JP2018159861A - Endless belt, endless belt unit, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an endless belt that reduces a difference in resistance in the axial direction.SOLUTION: An endless belt 101 for an image forming apparatus is formed of a resin composition that contains resin and a conductive agent and has surface resistivity dependent on a film thickness, where the thickness of the endless belt is increased from one end 102 toward the other end 103 in the axial direction, and the rate of increase in thickness based on the thickness at one end 102 is 0.7% or more and 2.9% or less per length of 100 mm in the axial direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an endless belt, an endless belt unit, and an image forming apparatus.

  In an image forming apparatus employing an electrophotographic system, an endless belt is applied to an intermediate transfer belt, a recording medium conveyance transfer belt, and the like.

  For example, in Patent Document 1, the belt has an endless belt shape, the surface roughness is in a specific range, the maximum value of volume resistance is within 90 times the minimum value, and the diameter and end diameter of the end circumference of the belt A transfer member in which the average thickness of the portions satisfies a specific relationship is disclosed.

  Patent Document 2 discloses a seamless belt characterized by having a single-layer base material having different properties on the front and back surfaces due to uneven distribution of the additive in the thickness direction.

  Further, in Patent Document 3, a mold having irregularities of 5 μm or more on the surface is used, and a tube formed in advance in a cylindrical shape is covered with a mold and heated to shrink the tube, and the volume resistance is specified. A range of cylindrical films is disclosed.

JP 2001-042654 A JP 2002-012681 A JP 2001-038804 A

  As a method for obtaining a film of a resin composition by heating a coating film applied to a core body in the process of manufacturing an endless belt, for example, high-temperature gas is fed from one end to the other end in the axial direction of the core body. A heating method (for example, heating with a downflow type heating device) may be mentioned. When heated by the above method, the heating efficiency on the leeward side (that is, the other end) is lower than that on the leeward side (that is, the one end). The resistance value is low in the region where the heating efficiency is high, and the resistance value is high in the region where the heating efficiency is low, so that the resistance value at one end in the axial direction of the endless belt (that is, the width direction of the endless belt) is obtained. And a resistance value at the other end may occur.

  The subject of this invention is comprised with the resin composition which has resin and a conductive agent and has the film thickness dependence of surface resistivity, The increase rate of the said thickness is less than 0.8% per 100 mm of axial lengths The object is to provide an endless belt in which the resistance difference in the axial direction is suppressed compared to the case.

The above problems are solved by the present invention described below. That is,
The invention according to claim 1
Consists of a resin composition containing a resin and a conductive agent and having a film thickness dependence of surface resistivity,
The thickness increases from one end in the axial direction toward the other end, and the rate of increase in thickness based on the thickness of the one end is 0.8% or more and 3.2% or less per 100 mm in the axial length. Endless belt for equipment.

The invention according to claim 2
2. The endless belt according to claim 1, wherein an increase amount of the thickness is not less than 0.5 μm and not more than 2.4 μm per 100 mm in the axial direction.

The invention according to claim 3
When the common logarithm value of the surface resistivity at the one end is logS ₁ and the common logarithm value of the surface resistivity at the other end is logS ₂ , the value of logS ₂ -logS ₁ is −0.16 logΩ / □ or more. The endless belt according to claim 1 or 2, wherein the endless belt is 16 logΩ / □ or less.

The invention according to claim 4
The endless belt according to any one of claims 1 to 3, wherein the resin includes polyamideimide.

The invention according to claim 5
The endless belt according to claim 1, wherein the conductive agent includes carbon black.

The invention according to claim 6
The endless belt according to any one of claims 1 to 5,
A plurality of rolls that span the endless belt under tension;
And an endless belt unit that is detachably attached to the image forming apparatus.

The invention according to claim 7 provides:
An image carrier,
Charging means for charging the surface of the image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
Developing means for developing, as a toner image, an electrostatic image formed on the surface of the image carrier with a developer containing toner;
A transfer means for transferring the toner image formed on the surface of the image carrier onto the surface of the recording medium via the endless belt;
An image forming apparatus comprising:

  According to the invention according to claim 1, claim 3, claim 4 or claim 5, the resin composition includes a resin and a conductive agent and has a film resistivity dependency of surface resistivity. An endless belt in which a difference in resistance in the axial direction is suppressed is provided compared to a case where the increase rate is less than 0.8% per 100 mm in the axial length.

  According to the invention which concerns on Claim 2, it is comprised with the resin composition which has resin and a conductive agent, and has the film thickness dependence of surface resistivity, The increase amount of the said thickness is 0.5 micrometer per 100 mm of axial length. The endless belt is provided in which the difference in resistance in the axial direction is suppressed as compared with the case where it is less than the above.

  According to the invention which concerns on Claim 6, it is comprised with the resin composition which has resin and a conductive agent, and has the film thickness dependence of surface resistivity, The increase rate of the said thickness is 0.8 per 100 mm of axial lengths. An endless belt unit in which the resistance difference in the axial direction of the endless belt is suppressed as compared with the case where an endless belt of less than% is applied is provided.

  According to the invention which concerns on Claim 7, it is comprised with the resin composition which has resin and a conductive agent, and has the film thickness dependence of surface resistivity, The increase rate of the said thickness is 0.8 per 100 mm of axial lengths. An image forming apparatus in which an image density difference is suppressed as compared with a case where an endless belt of less than% is applied is provided.

It is a schematic perspective view which shows an example of the endless belt which concerns on this embodiment. It is a schematic block diagram which shows a uniaxial eccentric screw pump. It is explanatory drawing for demonstrating an example of an application | coating process. It is explanatory drawing for demonstrating an example of an application | coating process. It is a figure which shows the structure of the heating apparatus used in an example of a heating process. (A) is a schematic plan view which shows an example of a circular electrode, (B) is the schematic sectional drawing. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows an example of the image forming apparatus which concerns on other this embodiment.

  Hereinafter, an embodiment which is an example of the present invention will be described in detail with reference to the drawings.

[Endless belt]
FIG. 1 is a schematic perspective view illustrating an example of an endless belt for an image forming apparatus according to an embodiment.

As shown in FIG. 1, the endless belt 101 according to the present embodiment is formed, for example, in an endless shape, and is configured by a single layer body.
Endless belt 101 includes a resin and a conductive agent, and is made of a resin composition having surface resistivity dependence on film thickness.
The endless belt 101 increases in thickness from one end 102 to the other end 103 in the axial direction of the endless belt 101 (that is, the rotational axis direction of the endless belt 101). And the increase rate of the thickness on the basis of the thickness of the one end 102 is 0.8% or more and 3.2% or less per 100 mm in the axial length. For example, when the length of the endless belt 101 in the axial direction is 330 mm, the increasing rate of the thickness at the other end 103 based on the thickness of the one end 102 is 2.6% or more and 10.7% or less. That is, when the length of the endless belt 101 in the axial direction is 330 mm, the thickness at the other end 103 is 1.026 times or more and 1.107 times or less than the thickness at the one end 102.

  The endless belt 101 may be used as it is as a single layer, or may be used as a laminate having a functional layer such as a release layer on at least one of the inner peripheral surface and the outer peripheral surface of the endless belt 101.

  Here, the “resin composition having the film thickness dependency of the surface resistivity” means that if only the film thickness is changed without changing the composition of the resin composition, the surface of the resin composition film according to the film thickness. It means a resin composition in which resistivity also changes. Specifically, for example, a resin composition in which the surface resistivity decreases as the film thickness increases, or a resin composition in which the surface resistivity increases as the film thickness increases.

Whether or not the surface resistivity depends on the film thickness is confirmed as follows.
Specifically, for example, one endless belt having a film thickness of 70 μm to one endless belt having a film thickness of 100 μm in increments of 5 μm (ie, a total of seven) is manufactured, and the surface resistivity of each endless belt is measured. Then, the measurement results are input to the coordinates with the horizontal axis representing the film thickness and the common logarithm of the surface resistivity as the vertical axis, and approximated by a straight line, and the slope of the straight line is 0.02 logΩ / □ or more per 1 μm film thickness or − When it is 0.02 log Ω / □ or less, it is determined that “the surface resistivity depends on the film thickness”.
The surface resistivity of each endless belt is an average value obtained by measuring three points in the axial direction from one end to the other end and measuring six points in the circumferential direction at each position (that is, 3 × 6 points in total). A method for measuring the surface resistivity will be described later.

  Endless belt 101 is made of a resin composition having a film thickness dependency of surface resistivity, and the thickness increases from one end 102 to the other end 103 in the axial direction, and the increase rate is within the above range. The resistance difference in the axial direction of the endless belt is suppressed. The reason is presumed as follows.

  The endless belt is, for example, a resin by applying a coating solution that becomes a resin composition by heating to the outer peripheral surface of the core, and heating the obtained coating film using, for example, a downflow type heating device. A film of the composition (ie an endless belt) is obtained. In the down flow type heating device, the coating film formed on the outer peripheral surface of the core body is heated by feeding a high-temperature gas from one end of the core body toward the other end in the axial direction. Therefore, the heating efficiency on the windward side (that is, the one end side) of the coating film is relatively higher than that on the leeward side (that is, the other end side), and the heating efficiency on the leeward side is relatively lower than that on the windward side. .

  Here, when a resin composition film containing a resin and a conductive agent is obtained, since the coating film also contains a conductive agent, the resistance value of the obtained resin composition film may vary depending on the heating efficiency of the coating film. is there. Specifically, for example, the higher the heating efficiency of the coating film, the lower the resistance value of the obtained film, and the lower the heating efficiency of the coating film, the higher the resistance value of the obtained film. Therefore, when a high-temperature gas is sent from one end to the other end to heat the coating film, the endless belt (that is, the resistance value of the other end 103 on the leeward side is higher than the resistance value of the one end on the leeward side (that is, An endless belt having a difference in resistance between one end and the other end may be obtained.

On the other hand, the endless belt 101 of the present embodiment is composed of a resin composition having a film thickness dependency of surface resistivity, and the thickness increases from one end 102 in the axial direction toward the other end 103. The increase rate is in the above range.
Specifically, for example, when a high-temperature gas is sent from one end 102 toward the other end 103 to sinter the coating film to obtain the endless belt 101, the resin composition that the surface resistivity decreases as the film thickness increases. Use things. As a result, one end 102 side of the obtained endless belt 101 has a relatively low heating value due to relatively high heating efficiency as compared with the other end 103 side, while a resistance value is reduced due to a relatively thin film thickness. The value becomes higher. On the other hand, the other end side 103 of the obtained endless belt 101 has a higher resistance value due to relatively low heating efficiency than the one end 102 side, and a resistance value due to a relatively thick film thickness. Becomes lower. Thus, by canceling out the influence of the heating efficiency on the resistance value and the influence of the film thickness on the resistance value, the resistance value of the same level is obtained on the one end 102 side and the other end 103 side of the endless belt 101. It is estimated that the resistance difference in the axial direction is suppressed.
When the endless belt 101 of this embodiment is used as a transfer belt (for example, an intermediate transfer belt) of the image forming apparatus, the difference in resistance in the axial direction of the endless belt 101 is suppressed. It is suppressed.

  In addition, as a method of controlling the thickness so that the thickness increases from one end 102 to the other end 103 in the axial direction and the increase rate is within the above range, for example, in the process of manufacturing the endless belt 101, the core body There is a method of adjusting the discharge rate of the coating liquid so that the thickness of the coating film formed in the above increases from the one end 102 to the other end 103 in the axial direction and the increase rate is within the above range. Also, after forming a film of the resin composition, it is processed from the one end 102 in the axial direction to the other end 103 by processing (for example, reducing the thickness toward one end by cutting with sandpaper or a wrapping film). You may obtain the endless belt 101 whose thickness increases toward the range within the said range.

  Hereinafter, the details of the endless belt 101 according to the present embodiment will be described together with the manufacturing method thereof. In addition, a code | symbol may be abbreviate | omitted.

<Resin composition>
As described above, the endless belt 101 is made of a resin composition that includes a resin and a conductive agent and has a film thickness dependency of surface resistivity.
The resin composition contains at least a resin and a conductive agent, and may contain other additives as necessary.

(resin)
The resin is not particularly limited as long as a resin composition having a film thickness dependency of surface resistivity can be obtained, and specific examples thereof include polyamideimide.
More preferably, the resin contains polyamideimide (hereinafter also referred to as “specific resin”). The resin may include only one type of the specific resin, may include two or more types of the specific resin, and may include other resins other than the specific resin. In addition, when other resin is included, it is preferable that the content of other resin is 10 mass% or less with respect to the whole resin, and it is more preferable that it is 5 mass% or less.

As content of resin with respect to the whole resin composition, 60 mass% or more and 86 mass% or less are mentioned, for example, 66 mass% or more and 82 mass% or less are preferable, and 70 mass% or more and 76 mass% or less are more preferable.
Hereinafter, a polyamideimide resin will be described as an example of the resin.

-Polyamideimide resin-
Examples of the polyamide-imide resin include a polyamide-imide resin obtained by subjecting a polyamide-polyamic acid resin, which is a condensate from a tricarboxylic acid and a diamine compound, to a dehydration ring-closing reaction.
Specifically, as the polyamide-imide resin,
(1) A method in which an equimolar amount of a tricarboxylic acid anhydride and a diamine compound is subjected to polycondensation and dehydration ring-closing reaction (imidation reaction) at high temperature in an organic polar solvent in the presence of a dehydration catalyst (2) Tricarboxylic anhydride monochloride (3) Polycondensation anhydride and diisocyanate are subjected to polycondensation and dehydration ring closure reaction at high temperature in an organic polar solvent in an organic polar solvent at an equimolar amount of diamine compound. Polyamideimide resin obtained by a method etc. is mentioned.

Examples of the tricarboxylic acid anhydride include trimellitic acid anhydride.
Examples of the tricarboxylic anhydride monochloride include trimellitic anhydride monochloride.

Specific examples of the diamine compound include 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 3,3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3 , 3′-diaminodiphenylsulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3′-dimethyl4,4′-biphenyldiamine, benzidine, 3,3′-dimethylbenzidine, 3 , 3′-dimethoxybenzidine, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylpropane, 2,4-bis (2-aminotert-butyl) toluene, bis (p-2-amino-tertiary) Butylphenyl) ether, bis (p-2-methyl-δ-aminophenyl) benzene, bis-p (1,1-dimethyl-5-amino-pentyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, di (p-aminocyclohexyl) methane, hexa Methylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2 -Bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-methylnonamethylenediamine, 2, 17 -Diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 12-diaminooctadecane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, piperazine H ₂ N (CH ₂ ) ₃ O (CH ₂ ) ₂ O (CH ₂ ) NH ₂ , H ₂ N (CH ₂ ) ₃ S (CH ₂ ) ₃ NH ₂ , H ₂ N (CH ₂ ) ₃ N ( _{CH 3) 2 (CH 2)} 3 NH 2, 3,3'- diaminodiphenyl, 4,4'-diaminodiphenyl, 4,4'-diaminodiphenyl amide, bis [4- {3- (4-aminophenoxy) Benzoyl} phenyl] ether, 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] sulfone 2,2′-bis [4- 3-aminophenoxy) phenyl] propane.

As the diamine compound, an aromatic diamine compound is particularly suitable.
Suitable aromatic diamine compounds include, for example, 3,3′-diaminobenzophenone, p-phenylenediamine, 4,4′-diaminodiphenyl, 4,4′-diaminodiphenylamide, 4,4′-diaminodiphenylmethane, 4 , 4′-diaminodiphenyl ether, bis [4- {3- (4-aminophenoxy) benzoyl} phenyl] ether, 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) Phenyl] sulfone 2,2′-bis [4- (3-aminophenoxy) phenyl] propane and the like.

Examples of the diisocyanate compound include those in which two amino groups in the diamine compound used for the synthesis of the polyamic acid are substituted with isocyanate groups, and aromatic diisocyanate compounds are particularly preferable.
Examples of the diisocyanate compound include 3,3′-dimethylbiphenyl-4,4′-diisocyanate, 2,2′-dimethylbiphenyl-4,4′-diisocyanate, biphenyl-4,4′-diisocyanate, biphenyl-3, 3'-diisocyanate, biphenyl-3,4'-diisocyanate, 3,3'-diethylbiphenyl-4,4'-diisocyanate, 2,2'-diethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxy Biphenyl-4,4′-diisocyanate, 2,2′-dimethoxybiphenyl-4,4′-diisocyanate and the like can be mentioned.
Examples of the diisocyanate compound include those obtained by stabilizing an isocyanato group with a blocking agent. The blocking agent includes alcohol, phenol, oxime, etc., but there is no particular limitation.

  When a polyamideimide resin is used as the resin, a coating solution containing a polyamideimide resin and a solvent may be used as the coating solution, and the polyamide-polyamic acid resin before the dehydration ring-closing reaction, which is a precursor of the polyamideimide resin, A coating solution containing a solvent may be used. When a coating solution containing a polyamide-polyamic acid resin and a solvent is used, the polyamide-polyamic acid resin contained in the coating film undergoes a dehydration ring-closing reaction by heating after coating of the coating solution, and includes a polyamide-imide resin A film of the composition is obtained.

(Conductive agent)
The conductive agent is conductive (for example, a volume resistivity of less than 10 ⁷ Ω · cm, the same shall apply hereinafter) or semiconductive (eg, a volume resistivity of 10 ⁷ Ω · cm to 10 ¹³ Ω · cm, and the same applies hereinafter). ) (A powder composed of particles having a primary particle size of less than 10 μm, preferably a powder composed of particles having a primary particle size of 1 μm or less).
The conductive agent is not particularly limited. For example, carbon black (for example, ketjen black, acetylene black, carbon black whose surface is oxidized), metal (for example, aluminum or nickel), metal oxide (for example, oxidized) Yttrium, tin oxide, etc.), ion conductive substances (for example, potassium titanate, LiCl, etc.) and the like.

  The conductive agent is selected depending on the purpose of use, but carbon black is preferable, and pH 5 or less (preferably pH 4) is preferable from the viewpoint of stability of electric resistance over time and electric field dependency for suppressing electric field concentration due to transfer voltage. An oxidation-treated carbon black (e.g., a carbon black obtained by imparting a carboxyl group, a quinone group, a lactone group, a hydroxyl group or the like to the surface) having a pH of 0.5 or less, more preferably pH 4.0 or less is preferable.

The average primary particle diameter of carbon black is, for example, preferably 10 nm to 50 nm, and more preferably 15 nm to 30 nm.
The average primary particle diameter of carbon black is measured by the following method.
First, the endless belt to be measured is cut with a microtome, a measurement sample having a thickness of 100 nm is collected, and this measurement sample is observed with a TEM (transmission electron microscope). The diameter of a circle equal to the projected area of each of the 50 carbon black particles is taken as the particle diameter, and the average value is taken as the average primary particle diameter.

The content of the conductive agent is selected depending on the target resistance. For example, the content is preferably 1% by mass or more and 50% by mass or less, more preferably 2% by mass or more and 40% by mass or less, based on the total mass. More preferably, it is at least 30% by mass. In particular, when the content of the conductive agent is small, that is, when the resistance value of the film is high, the resistance value of the film of the resin composition obtained by the heating process tends to depend on the heating efficiency of the coating film in the heating process.
The conductive agent may be used alone or in combination of two or more.

(Other additives)
Other additives include, for example, a dispersant for improving the dispersibility of the conductive agent, various fillers for imparting various functions such as mechanical strength, a catalyst for promoting the imidization reaction, and an improvement in film formation quality. Leveling agents and the like.

(Characteristics of resin composition)
As described above, the resin composition has the film thickness dependence of the surface resistivity. That is, the slope of the straight line obtained in the confirmation of whether the resin composition has the film thickness dependence of the surface resistivity is 0.02 logΩ / □ or more or −0.02 logΩ / □ or less per 1 μm film thickness. It is.
In addition, as a resin composition, from the viewpoint of both suppression of resistance difference in the axial direction and suppression of surface resistance unevenness due to local film thickness unevenness, among resin compositions having film thickness dependence of surface resistivity, A resin composition in which the slope of the straight line is 0.02 logΩ / □ or more and 0.3 logΩ / □ or less or −0.3 logΩ / □ or more and −0.02 logΩ / □ or less is preferable, and 0.05 logΩ / □ or more and 0.2 logΩ / □ or less. More preferably, the resin composition is □ or less or −0.2 logΩ / □ or more and −0.05 logΩ / □ or less.

<Method for producing endless belt>
As an endless belt manufacturing method, for example, a coating liquid preparation step of preparing a coating liquid that becomes a resin composition by heating, and a coating film by applying the coating liquid to the outer peripheral surface of a cylindrical or columnar core A method of undergoing a coating step to form, a heating step of forming an endless belt which is a film of a resin composition by heating the coating film, and a demolding step of demolding the obtained endless belt from the core body Can be mentioned.

  The heating process may include, for example, a plurality of processes for heating at different temperatures. Specifically, for example, a drying process of drying the coating film (that is, removing the solvent in the coating film), a baking process of heating and baking the dried coating film at a temperature higher than the drying process, A heating step including In particular, when a coating solution containing a polyamide-polyamic acid resin and a solvent is used as the coating solution, it is preferable to remove the solvent in the drying step and perform a dehydration ring-closing reaction of the polyamide-polyamic acid resin in the firing step.

(Coating solution preparation process)
In the coating solution preparation step, a coating solution to be a resin composition is prepared by heating.
As a coating liquid, what contains a solvent, at least one of the precursor of resin and resin, a electrically conductive agent, and another additive as needed is mentioned, for example.

The solvent is appropriately selected according to the precursor of the resin to be used and at least one kind of the resin, and specific examples thereof include organic polar solvents.
Specific examples of the organic polar solvent include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide; N, N-dimethylacetamide; Acetamide solvents such as N, N-diethylacetamide; Pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; Phenol, o-, m-, or p-cresol, xylenol, halogenated Phenolic solvents such as phenol and catechol; ether solvents such as tetrahydrofuran, dioxane and dioxolane; alcohol solvents such as methanol, ethanol and butanol; cellosolves such as butyl cellosolve; and hexamethylphosphoramide and γ-butyro Lactone and the like.
In addition, a solvent may use only 1 type or may use 2 or more types together.

  Among these, as the solvent, a solvent having low volatility, specifically, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; formamides such as N, N-dimethylacetamide A solvent is good.

  The content of the solvent in the coating solution is preferably in the range of 70% by mass or more and 80% by mass or less, more preferably 76% by mass or more and 78% by mass or less with respect to the total amount of the coating solution.

The viscosity of the coating solution (viscosity at 25 ° C.) is not particularly limited, but is preferably in the range of 1 Pa · s to 100 Pa · s, for example, in the range of 3 Pa · s to 50 Pa · s.
The viscosity of the coating solution is measured using a constant velocity viscometer PK100 manufactured by HAKKE under an environment of 25 ° C.

  Preparation of the coating solution may be, for example, a solution in which at least one of a resin precursor and a resin is dissolved in a solution in which a conductive agent is dispersed in a solvent, or a solution in which at least one of a resin precursor and a resin is dissolved in a solvent. A conductive agent may be dispersed in the substrate.

  Examples of the method for dispersing the conductive agent include known methods such as a ball mill, a sand mill, a bead mill, and a jet mill (opposing collision type disperser). The dispersion concentration of the conductive agent (content in the coating solution) is preferably 10 parts by mass or more and 40 parts by mass or less, and 15 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of at least one of the resin precursor and the resin. Is preferable, and 20 to 30 parts by mass is more preferable.

(Coating process)
In the coating step, the coating liquid is applied to the surface (outer peripheral surface) of the core body to form a coating film. As a method for forming a coating film on the surface of the core, for example, a spiral coating method is employed. A coating film is formed by applying a coating solution to the surface of the core body by a spiral coating method. Hereinafter, a method of applying a coating solution using a uniaxial eccentric screw pump (Mono pump) (an example of a solution discharge unit) in the coating process will be described as an example.

First, a uniaxial eccentric screw pump will be described with reference to FIG. The uniaxial eccentric screw pump is a rotary displacement type pump generally called a MONO pump. As shown in FIG. 2, the uniaxial eccentric screw pump 125 includes a male screw type rotating body 335 and a female screw type fixing body 336, and by rotating the male screw type rotating body 335, a predetermined capacity is set on the discharge side. It is structured to move toward. The uniaxial eccentric screw pump 125 adjusts the discharge amount per unit time discharged from the uniaxial eccentric screw pump 125 by controlling the rotational speed of the male screw type rotary body 335, and increases the rotational speed of the male screw type rotary body 335. Accordingly, the discharge amount of the coating liquid per time is configured to increase.
The solution discharge means for discharging the coating liquid is not limited to the uniaxial eccentric screw pump, and other solution discharging means may be used as long as it can discharge the coating liquid.

Next, the spiral coating method will be described with reference to FIGS. 3 and 4 are schematic views showing an example of a spiral coating method. As shown in FIGS. 3 and 4, the coating apparatus 140 includes a tank 121 that stores the coating liquid 121 </ b> A, a supply pipe 123 that is connected to the tank 121, a uniaxial eccentric screw pump 125 that is connected to the supply pipe 123, and a uniaxial eccentricity. A discharge-side tip 127 of the screw pump 125 and a spatula 131 are provided.
Furthermore, the coating apparatus 140 includes a control unit 160 that controls each unit in the coating apparatus.

  The controller 160 is configured to control the operation of each part of the coating apparatus 140. Although not specifically illustrated, the control unit 160 is configured as, for example, a computer, and includes a CPU (Central Processing Unit), various memories [for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a nonvolatile memory], The input / output interface (I / O) is connected via a bus. For example, a uniaxial eccentric screw pump 125 is connected to the I / O.

  For example, the CPU is configured to store a program stored in various memories (for example, uniaxial so that the discharge amount of the coating liquid discharged from the discharge-side tip portion 127 of the uniaxial eccentric screw pump 125 increases at a predetermined ratio. A control program such as a film thickness variation program for controlling the number of rotations of the eccentric screw pump 125) is executed, and the operation of each part of the coating apparatus 140 is controlled. Note that the storage medium for storing the program executed by the CPU is not limited to various memories. For example, it may be a flexible disk, DVD disk, magneto-optical disk, USB memory (universal serial bus memory) or the like (not shown), or a storage device of another device connected to communication means (not shown). May be.

  When the endless belt 101 is manufactured, the controller 160 controls the rotational speed of the uniaxial eccentric screw pump 125, the moving speed of the uniaxial eccentric screw pump 125 and the spatula 131, the rotational speed of the core, and the like. The controller 160 changes the number of rotations of the male screw type rotating body of the uniaxial eccentric screw pump 125, thereby adjusting the discharge amount of the coating liquid discharged from the discharge-side tip portion 127 of the uniaxial eccentric screw pump 125.

Hereinafter, the application process will be described more specifically.
As shown in FIGS. 3 and 4, a cylindrical or columnar core body 134 is turned around the axis (in the direction of arrow A) by a rotating device (not shown) with the axial direction of the core body 134 in the horizontal direction. The coating liquid 121 </ b> A is discharged from a uniaxial eccentric screw pump 125 (an example of a solution discharge unit) while being rotated, and is applied to the surface (outer peripheral surface) of the core body 134. In the coating device 140, the coating liquid 121 </ b> A is supplied to the uniaxial eccentric screw pump 125 from the tank 121 through the supply pipe 123. The coating liquid 121 </ b> A supplied to the uniaxial eccentric screw pump 125 is supplied to the surface of the core body 134 rotated in the direction of arrow A through the discharge-side tip portion 127 of the uniaxial eccentric screw pump 125. The coating liquid 121 </ b> A attached to the surface of the core body 134 is smoothed by the spatula 131.

  Examples of the material of the core body 134 include metals (aluminum, stainless steel, etc.), fluororesins, silicone resins, or metals whose surfaces are covered with these resins. When metal is used as the core material, the surface (belt) formed on the core body can be easily removed from the core body by, for example, pre-plating the surface with chromium or nickel, or using a release agent. It may be applied. Examples of the desirable shape of the core include a cylindrical shape and a columnar shape.

  The width of the core body 134 (that is, the length from the one end 132 to the other end 133 in the core body axial direction) is intended to ensure a margin area corresponding to the non-product portion generated at the end portion of the endless belt. For example, it is preferably longer than the width of the endless belt in the range of 10% to 40%. The circumferential length of the core body 134 (the length in the circumferential direction of the core body) is preferably equal to or greater than the main length of the target endless belt.

  In the coating device 140, the uniaxial eccentric screw pump 125 and the spatula 131 are supported in a movable state in the axial direction (arrow B direction) of the core body 134. Then, the uniaxial eccentric screw pump 125 and the spatula 131 move from one end side to the other end side in the axial direction (arrow B direction) of the core body 134 with the core body 134 rotated at a preset rotational speed. Meanwhile, the coating liquid 121A is discharged from the discharge-side tip portion 127 of the uniaxial eccentric screw pump 125. As a result, the coating liquid 121A is spirally applied to the surface of the core body 134 and smoothed by the spatula 131, thereby forming a seamless coating film 110A.

  At this time, the controller 160 increases the rotational speed of the uniaxial eccentric screw pump 125 so that the discharge amount of the coating liquid discharged from the discharge-side tip portion 127 of the uniaxial eccentric screw pump 125 increases at a predetermined ratio. Control. By increasing the rotation speed of the uniaxial eccentric screw pump 125, the discharge amount per unit time of the coating liquid 121A discharged from the discharge-side tip portion 127 of the uniaxial eccentric screw pump 125 increases. And the film thickness of 110 A of coating films in the other end 133 side becomes relatively thick compared with the end 132 side of the axial direction (arrow B direction) of the core body 134. In this way, the film thickness of the coating film 110A is controlled so that the thickness increases from the one end 132 side to the other end 133 side of the core body 134 so that the increase rate is within the above range. The endless belt 101 also increases in thickness from the one end 102 toward the other end 103, and the increase rate is in the above range.

(Heating process)
In the heating step, the coating film 110A is heated, the solvent in the coating film 110A is removed, and a resin composition film is obtained. In the heating step, for example, a high-temperature gas (a temperature higher than the heating temperature) is sent from one end 132 side of the core body 134 toward the other end 133 side to heat the coating film 110 </ b> A on the core body 134. Hereinafter, a downflow type heating apparatus will be described as an example of the heating apparatus used in the heating step.

  FIG. 5 shows a configuration of a heating device 31 which is an example of a downflow type heating device used in the heating process. The heating device 31 includes a hot air generator 34 that sends hot air (heated air) from above in a drying furnace 32, and a support base 36 that supports the core body 134. The core body 134 on which the coating film 110 </ b> A is formed in the coating step is placed so that the axial direction is, for example, a direction near to the support base 36. And the hot air sent out from the hot air generator 34 is sprayed toward the other end 133 from the one end 132 of the core body 134, and the coating film 110A is heated.

  In addition, as a heating process, the process including the drying process which dries the coating film 110A, and the baking process which heats and dries the dried coating film 110A as mentioned above is mentioned, for example. The heating temperature in the drying step (that is, the temperature of the hot air sent out by the hot air generator 34) is preferably, for example, 120 ° C. or higher and 220 ° C. or lower, and more preferably 140 ° C. or higher and 210 ° C. or lower. Moreover, the heating temperature in the baking process (that is, the temperature of the hot air sent out by the hot air generator 34) is, for example, higher than the heating temperature in the drying process, and is preferably 200 ° C or higher and 300 ° C or lower, preferably 240 ° C or higher and 280 ° C. The following is more preferable.

(Demolding process)
After the heat treatment in the heating step, the resin composition film is removed from the core 134 to obtain the endless belt 101.
If necessary, the endless belt 101 may be obtained by subjecting the outer peripheral surface and inner peripheral surface of the resin composition film to surface treatment such as polishing and etching. Further, the obtained endless belt 101 may be further subjected to drilling or ribbing.

<Characteristics of endless belt>
The film thickness at one end 102 of the endless belt 101 is, for example, preferably from 50 μm to 500 μm, preferably from 60 μm to 300 μm, and more preferably from 70 μm to 150 μm.

  The film thickness of the endless belt 101 is measured using an eddy current film thickness meter CTR-1500E manufactured by Sanko Electronics. The film thickness at a specific position in the axial direction of the endless belt 101 (for example, one end 102) is measured at five locations in the circumferential direction at the specific position of the endless belt 101 and is an average value.

The thickness of the endless belt 101 increases from the one end 102 toward the other end 103.
Whether or not the thickness of the endless belt 101 increases from one end 102 toward the other end 103 is determined by measuring the film thickness in the axial direction from one end 102 to the other end 103 at one end 102 and the other at intervals close to equal intervals. Confirmation is performed at 5 points including the end 103.

Further, the increasing rate of the thickness of the endless belt 101 increasing from the one end 102 toward the other end 103 is 0.7% or more and 2.9% or less per 100 mm in the axial length.
By setting the rate of increase in thickness per 100 mm in the axial direction within the above range, there is a problem (for example, an endless belt) that there is an excessive difference in thickness between the one end and the other end compared to the case where the rate of increase in thickness is too large. And the like, and the resistance difference in the axial direction is also suppressed.
The rate of increase in thickness per 100 mm in the axial direction is that the thickness of one end 102 is T ₁ (μm), the thickness of the other end 103 is T ₂ (μm), and the length from one end 102 to the other end 103 is L × Assuming 100 (mm), it is represented by the following formula.
Formula: Rate of increase (%) = (T ₂ −T ₁ ) × 100 / (L × T ₁ )
The increase rate of the thickness is preferably 0.8% or more and 3.2% or less, and more preferably 1.2% or more and 2.0% or less per 100 mm in the axial direction.

Further, the increase in thickness of the endless belt 101 from the one end 102 toward the other end 103 is preferably 0.5 μm or more and 2.4 μm or less per 100 mm in the axial direction. That is, for example, when the length of the endless belt 101 in the axial direction is 330 mm, the difference between the thickness of the one end 102 and the thickness of the other end 103 is 2 μm or more and 8 μm or less.
By setting the amount of increase in the thickness per 100 mm in the axial direction within the above range, there is a problem (for example, an endless belt) that there is an excessive difference in thickness between the one end and the other end compared to the case where the increase in thickness is too large. And the like, and the resistance difference in the axial direction is also suppressed.
The amount of increase in the thickness per 100 mm in the axial direction is that the thickness of one end 102 is T ₁ (μm), the thickness of the other end 103 is T ₂ (μm), and the length from one end 102 to the other end 103 is L × Assuming 100 (mm), it is represented by the following formula.
Formula: Increase (μm) = (T ₂ −T ₁ ) / L
The amount of increase in thickness is more preferably 0.5 μm or more and 2.3 μm or less, and further preferably 1 μm or more and 1.4 μm or less.

The length L from the one end 102 to the other end 103 of the endless belt 101 is not particularly limited, and examples thereof include 100 mm to 500 mm, preferably 200 mm to 400 mm, and more preferably 280 mm to 380 mm.
Further, the circumferential length (length in the circumferential direction) of the endless belt 101 is not particularly limited, and examples thereof include 263 mm to 3140 mm, preferably 502 mm to 1319 mm, and more preferably 785 mm to 942 mm.

The common logarithmic value (log S ₁ ) of the surface resistivity of the outer peripheral surface at one end 102 of the endless belt 101 is, for example, 9 when used as an intermediate transfer belt, a recording medium conveyance transfer belt, or the like in an image forming apparatus. It is preferably (logΩ / □) or more and 14 (logΩ / □) or less, more preferably 10 (logΩ / □) or more and 13 (logΩ / □) or less. The common logarithm of the surface resistivity is controlled by the type of conductive agent, the amount of conductive agent added, and the like.

The difference (logS ₂ -logS ₁ ) between the common logarithmic value of the surface resistivity (logS ₁ ) at the one end 102 of the endless belt 101 and the common logarithm value of the surface resistivity (logS ₂ ) at the other end 103 is −0.16 logΩ. / □ or more and 0.16 logΩ / □ or less is preferable, −0.10 logΩ / □ or more and 0.1 logΩ / □ or less is more preferable, and −0.05 logΩ / □ or more and 0.05 logΩ / □ or less is more preferable.

The surface resistivity is measured in accordance with JIS-K6911 using a circular electrode (for example, “UR probe” of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.).
A method for measuring the surface resistivity will be described with reference to the drawings. FIG. 6 is a schematic plan view (A) and a schematic cross-sectional view (B) showing an example of a circular electrode. The circular electrode shown in FIG. 6 includes a first voltage application electrode A and a plate-like insulator B. The first voltage application electrode A has a cylindrical electrode portion C and a cylindrical ring electrode having an inner diameter larger than the outer diameter of the cylindrical electrode portion C and surrounding the cylindrical electrode portion C at a constant interval. Part D is provided. The belt electrode T is sandwiched between the cylindrical electrode portion C and the ring electrode portion D in the first voltage application electrode A and the plate insulator B, and the cylindrical electrode portion C and the ring electrode portion in the first voltage application electrode A are sandwiched. A current I (A) that flows when a voltage V (V) is applied to D is measured, and a surface resistivity ρs (Ω / □) of the transfer surface of the belt T is calculated by the following equation. Here, in the following formula, 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: ρs = π × (D + d) / (D−d) × (V / I)

The surface resistivity is a circular electrode (UR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd .: outer diameter Φ16 mm of the cylindrical electrode portion C, inner diameter Φ30 mm, outer diameter Φ40 mm of the ring-shaped electrode portion D), Under a 22 ° C./55% RH environment, a voltage value of 500 V and a current value after application for 10 seconds are obtained and calculated.
Further, the surface resistivity at a specific position (for example, one end 102) in the axial direction of the endless belt 101 is measured and averaged at five locations in the circumferential direction at the specific position of the endless belt 101.

  The volume resistivity of the endless belt 101 is, for example, 8 (log Ωcm) or more and 13 (log Ωcm) as a common logarithmic value from the viewpoint of transferability when used as an intermediate transfer belt, a recording medium conveyance belt, or the like in an image forming apparatus. The following is preferable. The common logarithm of volume resistivity is controlled by the type of conductive agent and the amount of conductive agent added.

Here, the volume resistivity is measured according to JIS-K6911 using a circular electrode (for example, UR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.). A method for measuring the volume resistivity will be described with reference to FIG. The measurement is performed with the same device as the surface resistivity. However, the circular electrode shown in FIG. 6 includes a second voltage application electrode B ′ instead of the plate-like insulator B at the time of measuring the surface resistivity. Then, a belt T is sandwiched between the cylindrical electrode portion C and the ring electrode portion D in the first voltage application electrode A and the second voltage application electrode B ′, and the cylindrical electrode portion C in the first voltage application electrode A The current I (A) that flows when the voltage V (V) is applied between the second voltage application electrode B is measured, and the volume resistivity ρv (Ωcm) of the belt T is calculated by the following equation. Here, in the following formula, t represents the thickness of the belt T.
Formula ρv = 19.6 × (V / I) × t
The numerical value of 19.6 shown in the above formula is an electrode coefficient for conversion into resistivity, and from the outer diameter d (mm) of the cylindrical electrode portion and the thickness t (cm) of the sample, πd ² Calculated as / 4t. The thickness of the belt T is measured using an eddy current film thickness meter CTR-1500E manufactured by Sanko Electronics.

  The volume resistivity is 22 ° C. using a circular electrode (UR probe of Hiresta IP manufactured by Mitsubishi Oil Chemical Co., Ltd .: outer diameter Φ16 mm of cylindrical electrode portion C, inner diameter Φ30 mm of ring electrode portion D, outer diameter Φ40 mm). The current value after application of voltage 500 V for 10 seconds under the / 55% RH environment is calculated.

<Use of endless belt>
The endless belt 101 is a belt member in an image forming apparatus, for example, an intermediate transfer belt on which a toner image on an image carrier is transferred (primary transfer) and then transferred (secondary transfer) onto a recording medium again. A secondary transfer belt that conveys the recording medium in contact with the back surface (non-transfer surface) of the recording medium and applies a voltage for secondary transfer when the transferred toner image is secondarily transferred to the recording medium, and image holding In a mode in which the toner image on the body is directly transferred onto the surface of the recording medium, the recording medium is used as a recording medium conveying transfer belt for conveying the recording medium and applying a voltage for transfer.

[Endless belt unit for image forming apparatus]
The endless belt unit according to the present embodiment includes the endless belt. For example, the endless belt may be stretched in a state in which tension is applied by a driving roll and a driven roll that are arranged to face each other.
Here, when the endless belt unit is applied as an intermediate transfer member, the endless belt unit is a roll for supporting the endless belt, and a roll for primarily transferring the toner image on the surface of the photosensitive member (image holding member) onto the endless belt. A roll for secondary transfer of the toner image transferred onto the endless belt to the recording medium may be disposed.
The number of rolls that support the endless belt is not limited, and may be arranged according to the usage mode. The endless belt unit having the above configuration is used by being incorporated in the image forming apparatus, and rotates in a state where the endless belt is also supported as the driving roll and the driven roll rotate.

[Image forming apparatus]
The image forming apparatus according to the present embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic image forming unit that forms an electrostatic image on the surface of the charged image carrier, and toner And developing means for developing an electrostatic charge image formed on the surface of the image carrier as a toner image and the endless belt unit according to the present embodiment, and formed on the surface of the image carrier. And a transfer means for transferring the toner image to the surface of the recording medium via an endless belt.

  Specifically, in the image forming apparatus according to the present embodiment, for example, the transfer unit includes an intermediate transfer member, a primary transfer unit that primarily transfers a toner image formed on the image holding member to the intermediate transfer member, and the intermediate transfer member. And a secondary transfer unit that secondary-transfers the toner image transferred to the recording medium, and includes the endless belt according to the present embodiment as the intermediate transfer member.

  In addition, the image forming apparatus according to the present embodiment includes, for example, a recording medium conveyance body (recording medium conveyance belt) for the transfer unit to convey the recording medium, and a toner image formed on the image holding body. And a transfer means for transferring to the recording medium conveyed by the above-described recording medium, and the recording medium conveyance body includes the endless belt according to the present embodiment.

  The image forming apparatus according to the present embodiment is, for example, a normal monocolor image forming apparatus in which only a single color toner is accommodated in a developing device, and a toner image held on an image holding member is sequentially subjected to primary transfer to an intermediate transfer member. Examples thereof include a color image forming apparatus that repeats and a tandem type color image forming apparatus in which a plurality of image carriers each having a developing device for each color are arranged in series on an intermediate transfer member.

  Hereinafter, an image forming apparatus according to the present embodiment will be described with reference to the drawings. FIG. 7 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the embodiment. FIG. 8 is a schematic configuration diagram illustrating an image forming apparatus according to another embodiment. 7 is an image forming apparatus including an intermediate transfer member (intermediate transfer belt), and FIG. 8 is an image forming device including a recording medium transporting transfer member (recording medium transporting transfer belt).

  The image forming apparatus shown in FIG. 7 is a first to first electrophotographic method that outputs yellow (Y), magenta (M), cyan (C), and black (K) images based on color-separated image data. Fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) are provided. These image forming units (hereinafter simply referred to as “units”) 10Y, 10M, 10C, and 10K are juxtaposed at a specific distance in the horizontal direction. The units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the main body of the image forming apparatus.

Above each of the units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 20 (endless belt) as an intermediate transfer member is extended through each unit. The intermediate transfer belt 20 is provided by being wound around a drive roll 22 and a support roll 24 that are in contact with the inner surface of the intermediate transfer belt 20 that are spaced apart from each other from the left to the right in the drawing. A transfer unit (endless belt unit) for the image forming apparatus is configured to run in the direction toward 10K.
The support roll 24 is biased in a direction away from the drive roll 22 by a spring or the like (not shown), and a specific tension is applied to the intermediate transfer belt 20 wound around the support roll 24. An intermediate transfer member cleaning device 30 is provided on the side of the image carrier of the intermediate transfer belt 20 so as to face the drive roll 22.
Further, each of the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K includes yellow, magenta, cyan, and black contained in the toner cartridges 8Y, 8M, 8C, and 8K. The four colors of toner are supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K described above have the same configuration, here, the first unit that forms a yellow image disposed on the upstream side in the intermediate transfer belt traveling direction. 10Y will be described as a representative. Note that the second to fourth units are denoted by reference numerals with magenta (M), cyan (C), and black (K) instead of yellow (Y) in the same parts as the first unit 10Y. Description of 10M, 10C, 10K is omitted.

The first unit 10Y has a photoreceptor 1Y that functions as an image holding member. Around the photoreceptor 1Y, a charging roll 2Y for charging the surface of the photoreceptor 1Y to a specific potential, and the charged surface is exposed by a laser beam 3Y based on the color-separated image signal to form an electrostatic image. An exposure device 3; a developing device (developing means) 4Y for developing the electrostatic image by supplying toner charged to the electrostatic image; a primary transfer roll 5Y (primary) for transferring the developed toner image onto the intermediate transfer belt 20; A transfer unit) and a photoconductor cleaning device (cleaning unit) 6Y for removing toner remaining on the surface of the photoconductor 1Y after the primary transfer with a cleaning blade.
The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20 and is provided at a position facing the photoconductor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C, and 5K. Each bias power source varies the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described. First, prior to the operation, the surface of the photoreceptor 1Y is charged to a potential of about −600V to −800V by the charging roll 2Y.
The photoreceptor 1Y is formed by laminating a photosensitive layer on a conductive substrate (volume resistivity at 20 ° C .: 1 × 10 ⁶ Ωcm or less). This photosensitive layer usually has a high resistance (a resistance equivalent to that of a general resin), but has a property that the specific resistance of the portion irradiated with the laser beam changes when irradiated with the laser beam 3Y. Therefore, a laser beam 3Y is output to the surface of the charged photoreceptor 1Y via the exposure device 3 in accordance with yellow image data sent from a control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image of a yellow print pattern is formed on the surface of the photoreceptor 1Y.

The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flows. On the other hand, this is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the laser beam 3Y.
The electrostatic image formed on the photoreceptor 1Y in this way is rotated to a specific development position as the photoreceptor 1Y travels. At this development position, the electrostatic charge image on the photoreceptor 1Y is visualized (developed image) by the developing device 4Y.

  For example, yellow toner is accommodated in the developing device 4Y. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as the charged charge on the photoreceptor 1Y, and a developer roll (developer holder). Is held on. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. . The photoconductor 1Y on which the yellow toner image is formed continues to run at a specific speed, and the toner image developed on the photoconductor 1Y is conveyed to a specific primary transfer position.

When the yellow toner image on the photoreceptor 1Y is conveyed to the primary transfer, a specific primary transfer bias is applied to the primary transfer roll 5Y, and the electrostatic force directed from the photoreceptor 1Y to the primary transfer roll 5Y generates a toner image. The toner image on the photoreceptor 1 </ b> Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time is a (+) polarity opposite to the polarity (−) of the toner, and is controlled to about +10 μA by the control unit (not shown) in the first unit 10Y, for example.
On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the cleaning device 6Y.

Further, the primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K after the second unit 10M is also controlled according to the first unit.
Thus, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in a multiple manner.

  The intermediate transfer belt 20 onto which the four color toner images have been transferred through the first to fourth units is disposed on the image transfer surface side of the intermediate transfer belt 20, the support roll 24 that contacts the inner surface of the intermediate transfer belt 20. To the secondary transfer portion constituted by the secondary transfer roll (secondary transfer means) 26. On the other hand, the recording medium P is fed at a specific timing into a gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are pressed against each other via a supply mechanism, and a specific secondary transfer bias is applied to the support roll 24. The The transfer bias applied at this time is a (−) polarity that is the same polarity as the polarity (−) of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording medium P is applied to the toner image, so The toner image is transferred onto the recording medium P. Note that the secondary transfer bias at this time is determined according to the resistance detected by a resistance detecting means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

Thereafter, the recording medium P is sent to a fixing device (fixing means) 28, the toner image is heated, and the color-superposed toner image is melted and fixed on the recording medium P. The recording medium P on which the color image has been fixed is unloaded to the discharge unit, and a series of color image forming operations is completed.
The image forming apparatus exemplified above is configured to transfer the toner image to the recording medium P via the intermediate transfer belt 20, but is not limited to this configuration, and the toner image is directly transferred from the photoconductor. It may be a structure that is transferred to the recording medium P.

  On the other hand, in the image forming apparatus shown in FIG. 8, the image forming units Y, M, C, and BK rotate in a clockwise direction indicated by an arrow with a specific peripheral speed (process speed), respectively. , 201BK are provided. Around the photoreceptors 201Y, 201M, 201C, and 201BK, there are charging rollers 202Y, 202M, 202C, and 202BK, exposure units 203Y, 203M, 203C, and 203BK, and color developing devices (yellow developing device 204Y, magenta developing device 204M, Cyan developing device 204C and black developing device 204BK) and photosensitive member cleaning members 205Y, 205M, 205C, and 205BK are disposed, respectively.

  The four image forming units Y, M, C, and BK are arranged in parallel with the recording medium conveyance transfer belt 206 (endless belt) in the order of the image forming units BK, C, M, and Y. An appropriate order is set in accordance with the image forming method, such as the order of the units BK, Y, C, and M.

  The recording medium conveyance transfer belt 206 is supported from the inner surface side by belt support rolls 210, 211, 212, and 213 to form a transfer unit 220 (endless belt unit) for the image forming apparatus. The recording medium conveyance transfer belt 206 rotates in the counterclockwise direction indicated by an arrow at the same peripheral speed as the photoconductors 201Y, 201M, 201C, and 201BK, and one of them is located between the belt support rolls 212 and 213. Are disposed in contact with the photoconductors 201Y, 201M, 201C, and 201BK, respectively. The recording medium conveyance transfer belt 206 is provided with a belt cleaning member 214.

  The transfer rolls 207Y, 207M, 207C, and 207BK are located inside the recording medium conveyance transfer belt 206 and at positions facing the portions where the recording medium conveyance transfer belt 206 is in contact with the photosensitive members 201Y, 201M, 201C, and 201BK. Each of the photoconductors 201Y, 201M, 201C, and 201BK and a transfer area for transferring the toner image to the recording medium 216 via the recording medium conveyance transfer belt 206 are formed. The transfer rolls 207Y, 207M, 207C, and 207BK may be disposed immediately below the photoconductors 201Y, 201M, 201C, and 201BK, or may be disposed at positions shifted from directly below.

  The fixing device 209 is disposed so as to be conveyed after passing through the transfer areas of the recording medium conveyance transfer belt 206 and the photosensitive members 201Y, 201M, 201C, and 201BK.

  The recording medium 216 is conveyed to the recording medium conveyance transfer belt 206 by the recording medium conveyance roll 208.

  In the image forming unit BK, the photosensitive member 201BK is driven to rotate. In conjunction with this, the charging roll 202BK is driven to charge the surface of the photoreceptor 201BK to a specific polarity and potential. Next, the photosensitive member 201BK whose surface is charged is exposed imagewise by the exposure unit 203BK, and an electrostatic charge image is formed on the surface.

  Subsequently, the electrostatic charge image is developed by the black developing device 204BK. As a result, a toner image is formed on the surface of the photoreceptor 201BK. The developer at this time may be a one-component developer or a two-component developer.

  The toner image passes through the transfer area between the photosensitive member 201BK and the recording medium conveyance transfer belt 206, and the recording medium 216 is electrostatically attracted to the recording medium conveyance transfer belt 206 and conveyed to the transfer area, and the transfer roll 207BK. Are sequentially transferred onto the surface of the recording medium 216 by an electric field formed by a transfer bias applied from the recording medium.

  Thereafter, the toner remaining on the photoconductor 201BK is cleaned and removed by the photoconductor cleaning member 205BK. Then, the photoconductor 201BK is used for the next image transfer.

  The above image transfer is also performed in the image forming units C, M, and Y by the above method.

The recording medium 216 onto which the toner image has been transferred by the transfer rolls 207BK, 207C, 207M, and 207Y is further conveyed to the fixing device 209 and fixed.
As a result, an image is formed on the recording medium.

  EXAMPLES Hereinafter, although this invention is demonstrated using an Example, this invention is not limited at all by these Examples. In the following, “part” and “%” are based on mass unless otherwise specified.

[Example A1]
・ Preparation of coating liquid (coating liquid preparation process)
A coating solution (A1) containing a polyamideimide resin was prepared as follows.
Polyamideimide varnish (trade name: HPC-9000F-8, manufactured by Hitachi Chemical Co., Ltd., solid content concentration of 16.5% by mass, solvent is N-methyl-2-pyrrolidone) (solid content conversion), carbon black (product Name: FW1 manufactured by Orion Engineered Carbons) 40 parts, and the concentration of the conductive agent (carbon black) is 28% by mass in terms of solid content with respect to the liquid dispersed using a jet mill. The coating liquid (A1) which added the said polyimide varnish (HPC-9000F-8) further and adjusted the density | concentration was prepared.

-Application | coating process It apply | coated to the outer peripheral surface of the cylindrical metal mold | die (cylindrical core body) by the flow coating method using the obtained coating liquid (A1). Specifically, the discharge amount of the coating liquid increases linearly from the start of application on one end side of the core body to the end of application on the other end side of the core body, and the discharge amount at the end of application starts. The coating was applied so as to increase by 3% (2.2 μm) with respect to the discharge amount.

-Heating process and demolding process In a downflow type heating device, a cylindrical core body on which a coating film is formed, the axial direction of the core body is along the direction of hot air, and one end of the core body (begin coating) The coated film was heated so that the heated side was on the upstream side (that is, the upper side) of the hot air. Specifically, after removing the solvent in the coating film (ie, drying) by heating with hot air at 170 ° C. for 20 minutes, the coating film is heated by heating with hot air at 300 ° C. for 100 minutes. Firing was performed. Then, the film | membrane of the obtained resin composition was demolded from the core body, and endless belt A1 was obtained.

The endless belt A1 thus obtained had a length in the axial direction of 330 mm and a circumferential length of 829 mm. The thickness increased from one end (upward side of hot air) to the other end (downward side of hot air).
The obtained endless belt A1 has one end thickness T ₁ (“T ₁ (μm)” in Table 1), the other end thickness T ₂ (“T ₂ (μm)” in Table 1), and one end thickness T. rate of increase in thickness in the length per 100mm axial direction with reference ₁ (Table 1 in "100mm per increase rate (%)"), increase in thickness in the per axial length 100mm (in Table 1 of “Increase per 100 mm (μm)”), common logarithm logS ₁ of surface resistivity at one end (“logS ₁ (logΩ / □)” in Table 1), and common logarithm logS of surface resistivity at the other end About ₂ (Table 1 in the "log S ₂ (log .OMEGA / □)"), shown in Table 1 the results obtained by the aforementioned method.

-Film thickness dependence of surface resistivity in resin composition Using the obtained coating liquid (A1), it was confirmed whether or not it had film thickness dependence of surface resistivity in the resin composition by the above-described method. The slope of the straight line was −0.08 logΩ / □ per 1 μm of film thickness, and it was confirmed that the surface resistivity was dependent on the film thickness. In addition, the heating at the time of producing an endless belt for confirming the film thickness dependency was performed at 170 ° C. for 20 minutes and then at 300 ° C. for 100 minutes.

[Example A2]
In the coating process, the discharge amount of the coating liquid increases linearly from the start of coating on one end side of the core body to the end of coating on the other end side of the core body, and the discharge amount at the end of coating is An endless belt A2 was obtained in the same manner as the endless belt A1, except that the coating amount was increased by 4.5% (3.6 μm) with respect to the discharge amount.

The endless belt A2 thus obtained has the same axial length and circumferential length as the endless belt A1, and the thickness increased from one end (hot air windward side) to the other end (hot air leeward side).
The obtained endless belt A2 has a thickness T ₁ at one end, a thickness T _{2 at} the other end, a rate of increase in thickness, an amount of increase in thickness, a common logarithm logS ₁ of the surface resistivity at one end, and a surface resistivity at the other end. for common logarithm log S _2, Table 1 shows the results obtained by the aforementioned method.

[Example A3]
-Application | coating process It apply | coated to the outer peripheral surface of the cylindrical metal mold | die (cylindrical core body) by the flow coating method using the obtained coating liquid (A1). Specifically, the discharge amount of the coating liquid increases linearly from the start of application on one end side of the core body to the end of application on the other end side of the core body, and the discharge amount at the end of application starts. The coating was formed so as to increase 10.0% (7.3 μm) with respect to the discharge amount in the film.

-Heating process and demolding process In a downflow type heating device, a cylindrical core body on which a coating film is formed, the axial direction of the core body is along the direction of hot air, and one end of the core body (begin coating) The coated film was heated so that the heated side was on the upstream side (that is, the upper side) of the hot air. Specifically, first, the solvent in the coating film was removed (that is, dried) by heating with hot air at 170 ° C. for 20 minutes, and then heated with hot air at 280 ° C. for 80 minutes. Firing was performed. Then, the film | membrane of the obtained resin composition was demolded from the core body, and endless belt A3 was obtained.

The endless belt A3 thus obtained has the same axial length and circumference as the endless belt A1, and the thickness increased from one end (hot air upside) to the other end (hot air leeward side).
The obtained endless belt A1 has a thickness T ₁ at one end, a thickness T _{2 at} the other end, a rate of increase in thickness, an amount of increase in thickness, a common logarithm logS ₁ of the surface resistivity at one end, and a surface resistivity at the other end. for common logarithm log S _2, Table 1 shows the results obtained by the aforementioned method.

[Comparative Example A4]
In the coating process, the endless belt A1 is endless except that the coating liquid is applied so that the discharge amount of the coating liquid does not change from the start of application on one end side of the core to the end of application on the other end side of the core. Belt A4 was obtained.

The endless belt A4 thus obtained had the same axial length and circumference as the endless belt A1, and the thickness did not increase from one end (hot air windward side) to the other end (hot air leeward side).
The obtained endless belt A4 has a thickness T ₁ at one end, a thickness T _{2 at} the other end, a rate of increase in thickness, an amount of increase in thickness, a common logarithm logS ₁ of the surface resistivity at one end, and a surface resistivity at the other end. for common logarithm log S _2, Table 1 shows the results obtained by the aforementioned method.

[Comparative Example A5]
In the coating process, the discharge amount of the coating liquid increases linearly from the start of coating on one end side of the core body to the end of coating on the other end side of the core body, and the discharge amount at the end of coating is An endless belt A5 was obtained in the same manner as the endless belt A1, except that the coating amount was increased by 13.5% (9.8 μm) with respect to the discharge amount.

The obtained endless belt A5 has the same axial length and circumferential length as the endless belt A1, and the thickness increased from one end (hot air windward side) to the other end (hot air leeward side).
The endless belt A5 thus obtained has a thickness T ₁ at one end, a thickness T _{2 at} the other end, a rate of increase in thickness, an amount of increase in thickness, a common logarithm logS ₁ of the surface resistivity at one end, and a surface resistivity at the other end. for common logarithm log S _2, Table 1 shows the results obtained by the aforementioned method.

[Reference Example C1]
・ Preparation of coating liquid (coating liquid preparation process)
A coating solution (C1) containing a polyimide resin precursor was prepared as follows.
Polyimide precursor solution (trade name: U varnish, manufactured by Unitika, solid content concentration 18% by mass, solvent is N-methyl-2-pyrrolidone) 100 parts (in terms of solid content) and carbon black (trade name: FW1 Orion Engineered) 40 parts of carbons) was mixed, and a coating liquid (C1) was prepared by concentrating the liquid dispersed using a jet mill to 28 parts (removing the solvent).

-Application | coating process It apply | coated to the outer peripheral surface of the cylindrical metal mold | die (cylindrical core body) spirally by the flow coating method using the obtained coating liquid (C1). Specifically, the discharge amount of the coating liquid increases linearly from the start of application on one end side of the core body to the end of application on the other end side of the core body, and the discharge amount at the end of application starts. The coating was applied so as to increase by 4.1% (3.1 μm) with respect to the discharge amount in the film.

-Heating process and demolding process In a downflow type heating device, a cylindrical core body on which a coating film is formed, the axial direction of the core body is along the direction of hot air, and one end of the core body (begin coating) The coated film was heated so that the heated side was on the upstream side (that is, the upper side) of the hot air. Specifically, after removing the solvent in the coating film (ie, drying) by heating with hot air at 180 ° C. for 20 minutes, the coating film is heated by heating with hot air at 300 ° C. for 100 minutes. Firing was performed. Then, the film | membrane of the obtained resin composition was demolded from the core body, and the endless belt C1 was obtained.

The endless belt C1 thus obtained has the same axial length and circumference as the endless belt A1, and the thickness increased from one end (hot air windward side) to the other end (hot air leeward side).
The obtained endless belt C1 has a thickness T ₁ at one end, a thickness T _{2 at} the other end, a rate of increase in thickness, an amount of increase in thickness, a common logarithm logS ₁ of the surface resistivity at one end, and a surface resistivity at the other end. for common logarithm log S _2, Table 1 shows the results obtained by the aforementioned method.

-Film thickness dependence of surface resistivity in resin composition Using coating solution (C1) obtained, it was confirmed whether or not it had film thickness dependence of surface resistivity in the resin composition by the method described above. The slope of the straight line was −0.005 logΩ / □ per 1 μm of film thickness, and it was confirmed that the surface resistivity did not have film thickness dependence. In addition, the heating at the time of producing an endless belt for confirming the film thickness dependency was performed at 180 ° C. for 20 minutes and then at 300 ° C. for 100 minutes.

[Reference Example C2]
In the coating step, the endless belt C1 is endless except that the coating liquid is applied so that the discharge amount does not change from the start of application on one end side of the core body to the end of application on the other end side of the core body. Belt C2 was obtained.

The endless belt C2 thus obtained had the same axial length and circumference as the endless belt C1, and the thickness did not increase from one end (hot air windward side) to the other end (hot air leeward side).
The obtained endless belt C2 has a thickness T ₁ at one end, a thickness T _{2 at} the other end, a rate of increase in thickness, an amount of increase in thickness, a common logarithm logS ₁ of the surface resistivity at one end, and a surface resistivity at the other end. for common logarithm log S _2, Table 1 shows the results obtained by the aforementioned method.

[Evaluation]
-Evaluation of density difference and durability Using the obtained endless belt, the density difference and durability of the image were evaluated by the following methods.
The obtained endless belt was used as an intermediate transfer belt and incorporated in an image forming apparatus (Fuji Xerox Co., Ltd., DocuCentre-V C2633) to form 1000 magenta halftone images (image density 30%) continuously on A4 paper. . For the 1000th image, the difference between the image density at the position corresponding to one end in the axial direction of the endless belt and the image density at the position corresponding to the other end was visually confirmed and evaluated according to the following criteria. The results are shown in Table 1 (“Evaluation” in Table 1).
(Evaluation criteria)
G1: 1000 sheets of images could be formed continuously, and no difference in image density was confirmed.
G2: 1000 sheets of images could be formed continuously, and a slight difference in image density was confirmed, but this was within an allowable range.
G3: 1000 sheets of images could be formed continuously, but a clear difference in image density was confirmed.
G4: The endless belt broke and 1000 images could not be formed continuously.

  From the results shown in Table 1, in this example, while maintaining the durability of the endless belt as compared with the comparative example A5, the resistance difference of the endless belt is suppressed as compared with the comparative example A4. It can be seen that the difference is also suppressed.

1Y, 1M, 1C, 1K photoconductor (image carrier)
2Y, 2M, 2C, 2K Charging roll (charging means)
3Y, 3M, 3C, 3K Laser beam 3 exposure device (electrostatic charge image forming means)
4Y, 4M, 4C, 4K Development device (developing means)
5Y, 5M, 5C, 5K primary transfer roll (primary transfer means)
6Y, 6M, 6C, 6K Cleaning device (cleaning means)
8Y, 8M, 8C, 8K Toner cartridge 10Y, 10M, 10C, 10K Image forming unit 20 Intermediate transfer belt 22 Drive roll 24 Support roll 26 Secondary transfer roll (secondary transfer means)
28 Fixing device (fixing means)
30 Intermediate transfer member cleaning device 31 Heating device 32 Drying furnace 34 Hot air generator 36 Support base 101 Endless belt (transfer belt)
102 one end 103 other end 110A coating film 121 tank 121A coating liquid 123 supply pipe 125 uniaxial eccentric screw pump 127 discharge-side tip 131 spatula 132 one end 133 core 134 coating device 160 control unit 201Y, 201M, 201C, 201BK Body (image carrier)
202Y, 202M, 202C, 202BK Charging roll (charging means)
203Y, 203M, 203C, 203BK Exposure unit (electrostatic charge image forming means)
204Y, 204M, 204C, 204BK Developing device (developing means)
205Y, 205M, 205C, 205BK Photosensitive member cleaning member 206 Recording medium conveyance transfer belt 207Y, 207M, 207C, 207BK Transfer roll (transfer means)
208 Recording medium conveyance roll 209 Fixing devices 210, 211, 212, 213 Belt support roll 214 Belt cleaning member 216 Recording medium 220 Transfer unit (endless belt unit)
335 Male thread type rotating body 336 Female thread type fixed body Y, M, C, BK Image forming unit P Recording medium

Claims (7)

Consists of a resin composition containing a resin and a conductive agent and having a film thickness dependence of surface resistivity,
The thickness increases from one end in the axial direction toward the other end, and the rate of increase in thickness based on the thickness of the one end is 0.8% or more and 3.2% or less per 100 mm in the axial length. Endless belt for equipment.   2. The endless belt according to claim 1, wherein an increase amount of the thickness is not less than 0.5 μm and not more than 2.4 μm per 100 mm in the axial direction. When the common logarithm value of the surface resistivity at the one end is logS ₁ and the common logarithm value of the surface resistivity at the other end is logS ₂ , the value of logS ₂ -logS ₁ is −0.16 logΩ / □ or more. The endless belt according to claim 1 or 2, wherein the endless belt is 16 logΩ / □ or less.   The endless belt according to any one of claims 1 to 3, wherein the resin includes polyamideimide.   The endless belt according to claim 1, wherein the conductive agent includes carbon black. The endless belt according to any one of claims 1 to 5,
A plurality of rolls that span the endless belt under tension;
And an endless belt unit that is detachably attached to the image forming apparatus. An image carrier,
Charging means for charging the surface of the image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
Developing means for developing, as a toner image, an electrostatic image formed on the surface of the image carrier with a developer containing toner;
A transfer means for transferring the toner image formed on the surface of the image carrier onto the surface of the recording medium via the endless belt;
An image forming apparatus comprising: