Endless belt, method for manufacturing endless belt, transfer device, and image forming apparatus

Abstract

The present invention relates to an endless belt, a method for manufacturing the endless belt, a transfer device, and an image forming apparatus. The endless belt contains a first resin and first conductive carbon particles, and the first conductive carbon particles present in an evaluation area of 6.3 μm × 4.2 μm on the outer peripheral surface satisfy a specific spatial distribution.

Description

Technical Field

[0001] The present invention relates to an endless belt, a method for manufacturing the endless belt, a transfer device, and an image forming apparatus. Background Art

[0002] In an image forming apparatus (such as a copying machine, a facsimile machine, a printer, etc.) using an electrophotographic method, a toner image formed on the surface of an image carrier is transferred onto the surface of a recording medium, and fixed on the recording medium to form an image. It should be noted that, in such a transfer of a toner image onto a recording medium, for example, a conductive endless belt such as an intermediate transfer belt is used.

[0003] For example, Japanese Patent Application Laid-Open No. 2007-011117 discloses "an intermediate transfer belt having at least a surface layer on a substrate, characterized in that the surface layer contains an aggregate of conductive particles having an average particle size of 0.5 to 25 μm".

[0004] Japanese Patent Application Laid-Open No. 2007-078789 discloses "an intermediate transfer belt having at least a surface layer on a substrate, characterized in that the surface layer contains resin fine particles coated with a metal". Summary of the Invention

[0005] Technical Problem to be Solved by the Invention

[0006] In an image forming apparatus using an endless belt as an intermediate transfer member, when a recording medium having large surface irregularities such as embossed paper (hereinafter also referred to as "irregular paper") is used, when transferring a toner image from the intermediate transfer member onto the recording medium, the intermediate transfer member cannot follow the irregularities of the recording medium, the transfer property is reduced, and image blanking may occur.

[0007] The technical problem to be solved by the present invention is to provide an endless belt which, when used as an intermediate transfer member, has excellent transfer property to irregular paper as compared with a case where the endless belt contains a first resin and first conductive carbon particles and the integral value of the statistic L(r) is greater than 0.1.

[0008] Means for Solving the Technical Problem

[0009] According to a first aspect of the present invention, there is provided an endless belt, which contains a first resin and first conductive carbon particles, and in the spatial distribution of the first conductive carbon particles present in an evaluation region of 6.3 μm × 4.2 μm on the outer peripheral surface, the integral value of the statistic L(r) represented by the following formula (1) with the inter-particle distance r being 0.05 μm or more and 0.30 μm or less is 0 or more and 0.1 or less.

[0010]

[0011] In the above formula (1), r represents the distance between the above-mentioned particles, and K(r) represents the Ripley's K function K(r) expressed by the following formula (2).

[0012]

[0013] In the above formula (2), 1(|X i -X j |≦r) represents the indicator function, X i and X j represent the coordinates of point i and point j respectively, |X i -X j | represents the Euclidean distance between the coordinate X i and the coordinate X j r represents the distance between the above-mentioned particles, s(|X i -X j |) represents the edge correction coefficient s(x) of the evaluation region expressed by the following formula (3), x = |X i -X j |, N represents the total number of particles in the evaluation region, and λ represents the number density of particles in the evaluation region.

[0014]

[0015] In the above formula (3), L x and L y represent the lengths (μm) of the sides in the x-axis direction and y-axis direction of each evaluation region, x = |X i -X j |, X i and X j represent the coordinates of point i and point j respectively, |X i -X j | represents the Euclidean distance between the coordinate X i and the coordinate X j .

[0016] According to the second aspect of the present invention, the above-mentioned first resin contains at least one selected from the group consisting of polyimide resin, polyamideimide resin, aromatic polyetheretherketone resin, polyphenylene sulfide resin, and polyetherimide resin.

[0017] According to the third aspect of the present invention, the above-mentioned first resin contains polyimide resin.

[0018] According to the fourth aspect of the present invention, the potential decay rate dV / dt after charging the outer peripheral surface of the annular belt to +500V is 2.0 V / msec or more and 6.0 V / msec or less.

[0019] According to the fifth aspect of the present invention, the above-mentioned annular belt has: a base material layer; and a surface layer provided on the above-mentioned base material layer and containing the above-mentioned first resin and the above-mentioned first conductive carbon particles.

[0020] According to the sixth aspect of the present invention, the above-mentioned base material layer contains a second resin and second conductive carbon particles,

[0021] The number average primary particle diameter of the above-mentioned first conductive carbon particles is smaller than the number average primary particle diameter of the above-mentioned second conductive carbon particles.

[0022] According to the seventh aspect of the present invention, the number average primary particle diameter of the above-mentioned first conductive carbon particles is 10 nm or more and 20 nm or less.

[0023] According to the eighth aspect of the present invention, the number average primary particle diameter of the above-mentioned first conductive carbon particles is 10 nm or more and 15 nm or less.

[0024] According to the ninth aspect of the present invention, the above-mentioned first resin contains at least one selected from the group consisting of polyimide resins and polyamideimide resins, and the above-mentioned first conductive carbon particles contain channel black.

[0025] According to the tenth aspect of the present invention, the above-mentioned first resin contains at least one selected from the group consisting of aromatic polyetheretherketone resins, polyphenylene sulfide resins, and polyetherimide resins, and the above-mentioned first conductive carbon particles contain at least one selected from the group consisting of channel black and furnace black.

[0026] According to the eleventh aspect of the present invention, there is provided a method for manufacturing an annular belt, which includes the following steps: a coating liquid preparation step of preparing a coating liquid containing a first resin or its precursor, first conductive carbon particles, and a solvent; a coating film formation step of coating the above-mentioned coating liquid on the outer periphery of a material to be coated to form a coating film; and a drying step of drying the above-mentioned coating film while raising the temperature of the above-mentioned material to be coated. When the integral average value of the temperature of the above-mentioned material to be coated during the above-mentioned drying is A °C and the time from the start of the above-mentioned drying until the temperature of the above-mentioned material to be coated reaches the integral average value A °C is B min, the integral average heating rate A / B (°C / min) is 5.74 °C / min or more.

[0027] According to the twelfth aspect of the present invention, the above-mentioned drying step is a step of drying the above-mentioned coating film by supplying hot air with a temperature of 110 °C or more and 235 °C or less to the above-mentioned coating film.

[0028] According to the thirteenth aspect of the present invention, the hot air speed on the surface of the above-mentioned coating film is 1 m / s or more and 20 m / s or less.

[0029] According to the 14th aspect of the present invention, the hot air is supplied to the coating film by blowing the hot air from the slit nozzle toward the surface of the coating film.

[0030] According to the 15th aspect of the present invention, the manufacturing method further includes a firing step of firing the coating film dried by the drying step.

[0031] According to the 16th aspect of the present invention, the above manufacturing method is a method for manufacturing the above endless belt.

[0032] According to the 17th aspect of the present invention, there is provided a transfer device including: an intermediate transfer body which is the above endless belt; a primary transfer mechanism that primarily transfers a toner image formed on the surface of an image holding body to the surface of the intermediate transfer body; and a secondary transfer mechanism that secondarily transfers the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium.

[0033] According to the 18th aspect of the present invention, the difference between the common logarithm of the resistance value of the above primary transfer mechanism under the conditions of a temperature of 28 °C and a humidity of 85 RH% and the common logarithm of the resistance value under the conditions of a temperature of 10 °C and a humidity of 15 RH% is 0.1 (logΩ) or more and 0.6 (logΩ) or less.

[0034] According to the 19th aspect of the present invention, the above foamed elastic layer contains epichlorohydrin rubber and an electron-conductive conductive agent.

[0035] According to the 20th aspect of the present invention, there is provided an image forming apparatus including: an image holding body; a charging device that charges the surface of the image holding body; an electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged image holding body; a developing device that stores a developer containing toner and develops the electrostatic latent image formed on the surface of the image holding body with the developer to form a toner image; and the above transfer device that transfers the toner image to the surface of a recording medium.

[0036] According to the 21st aspect of the present invention, the volume average particle diameter of the above toner is 2 μm or more and 5 μm or less.

[0037] Effects of the Invention

[0038] According to the above 1st, 2nd, or 3rd aspect, there is provided an endless belt which has excellent transferability to uneven paper when used as an intermediate transfer body as compared with a case where the endless belt contains a first resin and first conductive carbon particles and the integral value of the statistic L(r) is greater than 0.1.

[0039] According to the above-described fourth embodiment, there is provided an endless belt which, when used as an intermediate transfer member, has excellent transferability to corrugated paper as compared with the case where the potential decay rate dV / dt is less than 2.0 V / msec and greater than 6.0 V / msec.

[0040] According to the above-described fifth embodiment, there is provided an endless belt which, when used as an intermediate transfer member, has excellent transferability to corrugated paper as compared with the case where, even in the case of having a base material layer and a surface layer, the integrated value of the statistic L(r) is greater than 0.1.

[0041] According to the above-described sixth embodiment, there is provided an endless belt which, when used as an intermediate transfer member, has excellent transferability to corrugated paper as compared with the case where the number average primary particle diameter of the first conductive carbon particles is equal to or greater than the number average primary particle diameter of the second conductive carbon particles.

[0042] According to the above-described seventh embodiment, there is provided an endless belt which, when used as an intermediate transfer member, has excellent transferability to corrugated paper as compared with the case where the number average primary particle diameter of the first conductive carbon particles is greater than 20 nm.

[0043] According to the above-described eighth embodiment, there is provided an endless belt which, when used as an intermediate transfer member, has excellent transferability to corrugated paper as compared with the case where the number average primary particle diameter of the first conductive carbon particles is greater than 15 nm.

[0044] According to the above-described ninth embodiment, there is provided an endless belt which, when used as an intermediate transfer member, has excellent transferability to corrugated paper as compared with the case where the first resin is a polyimide resin or a polyamideimide resin and the first conductive carbon particles are furnace black.

[0045] According to the above-described tenth embodiment, there is provided an endless belt which, when used as an intermediate transfer member, has excellent transferability to corrugated paper as compared with the case where the first resin is an aromatic polyether ether ketone resin, a polyphenylene sulfide resin, or a polyetherimide resin, and the first conductive carbon particles are thermal cracking carbon black.

[0046] According to the above-described eleventh or sixteenth embodiment, there is provided a method for manufacturing an endless belt which, as compared with the case where the integrated average heating rate A / B (°C / min) in the drying step is less than 5.74 °C / min, can obtain an endless belt having excellent transferability to corrugated paper when used as an intermediate transfer member.

[0047] According to the above-described twelfth embodiment, there is provided a method for manufacturing an endless belt which, as compared with the case where the hot air temperature is less than 110 °C, can obtain an endless belt having excellent transferability to corrugated paper when used as an intermediate transfer member.

[0048] According to the above-described 13th aspect, there is provided a method for manufacturing a toroidal belt. Compared with the case where the hot air speed is less than 1 m / s, the above method can obtain a toroidal belt having excellent transferability to uneven paper when used as an intermediate transfer body.

[0049] According to the above-described 14th aspect, there is provided a method for manufacturing a toroidal belt. Compared with the case where hot air is directly blown from a drying furnace to the surface of a coating film without using a slit nozzle, the above method can obtain a toroidal belt having excellent transferability to uneven paper when used as an intermediate transfer body.

[0050] According to the above-described 15th aspect, for example, when the first resin is a polyimide resin, polyamic acid contained in the coating film is imidized by a firing step to obtain polyimide.

[0051] According to the above-described 17th or 19th aspect, there is provided a transfer device. Compared with the case where a toroidal belt containing the first resin and the first conductive carbon particles and having an integral value of the statistic L(r) greater than 0.1 is used as an intermediate transfer body, the transferability to uneven paper is excellent.

[0052] According to the above-described 18th aspect, there is provided a transfer device. Compared with the case where the difference between the common logarithm of the resistance value under the conditions of a temperature of 28°C and a humidity of 85 RH% and the common logarithm of the resistance value under the conditions of a temperature of 10°C and a humidity of 15 RH% is greater than 0.6 (logΩ), the transferability to uneven paper is excellent.

[0053] According to the above-described 20th aspect, there is provided an image forming device. Compared with the case where a toroidal belt containing the first resin and the first conductive carbon particles and having an integral value of the statistic L(r) greater than 0.1 is used as an intermediate transfer body, the transferability to uneven paper is excellent.

[0054] According to the above-described 21st aspect, there is provided an image forming device. Compared with the case where a toroidal belt containing the first resin and the first conductive carbon particles and having an integral value of the statistic L(r) greater than 0.1 is used as an intermediate transfer body even when a toner having a volume average particle diameter of 5 μm or less is used, the transferability to uneven paper is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a schematic configuration diagram showing an example of the image forming device of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0056] The present embodiment will be described below. These descriptions and examples are for illustrating the embodiment and do not limit the scope of the embodiment.

[0057] In the numerical ranges described step by step in this embodiment, the upper limit value or the lower limit value described in one numerical range can be replaced with the upper limit value or the lower limit value of the numerical range of other steps described. In addition, in the numerical ranges described in this embodiment, the upper limit value or the lower limit value of the numerical range can be replaced with the value shown in the examples.

[0058] The term "step" in this embodiment includes not only independent steps, but also, even in cases where it cannot be clearly distinguished from other steps, as long as the desired purpose of the step can be achieved, it is also included in this term.

[0059] When describing the embodiments in this embodiment with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the sizes of the components in each drawing are schematic, and the relative relationship of the sizes between the components is not limited thereto.

[0060] Each component in this embodiment may include two or more corresponding substances. When referring to the amount of each component in the composition of this embodiment, in the case where there are two or more substances corresponding to each component in the composition, unless otherwise specified, it refers to the total amount of the two or more substances present in the composition.

[0061] [Annular belt]

[0062] The annular belt of this embodiment includes a first resin and first conductive carbon particles. In the spatial distribution of the first conductive carbon particles present in an evaluation area of 6.3 μm × 4.2 μm on the outer peripheral surface, the integral value of the statistic L(r) represented by the following formula (1) where the inter-particle distance r is 0.05 μm or more and 0.30 μm or less is 0 or more and 0.1 or less.

[0063] [Equation 4]

[0064]

[0065] In the above formula (1), r represents the inter-particle distance, and K(r) represents the Ripley's K function K(r) represented by the following formula (2).

[0066] [Equation 5]

[0067]

[0068] In the above formula (2), 1(|X i -X j |≦r) represents an indicator function, X i and X j represent the coordinates of point i and point j respectively, and |X i -X j | represents the coordinate Xi The Euclidean distance from the coordinate X j , r represents the distance between the above-mentioned particles, and s(|X i −X j |) represents the edge correction coefficient s(x) of the evaluation region represented by the following formula (3), where x = |X i −X j |, N represents the total number of particles in the evaluation region, and λ represents the number density of particles in the evaluation region.

[0069] [Number 6]

[0070]

[0071] In the above formula (3), L x and L y represent the lengths (μm) of the sides in the x-axis direction and y-axis direction of each evaluation region, x = |X i −X j |, X i and X j represent the coordinates of point i and point j respectively, and |X i −X j | represents the Euclidean distance from the coordinate X i to the coordinate X j .

[0072] Here, the spatial distribution of the above-mentioned conductive carbon particles is obtained as follows: The outer peripheral surface of the annular belt is observed with a scanning electron microscope (for example, manufactured by Hitachi High-Technologies Corporation, model: SU8010) at a magnification of 20,000 times, and the obtained 256-level grayscale image is binarized with a threshold of 128 using analysis software (for example, the free software "ImageJ") as needed, thereby obtaining this spatial distribution. Then, based on the above formula, the statistic L(r) value with the particle distance r of 0.05 μm or more and 0.30 μm or less is calculated for every 0.05 μm, and the integral value in the range of 0.05 μm or more and 0.30 μm or less is obtained.

[0073] In the following, in the spatial distribution of the first conductive carbon particles existing in the 6.3 μm × 4.2 μm evaluation region on the outer peripheral surface of the annular belt, the integral value of the statistic L(r) represented by formula (1) with the particle distance r of 0.05 μm or more and 0.30 μm or less is referred to as the "L(r) integral value".

[0074] In this embodiment, by making the L(r) integral value 0 or more and 0.1 or less, when the annular belt is used as an intermediate transfer body, the transferability to the embossed paper is excellent. The reason is not yet determined and is presumably as follows.

[0075] In an image forming apparatus using a endless belt as an intermediate transfer member, when using uneven paper as a recording medium, when transferring a toner image from the intermediate transfer member to the recording medium, the intermediate transfer member cannot follow the unevenness of the recording medium, the transfer property is reduced, and image blanking may occur. Specifically, for example, if the electric field during transfer is increased because it is difficult to form a sufficient transfer electric field in the concave portion of the recording medium, an excessive electric field will be locally applied to the convex portion of the recording medium, and abnormal discharge will occur. As a result, the transfer property may be reduced due to a decrease in the charge amount of the toner or reverse charging.

[0076] Particularly in a tandem type image forming apparatus that repeatedly prints a plurality of monochromatic images on an intermediate transfer member and transfers the obtained multicolor image from the intermediate transfer member to a recording medium, especially in an image forming apparatus using small particle size toner, the above reduction in transfer property tends to become significant.

[0077] In contrast, in the present embodiment, the L(r) integral value is 0 or more and 0.1 or less. That is, conductive carbon particles are finely dispersed on the outer peripheral surface of the endless belt. Therefore, it is speculated that even if the intermediate transfer member cannot follow the unevenness of the recording medium and an excessive electric field is locally applied to the convex portion of the uneven paper, small discharges will occur at the respective conductive points finely dispersed on the outer peripheral surface of the endless belt, and the current will be dispersed. As a result, a decrease in the charge amount of the toner or reverse charging caused by abnormal discharge is suppressed, and the transfer property is improved.

[0078] It should be noted that the conductivity in this specification means that the volume resistivity at 20 °C is less than 1×10 13 Ωcm.

[0079] The method for making the L(r) integral value fall within the above range is not particularly limited. For example, a method of using particles having a small number average primary particle size as the first conductive carbon particles, a method of selecting the type of the first conductive carbon particles used, a method of adjusting the conditions (such as drying conditions) during the manufacturing process of the endless belt, etc. can be cited.

[0080] It should be noted that from the aspect of the transfer property to uneven paper, the above L(r) integral value is preferably 0 or more and 0.08 or less, and more preferably 0 or more and 0.06 or less.

[0081] The endless belt may be a single layer body or a laminated body.

[0082] When the endless belt is a single layer body, the above single layer body is a layer containing a first resin and first conductive carbon particles and having an L(r) integral value of 0 or more and 0.1 or less.

[0083] In the case where the annular belt is a laminate, the above laminate has, for example, a base material layer and a surface layer provided on the base material layer. The surface layer is the outermost layer of the annular belt. The laminate may have other layers between the base material layer and the surface layer.

[0084] In the case where the annular belt is a laminate having a base material layer and a surface layer, the above surface layer is a layer containing a first resin, first conductive carbon particles, and having an integrated value of L(r) of 0 or more and 0.1 or less. The base material layer is not particularly limited, and examples thereof include a layer containing a second resin and second conductive carbon particles.

[0085] Hereinafter, the layer of the single-layer annular belt will be referred to as "single layer". In addition, the surface layer containing the first resin and the first conductive carbon particles in the annular belt as a laminate will be referred to as the "first layer", and the base material layer containing the second resin and the second conductive carbon particles will be referred to as the "second layer".

[0086] <Resin>

[0087] Examples of the first resin contained in the single layer or the first layer include polyimide resin (PI resin), polyamideimide resin (PAI resin), aromatic polyether ketone resin (such as aromatic polyether ether ketone resin, etc.), polyphenylene sulfide resin (PPS resin), polyetherimide resin (PEI resin), polyester resin, polyamide resin, polycarbonate resin, etc. From the viewpoints of mechanical strength and dispersibility of the first conductive carbon particles, the first resin preferably contains at least one selected from the group consisting of polyimide resin, polyamideimide resin, aromatic polyether ether ketone resin, polyetherimide resin, and polyphenylene sulfide resin, and more preferably contains at least one selected from the group consisting of polyimide resin and polyamideimide resin. Among them, from the viewpoint of mechanical strength, polyimide resin is more preferred. The first resin may be composed of one resin or may be a mixture of two or more resins.

[0088] Specific examples and preferred examples of the second resin contained in the second layer are the same as the specific examples and preferred examples of the first resin. The second resin may be composed of one resin or may be a mixture of two or more resins.

[0089] It should be noted that when the annular belt has a first layer and a second layer, the first resin and the second resin may be the same resin or different resins, and preferably the same kind of resin (for example, both the first resin and the second resin are polyimide resin).

[0090] (Polyimide resin)

[0091] Examples of the polyimide resin include imidized products of polyamic acid (precursor of polyimide resin), which is a polymer of tetracarboxylic dianhydride and diamine compound.

[0092] As the polyimide resin, for example, a resin having a structural unit represented by the following general formula (I) can be cited.

[0093] [Chemical Formula 1]

[0094]

[0095] In the general formula (I), R 1 represents a tetravalent organic group, and R 2 represents a divalent organic group.

[0096] As the tetravalent organic group represented by R 1 , an aromatic group, an aliphatic group, a cycloaliphatic group, a group formed by combining an aromatic group and an aliphatic group, or a group obtained by substituting them can be cited. Specifically, as the tetravalent organic group, for example, the residue of a tetracarboxylic dianhydride described later can be cited.

[0097] As the divalent organic group represented by R 2 , an aromatic group, an aliphatic group, a cycloaliphatic group, a group formed by combining an aromatic group and an aliphatic group, or a group obtained by substituting them can be cited. Specifically, as the divalent organic group, for example, the residue of a diamine compound described later can be cited.

[0098] Specifically, as the tetracarboxylic dianhydride used as a raw material of the polyimide resin, pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic 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-naphthalenetetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)sulfone dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, ethylenetetracarboxylic dianhydride, etc. can be cited.

[0099] Specific examples of the diamine compound used as a raw material for the polyimide resin include 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl methane, 3,3'-diaminodiphenyl methane, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3'-dimethyl-4,4'-biphenyldiamine, benzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl propane, 2,4-bis(β-aminotert-butyl)toluene, bis(p-β-amino-tert-butylphenyl) ether, bis(p-β-methyl-δ-aminophenyl) benzene, bis-p-(1,1-dimethyl-5-aminopentyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, di(p-aminocyclohexyl) methane, 1,6-hexanediamine, heptamethylenediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, diaminopropyltetramethylene, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis(3-aminopropoxy)ethane, 2,2-dimethylpropylenediamine, 3-methoxy-1,6-hexanediamine, 2,5-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-methyl-1,9-nonanediamine, 2,17-diaminoeicosadecane, 1,4-cyclohexanediamine, 1,10-diamino-1,10-dimethyldecane, 1,2-diaminooctadecane, 2,2-bis[4-(4-aminophenoxy)phenyl] propane, piperazine, H2N(CH2)3O(CH2)2O(CH2)NH2, H2N(CH2)3S(CH2)3NH2, H2N(CH2)3N(CH3)2(CH2)3NH2, etc.

[0100] (Polyamide-imide resin)

[0101] As the polyamide-imide resin, a resin having an imide bond and an amide bond in the repeating unit can be cited.

[0102] More specifically, the polyamide-imide resin can be a polymer of a trivalent carboxylic acid compound (also called tricarboxylic acid) having an acid anhydride group and a diisocyanate compound or a diamine compound.

[0103] As the tricarboxylic acid, trimellitic anhydride and its derivatives are preferred. In addition to the tricarboxylic acid, a tetracarboxylic dianhydride, an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid, etc. can also be used in combination.

[0104] 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'-dimethoxybiphenyl-4,4'-diisocyanate, 2,2'-dimethoxybiphenyl-4,4'-diisocyanate, naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate, and the like.

[0105] Examples of the diamine compound include compounds having the same structure as the above-mentioned isocyanate and having an amino group in place of the isocyanate group.

[0106] (Aromatic polyether ketone resin)

[0107] Examples of the aromatic polyether ketone resin include resins in which aromatic rings such as benzene rings are linearly bonded through ether bonds and ketone bonds.

[0108] Examples of the aromatic polyether ketone resin include: polyether ketone (PEK) in which ether bonds and ketone bonds are alternately arranged; polyether ether ketone (PEEK) in which ether bonds, ether bonds, and ketone bonds are arranged in this order; polyether ketone ketone (PEKK) in which ether bonds, ketone bonds, and ketone bonds are arranged in this order; polyether ether ketone ketone (PEEKK) in which ether bonds, ether bonds, ketone bonds, and ketone bonds are arranged in this order; polyether ketone ester containing an ester bond; and the like.

[0109] From the aspect of adjusting mechanical strength, volume resistivity, etc., the content of the first resin relative to the entire single layer is preferably 60% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 95% by mass or less, and further preferably 75% by mass or more and 90% by mass or less.

[0110] From the aspect of adjusting mechanical strength, volume resistivity, etc., the content of the first resin relative to the entire first layer is preferably 60% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 95% by mass or less, and further preferably 75% by mass or more and 90% by mass or less.

[0111] From the aspect of adjusting mechanical strength, volume resistivity, etc., the content of the second resin relative to the entire second layer is preferably 60% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 95% by mass or less, and further preferably 75% by mass or more and 90% by mass or less.

[0112] (Conductive carbon particles)

[0113] Examples of the first conductive carbon particles included in the single layer or the first layer include carbon black.

[0114] Examples of carbon black include Ketjen black, oil furnace black, channel black, acetylene black, etc. As the carbon black, surface-treated carbon black (hereinafter also referred to as "surface-treated carbon black") can be used.

[0115] The surface-treated carbon black is obtained by imparting, for example, carboxyl groups, quinone groups, lactone groups, hydroxyl groups, etc. to its surface. Examples of the surface treatment method include: an air oxidation method in which it reacts with air in a high-temperature atmosphere; a method in which it reacts with nitrogen oxides or ozone at normal temperature (e.g., 22 °C); a method in which it is air-oxidized in a high-temperature atmosphere and then oxidized with ozone at a low temperature; and so on.

[0116] Examples of the number-average primary particle diameter of the first conductive carbon particles include a range of 20 nm or less. From the aspect of adjusting the integrated value of L(r) to the above range, it is preferably in the range of 18 nm or less, more preferably in the range of 15 nm or less, and further preferably in the range of 13 nm or less. In addition, examples of the number-average primary particle diameter of the first conductive carbon particles include a range of 2 nm or more. From the aspect of adjusting the integrated value of L(r) to the above range, it is preferably in the range of 5 nm or more, more preferably in the range of 10 nm or more.

[0117] Examples of the number-average primary particle diameter of the second conductive carbon particles include a range of 2 nm or more and 40 nm or less. From the aspects of dispersibility, mechanical strength, volume resistivity, film-forming property, etc., it is preferably in the range of 20 nm or more and 40 nm or less, more preferably in the range of 20 nm or more and 35 nm or less, and further preferably in the range of 20 nm or more and 28 nm or less.

[0118] When the annular belt has the first layer and the second layer, the number-average primary particle diameter of the first conductive carbon particles is preferably smaller than that of the second conductive carbon particles. The number-average primary particle diameter of the first conductive carbon particles is preferably 0.5 times or more and less than 1.0 times that of the second conductive carbon particles, more preferably 0.5 times or more and 0.8 times or less, and further preferably 0.5 times or more and 0.7 times or less.

[0119] The number-average primary particle diameter of the conductive carbon particles is measured by the following method.

[0120] First, a measurement sample with a thickness of 100 nm is collected from each layer of the obtained tape using a slicing machine, and the measurement sample is observed using a TEM (transmission electron microscope). Then, the diameter of a circle (i.e., the equivalent circle diameter) equal to the projected area of each of the 50 conductive carbon particles is used as the particle diameter, and the average value thereof is used as the number-average primary particle diameter.

[0121] When the first resin contains at least one selected from the group consisting of a polyimide resin and a polyamide-imide resin, and a single layer or the first layer is formed using the first coating liquid described below, from the aspect of adjusting the L(r) integral value to the above range, the first conductive carbon particles are preferably channel black among these, and more preferably channel black whose surface has been treated.

[0122] When a single layer or the first layer is formed using the first coating liquid, the pH of the first conductive carbon particles can be, for example, in the range of 1.0 or more and 5.5 or less. From the aspect of adjusting the L(r) integral value to the above range, it is preferably in the range of 1.0 or more and 3.0 or less.

[0123] In addition, when the second layer is formed using the second coating liquid described below, the pH of the second conductive carbon particles can be, for example, in the range of 1.0 or more and 5.5 or less. From the aspect of adjusting the L(r) integral value to the above range, it is preferably in the range of 1.0 or more and 3.0 or less.

[0124] It should be noted that when the annular tape has a first layer formed using the first coating liquid and a second layer formed using the second coating liquid, it is preferable that the pH of the first conductive carbon particles is less than the pH of the second conductive carbon particles.

[0125] When the first resin contains at least one selected from the group consisting of a polyetherimide resin, an aromatic polyether ether ketone resin, and a polyphenylene sulfide resin, and a single layer or the first layer is formed by melt extrusion described below, from the aspect of adjusting the L(r) integral value to the above range, the first conductive carbon particles are preferably channel black and furnace black among these, and more preferably those whose surface has not been treated.

[0126] The first conductive carbon particles can be composed of one type of conductive carbon particles or a mixture of two or more types of conductive carbon particles.

[0127] Specific examples of the second conductive carbon particles contained in the second layer can also be the same as the specific examples of the first conductive carbon particles.

[0128] From the aspect of reducing the integral value of L(r) and ensuring strength, the content of the first conductive carbon particles relative to the entire monolayer is preferably 10% by mass or more and 50% by mass or less, more preferably 13% by mass or more and 40% by mass or less, and still more preferably 15% by mass or more and 30% by mass or less.

[0129] From the aspect of reducing the integral value of L(r) and ensuring strength, the content of the first conductive carbon particles relative to the entire first layer is preferably 10% by mass or more and 50% by mass or less, more preferably 13% by mass or more and 40% by mass or less, and still more preferably 15% by mass or more and 30% by mass or less.

[0130] From the aspect of adjusting dispersibility, mechanical strength, and volume resistivity, the content of the second conductive carbon particles relative to the entire second layer is preferably 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 30% by mass or less, and still more preferably 20% by mass or more and 30% by mass or less.

[0131] <Other components>

[0132] In addition to the resin and conductive carbon particles, the monolayer, the first layer, and the second layer may each contain other components.

[0133] As other components, for example, conductive agents other than conductive carbon particles, fillers for improving the strength of the belt, antioxidants for preventing thermal deterioration of the belt, surfactants for improving fluidity, heat-resistant anti-aging agents, etc. can be cited.

[0134] When other components are included in the above layers, the content of the other components is preferably greater than 0% by mass and 10% by mass or less, more preferably greater than 0% by mass and 5% by mass or less, and still more preferably greater than 0% by mass and 1% by mass or less relative to the total mass of the layer in question.

[0135] <Characteristics of the endless belt>

[0136] (Thickness of the endless belt)

[0137] From the aspect of the mechanical strength of the belt, the thickness of the monolayer is preferably 60 μm or more and 120 μm or less, more preferably 80 μm or more and 120 μm or less.

[0138] From the aspects of manufacturing suitability and suppressing discharge, the thickness of the first layer is preferably 1 μm or more and 60 μm or less, more preferably 3 μm or more and 60 μm or less.

[0139] From the aspect of the mechanical strength of the belt, the thickness of the second layer is preferably 10 μm or more and 80 μm or less, more preferably 20 μm or more and 40 μm or less.

[0140] When the endless belt has a first layer and a second layer, from the viewpoint of transferability to embossed paper, the ratio of the first layer to the total thickness is preferably 3% or more and 90% or less, more preferably 5% or more and 80% or less.

[0141] It should be noted that the film thickness of each layer is measured as follows.

[0142] That is, the cross-section in the thickness direction of the endless belt is observed with an optical microscope or a scanning electron microscope, and the thickness of the layer to be measured is measured at 10 points, and the average value thereof is taken as the thickness.

[0143] (Potential decay rate of the endless belt)

[0144] From the viewpoint of transferability to embossed paper, the potential decay rate dV / dt (hereinafter also simply referred to as "potential decay rate") after charging the outer peripheral surface of the endless belt to +500 V is preferably 2.0 V / msec or more and 6.0 V / msec or less, more preferably 2.3 V / msec or more and 5.2 V / msec or less, and further preferably 2.3 V / msec or more and 3.8 V / msec or less.

[0145] That is, the endless belt more preferably has an L(r) integral value of 0 or more and 0.1 or less and a potential decay rate of 2.0 V / msec or more and 6.0 V / msec or less. In particular, when the endless belt is a laminate, by making the L(r) integral value 0 or more and 0.1 or less and the potential decay rate 2.0 V / msec or more and 6.0 V / msec or less, the transferability to embossed paper can also be improved.

[0146] The reason why the transferability to embossed paper can be improved by making the L(r) integral value in the endless belt 0 or more and 0.1 or less and making the potential decay rate 2.0 V / msec or more and 6.0 V / msec or less is not yet certain, but is presumed as follows.

[0147] When the endless belt is used as an intermediate transfer body of an image forming apparatus, for example, in a region where a toner image is transferred from the intermediate transfer body to a recording medium (hereinafter also referred to as "secondary transfer region"), a transfer electric field is applied from the inner peripheral surface side of the intermediate transfer body. By passing the intermediate transfer body through this secondary transfer region, charges are generated on the inner peripheral surface of the intermediate transfer body due to the action of the transfer electric field, and the generated charges move within the intermediate transfer body and thus reach the outer peripheral surface of the intermediate transfer body.

[0148] Further, in an image forming apparatus of a high-speed machine in which the conveyance speed of a recording medium passing through a secondary transfer area is 300 mm / s or more, if a large amount of charge reaches the outer peripheral surface of the intermediate transfer member during the intermediate transfer member passing through the secondary transfer area, abnormal discharge is likely to occur. On the other hand, if the amount of charge reaching the outer peripheral surface of the intermediate transfer member during the intermediate transfer member passing through the secondary transfer area is too small, the charge flows from the toner into the intermediate transfer member, thereby possibly reducing the charge amount of the toner and making it difficult to perform transfer.

[0149] In contrast, when the L(r) integral value of the annular belt is 0 or more and 0.1 or less and the potential decay rate is 2.0 V / msec or more and 6.0 V / msec or less, it is presumed that even when used as the intermediate transfer member of an image forming apparatus of a high-speed machine, the amount of charge reaching the outer peripheral surface of the intermediate transfer member during the intermediate transfer member passing through the secondary transfer area is appropriate, and the conductive points are finely dispersed on the outer peripheral surface of the intermediate transfer member. Thereby, abnormal discharge and a reduction in the charge amount of the toner can be suppressed, and the transfer property can be improved.

[0150] Here, the potential decay rate of the above annular belt is calculated as follows: A 50 mm × 60 mm belt piece is pasted on an insulating plate, a surface potentiometer (for example, manufactured by Trek Japan, model: Model 314) is provided on the belt surface (i.e., the outer peripheral surface), and after the belt piece is charged to 500 V by a grid corona tube with a set grid voltage of 580 V and an opening width of 18 mm, the surface potential of the belt just after charging and the decayed surface potential are measured every 10 msec, and the potential decay rate is calculated from the obtained results.

[0151] The method for controlling the potential decay rate of the annular belt is not particularly limited. For example, a method of selecting the number average primary particle diameter and type of the conductive carbon particles used, a method of adjusting the conditions (such as drying conditions, etc.) during the manufacturing process of the annular belt, etc. can be cited. In particular, when the annular belt is a laminate, in addition to the drying conditions of the surface layer and the drying conditions of the base material layer, by adjusting the combination manner of the drying conditions of the surface layer and the drying conditions of the base material layer, the potential decay rate can also be controlled.

[0152] In addition, the recording medium conveyance speed (i.e., the conveyance speed of the recording medium passing through the secondary transfer area) of the image forming apparatus using the annular belt with a potential decay rate of 2.0 V / msec or more and 6.0 V / msec or less is preferably 50 mm / s or more and 600 mm / s or less, more preferably 100 mm / s or more and 600 mm / s or less, and further preferably 300 mm / s or more and 600 mm / s or less.

[0153] (Volume resistivity of the annular belt)

[0154] From the aspect of transferability to uneven paper, the common logarithm of the volume resistivity when a voltage of 500 V is applied to the endless belt for 10 seconds is preferably 9.0 (logΩ·cm) or more and 13.5 (logΩ·cm) or less, more preferably 9.5 (logΩ·cm) or more and 13.2 (logΩ·cm) or less, and particularly preferably 10.0 (logΩ·cm) or more and 12.5 (logΩ·cm) or less.

[0155] The measurement of the volume resistivity when a voltage of 500 V is applied to the endless belt for 10 seconds is carried out by the following method.

[0156] Using a microammeter (R8430A manufactured by Advantest Corporation) as a resistance measuring machine and a UR probe (manufactured by Mitsubishi Chemical Analysis Co., Ltd.) as a probe, six points are taken at equal intervals in the circumferential direction of the endless belt, and three points are taken at the central part and both ends in the width direction, for a total of 18 points. The volume resistivity (logΩ·cm) is measured under the conditions of a voltage of 500 V, an application time of 10 seconds, and a pressure of 1 kgf, and the average value is calculated. In addition, the measurement is carried out in an environment of a temperature of 22 °C and a humidity of 55% RH.

[0157] (Surface resistivity of the endless belt)

[0158] From the aspect of transferability to uneven paper, the common logarithm of the surface resistivity when a voltage of 500 V is applied to the outer peripheral surface of the endless belt for 10 seconds is preferably 10.0 (logΩ / suq.) or more and 15.0 (logΩ / suq.) or less, more preferably 10.5 (logΩ / suq.) or more and 14.0 (logΩ / suq.) or less, and particularly preferably 11.0 (logΩ / suq.) or more and 13.5 (logΩ / suq.) or less.

[0159] It should be noted that the unit logΩ / suq. of the above surface resistivity is a value obtained by expressing the surface resistivity as the logarithm of the resistance value per unit area, and is also denoted as log(Ω / suq.), logΩ / suquare, logΩ / □, etc.

[0160] The measurement of the surface resistivity when a voltage of 500 V is applied to the outer peripheral surface of the endless belt for 10 seconds is carried out by the following method.

[0161] Using a microammeter (R8430A manufactured by Advantest Corporation) as a resistance measuring machine and a UR probe (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) as a probe, six points are taken at equal intervals in the circumferential direction on the outer peripheral surface of the annular belt, and three points are taken at the central part and both end parts in the width direction, for a total of 18 points. The surface resistivity (logΩ / suq.) of the outer peripheral surface of the annular belt is measured under the conditions of a voltage of 500 V, an application time of 10 seconds, and a pressure of 1 kgf, and the average value is calculated. In addition, the measurement is carried out in an environment of a temperature of 22°C and a humidity of 55%RH.

[0162] <Manufacturing method of annular belt>

[0163] The manufacturing method of the annular belt of the present embodiment is not particularly limited.

[0164] In an example of the manufacturing method of the annular belt, for example, the following steps are experienced: a first coating liquid preparation step of preparing a first coating liquid containing a first resin or its precursor, first conductive carbon particles, and a first solvent; a first coating film formation step of coating the first coating liquid on the outer periphery of the coated material to form a first coating film; and a first drying step of drying the first coating film while raising the temperature of the coated material. In the manufacturing method of the above annular belt, other steps may also be experienced in addition to the first coating liquid preparation step, the first coating film formation step, and the first drying step. As other steps, for example, in the case of using a precursor of the first resin, a first firing step of firing the first coating film dried by the first drying step can be cited.

[0165] In the case of manufacturing an annular belt as a single layer body, by experiencing the above first coating liquid preparation step, first coating film formation step, and first drying step, a single layer containing the first resin and the first conductive carbon particles is formed on the outer peripheral surface of the coated material. It should be noted that the single layer can be formed, for example, by producing a pellet containing the first resin and the first conductive carbon particles and melt-extruding the pellet.

[0166] In the case of manufacturing an annular belt as a laminate, for example, by experiencing the above first coating liquid preparation step, first coating film formation step, and first drying step, a first layer containing the first resin and the first conductive carbon particles is formed on the outer peripheral surface of the second layer formed on the coated material.

[0167] In the case of manufacturing an annular belt as a laminate, for example, the second layer is formed on the outer peripheral surface of the coated material by undergoing the following steps: a second coating liquid preparation step of preparing a second coating liquid containing a second resin or its precursor, second conductive carbon particles, and a second solvent; a second coating film formation step of coating the second coating liquid on the outer periphery of the coated material to form a second coating film; and a second drying step of drying the second coating film. It should be noted that the second layer can also be formed, for example, by producing pellets containing a second resin and second conductive carbon particles and melt-extruding the pellets.

[0168] (Coating liquid preparation step)

[0169] In the first coating liquid preparation step, a first coating liquid containing a first resin or its precursor, first conductive carbon particles, and a first solvent is prepared. For example, when the first resin is a polyimide resin and the first conductive carbon particles are carbon black, as the first coating liquid, for example, a solution in which carbon black is dispersed and polyamic acid as a polyimide resin precursor is dissolved in the first solvent is prepared. In addition, for example, when the first resin is a polyamideimide resin and the first conductive carbon particles are carbon black, as the first coating liquid, for example, a solution in which carbon black is dispersed and the polyamideimide resin is dissolved in the first solvent is prepared.

[0170] As a method for preparing the first coating liquid, from the aspect of pulverizing aggregates of the first conductive carbon particles and from the aspect of improving the dispersibility of the first conductive carbon particles, it is preferable to perform a dispersion treatment using a pulverizer such as a ball mill or a jet mill.

[0171] The first solvent is not particularly limited and can be appropriately determined according to the type of resin used as the first resin, etc. For example, when the first resin is a polyimide resin or a polyamideimide resin, as the first solvent, it is preferable to use a polar solvent described later.

[0172] Examples of the polar solvent include N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide (DEAc), dimethyl sulfoxide (DMSO), hexamethylphosphoramide (HMPA), N-methylcaprolactam, N-acetyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone (N,N-dimethylimidazolidinone, DMI), etc. They can be used alone as one kind, or two or more kinds can be used in combination.

[0173] It should be noted that in the case of undergoing the second coating liquid preparation step, in the second coating liquid preparation step, a second coating liquid containing a second resin, second conductive carbon particles, and a second solvent is prepared. The second resin and the second conductive carbon particles are as described above, and the preparation method of the second coating liquid and the second solvent are the same as the preparation method of the first coating liquid and the first solvent described above, respectively.

[0174] (Coating film formation step)

[0175] In the first coating film formation step, the above-mentioned first coating liquid is coated on the outer periphery of the material to be coated to form a first coating film.

[0176] As the material to be coated, for example, a cylindrical or columnar mold or the like can be cited. The material to be coated can be a material obtained by subjecting the outer peripheral surface of the above-mentioned mold to an anti-sticking agent treatment. In the case of manufacturing a single-layer annular belt, in the first coating film formation step, for example, the first coating liquid is directly coated on the outer peripheral surface of the above-mentioned material to be coated or the material to be coated subjected to the anti-sticking agent treatment. In the case of manufacturing a laminated annular belt, in the first coating film formation step, for example, the first coating liquid is coated on the outer peripheral surface of the material to be coated on which the second layer or the second coating film is formed.

[0177] As the coating method of the first coating liquid, for example, known methods such as spraying method, spiral coating (flow coating) method, blade coating method, wire bar coating method, dipping coating method, microbead coating method, air knife coating method, curtain coating method, etc. can be cited.

[0178] It should be noted that in the case of undergoing the second coating film formation step, in the second coating film formation step, the second coating liquid is coated on the outer periphery of the material to be coated to form a second coating film. The coating method of the second coating liquid is also the same as the coating method of the first coating liquid.

[0179] (Drying step)

[0180] In the first drying step, the first coating film formed in the first coating film formation step is dried. By the first drying step, the first solvent contained in the first coating film is removed to obtain a single layer or the first layer.

[0181] As the method of drying the first coating film, for example, a method of supplying hot air to the first coating film, a method of heating the material to be coated, etc. can be cited.

[0182] In the first drying step, when the integrated average temperature of the coated material in the drying step is A °C and the time from the start of the above drying until the temperature of the coated material reaches the integrated average temperature A °C is B min, the integrated average heating rate A / B (°C / min) is preferably 5.74 °C / min or more. By setting the integrated average heating rate A / B (°C / min) to 5.74 °C / min or more, an endless belt with excellent transferability to embossed paper can be obtained when used as an intermediate transfer body. The reason is not yet certain, but it is speculated as follows.

[0183] Specifically, if the integrated average heating rate A / B is large, the first coating film dries quickly, so the first conductive carbon particles in the first coating film are fixed before they agglomerate. Thus, a layer in which the first conductive carbon particles maintain a good dispersed state can be obtained. And it is speculated that the first conductive carbon particles in the obtained layer are finely dispersed, so that it is easy to make the integral value of L(r) in the range of 0 or more and 0.1 or less. When the endless belt of the above solution is used as an intermediate transfer body, an endless belt with excellent transferability to embossed paper is formed.

[0184] Here, the integrated average heating rate A / B is measured as follows: First, the temperature change of the coated material in the drying step is measured by connecting a thermometer (for example, K thermocouple of Graphtec Corporation, model: JBS-7115-5M-K) to a data logger (model: GL240) of Graphtec Corporation. Then, the temperature at which the integrated value (area) of the temperature of the coated material from the start of drying reaches half of the integrated value (area) of the temperature of the coated material from the start of drying to the end of drying is taken as the "integrated average value (A °C)", and the time (B min) from the start of drying until the temperature of the coated material reaches the integrated average temperature A °C is obtained, and the integrated average heating rate A / B (°C / min) is calculated.

[0185] The integrated average heating rate A / B (°C / min) is more preferably 5.74 °C / min or more, and further preferably 8.0 °C / min or more.

[0186] The method of controlling the integrated average heating rate A / B within the above range is not particularly limited. For example, in the case of drying the first coating film by supplying hot air to the surface of the first coating film, methods such as adjusting the hot air speed on the surface of the first coating film and adjusting the hot air temperature can be cited.

[0187] As the hot air speed on the surface of the first coating film, for example, a range of 0.1 m / s or more and 50 m / s or less can be cited, preferably a range of 1 m / s or more and 40 m / s or less, and more preferably a range of 1 m / s or more and 20 m / s or less.

[0188] Here, the hot air velocity on the surface of the first coating film is measured as follows. Specifically, an anemometer (TM350, manufactured by TASCO) is used, and the probe is set on the coating film surface for measurement.

[0189] As the hot air temperature on the surface of the first coating film, for example, a range of 100°C or higher and 280°C or lower can be cited, preferably a range of 100°C or higher and 250°C or lower, and more preferably a range of 110°C or higher and 235°C or lower.

[0190] The hot air temperature on the surface of the first coating film is measured by connecting a thermometer (for example, K thermocouple of Graphtec, model: JBS-7115-5M-K) to a data logger of Graphtec (model: GL240).

[0191] The method of supplying hot air to the surface of the first coating film is not particularly limited. For example, a method of blowing the hot air of the drying furnace from a slit nozzle toward the surface of the first coating film, a method of directly supplying the hot air of the drying furnace to the first coating film, etc. can be cited. Among them, from the aspect of being easy to control the hot air velocity on the surface of the first coating film, the method using a slit nozzle is preferred.

[0192] It should be noted that in the case of undergoing the second drying step, in the second drying step, the second coating film formed by the second coating film forming step is dried. The method of drying the second coating film is the same as the method of drying the first coating film. The second drying step can be completed before the first coating film forming step, or the first coating film forming step can be carried out before the second drying step is completed, so that the first drying step also serves as a part of the second drying step.

[0193] (Firing step)

[0194] As described above, the manufacturing method of the annular belt can undergo the first firing step. In the first firing step, firing is carried out by heating the first coating film dried by the first drying step. For example, when the first resin is a polyimide resin, the polyamic acid in the first coating film is imidized through the first firing step to obtain polyimide.

[0195] The heating temperature in the first firing step can be, for example, in the range of 150°C or higher and 450°C or lower, preferably in the range of 200°C or higher and 430°C or lower. In addition, the heating time in the first firing step can be, for example, in the range of 20 minutes or longer and 180 minutes or shorter, preferably in the range of 60 minutes or longer and 150 minutes or shorter.

[0196] Note that when manufacturing the annular belt as a laminate, in the case of forming the second layer through the second coating liquid preparation step, the second coating film formation step, and the second drying step, a second firing step of firing the second coating film dried in the second drying step may be performed. The second firing step may also serve as the first firing step.

[0197] [Transfer device]

[0198] The transfer device of the present embodiment includes: an intermediate transfer body; a primary transfer mechanism that primarily transfers the toner image formed on the surface of the image holding body to the surface of the intermediate transfer body; and a secondary transfer mechanism that secondarily transfers the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium. The transfer device of the present embodiment uses the above annular belt as the intermediate transfer body.

[0199] The primary transfer mechanism, for example, includes a primary transfer roller that is arranged opposite to the image holding body in a manner that sandwiches the intermediate transfer body that is an annular belt. In the primary transfer mechanism, by applying a voltage with a polarity opposite to the charge polarity of the toner to the intermediate transfer body using the above primary transfer roller, the toner image is primarily transferred to the outer peripheral surface of the intermediate transfer body.

[0200] The secondary transfer mechanism, for example, includes a secondary transfer roller arranged on the toner image holding side of the intermediate transfer body and a back roller arranged on the side of the intermediate transfer body opposite to the toner image holding side. In the secondary transfer mechanism, by forming a transfer electric field by sandwiching the intermediate transfer body and the recording medium with the secondary transfer roller and the back roller, the toner image on the intermediate transfer body is secondarily transferred to the recording medium.

[0201] In the transfer device of the present embodiment, since the above annular belt is used as the intermediate transfer body, even when a large electric field is applied in the secondary transfer mechanism for secondary transfer, abnormal discharge is not likely to occur, and the transferability to uneven paper is excellent.

[0202] The primary transfer roller in the above primary transfer mechanism is preferably a conductive roller having a foamed elastic layer containing epichlorohydrin rubber and an electron-conductive conductive agent on the outermost layer.

[0203] In addition, in the above foamed elastic layer, the difference between the common logarithm of the resistance value under the conditions of a temperature of 28°C and a humidity of 86RH% (in a high-temperature and high-humidity environment) and the common logarithm of the resistance value under the conditions of a temperature of 10°C and a humidity of 15RH% (in a low-temperature and low-humidity environment) (hereinafter also referred to as "resistance environmental variation") is preferably 0.6 (logΩ) or less, more preferably 0.1 (logΩ) or more and 0.6 (logΩ) or less, and further preferably 0.1 (logΩ) or more and 0.4 (logΩ) or less.

[0204] By using an annular belt with an L(r) integral value of 0 or more and 0.1 or less as an intermediate transfer body and using a conductive roller with a foamed elastic layer containing epichlorohydrin rubber and an electron-conductive conductive agent and a resistance environmental change of 0.1 (logΩ) or more and 0.6 (logΩ) or less as a primary transfer roller, the transferability to uneven paper at low temperature and low humidity (for example, in an environment of temperature 10°C and humidity 15RH%) can be particularly improved. The reason is not yet certain and is presumed as follows.

[0205] It is considered that by using a primary transfer roller with a foamed elastic layer having a small resistance environmental change, in the primary transfer area where the toner image is transferred from the image holding body to the intermediate transfer body, regardless of the environment, a sufficient electric field is applied, and in a state where the entire toner image is sufficiently charged and the charge amount deviation is suppressed, the toner image protrudes into the secondary transfer area (that is, the area where the toner image is transferred from the intermediate transfer body to the recording medium). In addition, it can be presumed that since the L(r) integral value in the intermediate transfer body is 0 or more and 0.1 or less, a sufficient transfer electric field can be formed even in the concave part of the recording medium, and abnormal discharge is difficult to occur, and the transferability to uneven paper at low temperature and low humidity can be improved.

[0206] Here, the resistance environmental change of the foamed elastic layer is obtained as follows.

[0207] Specifically, the conductive roller is held in a roller resistance measuring device, and then the electrode is brought into contact with the foamed elastic layer, and the resistance value under the conditions of temperature 10°C and humidity 15RH% and the resistance value under the conditions of temperature 28°C and humidity 85RH% are measured using a micro-resistance measuring device (for example, ADC Corporation, model: 8340A), and the difference in their common logarithms is used as the resistance environmental change. It should be noted that the above resistance value is the resistance value when a 10V voltage is applied for 5 seconds.

[0208] Examples of the method for controlling the resistance environmental change of the foamed elastic layer include a method of adjusting the types and ratios of epichlorohydrin rubber and electron-conductive conductive agents.

[0209] The following describes a conductive roller having a foamed elastic layer containing epichlorohydrin rubber and an electron-conductive conductive agent on the outermost layer.

[0210] <Conductive roller>

[0211] The conductive roller includes, for example, a support member and a foamed elastic layer disposed on the support member.

[0212] The support member functions as a support member when the conductive roller is mounted on the image forming apparatus, and functions as an electrode during image formation. The support member can be a hollow member or a solid member.

[0213] The support member is a conductive member, and examples thereof include: metal members such as iron (free-cutting steel, etc.), copper, brass, stainless steel, aluminum, nickel; resin members or ceramic members having a plating treatment on the outer surface; resin members or ceramic members containing a conductive agent.

[0214] (Foamed elastic layer)

[0215] The foamed elastic layer is a foam containing at least a rubber material (elastic material) containing epichlorohydrin rubber and an electron-conductive conductive agent. The rubber material may also contain other rubbers other than epichlorohydrin rubber. In addition, the foam may contain other components such as additives.

[0216] Examples of epichlorohydrin rubber include epichlorohydrin homopolymer rubber, copolymer rubber (epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-allyl glycidyl ether copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer rubber, etc.), and their mixed rubbers.

[0217] Examples of other rubbers include isoprene rubber, chloroprene rubber, butyl rubber, polyurethane, silicone rubber, fluororubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene-propylene rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), natural rubber, etc., and rubbers obtained by mixing them.

[0218] The rubber material is preferably a mixed rubber of epichlorohydrin rubber and other rubbers, and more preferably a mixed rubber of epichlorohydrin rubber and acrylonitrile-butadiene copolymer rubber.

[0219] From the aspect of reducing the change in resistance due to environmental changes, with respect to 100 parts by mass of the above rubber material, the content of epichlorohydrin rubber is preferably 10 parts by mass or more and 100 parts by mass or less, more preferably 20 parts by mass or more and 100 parts by mass or less, further preferably 30 parts by mass or more and 100 parts by mass or less, particularly preferably 30 parts by mass or more and 80 parts by mass or less, and most preferably 30 parts by mass or more and 60 parts by mass or less.

[0220] Examples of the electron-conductive conductive agent include: carbon blacks such as Ketjen black and acetylene black; pyrolytic carbon and graphite; metals or alloys such as aluminum, copper, nickel, and stainless steel; conductive metal oxides such as tin oxide, indium oxide, titanium oxide, tin oxide-antimony oxide solid solution, and tin oxide-indium oxide solid solution; substances obtained by conducting a conductive treatment on the surface of an insulating substance; and powders thereof. The electron-conductive conductive agent may be used alone or in combination of two or more.

[0221] Among them, the electron-conductive conductive agent is preferably carbon black, and the number-average primary particle diameter of the electron-conductive conductive agent is preferably 10 nm or more and 150 nm or less, more preferably 20 nm or more and 100 nm or less, and still more preferably 30 nm or more and 80 nm or less.

[0222] From the aspect of reducing the environmental variation of resistance, the content of carbon black is preferably 10 parts by mass or more and 70 parts by mass or less, more preferably 20 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the rubber material.

[0223] The foamed elastic layer may contain a foaming agent as an additive.

[0224] Examples of the foaming agent include: water; azo compounds such as azodicarbonamide, azobisisobutyronitrile, and diazoaminobenzene; benzenesulfonylhydrazide compounds such as benzenesulfonylhydrazide, 4,4'-oxybis(benzenesulfonylhydrazide), and toluenesulfonylhydrazide; bicarbonates such as sodium bicarbonate that generate carbon dioxide by thermal decomposition; a mixture of NaNO2 and NH4Cl that generates nitrogen; peroxides that generate oxygen; and the like. Foaming aids, foam stabilizers, catalysts, etc. may also be used as needed.

[0225] The foaming agent may be used alone or in combination of two or more.

[0226] The amount of the foaming agent is appropriately adjusted according to the characteristics of the rubber material used, etc., and is preferably 0.1 part by mass or more and 30 parts by mass or less, more preferably 0.5 part by mass or more and 20 parts by mass or less, still more preferably 1 part by mass or more and 15 parts by mass or less, and particularly preferably 2 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the rubber material. When the amount is within the above range, the resistance stability is more excellent.

[0227] The foamed elastic layer may contain a vulcanizing agent as an additive.

[0228] Examples of the vulcanizing agent include sulfur, organic sulfur-containing compounds, and organic peroxides. Examples of the organic sulfur-containing compounds include tetramethylthiuram disulfide, N,N'-dithiobis(morpholine), etc. In addition, examples of the organic peroxides include dicumyl peroxide, benzoyl peroxide, etc.

[0229] The vulcanizing agent may be used alone or in combination of two or more.

[0230] The addition amount of the vulcanizing agent is appropriately adjusted according to the characteristics of the rubber material used, etc., and is preferably 0.3 part by mass or more and 10 parts by mass or less, more preferably 1 part by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the rubber material contained in the elastic layer.

[0231] The foamed elastic layer may contain a vulcanization accelerator as an additive.

[0232] As a vulcanization accelerator, various substances used in the past are used, and sulfenamide-based vulcanization accelerators are particularly preferably used. The addition amount of the vulcanization accelerator is preferably 0.3 parts by mass or more and 4 parts by mass or less, more preferably 0.5 parts by mass or more and 3 parts by mass or less, based on 100 parts by mass of the rubber material.

[0233] The vulcanization accelerator may be used alone or in combination of two or more.

[0234] The foamed elastic layer may contain other additives.

[0235] As other additives, various known additives for rubber can be cited. Specifically, for example, processing aids (such as stearic acid), foaming aids, softeners, plasticizers, curing agents, antioxidants, surfactants, coupling agents, fillers (such as silica, calcium carbonate, etc.) can be cited.

[0236] The thickness of the foamed elastic layer is not particularly limited, and for example, 1 mm or more and 20 mm or less can be cited, and preferably 2 mm or more and 15 mm or less.

[0237] (Manufacturing method of the conductive roller)

[0238] The conductive roller is obtained by disposing a foamed elastic layer on a support member. The method of disposing the foamed elastic layer on the support member is not particularly limited, and for example, a method of preparing a cylindrical foamed elastic body and inserting the support member into the cylindrical foamed elastic body can be cited.

[0239] The method of forming the cylindrical foamed elastic layer is not particularly limited, and preferably the following method can be cited: A rubber composition containing a rubber component, an electron-conductive conductive agent, and other additives is formed into a cylindrical shape by kneading and extrusion molding, and then vulcanized and foamed to form a foamed elastic layer.

[0240] It should be noted that vulcanization and foaming are preferably carried out by heating, and as the heating temperature, 100 °C or more and 200 °C or less are preferred.

[0241] [Image forming apparatus]

[0242] The image forming apparatus of the present embodiment includes: an image carrier; a charging device that charges the surface of the image carrier; an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the image carrier; a developing device that stores a developer containing toner and develops the electrostatic latent image formed on the surface of the image carrier with the developer to form a toner image; and a transfer device that transfers the toner image to the surface of a recording medium, and the transfer device of the present embodiment uses the above-mentioned transfer device as the transfer device.

[0243] In this embodiment, even when a toner having a volume average particle diameter of 5 μm or less (hereinafter also referred to as "small-diameter toner") is used as the toner, the transferability to the embossed paper is excellent. When forming an image using the small-diameter toner, the resolution of the image can be improved, and a high-quality image can be obtained. On the other hand, since the charge amount per unit volume of the small-diameter toner increases, abnormal discharge is likely to occur when a transfer voltage is applied in the secondary transfer area. In addition, since the van der Waals force of the small-diameter toner is strong, when the toner is reversely charged due to abnormal discharge, the image blanking is likely to become significant.

[0244] However, in this embodiment, since an annular belt having an L(r) integral value of 0 or more and 0.1 or less is used as the intermediate transfer body of the transfer device, conductive points are finely dispersed on the outer peripheral surface of the intermediate transfer body, and the above abnormal discharge is not likely to occur. Therefore, it is speculated that even when using the small-diameter toner, the image blanking can be suppressed, and the transferability to the embossed paper is excellent.

[0245] It should be noted that the volume average particle diameter of the toner is preferably in the range of 2 μm or more and 5 μm or less, more preferably in the range of 3.5 μm or more and 4.8 μm or less.

[0246] It should be noted that regarding the volume average particle diameter of the toner, Coulter Multisizer II (manufactured by Beckman Coulter) is used, and ISOTON-II (manufactured by Beckman Coulter) is used as the electrolyte for measurement.

[0247] When performing the measurement, as a dispersant, 0.5 mg or more and 50 mg or less of the measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzenesulfonate). It is added to 100 ml or more and 150 ml or less of the electrolyte.

[0248] The electrolyte in which the sample is suspended is dispersed for 1 minute using an ultrasonic disperser, and using Coulter Multisizer II, the particle size distribution of particles in the range of 2 μm or more and 60 μm or less is measured using a 100-μm pore diameter. It should be noted that the number of sampled particles is 50,000.

[0249] With respect to the particle size ranges (sections) divided based on the measured particle size distribution, the cumulative distribution of volume is drawn from the small-diameter side, and the particle diameter at the cumulative 50% point is defined as the volume average particle diameter.

[0250] Hereinafter, an example of the image forming apparatus of this embodiment will be described with reference to the drawings.

[0251] Figure 1It is a schematic configuration diagram showing the configuration of the image forming apparatus according to the present embodiment.

[0252] It should be noted that the above-mentioned endless belt is applied as the intermediate transfer belt, and the above-mentioned conductive roller is applied as the primary transfer roller.

[0253] In addition, in the image forming apparatus according to the present embodiment, for example, at least a part including the transfer device may be a cartridge structure (processing cartridge) that can be attached to and detached from the image forming apparatus.

[0254] As Figure 1 shown, the image forming apparatus 100 according to the present embodiment is, for example, an image forming apparatus of an intermediate transfer method generally called a tandem type, which includes: a plurality of image forming units 1Y, 1M, 1C, 1K that form toner images of respective color components by an electrophotographic method; a primary transfer unit 10 (i.e., a primary transfer area) that sequentially transfers (primary transfer) the toner images of respective color components formed by the respective image forming units 1Y, 1M, 1C, 1K to an intermediate transfer belt 15; a secondary transfer unit 20 (i.e., a secondary transfer area) that transfers (secondary transfer) the overlapping toner images transferred onto the intermediate transfer belt 15 together to a sheet of paper K as a recording medium; and a fixing device 60 that fixes the image after secondary transfer on the sheet of paper K (an example of a recording medium). In addition, the image forming apparatus 100 has a control unit 40 that controls the operations of the respective devices (respective parts).

[0255] Among the respective image forming units 1Y, 1M, 1C, 1K of the image forming apparatus 100, as an example of an image holding body for holding the toner image formed on the surface, a photosensitive member 11 (an example of an image holding body) that rotates in the direction of arrow A is provided.

[0256] Around the photosensitive member 11, as an example of a charging device, a charger 12 that charges the photosensitive member 11 is provided, and as an example of an electrostatic latent image forming device, a laser exposure device 13 that writes an electrostatic latent image onto the photosensitive member 11 (in the figure, the exposure light beam is denoted by the symbol Bm) is provided.

[0257] In addition, around the photosensitive member 11, as an example of a developing device, a developer 14 that stores toner of respective color components and forms a visible image by using the toner for the electrostatic latent image on the photosensitive member 11 is provided, and a primary transfer roller 16 that transfers the toner images of respective color components formed on the photosensitive member 11 to the intermediate transfer belt 15 by the primary transfer unit 10 is provided.

[0258] Furthermore, a photoreceptor cleaner 17 is provided around the photoreceptor 11 to remove residual toner on the photoreceptor 11, and an electrophotographic device including a charger 12, a laser exposure device 13, a developer 14, a primary transfer roller 16, and the photoreceptor cleaner 17 is provided in this order along the rotation direction of the photoreceptor 11. These image forming units 1Y, 1M, 1C, and 1K are arranged in a straight line in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the upstream side of the intermediate transfer belt 15.

[0259] The intermediate transfer belt 15 as an intermediate transfer body has a volume resistivity of, for example, 1×10 6 Ωcm or more 1×10 14 The thickness is formed to be less than Ωcm, and the thickness is, for example, about 0.1mm.

[0260] The intermediate transfer belt 15 is formed by various rollers. Figure 1 The intermediate transfer belt 15 is cyclically driven (rotated) at a speed corresponding to the purpose in the direction B shown. The various rollers include the following rollers: a driving roller 31 driven by a motor (not shown) having excellent uniform speed to rotate the intermediate transfer belt 15; a supporting roller 32 supporting the intermediate transfer belt 15 extending substantially linearly along the arrangement direction of the photosensitive bodies 11; a tensioning roller 33 that applies tension to the intermediate transfer belt 15 and functions as a correction roller to prevent the intermediate transfer belt 15 from meandering; a back roller 25 provided in the secondary transfer section 20; and a cleaning back roller 34 provided in the cleaning section to scrape off residual toner on the intermediate transfer belt 15.

[0261] The primary transfer section 10 is composed of a primary transfer roller 16 disposed opposite to the photoreceptor 11 in a manner of sandwiching the intermediate transfer belt 15. The primary transfer roller 16 is disposed in pressure contact with the photoreceptor 11 in a manner of sandwiching the intermediate transfer belt 15, and a voltage (primary transfer bias) having a polarity opposite to the charging polarity of the toner (negative polarity, the same below) is applied to the primary transfer roller 16. As a result, the toner images on the respective photoreceptors 11 are electrostatically attracted to the intermediate transfer belt 15 in sequence, forming toner images superimposed on the intermediate transfer belt 15.

[0262] The secondary transfer section 20 includes a back roller 25 and a secondary transfer roller 22 disposed on the toner image holding surface side of the intermediate transfer belt 15 .

[0263] The back roller 25 has a surface resistivity of 1×10 7 Ω / □ or more 1×10 10It is formed to be Ω / □ or less, and the hardness is set to, for example, 70° (manufactured by KOBUNSHI KEIKI CO., LTD., the same applies hereinafter). The back roller 25 is disposed on the back side of the intermediate transfer belt 15, constitutes the counter electrode of the secondary transfer roller 22, and is disposed in contact with the power supply roller 26 made of metal to which the secondary transfer bias is stably applied.

[0264] On the other hand, the secondary transfer roller 22 is a cylindrical roller having a volume resistivity of 10 7.5 Ω·cm or more and 10 8.5 Ω·cm or less. Further, the secondary transfer roller 22 is press-fitted and disposed on the back roller 25 in a manner of sandwiching the intermediate transfer belt 15. Furthermore, the secondary transfer roller 22 is grounded and a secondary transfer bias is formed between the secondary transfer roller 22 and the back roller 25, and the toner image is secondarily transferred onto the sheet K conveyed to the secondary transfer unit 20.

[0265] It should be noted that, as the conveyance speed of the sheet K in the secondary transfer unit 20, for example, a range of 50 mm / s or more and 600 mm / s or less can be cited.

[0266] In addition, an intermediate transfer belt cleaner 35 is provided on the downstream side of the secondary transfer unit 20 of the intermediate transfer belt 15 so as to be freely contactable and detachable. The intermediate transfer belt cleaner 35 removes the residual toner or paper dust on the intermediate transfer belt 15 after secondary transfer and cleans the surface of the intermediate transfer belt 15.

[0267] It should be noted that the intermediate transfer belt 15, the primary transfer unit 10 (primary transfer roller 16), and the secondary transfer unit 20 (secondary transfer roller 22) are examples of a transfer device.

[0268] On the other hand, a reference sensor (home position sensor) 42 is disposed on the upstream side of the yellow image forming unit 1Y. The reference sensor (home position sensor) 42 generates a reference signal as a reference for controlling the image forming timing in each of the image forming units 1Y, 1M, 1C, 1K. In addition, an image density sensor 43 for performing image quality adjustment is disposed on the downstream side of the black image forming unit 1K. The reference sensor 42 is configured as follows: it recognizes a mark provided on the back side of the intermediate transfer belt 15, generates a reference signal, and based on the recognition of the reference signal, according to an instruction from the control unit 40, each of the image forming units 1Y, 1M, 1C, 1K starts image formation.

[0269] Furthermore, in the image forming apparatus of the present embodiment, as a conveyance mechanism for conveying the sheet K, the following are provided: a sheet storage unit 50 for storing the sheet K; a paper feed roller 51 for taking out and conveying the sheets K gathered in the sheet storage unit 50 at a preset timing; a conveyance roller 52 for conveying the sheet K sent out by the paper feed roller 51; a conveyance guide 53 for feeding the sheet K conveyed by the conveyance roller 52 into the secondary transfer unit 20; a conveyor belt 55 for conveying the sheet K transferred after secondary transfer by the secondary transfer roller 22 to the fixing device 60; and a fixing entrance guide 56 for guiding the sheet K into the fixing device 60.

[0270] Next, the basic imaging process of the image forming apparatus of the present embodiment will be described.

[0271] In the image forming apparatus of the present embodiment, after image data output from an image reading device (not shown) or a personal computer (PC) (not shown) is subjected to image processing by an image processing device (not shown), an imaging operation is performed using the image forming units 1Y, 1M, 1C, 1K.

[0272] In the image processing device, various image editing processes such as shadow correction, position offset correction, brightness / color space conversion, γ correction, border elimination, color editing, and movement editing are performed on the input reflectance data. The image data subjected to the image processing is converted into toner gradation data of four colors, Y, M, C, and K, and output to the laser exposure unit 13.

[0273] In the laser exposure unit 13, according to the input toner gradation data, an exposure beam Bm emitted from, for example, a semiconductor laser is irradiated onto each photoreceptor 11 of the image forming units 1Y, 1M, 1C, 1K. In each photoreceptor 11 of the image forming units 1Y, 1M, 1C, 1K, after the surface is charged by the charger 12, the surface is scanned and exposed by the laser exposure unit 13 to form an electrostatic latent image. The formed electrostatic latent image is developed in the form of toner images of various colors, Y, M, C, and K, by each of the image forming units 1Y, 1M, 1C, 1K.

[0274] For the toner images formed on the photoreceptors 11 of the image forming units 1Y, 1M, 1C, 1K, they are transferred to the intermediate transfer belt 15 at the primary transfer unit 10 where each photoreceptor 11 contacts the intermediate transfer belt 15. More specifically, at the primary transfer unit 10, a voltage (primary transfer bias) having a polarity opposite to the charge polarity (negative polarity) of the toner is applied to the base material of the intermediate transfer belt 15 by the primary transfer roller 16, and the toner images are sequentially overlapped on the surface of the intermediate transfer belt 15 for primary transfer.

[0275] After the toner image is sequentially transferred onto the surface of the intermediate transfer belt 15 one by one, the intermediate transfer belt 15 is moved to convey the toner image to the secondary transfer unit 20. When the toner image is conveyed to the secondary transfer unit 20, in the conveying mechanism, the paper feed roller 51 rotates according to the timing of conveying the toner image to the secondary transfer unit 20, and the paper K of the target size is supplied from the paper storage unit 50. The paper K supplied by the paper feed roller 51 is conveyed by the conveying roller 52 and reaches the secondary transfer unit 20 via the conveying guide 53. Before reaching the secondary transfer unit 20, the paper K is temporarily stopped, and the alignment roller (not shown) rotates according to the moving timing of the intermediate transfer belt 15 holding the toner image, whereby the positioning of the position of the paper K and the position of the toner image can be performed. Even when, for example, embossed paper or the like having irregularities on the surface is used as the paper K, good transferability to the paper K can be obtained.

[0276] In the secondary transfer unit 20, the secondary transfer roller 22 is pressed against the back roller 25 by the intermediate transfer belt 15. At this time, the paper K conveyed according to the timing is clamped between the intermediate transfer belt 15 and the secondary transfer roller 22. At this time, when a voltage (secondary transfer bias voltage) having the same polarity as the charging polarity (negative polarity) of the toner is applied by the power supply roller 26, a transfer electric field is formed between the secondary transfer roller 22 and the back roller 25. Thereafter, the unfixed toner image held on the intermediate transfer belt 15 is electrostatically transferred onto the paper K together in the secondary transfer unit 20 where the secondary transfer roller 22 and the back roller 25 are pressed.

[0277] Thereafter, the paper K onto which the toner image has been electrostatically transferred is directly conveyed in a state of being peeled off from the intermediate transfer belt 15 by the secondary transfer roller 22, and is conveyed to the conveyor belt 55 provided on the downstream side in the paper conveying direction of the secondary transfer roller 22. On the conveyor belt 55, the paper K is conveyed to the fixing device 60 according to the optimum conveying speed in the fixing device 60. The unfixed toner image on the paper K conveyed to the fixing device 60 is subjected to a fixing process under heat and pressure by the fixing device 60, whereby it is fixed on the paper K. Thereafter, the paper K on which the fixed image has been formed is conveyed to a paper discharge storage unit (not shown) provided in the discharge unit of the image forming apparatus.

[0278] On the other hand, after the transfer to the paper K is completed, the residual toner remaining on the intermediate transfer belt 15 is conveyed to the cleaning unit as the intermediate transfer belt 15 rotates, and is removed from the intermediate transfer belt 15 by the cleaning back roller 34 and the intermediate transfer belt cleaner 35.

[0279] The above describes the present embodiment, but it is not construed as being limited to the above embodiment, and various modifications, changes, and improvements can be made.

[0280] [Embodiment]

[0281] The embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. It should be noted that in the following description, unless otherwise specified, "parts" and "%" are all based on mass.

[0282] [Example A1]

[0283] [Synthesis of polyamic acid]

[0284] By the following method, polyamic acid DA-A1 with amino groups at both ends of the molecular chain was synthesized as polyamic acid, and polyamic acid DC-A1 with carboxyl groups at both ends of the molecular chain was synthesized as polyamic acid.

[0285] [Preparation of polyamic acid solution DA-A1]

[0286] 83.48 g (416.9 mmol) of 4,4'-diaminodiphenyl ether (hereinafter abbreviated as "ODA") as a diamine compound was added to 800 g of N-methyl-2-pyrrolidone (hereinafter abbreviated as "NMP") and dissolved under stirring at room temperature (25°C).

[0287] Then, 116.52 g (396.0 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter abbreviated as "BPDA") as a tetracarboxylic dianhydride was slowly added. After the addition and dissolution of the tetracarboxylic dianhydride, the temperature of the reaction solution was heated to 60°C, and then a polymerization reaction was carried out for 20 hours while maintaining the temperature of the reaction solution to obtain a reaction solution containing polyamic acid DA-A1 and NMP.

[0288] The obtained reaction solution was filtered through a #800 stainless steel mesh and cooled to room temperature (25°C) to obtain a polyamic acid solution DA-A1 with a solution viscosity of 2.0 Pa·s at 25°C.

[0289] It should be noted that the solution viscosity of the polyamic acid solution is the value obtained as follows: Using an E-type rotational viscometer TV-20H manufactured by Toki Sangyo Co., Ltd., under the conditions of a measuring temperature of 25°C, a rotation speed of 0.5 rpm (for 100 Pa·s or more) and 1 rpm (for less than 100 Pa·s) with a standard rotor (1°34"×R24), the obtained value is the solution viscosity.

[0290] The solution viscosities of the polyamic acid solutions obtained in the following synthesis examples are also the values measured in the same way.

[0291] [Preparation of polyamic acid solution DC-A1]

[0292] A polyamic acid solution DC-A1 with a solution viscosity of 6.0 Pa·s containing polyamic acid DC-A1 and NMP was obtained in the same manner as the preparation of the polyamic acid solution DA-A1, except that ODA was 79.57 g (397.4 mmol) and BPDA was 120.43 g (409.3 mmol).

[0293] <Preparation of Coating Liquid>

[0294] - Preparation of Coating Liquid A1 (Second Coating Liquid)-

[0295] · 70 parts by mass of polyamic acid solution DA-A1 (solid content concentration: 45% by mass)

[0296] · 30 parts by mass of polyamic acid solution DC-A1 (solid content concentration: 15% by mass)

[0297] · Acidic carbon black (dry state; conductive carbon particles)

[0298] [SPECIAL BLACK 4: Manufactured by Orion Engineered Carbons S.A., pH 4.5, volatile component: 18.0%, gas black (i.e., channel black), number average primary particle size: 25 nm (hereinafter simply referred to as "SB-4")] 26 parts by mass

[0299] The polyamic acid solution DA-A1 and the polyamic acid solution DC-A1 with the above composition were mixed, SB-4 was added, and dispersion treatment was carried out at 30 °C for 12 hours using a ball mill, thereby dispersing it in the mixed solution of the polyamic acid solution. Then, the mixed solution in which SB-4 was dispersed was filtered through a #400 stainless steel mesh to obtain coating liquid A1 as the second coating liquid.

[0300] - Preparation of Coating Liquid B1 (First Coating Liquid)-

[0301] · 70 parts by mass of polyamic acid solution DA-A1 (solid content concentration: 45% by mass)

[0302] · 30 parts by mass of polyamic acid solution DC-A1 (solid content concentration: 15% by mass)

[0303] · Acidic carbon black (dry state; conductive carbon particles)

[0304] [Color Black FW200, manufactured by Orion Engineered Carbons S.A., gas black (i.e., channel black), number average primary particle size: 13 nm, pH: 3.0 (hereinafter simply referred to as "FW200")] 18 parts by mass

[0305] Mix the above-prepared polyamic acid solution DA-A1 and polyamic acid solution DC-A1, add FW200, and disperse it in the mixed polyamic acid solution by treating it with a ball mill at 30°C for 12 hours. Then, filter the mixed solution in which FW200 is dispersed through a #800 stainless steel mesh to obtain coating solution B1 as the first coating solution.

[0306] <Fabrication of Tape A1>

[0307] -Anti-sticking agent treatment of the material to be coated-

[0308] As the material to be coated, prepare a cylindrical mold made of SUS material with an outer diameter of 366 mm and a length of 400 mm. Coat the outer surface with a silicone-based anti-sticking agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name: SEPA-COAT SP), and perform a drying treatment (anti-sticking agent treatment).

[0309] -Formation of the second coating film-

[0310] While rotating the cylindrical mold that has been treated with the anti-sticking agent in the circumferential direction at a speed of 10 rpm, discharge the above coating solution A1 from the end of the cylindrical mold through a dispenser with a diameter of 1.0 mm, and perform coating by pressing it with a metal squeegee provided on the mold with a uniform pressure. By moving the dispenser unit along the axial direction of the cylindrical mold at a speed of 100 mm / min, coat the coating solution A1 on the cylindrical mold in a spiral shape to form the second coating film.

[0311] -Drying of the second coating film-

[0312] Then, dry the mold and the second coating film in a drying furnace at 140°C in an air atmosphere while rotating at 10 rpm for 15 minutes.

[0313] After drying, by volatilizing the solvent from the second coating film, change the second coating film into a self-supporting polyamic acid resin molded product (substrate 1).

[0314] -Formation and drying of the first coating film-

[0315] Coat coating solution B1 on the outer peripheral surface of substrate 1 to form the first coating film using the same spin coating method as that for coating solution A1. Then, dry the first coating film in a drying furnace at 140°C in an air atmosphere while rotating at 10 rpm for 15 minutes. It should be noted that in the drying step of the first coating film, the integral average heating rate A / B is 6.00°C / min.

[0316] -Firing-

[0317] Next, it was placed in an oven set to a temperature of 320 °C for 4 hours to obtain the annular belt A1. The overall film thickness of the annular belt A1 (the combined film thickness of the base layer and the surface layer) was 80 μm, of which the film thickness of the base layer was 26.7 μm and the film thickness of the surface layer was 53.3 μm.

[0318] The annular belt A1 was removed from the mold, and the pulled-out annular belt A1 was tensioned and mounted on a holder, and cut with a cutter with an adjusted insertion angle to obtain a ring-shaped body with a width of 369 mm. The intermediate transfer belt thus produced was used as the belt A1.

[0319] It should be noted that the content of the conductive carbon particles in the belt A1 relative to the entire base layer was 22% by mass, and the content of the conductive carbon particles relative to the entire surface layer was 18% by mass.

[0320] In addition, the volume resistivity and the surface resistivity of the outer peripheral surface of the belt A1 were measured by the above method. As a result, the common logarithm of the volume resistivity was 11.5 (logΩ·cm), and the common logarithm of the surface resistivity was 11.5 (logΩ / suq.).

[0321] [Example A2]

[0322] [Production of Belt A2]

[0323] In the drying step of the first coating film, drying treatment was carried out in an air atmosphere at 170 °C for 20 minutes instead of drying treatment in an air atmosphere at 140 °C for 15 minutes. Except for this, the annular belt A2 was obtained in the same manner as the annular belt A1. The overall film thickness of the annular belt A2 (the combined film thickness of the base layer and the surface layer) was 80 μm, of which the film thickness of the base layer was 26.7 μm and the film thickness of the surface layer was 53.3 μm. It should be noted that the integral average heating rate A / B in the drying step of the first coating film was 6.5 °C / min.

[0324] In addition, the annular belt A2 was cut in the same manner as the annular belt A1 to obtain a ring-shaped body with a width of 369 mm. The intermediate transfer belt thus produced was used as the belt A2.

[0325] It should be noted that the content of the conductive carbon particles in the belt A2 relative to the entire base layer was 22% by mass, and the content of the conductive carbon particles relative to the entire surface layer was 19% by mass.

[0326] In addition, for the belt A2, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method. As a result, the common logarithm of the volume resistivity was 11.8 (logΩ·cm), and the common logarithm of the surface resistivity was 12.0 (logΩ / suq.).

[0327] [Example A3]

[0328] <Manufacture of Belt A3>

[0329] In the drying step of the first coating film, a 15-minute drying treatment is carried out in an air atmosphere at 115°C instead of a 15-minute drying treatment in an air atmosphere at 140°C. Except for this, the annular belt A3 is obtained in the same manner as the annular belt A1. The overall film thickness of the annular belt A3 (the total film thickness of the base material layer and the surface layer) is 80 μm, of which the film thickness of the base material layer is 26.7 μm and the film thickness of the surface layer is 53.3 μm. It should be noted that the integrated average heating rate A / B in the drying step of the first coating film is 5.74 °C / min.

[0330] In addition, the annular belt A3 is cut in the same manner as the annular belt A1 to obtain A ring with a width of 369 mm. The intermediate transfer belt thus produced is used as belt A3.

[0331] It should be noted that the content of conductive carbon particles in belt A3 relative to the entire base material layer is 22% by mass, and the content of conductive carbon particles relative to the entire surface layer is 18% by mass.

[0332] In addition, for belt A3, the volume resistivity and the surface resistivity of the outer peripheral surface are measured by the above method. As a result, the common logarithm of the volume resistivity is 10.8 (logΩ·cm), and the common logarithm of the surface resistivity is 11.2 (logΩ / suq.).

[0333] [Example A4]

[0334] <Manufacture of Belt A4>

[0335] In the drying step of the second coating film, a 15-minute drying treatment is carried out in an air atmosphere at 135°C instead of a 15-minute drying treatment in an air atmosphere at 140°C. Except for this, the annular belt A4 is obtained in the same manner as the annular belt A1. The overall film thickness of the annular belt A4 (the total film thickness of the base material layer and the surface layer) is 80 μm, of which the film thickness of the base material layer is 26.7 μm and the film thickness of the surface layer is 53.3 μm. It should be noted that the integrated average heating rate A / B in the drying step of the first coating film is 5.9 °C / min.

[0336] In addition, the annular belt A4 is cut in the same manner as the annular belt A1 to obtain A ring with a width of 369 mm. The intermediate transfer belt thus produced is used as belt A4.

[0337] It should be noted that the content of conductive carbon particles in belt A4 relative to the entire base material layer is 22% by mass, and the content of conductive carbon particles relative to the entire surface layer is 18.2% by mass.

[0338] In addition, for Belt A4, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method, and as a result, the common logarithm of the volume resistivity was 11.3 (logΩ·cm), and the common logarithm of the surface resistivity was 11.3 (logΩ / suq.).

[0339] [Example B1]

[0340] [Production of Belt B1]

[0341] Prepare the same mold as the coated material used in the production of the annular Belt A1 and perform the same anti-sticking agent treatment.

[0342] Using the same spin coating method as the coating of Coating Liquid A1 in the production of the annular Belt A1, Coating Liquid B1 was coated on the outer peripheral surface of the coated material after the anti-sticking agent treatment. After forming the first coating film, the first coating film was dried in a drying oven at 140°C in an air atmosphere while rotating at 10 rpm for 15 minutes. It should be noted that the integrated average heating rate A / B in the drying step of the first coating film was 6.00°C / min.

[0343] Next, it was placed in an oven set to a temperature of 320°C for 4 hours to obtain the annular Belt B1. The overall film thickness (i.e., the film thickness of a single layer) of the annular Belt B1 was 80 μm.

[0344] The annular Belt B1 was removed from the mold and cut in the same way as the annular Belt A1 to obtain a ring-shaped body with a width of 369 mm. The intermediate transfer belt thus produced was used as Belt B1.

[0345] It should be noted that the content of the conductive carbon particles relative to the entire Belt B1 was 20% by mass.

[0346] In addition, for Belt B1, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method, and as a result, the common logarithm of the volume resistivity was 11.4 (logΩ·cm), and the common logarithm of the surface resistivity was 11.2 (logΩ / suq.).

[0347] [Example B2]

[0348] [Production of Belt B2]

[0349] In 1000 g of a fully aromatic polyimide varnish (solid content rate: 18 wt%, manufactured by Unitika, U-Imide KX, solvent: NMP), 36 g (20 phr) of oxidized gas black (channel black, manufactured by Orion Engineered Carbons S.A., FW200, number average primary particle size: 13 nm) as the first conductive carbon particles was added, and the resulting composition was passed through the pores of using a high-pressure collision type disperser (manufactured by Genus) at a pressure of 200 MPa, and at the same time, the operation of colliding the slurry divided into two parts was performed 5 times for dispersion, to obtain coating liquid B2 as the first coating liquid.

[0350] The obtained coating liquid B2 was applied by the flow coating method in such a manner as to obtain a specified film thickness on the outer surface of the SUS pipe of . After rotary drying at 150 °C for 30 minutes, it was placed in an oven at 320 °C for 4 hours and then taken out, thereby obtaining an SUS pipe with an annular band B2 formed on the outer surface. The overall film thickness (i.e., the film thickness of a single layer) of the annular band B2 was 80 μm. It should be noted that the integrated average heating rate A / B in the drying step was 8.0 °C / min.

[0351] The annular band B2 coated on the outer surface was removed from the SUS pipe and cut into a width of 369 mm to obtain band B2 as the strip-shaped intermediate transfer body. It should be noted that the content of the conductive carbon particles in the entire band B2 was 22 mass%.

[0352] In addition, for band B2, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method. As a result, the common logarithm of the volume resistivity was 10.1 (logΩ·cm), and the common logarithm of the surface resistivity was 10.0 (logΩ / suq.).

[0353] [Example B3]

[0354] [Production of Band B3]

[0355] Using 37.8 g (21 phr) of oxidized gas black (channel black, manufactured by Orion Engineered Carbons S.A., FW200, number average primary particle size: 13 nm) as the first conductive carbon particles, the operation of colliding the slurry was performed 10 times using a high-pressure collision type disperser (manufactured by Genus). Except for this, in the same manner as in Example B2, an annular band B3 was obtained, and band B3 as the strip-shaped intermediate transfer body was obtained. The overall film thickness (i.e., the film thickness of a single layer) of the annular band B3 was 80 μm. In addition, the content of the conductive carbon particles in the entire annular band B3 was 21.5 mass%.

[0356] In addition, for Belt B3, the volume resistivity and the surface resistivity of the outer peripheral surface were measured using the above method. As a result, the common logarithm of the volume resistivity was 10.0 (logΩ·cm), and the common logarithm of the surface resistivity was 9.8 (logΩ / suq.).

[0357] [Example B4]

[0358] <Manufacture of Belt B4>

[0359] As the first conductive carbon particles, 39.6 g (22 phr) of oxidized gas black (channel black, manufactured by Orion Engineered Carbons S.A., FW200, number average primary particle size: 13 nm) was used, and the operation of colliding the slurry was performed 20 times using a high-pressure collision type disperser (manufactured by Genus). Except for this, Belt B4 as a belt-shaped intermediate transfer body was obtained in the same manner as in Example B2. The overall film thickness (i.e., the film thickness of a single layer) of the annular Belt B4 was 80 μm. In addition, the content of the conductive carbon particles relative to the entire Belt B4 was 22.5% by mass.

[0360] In addition, for Belt B4, the volume resistivity and the surface resistivity of the outer peripheral surface were measured using the above method. As a result, the common logarithm of the volume resistivity was 9.8 (logΩ·cm), and the common logarithm of the surface resistivity was 9.5 (logΩ / suq.).

[0361] [Example B5]

[0362] <Manufacture of Belt B5>

[0363] As the first conductive carbon particles, 43.2 g (24 phr) of oxidized gas black (channel black, manufactured by Orion Engineered Carbons S.A., SB6, number average primary particle size: 17 nm) was used, and the operation of colliding the slurry was performed 20 times using a high-pressure collision type disperser (manufactured by Genus). Except for this, Belt B5 as a belt-shaped intermediate transfer body was obtained in the same manner as in Example B2. The overall film thickness (i.e., the film thickness of a single layer) of the annular Belt B5 was 80 μm. In addition, the content of the conductive carbon particles relative to the entire Belt B5 was 24.6% by mass.

[0364] In addition, for Belt B5, the volume resistivity and the surface resistivity of the outer peripheral surface were measured using the above method. As a result, the common logarithm of the volume resistivity was 9.9 (logΩ·cm), and the common logarithm of the surface resistivity was 9.6 (logΩ / suq.).

[0365] [Example B6]

[0366] <Manufacture of Belt B6>

[0367] - Formation and Drying of the First Coating Film -

[0368] On the outer periphery of a SUS mold with an outer diameter of 366 mm and a thickness of 10 mm, a polyimide precursor solution (coating solution B1) was coated by the flow coating method in a manner to obtain a desired film thickness to form the first coating film, and drying was performed as follows.

[0369] Specifically, a slit nozzle (manufactured by Daiho Kenki Co., Ltd., DLX series, slit width 0.8 mm) provided at the ejection part of a downflow hot air drying furnace was used, the wind speed near the mold was set to 6 m / s, and heating was carried out at 200 °C for 24 minutes. The integrated average heating rate A / B in the drying step was 5.74 °C / min.

[0370] After drying, firing was carried out at 320 °C for 4 hours to obtain an annular belt B6. The overall film thickness (i.e., the film thickness of a single layer) of the annular belt B6 was 80 μm.

[0371] The obtained annular belt B6 was demolded and cut to a bandwidth of 369 mm to obtain a belt B6. The content of conductive carbon particles relative to the entire belt B6 was 19% by mass.

[0372] In addition, for the belt B6, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method. As a result, the common logarithm of the volume resistivity was 11.5 (logΩ·cm), and the common logarithm of the surface resistivity was 11.3 (logΩ / suq.).

[0373] [Example B7]

[0374] <Fabrication of Belt B7>

[0375] In the drying step, heating at 235 °C for 21 minutes using a slit nozzle was performed instead of heating at 200 °C for 24 minutes using a slit nozzle. Except for this, an annular belt B7 was obtained in the same manner as the annular belt B6. It should be noted that the integrated average heating rate A / B in the drying step was 6.84 °C / min, and the overall film thickness (i.e., the film thickness of a single layer) of the annular belt B7 was 80 μm.

[0376] The obtained annular belt B7 was demolded and cut to a bandwidth of 369 mm to obtain a belt B7. The content of conductive carbon particles relative to the entire belt B7 was 19% by mass.

[0377] In addition, for the belt B7, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method. As a result, the common logarithm of the volume resistivity was 11.6 (logΩ·cm), and the common logarithm of the surface resistivity was 11.4 (logΩ / suq.).

[0378] [Example B8]

[0379] <Manufacture of Belt B8>

[0380] In the drying step, instead of using a slit nozzle to heat at 200 °C for 24 minutes, a slit nozzle is used to make the wind speed near the mold 16 m / s and heat at 200 °C for 16 minutes. Except for this, the annular belt B8 is obtained in the same manner as the annular belt B6. It should be noted that the integral average heating rate A / B in the drying step is 9.56 °C / min, and the overall film thickness of the annular belt B8 (i.e., the film thickness of a single layer) is 80 μm.

[0381] The obtained annular belt B8 is demolded and cut according to a bandwidth of 369 mm to obtain belt B8. The content of the conductive carbon particles relative to the whole of belt B8 is 19% by mass.

[0382] In addition, for belt B8, the volume resistivity and the surface resistivity of the outer peripheral surface are measured by the above method. As a result, the common logarithm of the volume resistivity is 11.2 (logΩ·cm), and the common logarithm of the surface resistivity is 11.1 (logΩ / suq.).

[0383] [Example C1]

[0384] <Manufacture of Belt C1>

[0385] Add 37.8 g (22 phr) of oxidized gas black (channel black, manufactured by Orion Engineered Carbons S.A., FW200, number average primary particle size: 13 nm), which is the first conductive carbon particle, to 1000 g of an aromatic polyamideimide varnish (solid content rate 18 wt%, HPC-9000 manufactured by Hitachi Chemical Co., Ltd., solvent: NMP). The obtained composition is passed through the holes at a pressure of 200 MPa by a high-pressure collision type disperser (manufactured by Genus), and is dispersed by performing an operation of colliding the slurry divided into two parts 10 times to obtain coating liquid C1 as the first coating liquid.

[0386] Prepare the same mold as the coated material used in the manufacture of the annular belt A1 and perform the same anti-sticking agent treatment.

[0387] Using the same spin coating method as the coating of coating liquid A1 in the manufacture of the annular belt A1, coating liquid C1 is coated on the outer peripheral surface of the above-mentioned coated material after the anti-sticking agent treatment. After forming the first coating film, the first coating film is dried in a drying furnace at 150 °C in an air atmosphere while rotating at 10 rpm for 15 minutes. It should be noted that the integral average heating rate A / B in the drying step of the first coating film is 6.0 °C / min.

[0388] Next, it was placed in an oven set to a temperature of 290 °C for 4 hours to obtain an annular belt C1. The overall film thickness of the annular belt C1 (i.e., the film thickness of a single layer) was 80 μm.

[0389] The annular belt C1 was removed from the mold and cut in the same manner as the annular belt A1 to obtain a ring-shaped body with a width of 369.5 mm. The intermediate transfer belt thus produced was designated as belt C1.

[0390] It should be noted that the content of the conductive carbon particles relative to the entire belt C1 was 19% by mass.

[0391] In addition, for belt C1, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method. As a result, the common logarithm of the volume resistivity was 11.2 (log Ω·cm), and the common logarithm of the surface resistivity was 11.2 (log Ω / suq.).

[0392] [Example C2]

[0393] [Production of Belt C2]

[0394] To 1000 g of an aromatic polyamideimide varnish (solid content rate 18 wt%, manufactured by Hitachi Chemical Co., Ltd., HPC-9000, solvent: NMP), 37.8 g (22 phr) of oxidized gas black (channel black, manufactured by Orion Engineered Carbons S.A., FW200, number average primary particle size: 13 nm) as the first conductive carbon particles was added, and the resulting composition was passed through holes at a pressure of 200 MPa using a high-pressure collision type disperser (manufactured by Genus), and dispersion was carried out by performing an operation of colliding the slurry divided into two parts 10 times to obtain a coating liquid C2 as the first coating liquid.

[0395] The obtained coating liquid C2 was applied to the outer surface of a SUS tube by the flow coating method in a manner to obtain a specified film thickness. After rotary drying at 150 °C for 30 minutes, it was taken out after being placed in an oven at 290 °C for 1 hour, thereby obtaining a SUS tube with an annular belt C2 formed on its outer surface. The overall film thickness of the annular belt C2 (i.e., the film thickness of a single layer) was 80 μm. It should be noted that the integrated average heating rate A / B in the drying step was 7.2 °C / min.

[0396] The annular belt C2 coated on the outer surface was removed from the SUS tube and cut into a width of 369 mm to obtain a belt C2 as a strip-shaped intermediate transfer body. It should be noted that the content of the conductive carbon particles relative to the entire belt C2 was 19% by mass.

[0397] ​In addition, for Belt C2, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method. As a result, the common logarithm of the volume resistivity was 10.3 (logΩ·cm), and the common logarithm of the surface resistivity was 10.2 (logΩ / sq.).

[0398] [Example C3]

[0399] <Manufacture of Belt C3>

[0400] As the first conductive carbon particles, 36 g (20 phr) of acetylene black (channel black, manufactured by Orion Engineered Carbons S.A., FW1, number average primary particle diameter: 13 nm) was used, and the operation of colliding the slurry was performed 20 times using a high-pressure collision type disperser (manufactured by Genus). Except for this, Belt C3 was obtained in the same manner as in Example C2, and Belt C3 as a belt-shaped intermediate transfer body was obtained. The overall film thickness (i.e., the film thickness of a single layer) of Belt C3 was 80 μm. In addition, the content of the conductive carbon particles relative to the entire Belt C3 was 19% by mass.

[0401] In addition, for Belt C3, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method. As a result, the common logarithm of the volume resistivity was 10.1 (logΩ·cm), and the common logarithm of the surface resistivity was 9.9 (logΩ / sq.).

[0402] [Example D1]

[0403] <Manufacture of Belt D1>

[0404] PEEK resin pellets (450G manufactured by Victrex) and furnace black (the first conductive carbon particles, manufactured by Orion Engineered Carbons S.A., FW171, number average primary particle diameter: 11 nm) were put into a Henschel mixer (FM10C manufactured by Nippon Cokes) in a ratio of 180 g of PEEK resin and 27 g (15 phr) of furnace black, and mixed. The mixture obtained was melt-kneaded using a twin-screw extrusion melt-kneader (L / D60, manufactured by Parker Corporation), and the kneaded product was extruded in a rope shape from a hole with a diameter of 5 mm. The extruded product was put into a water tank, cooled and solidified, and then cut to obtain mixed resin pellets containing furnace black.

[0405] The obtained mixed resin pellets are put into a single-screw melt extruder (L / D 24, melt extrusion device manufactured by Mitsuboshi Seisakusho Co., Ltd.) set at a specified temperature (380 °C), and are extruded into a cylindrical shape through the gap between an annular die head and a nipple under melting. In order to fix the cylindrical shape and diameter of the film while taking out the cylindrical film at the take-out position, the inner peripheral surface of the cylindrical film is brought into contact with a sizing die (cooling die) set at a specified temperature (50 °C) for cooling, to obtain an endless belt D1.

[0406] The endless belt D1 is removed from the cooling die, and the taken-out endless belt D1 is tensioned and mounted on a holder, and is cut with a cutter with an adjusted insertion angle, to obtain an endless body with a width of 369 mm. The intermediate transfer belt thus produced is used as the belt D1. The overall film thickness (i.e., the film thickness of a single layer) of the belt D1 is 80 μm.

[0407] It should be noted that the content of the conductive carbon particles relative to the entire belt D1 is 13% by mass.

[0408] In addition, for the belt D1, the volume resistivity and the surface resistivity of the outer peripheral surface are measured by the above method, and as a result, the common logarithm of the volume resistivity is 11.1 (logΩ·cm), and the common logarithm of the surface resistivity is 11.3 (logΩ / suq.).

[0409] [Example E1]

[0410] <Production of endless belt E1>

[0411] PPS resin (Torelina T1881 manufactured by Toray) powder and channel black (the first conductive carbon particles, channel black, manufactured by Orion Engineered Carbons S.A., FW1, number-average primary particle diameter: 13 nm) are put into a Henschel mixer (FM10C manufactured by Nippon Cokes) in a ratio of 180 g of PPS resin and 27 g (15 phr) of channel black (i.e., channel black), and are mixed. The obtained composition is melt-kneaded using a twin-screw extrusion melt-kneader (L / D 60 (manufactured by Parker Corporation)), and the obtained kneaded product is extruded in a string shape through the holes, and the extruded product is put into a water tank, cooled and solidified, and then cut, to obtain mixed resin pellets compounded with channel black (i.e., channel black).

[0412] The obtained mixed resin pellets are put into a single-screw melt extruder (L / D 24, melt extrusion device manufactured by Mitsuboshi Seisakusho Co., Ltd.) set at a specified temperature (350 °C), and are extruded in a molten state into a cylindrical shape through the gap between the annular die head and the pipe joint. In order to fix the cylindrical shape and diameter of the film while taking up the extruded cylindrical film, the inner peripheral surface of the cylindrical film is brought into contact with a finishing die (cooling die) set at a specified temperature (50 °C) for cooling, thereby obtaining an annular belt E1.

[0413] The annular belt E1 is removed from the cooling die, and the pulled-out annular belt E1 is tensioned and mounted on a holder, and is cut with a cutter having an adjusted insertion angle to obtain a ring-shaped body with a width of 369 mm. The intermediate transfer belt thus produced is used as belt E1. The overall film thickness (i.e., the film thickness of a single layer) of belt E1 is 80 μm.

[0414] It should be noted that the content of the conductive carbon particles relative to the entire belt E1 is 13% by mass.

[0415] In addition, for belt E1, the volume resistivity and the surface resistivity of the outer peripheral surface are measured by the above method. As a result, the common logarithm of the volume resistivity is 10.9 (log Ω·cm), and the common logarithm of the surface resistivity is 11.2 (log Ω / sq.).

[0416] [Comparative Example F1]

[0417] [Production of Belt F1]

[0418] A mold identical to the coated material used in the production of the annular belt A1 is prepared, and the same anti-sticking agent treatment is performed.

[0419] Using the same spin coating method as the coating of coating liquid A1 in the production of the annular belt A1, coating liquid A1 is coated on the outer peripheral surface of the coated material after the above anti-sticking agent treatment. After forming a coating film, the coating film is dried in a drying oven at 140 °C in an air atmosphere while rotating at 10 rpm for 15 minutes.

[0420] Next, it is placed in an oven set at a temperature of 320 °C for 4 hours to obtain an annular belt F1. The overall film thickness (i.e., the film thickness of a single layer) of the annular belt F1 is 80 μm.

[0421] The annular belt F1 is removed from the mold, and the same cutting as that of the annular belt A1 is performed to obtain a ring-shaped body with a width of 369.5 mm. The intermediate transfer belt thus produced is used as belt F1.

[0422] It should be noted that the content of the conductive carbon particles relative to the entire belt F1 is 19% by mass.

[0423] In addition, for Belt F1, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method. As a result, the common logarithm of the volume resistivity was 11.1 (logΩ·cm), and the common logarithm of the surface resistivity was 11.1 (logΩ / suq.).

[0424] [Comparative Example F2]

[0425] <Manufacture of Belt F2>

[0426] In the drying step, instead of using the slit nozzle to heat at 200°C for 24 minutes, the hot air of the drying furnace was directly supplied to the first coating film without using the slit nozzle, the wind speed near the die was 0.8 m / s, and it was heated at 200°C for 28 minutes. Except for this, the annular belt F2 was obtained in the same manner as the annular belt B6. It should be noted that the integrated average heating rate A / B was 3.55°C / min, and the overall film thickness of the annular belt F2 (i.e., the film thickness of a single layer) was 80 μm.

[0427] The obtained annular belt F2 was demolded and cut according to a bandwidth of 369 mm to obtain Belt F2. The content of the conductive carbon particles relative to the whole of Belt F2 was 19% by mass.

[0428] In addition, for Belt F2, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method. As a result, the common logarithm of the volume resistivity was 11.8 (logΩ·cm), and the common logarithm of the surface resistivity was 13.1 (logΩ / suq.).

[0429] [Comparative Example F3]

[0430] <Manufacture of Belt F3>

[0431] In the drying step, instead of using the slit nozzle to heat at 200°C for 24 minutes, the hot air of the drying furnace was directly supplied to the first coating film without using the slit nozzle, the wind speed near the die was 0.9 m / s, and it was heated at 235°C for 24 minutes. Except for this, the annular belt F3 was obtained in the same manner as the annular belt B6. It should be noted that the integrated average heating rate A / B was 4.36°C / min, and the overall film thickness of the annular belt F3 (i.e., the film thickness of a single layer) was 80 μm.

[0432] The obtained annular belt F3 was demolded and cut according to a bandwidth of 369 mm to obtain Belt F3. The content of the conductive carbon particles relative to the whole of Belt F3 was 18% by mass.

[0433] In addition, for Belt F3, the volume resistivity and the surface resistivity of the outer peripheral surface were measured by the above method. As a result, the common logarithm of the volume resistivity was 12.2 (logΩ·cm), and the common logarithm of the surface resistivity was 12.8 (logΩ / suq.).

[0434] [Measurement of the annular belt]

[0435] For the obtained annular belt, the integral value of L(r) and the potential decay rate (V / msec) are respectively obtained by using the above method. The results are shown in Table 1.

[0436] In addition, the layer structure of the annular belt, the type of resin contained in the single layer or the first layer, and the average primary particle diameter of the number of conductive carbon particles contained in the single layer or the first layer are also shown in Table 1.

[0437] [Evaluation of the annular belt (1)]

[0438] [Evaluation of the transferability to the embossed paper (1)]

[0439] The obtained transfer belt is assembled into a modified machine of DocuColor-7171P (that is, after installing the transfer belt, the modified machine with the cleaning blade adjusted according to the film thickness of the belt), and a blue solid image is formed on the embossed paper (Lesac 66, 204 gsm) under the conditions of an environment of temperature 22°C and humidity 55RH% and a conveying speed of the recording medium in the secondary transfer area of 308 mm / s, and the white showing in the concave part is visually evaluated. The evaluation criteria are as follows, and the results are shown in Table 1.

[0440] It should be noted that as the primary transfer roller, the following conductive roller (1) is used.

[0441] In addition, as the toner, a toner with a volume average particle diameter of 4.7 μm is used.

[0442] -Evaluation criteria-

[0443] A: No white showing occurred

[0444] B: Some color changes occurred

[0445] C: Clear color changes occurred

[0446] D: White showing occurred

[0447] [Manufacture of the conductive roller (1)]

[0448] 40 parts by mass of an epoxy chloropropane-allyl glycidyl ether binary copolymer (ECO) (manufactured by Zeon Corporation, Japan, trade name: Gechron 1100)

[0449] 60 parts by mass of nitrile rubber (NBR) (manufactured by Zeon Corporation, Japan, trade name: Nipol DN223)

[0450] 6 parts by mass of a foaming agent (benzenesulfonyl hydrazide)

[0451] 1 part by mass of vulcanizing agent (manufactured by Tsurumi Chemical Industry Co., Ltd., trade name: Sulfur, 200 mesh)

[0452] 1.5 parts by mass of vulcanization accelerator (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: NOCCELER M)

[0453] The rubber composition containing the above components was kneaded using an open mill. The kneaded rubber composition was extruded in a state with a hole in the center (doughnut shape) and formed into a cylindrical roller. Then, the cylindrical roller was heated at 160 °C for 20 minutes to perform vulcanization foaming, and a conductive roller (1) was obtained.

[0454] [Table 1]

[0455]

[0456] [Evaluation of the endless belt (2)]

[0457] [Evaluation of the transferability to the embossed paper (2)]

[0458] The obtained transfer belt was assembled into a modified machine of DocuColor-7171P (that is, after installing the transfer belt, the modified machine with the cleaning blade adjusted according to the film thickness of the belt). The conductive roller shown in Table 2 was used as the primary transfer roller. Under the environment of a temperature of 22 °C and a humidity of 55 RH% (in the "normal environment" of Table 2) and a temperature of 10 °C and a humidity of 15 RH% (in the "low temperature and low humidity" of Table 2), and under the condition that the recording medium conveyance speed in the secondary transfer area was 308 mm / s, a blue solid image was formed on the embossed paper (Lesac 66, 204 gsm), and the white showing through in the concave part was visually evaluated. The evaluation criteria are as described below, and the results are shown in Table 2.

[0459] It should be noted that as the toner, a toner with a volume average particle diameter of 4.7 μm was used.

[0460] - Evaluation criteria -

[0461] A: No white showing through occurred

[0462] B+: Slight color change occurred

[0463] B: Some color change occurred

[0464] C: Clear color change occurred

[0465] D: White showing through occurred

[0466] [Discharge defect evaluation]

[0467] The obtained transfer belt was assembled into a modified machine of DocuColor-7171P (i.e., after installing the transfer belt, the modified machine with the cleaning blade adjusted according to the film thickness of the belt), and the conductive rollers shown in Table 2 were used as the primary transfer rollers. A K-color semi-toning 50% image was formed on a fiberless paper (84 gsm) in an environment of 28°C and 85% humidity (high temperature and high humidity), and the number of white dots generated in the image was visually evaluated to conduct a discharge defect evaluation. The evaluation criteria are as follows, and the results are shown in Table 2.

[0468] - Evaluation Criteria -

[0469] A: No white dots were generated.

[0470] B: Several white dots were generated.

[0471] C: Multiple white dots were generated in part.

[0472] D: Multiple white dots were generated on the entire surface.

[0473] It should be noted that the conductive rollers (1) to (3) shown in Table 2 are rollers made as follows.

[0474] <Manufacture of Conductive Roller (1)>

[0475] 40 parts by mass of an epichlorohydrin-allyl glycidyl ether binary copolymer (ECO) (manufactured by Zeon Corporation, Japan, trade name: Gechron 1100)

[0476] 60 parts by mass of nitrile rubber (NBR) (manufactured by Zeon Corporation, Japan, trade name: Nipol DN223)

[0477] 6 parts by mass of a foaming agent (benzenesulfonyl hydrazide)

[0478] 1 part by mass of a vulcanizing agent (manufactured by Tsurumi Chemical Industry Co., Ltd., trade name: Sulfur, 200 mesh)

[0479] 1.5 parts by mass of a vulcanization accelerator (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: NOCCELER M)

[0480] The rubber composition containing the above components was kneaded using an open mill. The kneaded rubber composition was extruded in a state with a hole in the center (doughnut shape) and formed into a cylindrical roller. Then, the cylindrical roller was heated at 160°C for 20 minutes for vulcanization and foaming to obtain the conductive roller (1).

[0481] <Manufacture of Conductive Roller (2)>

[0482] 40 parts by mass of epichlorohydrin-allyl glycidyl ether binary copolymer (ECO) (manufactured by Zeon Corporation, Japan, trade name: Gechron 1100)

[0483] 60 parts by mass of nitrile rubber (NBR) (manufactured by Zeon Corporation, Japan, trade name: Nipol DN223)

[0484] 10 parts by mass of carbon black 1 (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name: granular acetylene black)

[0485] 50 parts by mass of carbon black 2 (manufactured by Asahi Carbon Co., Ltd., trade name: Asahi Thermal FT)

[0486] 6 parts by mass of foaming agent (benzenesulfonyl hydrazide)

[0487] 1 part by mass of vulcanizing agent (manufactured by Tsurumi Chemical Industry Co., Ltd., trade name: Sulfur, 200 mesh)

[0488] 1.5 parts by mass of vulcanization accelerator (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name: NOCCELER M)

[0489] The rubber composition containing the above components is kneaded using a two-roll mill. The kneaded rubber composition is extruded in a state with a hole in the center (doughnut shape) and formed into a cylindrical roller. Then, the cylindrical roller is heated at 160 °C for 20 minutes to perform vulcanization foaming, obtaining a conductive roller (2).

[0490] <Manufacture of Conductive Roller (3)>

[0491] A conductive roller (3) is obtained in the same manner as the conductive roller (2), except that the vulcanization foaming temperature is changed from 160 °C to 140 °C.

[0492] It should be noted that in Table 2, the "initial resistance" refers to the initial resistance at a temperature of 22 °C and a humidity of 55 RH%, the "resistance environmental change" refers to the value obtained by the above method, the "resistance at low temperature and low humidity" refers to the resistance at a temperature of 10 °C and a humidity of 15 RH%, and the "resistance at high temperature and high humidity" refers to the resistance at a temperature of 28 °C and a humidity of 85 RH%.

[0493] In addition, the "power supply capacity" is the maximum capacity of the power supply for supplying power to the conductive roller.

[0494] [Table 2]

[0495]

[0496] As can be seen from the results shown in Table 1 and Table 2 above, compared with the belt of the comparative example, the belt of the present embodiment has excellent transferability even when using a recording medium with large surface irregularities.

Claims

1. An annular belt, wherein, the annular belt contains a first resin and first conductive carbon particles, in the spatial distribution of the first conductive carbon particles present in an evaluation area of 6.3 μm × 4.2 μm on the outer peripheral surface, the integral value of the statistic L(r) represented by the following formula (1) where the inter-particle distance r is 0.05 μm or more and 0.30 μm or less is 0 or more and 0.1 or less, in the above formula (1), r represents the inter-particle distance, and K(r) represents Ripley's K function K(r) represented by the following formula (2), In the above formula (2), 1(|X i -X j |≤r) represents an indicator function, X i and X j represent the coordinates of point i and point j respectively, |X i -X j | represents the Euclidean distance between the coordinate X i and the coordinate X j , r represents the above-mentioned inter-particle distance, s(|X i -X j |) represents the edge correction coefficient s(x) of the evaluation region represented by the following formula (3), x = |X i -X j |, N represents the total number of particles in the evaluation region, and λ represents the number density of particles in the evaluation region. In the above formula (3), L x and L y represent the lengths (μm) of the sides in the x-axis and y-axis directions of each evaluation region, x = |X i −X j |, X i and X j represent the coordinates of point i and point j respectively, and |X i −X j | represents the Euclidean distance between the coordinate X i and the coordinate X j .

2. The endless belt according to claim 1, wherein, the first resin contains at least one selected from the group consisting of a polyimide resin, a polyamideimide resin, an aromatic polyetheretherketone resin, a polyphenylene sulfide resin, and a polyetherimide resin.

3. The endless belt according to claim 2, wherein, The first resin contains a polyimide resin.

4. The endless belt according to any one of claims 1 to 3, wherein, The potential decay rate dV / dt after charging the outer peripheral surface of the annular belt to +500 V is 2.0 V / msec or more and 6.0 V / msec or less.

5. The annular belt according to claim 1, which has: a base material layer, and a surface layer provided on the base material layer, containing the first resin and the first conductive carbon particles.

6. The annular belt according to claim 5, wherein, the base material layer contains a second resin and second conductive carbon particles, the number average primary particle diameter of the first conductive carbon particles is smaller than the number average primary particle diameter of the second conductive carbon particles.

7. The endless belt according to claim 1, wherein, The number average primary particle diameter of the first conductive carbon particles is 10 nm or more and 20 nm or less.

8. The endless belt according to claim 7, wherein, The number average primary particle diameter of the first conductive carbon particles is 10 nm or more and 15 nm or less.

9. The endless belt according to claim 1, wherein, The first resin contains at least one selected from the group consisting of a polyimide resin and a polyamideimide resin, and the first conductive carbon particles contain channel black.

10. The endless belt according to claim 1, wherein, The first resin contains at least one selected from the group consisting of an aromatic polyetheretherketone resin, a polyphenylene sulfide resin, and a polyetherimide resin, and the first conductive carbon particles contain at least one selected from the group consisting of channel black and furnace black.

11. A method for manufacturing an annular belt, the annular belt contains a first resin and first conductive carbon particles, and in the spatial distribution of the first conductive carbon particles present in an evaluation area of 6.3 μm × 4.2 μm on the outer peripheral surface, the integral value of the statistic L(r) represented by the following formula (1) where the inter-particle distance r is 0.05 μm or more and 0.30 μm or less is 0 or more and 0.1 or less, the manufacturing method includes the following steps: a coating liquid preparation step of preparing a coating liquid containing the first resin or its precursor, the first conductive carbon particles, and a solvent, a coating film formation step of coating the coating liquid on the outer periphery of the material to be coated to form a coating film, and A drying step of drying the coating film while raising the temperature of the coated material, wherein when the integrated average value of the temperature of the coated material during the drying is set to A °C and the time from the start of the drying until the temperature of the coated material reaches the integrated average value A °C is set to B min, the integrated average heating rate A / B (°C / min) is 5.74 °C / min or more. In the above formula (1), r represents the interparticle distance, and K(r) represents the Ripley's K function K(r) represented by the following formula (2). In the above formula (2), 1(|X i −X j |≤r) represents an indicator function, X i and X j represent the coordinates of point i and point j respectively, |X i −X j | represents the Euclidean distance between the coordinate X i and the coordinate X j , r represents the above-mentioned inter-particle distance, s(|X i −X j |) represents the edge correction coefficient s(x) of the evaluation region represented by the following formula (3), x = |X i −X j |, N represents the total number of particles in the evaluation region, and λ represents the number density of particles in the evaluation region. In the above formula (3), L x and L y represent the lengths (μm) of the sides in the x-axis and y-axis directions of each evaluation region, x = |X i −X j |, X i and X j represent the coordinates of point i and point j respectively, and |X i −X j | represents the Euclidean distance between the coordinate X i and the coordinate X j .

12. The manufacturing method of the endless belt according to claim 11, wherein, The above drying step is a step of drying the coating film by supplying hot air with a temperature of 110 °C or more and 235 °C or less to the coating film.

13. The manufacturing method of the endless belt according to claim 12, wherein, The hot air velocity on the surface of the above coating film is 1 m / s or more and 20 m / s or less.

14. The manufacturing method of the endless belt according to claim 12 or claim 13, wherein, The above hot air is supplied to the coating film by blowing it from a slit nozzle toward the surface of the coating film.

15. The method for manufacturing an endless belt according to claim 11, further comprising a firing step of firing the coating film dried by the above drying step.

16. The method for manufacturing an endless belt according to claim 11, which is a method for manufacturing the endless belt according to any one of claims 1 to 10.

17. A transfer device, comprising: An intermediate transfer member, which is the endless belt according to any one of claims 1 to 10, A primary transfer mechanism for primarily transferring the toner image formed on the surface of the image holding member to the surface of the intermediate transfer member, and A secondary transfer mechanism for secondarily transferring the toner image transferred to the surface of the intermediate transfer member to the surface of the recording medium.

18. The transfer device according to claim 17, wherein, The above primary transfer mechanism includes a conductive roller having a foamed elastic layer on its outermost layer, and the difference between the common logarithm of the resistance value of the foamed elastic layer under the conditions of a temperature of 28 °C and a humidity of 85 RH% and the common logarithm of the resistance value under the conditions of a temperature of 10 °C and a humidity of 15 RH% is 0.1 (logΩ) or more and 0.6 (logΩ) or less.

19. The transfer device according to claim 18, wherein, The above foamed elastic layer contains epichlorohydrin rubber and an electron-conductive conductive agent.

20. An image forming apparatus, comprising: An image holding member, A charging device for charging the surface of the above image holding member, An electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged image holding member, A developing device for storing a developer containing toner and developing the electrostatic latent image formed on the surface of the image holding member with the above developer to form a toner image, and The transfer device according to any one of claims 17 to 19 for transferring the above toner image to the surface of the recording medium.

21. The image forming apparatus according to claim 20, wherein, The volume average particle diameter of the above toner is 2 μm or more and 5 μm or less.

Images