyimide resin endless belt (intermediate transfer belt) of the present invention described above. When a polyimide resin endless belt is used as the intermediate transfer belt, the thickness is preferably 60 to 100 μm.

  A specific example of such a tandem type color image forming apparatus will be described below with reference to the drawings.

  FIG. 5 is a schematic diagram showing a configuration example of an image forming apparatus for forming an image by the image forming method of the present invention. In the illustrated image forming apparatus 200, four electrophotographic photosensitive members 401 a to 401 d are disposed in parallel in the housing 400 along the intermediate transfer belt 409. The electrophotographic photoreceptors 401a to 401d form, for example, images in which the electrophotographic photoreceptor 401a is yellow, the electrophotographic photoreceptor 401b is magenta, the electrophotographic photoreceptor 401c is cyan, and the electrophotographic photoreceptor 401d is black. Is possible.

  Each of the electrophotographic photosensitive members 401a to 401d can be rotated in a predetermined direction (counterclockwise on the paper surface), and the charging rolls 402a to 402d, the developing devices 404a to 404d, and the primary transfer roll 410a along the rotation direction. To 410d and cleaning blades 415a to 415d are arranged. Each of the developing devices 404a to 404d can be supplied with toner of four colors of black, yellow, magenta and cyan accommodated in the toner cartridges 405a to 405d, and the primary transfer rolls 410a to 410d are respectively intermediate transfer belts. 409 is in contact with the electrophotographic photoreceptors 401a to 401d.

  Further, an exposure device 403 is disposed at a predetermined position in the housing 400, and it becomes possible to irradiate the surfaces of the charged electrophotographic photoreceptors 401a to 401d with a light beam emitted from the exposure device 403. ing. Accordingly, charging, exposure, development, primary transfer, and cleaning are sequentially performed in the rotation process of the electrophotographic photosensitive members 401a to 401d, and the toner images of the respective colors are transferred onto the intermediate transfer belt 409 in an overlapping manner.

  Here, the charging rolls 402a to 402d contact the surface of the electrophotographic photoreceptors 401a to 401d with a conductive member (charging roll), and apply a voltage uniformly to the photoreceptor to charge the photoreceptor surface to a predetermined potential. (Charging process). In addition to the charging roll shown in this embodiment, charging by a contact charging method may be performed using a charging brush, a charging film, a charging tube, or the like. Moreover, you may charge by the non-contact system using a corotron or a scorotron.

  As the exposure apparatus 403, an optical system apparatus or the like that can expose a light source such as a semiconductor laser, an LED (light emitting diode), a liquid crystal shutter, or the like on the surfaces of the electrophotographic photosensitive members 401a to 401d can be used. Among these, when an exposure apparatus capable of exposing non-interference light is used, interference fringes between the electroconductive substrates of the electrophotographic photoreceptors 401a to 401d and the photosensitive layer can be prevented.

  For the developing devices 404a to 404d, a general developing device that develops the developer for developing the two-component electrostatic charge image in contact or non-contact can be used (developing step). Such a developing device is not particularly limited as long as a two-component electrostatic image developing developer is used, and a known one can be appropriately selected according to the purpose.

  In the primary transfer process, a primary transfer bias having a polarity opposite to that of the toner carried on the image carrier is applied to the primary transfer rolls 410a to 410d, so that each color toner is transferred from the image carrier to the intermediate transfer belt 409. The primary transfer is performed sequentially.

  The cleaning blades 415a to 415d are for removing residual toner adhering to the surface of the electrophotographic photosensitive member after the transfer process, and the electrophotographic photosensitive member cleaned by this cleaning process is repeatedly used in the above-described image forming process. Is done. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

  The intermediate transfer belt 409 is supported with a predetermined tension by a drive roll 406, a backup roll 408, and a tension roll 407, and can rotate without causing deflection due to the rotation of these rolls. Further, the secondary transfer roll 413 is disposed so as to contact the backup roll 408 via the intermediate transfer belt 409.

  By applying a secondary transfer bias having a reverse polarity to the toner on the intermediate transfer member to the secondary transfer roll 413, the toner is secondarily transferred from the intermediate transfer belt to the recording medium. The intermediate transfer belt 409 that has passed between the backup roll 408 and the secondary transfer roll 413 is cleaned by, for example, a cleaning blade 416 disposed near the drive roll 406 or a static eliminator (not shown). It is repeatedly used for the next image forming process. A tray (transfer medium tray) 411 is provided at a predetermined position in the housing 400, and the transfer medium 500 such as paper in the tray 411 is transferred to the intermediate transfer belt 409 and the secondary transfer roll by the transfer roll 412. Then, the paper is sequentially transferred between the two fixing rolls 414 that are in contact with each other and the two fixing rolls 414, and then discharged to the outside of the housing 400.

  Hereinafter, the present invention will be specifically described by way of examples. However, each example does not limit the present invention.

(Example 1)
100 parts by mass of Uwanis A manufactured by Ube Industries, Ltd. (formula A: NMP solution of polyamic acid consisting of biphenyltetracarboxylic dianhydride and 4,4′-diaminobiphenyl ether (each molar ratio 1: 1), 9 parts by mass of carbon black (Special Black 4 Degussa, pH 3, volatile content 14 wt%) was added to the solid content ratio after imide conversion of 18 wt% and viscosity of about 5 Pa · s. Using (Geanus PY: minimum cross-sectional area of the collision part 0.032 mm ² ), the pressure was 200 MPa, the solution was divided into two after colliding, and the path divided into two again was passed five times to disperse and mix. The viscosity of the obtained dispersion was about 8 Pa · s at room temperature.

  100 parts by weight of the resulting dispersion, Euvarnish S manufactured by Ube Industries, Ltd. (formula B: biphenyltetracarboxylic dianhydride and paraphenylenediamine (each molar ratio 1: 1) NMP solution of polyamic acid 70 parts of a solid fraction after imide conversion and a viscosity of about 5 Pa · s) are added, and stirred and mixed using an Aiko mixer manufactured by Aikosha Mfg. Co., Ltd. Prepared. The viscosity of the obtained raw material liquid was about 6 Pa · s at room temperature (the raw material liquid was 28.4 parts of carbon black relative to the polyimide resin after imide conversion, and the Euvarnish A component in the polyimide resin was about 51 mol%).

  Using the obtained raw material liquid, a polyimide precursor coating film A was formed by a protruding annular coating method as shown in FIG.

  As the cylindrical formed tube 11, an aluminum cylindrical body having an outer diameter of 364.5 mm and a length of 650 mm was prepared. Such an aluminum cylinder is made by heating an aluminum tube having an outer diameter of 377 mm and a length of 700 mm at 350 ° C. for 10 minutes and naturally cooling, then cutting the surface to an outer diameter of 364.5 m, The surface is roughened to Ra: 0.3 μm by blasting with spherical glass particles. A silicone mold release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) is applied to the surface of the cylindrical tube 31 and subjected to a baking treatment at 300 ° C. for 1 hour to produce an aluminum cylinder A first. Furthermore, the following release agent removing step was performed on the aluminum cylinder A to produce an aluminum cylinder B.

  On the other hand, the annular body 15 was made of aluminum having an outer diameter of 445 mm, a minimum inner diameter of 366 mm, and a height of 50 mm. The inner wall is inclined.

  The cylindrical tube 11 (aluminum cylinder B) was passed through an annular coating tank 17 having an inner diameter of 370 mm and a height of 150 mm, to which a polyethylene annular sealing material 18 having a center hole having an inner diameter of 360 mm was attached. . And the polyimide precursor solution 12 (polyimide precursor solution A) was put into the cyclic | annular application | coating tank 17, the cyclic | annular body 15 was arrange | positioned, the cylindrical molded tube 11 was raised at 5.0 m / min, and it apply | coated. Thereby, the polyimide precursor coating film 14 having a wet film thickness of about 420 μm was formed on the surface of the cylindrical tube 11.

  Next, the cylindrical molded tube 11 was horizontal and heated and dried at 170 ° C. for 30 minutes while rotating at 6 rpm. Then, it heated at 320 degreeC for 30 minutes, imide conversion was carried out, and the polyimide resin film in which carbon black was disperse | distributed was formed.

  After the temperature of the cylindrical molded tube 11 is cooled to room temperature, the sticking of the polyimide resin film is released by blowing 2.0 MPa air from a φ1.5 nozzle into the gap between the cylindrical molded tube 11 and the polyimide resin film. The entire film was peeled off and extracted from the core. The polyimide resin film in which carbon black having an average film thickness of 78 μm without wrinkles was dispersed could be peeled off.

  Both ends were trimmed so that the width of the obtained polyimide resin film was 369 mm, and a polyimide endless belt could be obtained. The endless belt made of polyimide resin was mounted as an intermediate transfer belt in a copier / printer combined machine DocuCenter Color C6505 manufactured by Fuji Xerox Co., Ltd., and a print sample was obtained to evaluate the image quality.

  The evaluation of image quality includes (i) “color registration” for evaluating positional deviation in the process direction of four colors, (ii) “thin line reproducibility” in which fine lines in the process direction are reproduced without fading, and (iii) halftone. In the image (each color, density 30% and 50%), “spotted density unevenness (due to peeling discharge from the photoreceptor in primary transfer), (iv) A4 half after printing 3,000 sheets on postcard “Through-sheet passing through” is printed when a tone image (magenta, 50%) is printed, and (v) other comprehensive image quality evaluation is performed.

  The evaluation method is as follows. The following examples and comparative examples were also evaluated in the same manner.

(Surface resistivity)
As described above, the surface resistivity was measured according to JIS K6991 (1995) using a Hirester IP and HR probe manufactured by Mitsubishi Yuka Co., Ltd. 24 points (3 places in the width direction × 8 places in the circumferential direction) of the belt were measured, and the average value was taken as the surface resistivity of the belt.

(Electric field dependence of surface resistivity)
The electric field dependency of the surface resistivity was measured at an applied voltage of 100 V and 1000 V, and the difference in common logarithm was defined as the electric field dependency of the surface resistivity. The voltage application time was 10 seconds each.

(Environmental dependence of surface resistivity)
Also, the environmental dependency of the surface resistivity is that the surface resistivity when the belt is applied at 100 ° C. and 15 RH% for 24 hours and then applied at 100 V, and that the belt is applied at 28 ° C. and 80 RH% for 24 hours after 100 V is applied. The surface resistivity was measured, and the difference between the common logarithm values was defined as the environmental dependency of the surface resistivity. In addition, the environmental dependence set the 0.3 or less as the pass.

(Tensile modulus)
The tensile modulus was measured according to JIS K7127 (1999), and the average value measured five times only in the circumferential direction was taken as the measured value. More specifically, a dumbbell No. 3 punched specimen (width 5 mm) was prepared and measured using MODEL-1605N manufactured by Aiko Engineering Co., Ltd. at a tensile speed of 20 mm / min. In addition, the tensile elastic modulus of the endless belt in which carbon black was dispersed was 4.0 GMpa or higher.

(Number of folding times)
Folding resistance measurement by the MIT test method is a method based on JIS P8115 (2001) (“paper and paperboard” in JIS P8115 (2001) is replaced with “endless belt made of polyimide resin”), as described above. Measured using the MIT testing machine shown in FIG. Folding was repeated and stressed to cause breakage, and the number of times of bending N until breakage (average value of five measurements) was defined as the number of folding times. In addition, 1000 times or more of folding-resistant frequency | count by the MIT test method performed by applying a tensile load of 1 kg weight was set as the pass.

(Example 2)
In the same manner as in Example 1, 18.5 parts by mass of carbon black was added to 100 parts by mass of Uwanis A manufactured by Ube Industries, Ltd., and dispersed and mixed. To 100 parts by mass of the resulting dispersion, 210 parts by mass of Ube Industries' Euvarnish S was added and stirred and mixed to prepare a raw material liquid for an endless belt made of polyimide (the raw material liquid was an imide conversion). The carbon black for the subsequent polyimide resin is 31.2 parts, and the Euvarnish A component in the polyimide resin is about 26 mol%).

  Using the obtained raw material liquid, an endless belt made of polyimide resin was produced in the same manner as in Example 1, and mounted on DocuCenterColor C6550 as an intermediate transfer belt, and a print sample was obtained to evaluate the image quality.

(Example 3)
Similarly to Example 1, 7.3 parts by mass of carbon black was added to 100 parts by mass of Euvarnish A manufactured by Ube Industries, Ltd., and dispersed and mixed. 35 parts by mass of Ube Kosan Co., Ltd. Euvarnish S was added to 100 parts by mass of the obtained dispersion, and a raw material liquid for an endless belt made of polyimide was prepared by mixing and stirring (the raw material liquid was an imide conversion). The carbon black for the later polyimide resin is 29.4 parts, and the Euvarnish A component in the polyimide resin is about 68 mol%).

  Using the obtained raw material liquid, an endless belt made of polyimide resin was produced in the same manner as in Example 1, and mounted on DocuCenterColor C6550 as an intermediate transfer belt, and a print sample was obtained to evaluate the image quality.

(Comparative Example 1)
In the same manner as in Example 1, 6.15 parts by mass of carbon black was added to 100 parts by mass of Uwanis A manufactured by Ube Industries, Ltd., and dispersed and mixed. 18 parts by mass of Ube Kosan Co., Ltd. Euvarnish S was added to 100 parts by mass of the obtained dispersion, and a raw material liquid for an endless belt made of polyimide was prepared by mixing and stirring (the raw material liquid was an imide conversion). The carbon black with respect to the subsequent polyimide resin is 28.6 parts by mass, and the Euvarnish A component in the polyimide resin is about 80 mol%).

  Using the obtained raw material liquid, an endless belt made of polyimide resin was produced in the same manner as in Example 1, and mounted on DocuCenterColor C6550 as an intermediate transfer belt, and a print sample was obtained to evaluate the image quality.

(Comparative Example 2)
In the same manner as in Example 1, 22 parts by mass of carbon black was added to 100 parts by mass of Uwanis A manufactured by Ube Industries, Ltd., and dispersed and mixed. To 100 parts by mass of the resulting dispersion, 300 parts by mass of Ube Industries S, made by Ube Industries Co., Ltd. was added, and stirred and mixed to prepare a raw material liquid for an endless belt made of polyimide (the raw material liquid was an imide conversion). The carbon black with respect to the subsequent polyimide resin is 28.6 parts by mass, and the Euvarnish A component in the polyimide resin is about 20 mol%).

  Using the obtained raw material liquid, an endless belt made of polyimide resin was produced in the same manner as in Example 1, and mounted on DocuCenterColor C6550 as an intermediate transfer belt, and a print sample was obtained to evaluate the image quality.

Example 4
Similarly to Example 1, 11 parts by mass of carbon black was added to 100 parts by mass of Uwanis A manufactured by Ube Industries, Ltd., and dispersed and mixed. 70 parts by mass of Ube Kosan Co., Ltd. Euvarnish S was added to 100 parts by mass of the obtained dispersion, and a raw material liquid for an endless belt made of polyimide was prepared by stirring and mixing ( (The raw material liquid is 34.7 parts of carbon black relative to the polyimide resin after imide conversion, and the Euvarnish A component in the polyimide resin is about 51 mol%).

  Using the obtained raw material liquid, an endless belt made of polyimide resin was produced in the same manner as in Example 1, and mounted on DocuCenterColor C6550 as an intermediate transfer belt, and a print sample was obtained to evaluate the image quality.

(Example 5)
Similarly to Example 1, 8.5 parts by mass of carbon black was added to 100 parts by mass of Uwanis A manufactured by Ube Industries, Ltd., and dispersed and mixed. 70 parts by mass of Ube Kosan Co., Ltd. Euvarnish S was added to 100 parts by mass of the obtained dispersion, and a raw material liquid for an endless belt made of polyimide was prepared by stirring and mixing ( The raw material liquid is 26.8 parts by mass of carbon black relative to the polyimide resin after imide conversion, and the Euvarnish A component in the polyimide resin is about 51 mol%).

  Using the obtained raw material liquid, an endless belt made of polyimide resin was produced in the same manner as in Example 1, and mounted on DocuCenterColor C6550 as an intermediate transfer belt, and a print sample was obtained to evaluate the image quality.

(Comparative Example 3)
12 parts of carbon black was added to 100 parts by mass of Uwanisu S manufactured by Ube Industries, Ltd., and dispersed and mixed in the same manner as in Example 1. 120 parts by mass of Ube Kosan Co., Ltd. Euvarnish A was added to 100 parts by mass of the resulting dispersion, and a raw material liquid for an endless belt made of polyimide was prepared by mixing and stirring (the raw material liquid was an imide). The carbon black relative to the polyimide resin after conversion is 28.9 parts, and the Euvarnish A component in the polyimide resin is about 51 mol%).

  Using the obtained raw material liquid, an endless belt made of polyimide resin was produced in the same manner as in Example 1, and mounted on DocuCenterColor C6550 as an intermediate transfer belt, and a print sample was obtained to evaluate the image quality.

(Image evaluation)
The following image evaluation was performed in the above Examples and Comparative Examples. The results are shown in Table 1.

-Color register-
The positional deviation in the process direction of the four colors is evaluated. The evaluation criteria are as follows.
A: Deviation amount is 50 μm or less B: Deviation amount exceeds 50 μm and 80 μm or less Δ: Deviation amount exceeds 80 μm and 120 μm or less X: Deviation amount exceeds 120 μm

-Fine line reproducibility-
A line break when a line image having a width of 150 μm was created was determined by observing with a digital microscope VH-6200 (manufactured by Keyence Corporation). Specific evaluation criteria are as follows.
A: The fine line is uniformly filled with toner.
○: The fine line is almost uniformly filled with toner, but the density is uneven.
Δ: Toner missing in part of fine line.
X: A thin line is observed in a dotted line state.

-Spotted density unevenness due to discharge-
The polyimide belt obtained in each example was incorporated into DocuCentreColor C6550 (manufactured by Fuji Xerox Co., Ltd.), and an image obtained by transferring a halftone image (30% magenta) onto A3 vertical paper was visually observed. The number of spot-like density unevenness was determined at five locations, and the average number was determined according to the following criteria.
<Criteria>
◎: No spotted density unevenness ○: Spotted density unevenness exceeding 1 and 3 or less △: Spotted density unevenness exceeding 3 and 10 or less ×: Spotted density unevenness exceeding 10

-Paper passing through-:
After printing 3,000 sheets on a postcard, the “paper passing part white spot” when an A4 halftone image (magenta, 50%) was printed was visually observed.
(Double-circle): The passage part of a postcard is not recognized at all on the image of A4.
○: When the image of A4 is observed well, the density corresponding to the postcard passing portion is slightly light.
Δ: It can be seen that the density of the portion corresponding to the passage portion of the postcard is reduced on the A4 image.
X: It can be clearly seen that the portion corresponding to the passage portion of the postcard is blank on the A4 image.

-Evaluation of electric field-dependent images-:
The reduction in the electric field dependency has a great influence on the use of the whole system (ease of design). However, here, as an example of the influence on the image, a multiple blur on thick paper was used as an evaluation index. Multiple blur was determined by observing the state of toner scattered around the line image having a width of 150 μm with a digital microscope VH-6200 (manufactured by Keyence Corporation).
◎: Almost no scattering ○: Slightly scattered, but no problem level △: There is scattering and the edges of fine lines are blurred ×: There is considerable scattering, and the edges of thin lines are unclear

  The smaller the electric field dependency of the surface resistivity, the easier it is to use as a transfer belt of an electrophotographic image forming apparatus. This is because the change in system resistance is small even if the transfer current and voltage are changed in the environment used, the type and thickness of the paper used, double-sided printing, and the like. In addition, the fact that the electric field dependency is small means that carbon black is well dispersed in the imide resin, and resistance reduction due to repeated transfer (electric field application) is also improved.

  The endless belt made of polyimide resin of this example has a surface resistivity of 0.3 or less, and can have a wider range of transfer latitude than before. In addition, resistance reduction due to repeated transfer (electric field application) can be prevented (Δ0.0 LogΩ), and a transfer image with extremely high image quality can be provided for a long period of time (long life as a belt). .

  Further, since the endless belt made of polyimide resin of this example does not use an ion conductive mechanism, the environmental dependency of the surface resistivity is 0.3 or less, and has a wide range of transfer latitude with respect to the environment. . Therefore, a mechanism for controlling the transfer current and electric field depending on the use environment is unnecessary, and an inexpensive transfer system can be provided.

  The endless belt made of polyimide resin of this example has a tensile elastic modulus of 4.0 GPa or more, and even when high-speed rotation / transfer is performed in a state where high tension is applied, the belt does not touch the surface contact object. It has become possible to provide an extremely high-quality transfer image with almost no deflection and no color shift.

  In addition, the endless belt made of polyimide resin of this example is so flexible that the folding endurance is 1000 times or more according to the MIT test method in which a tensile load of 1 kg is applied. In addition, the nip following property between the photosensitive member and the transfer roll is excellent, the reproducibility of the thin line is excellent, and the spot-like density unevenness due to the discharge can be suppressed.

  As an application example of the present invention, it can be applied to belt applications that require heat resistance, high strength and conductivity, for example, an antistatic member, an electromagnetic wave shielding member, and copying using an electrophotographic system There are also applications to belts used in image forming apparatuses such as printers and printers.

It is the schematic plan view (a) and schematic sectional drawing (b) which show an example of the circular electrode which measures a surface resistivity and volume resistivity. It is a schematic block diagram explaining the structure of the MIT test device for measuring bending resistance. It is explanatory drawing for demonstrating the division | segmentation and mixing mechanism of the carbon black containing polyamic acid solution in an example of the manufacturing method of the transfer member of this invention. It is a schematic sectional drawing of the coating device in process of application | coating. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention.

Explanation of symbols

  200 Image forming apparatus, 400 housing, 401a to 401d electrophotographic photosensitive member, 402a to 402d charging roll, 403 exposure apparatus, 404a to 404d developing apparatus, 405a to 405d toner cartridge, 409 intermediate transfer belt, 410a to 410d primary transfer roll 411 Tray (transfer medium tray), 413 Secondary transfer roll, 414 Fixing roll, 415a to 415d, 416 Cleaning blade, 500 Transfer medium.

Claims (8)

A first polyimide resin formed by imide bonding of a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton, a tetracarboxylic dianhydride having a wholly aromatic skeleton, and a p-phenylene skeleton A second polyimide resin formed by imide bond with a diamine having, and a conductive agent,
The difference between the common logarithm values of the surface resistivity when the first polyimide resin is 25 mol% or more and 70 mol% or less of the total polyimide resin, and the voltage of 100 V and 1000 V is applied under the condition of 22 ° C. and 55 RH%. An endless belt made of polyimide resin characterized by being 0.3 (log Ω / □) or less. The first polyimide resin contains a polyimide resin (A) formed by imide bonding of a 3,3 ′, 4,4′-biphenyltetracarboxylic acid skeleton and a 4,4′-diaminodiphenyl ether skeleton, The second polyimide resin contains a polyimide resin (B) formed by imide bonding of a 3,3 ', 4,4'-biphenyltetracarboxylic acid skeleton and a p-phenylene skeleton. The endless belt made of polyimide resin according to 1.

  3. The difference in common logarithm of surface resistivity when a voltage of 100 V and 1000 V is applied under the conditions of 22 ° C. and 55 RH% is 0.3 (log Ω / □) or less. Endless belt made of polyimide resin as described in 1.   The endless belt made of polyimide resin according to any one of claims 1 to 3, wherein a tensile elastic modulus defined in JIS K7127 (1999) is 4.0 GPa or more.   The endless belt made of polyimide resin according to any one of claims 1 to 4, wherein the folding endurance by the MIT test method applied with a load of 9.8 N is 1000 times or more. An image carrier, a charging unit for charging the surface of the image carrier, a latent image forming unit for forming a latent image on the surface of the image carrier, and a developing unit for developing the latent image with toner to form a toner image And a transfer means for transferring the toner image to a recording medium, and a fixing means for heating and fixing the toner image to the recording medium,
A first polyimide resin formed by imide bonding of a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton, and a tetracarboxylic dianhydride having a wholly aromatic skeleton; A second polyimide resin formed by imide bonding with a diamine having a p-phenylene skeleton and a conductive agent are contained, and the first polyimide resin is 25 mol% or more and 70 mol% or less of the total polyimide resin. And having an endless belt made of polyimide resin having a difference in common logarithm of surface resistivity of 0.3 (logΩ / □) or less when a voltage of 100 V and 1000 V is applied under the condition of 22 ° C. and 55 RH% An image forming apparatus. A method for producing an endless belt made of polyimide resin, comprising at least the following steps (a) to (c).
(A) A polyamic acid solution (i) containing a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a diphenyl ether skeleton is mixed with carbon black to prepare a carbon black-dispersed polyamic acid solution (A). Process.
(B) The carbon black-dispersed polyamic acid solution (A) is mixed with a polyamic acid solution (ii) containing a tetracarboxylic dianhydride having a wholly aromatic skeleton and a diamine having a p-phenylene skeleton, A step of preparing a black-dispersed polyimide reamic acid solution (B).
(C) A step of forming an endless belt by heating the carbon black-dispersed polyamic acid solution (B) and performing an imidization reaction after the steps (a) and (b). The polyamic acid (a) is a polyamic acid composed of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether, and the polyamic acid (b) is 3,3 ′. The method for producing an endless belt made of polyimide resin according to claim 7, which is a polyamic acid composed of 3,4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine.

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