JP2004077727A - Transfer roll and transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device with a long service life in which the occurrence of transfer failure due to variation in the environment is prevented by preventing the occurrence of variation of volume resistivity in the axial direction of a transfer roll due to the environmental variation and in which the occurrence of transfer failure due to environmental variation is prevented. <P>SOLUTION: A transfer roll BTR in which a cylindrical semi-conductive resin layer 2 formed on the surface of core metal 1 is coated with a water-tight and semi-conductive surface layer 3 is provided with a semi-conductive resin layer 2 in which the axial central part is easily influenced by open air, a semi-conductive resin layer 2 in which the axial end parts is hardly influenced by the open air or a semi-conductive resin layer 2 in which the resistive environment dependency is below a fixed value are provided. Moreover, the transfer device is provided with a transfer roll BTR in which the surface layer 3 is formed by polyimide resin or polyetherimide resin and a transfer roll cleaner CL with a metallic cleaning blade CLb provided with a blade tip part abutting on the transfer roll surface. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transfer roll that transfers a toner image on an image carrier to a recording material when the recording material is nipped and conveyed (nipped and conveyed) between the recording material and an image carrier of an electrophotographic image forming apparatus. With respect to a transfer device provided with the transfer roll, in particular, a metal core, a cylindrical semiconductive resin layer formed on the outer peripheral surface of the metal core, and a surface covering the outer peripheral surface of the semiconductive resin layer The present invention relates to a transfer roll having a layer (resin tube) and a transfer device having the transfer roll and a cleaner for cleaning the transfer roll.
[0002]
[Prior art]
Conventionally, in an image forming apparatus employing the above-described electrophotographic recording method, a device capable of forming a color image with high speed and high image quality includes four images each forming a single color toner image of yellow, magenta, cyan, and black. The forming units are arranged in parallel with each other, and the yellow, magenta, cyan, and black single-color toner images sequentially formed by these image forming units are directly transferred onto a transfer sheet carried on a transfer material conveying belt. A color image is formed by transferring the image in a multiplex manner or once on the intermediate transfer belt, and then transferring the image onto the transfer sheet from the intermediate transfer belt and fixing the toner image on the transfer sheet. Various image forming apparatuses configured as described above have been proposed and actually commercialized.
[0003]
By the way, in the case of such an image forming apparatus, a transfer material transport belt made of a flexible member or an intermediate transfer belt also made of a flexible member is used. The intermediate transfer belt is stretched between a plurality of rolls so as to be circulated and driven across the four image forming units of yellow, magenta, cyan, and black. Therefore, meandering occurs, expansion and contraction occurs due to temperature change, and the like, and a technique for preventing image displacement is essential. Further, since the transfer material transport belt and the intermediate transfer belt are stretched over four image forming units, there is a problem that the size of the apparatus is increased.
[0004]
Therefore, as disclosed in Japanese Patent Application Laid-Open No. H10-78686, the present applicant can solve the above-described problem, simplify the configuration of the drive system, and reduce the size of the device. Further, an image forming apparatus capable of forming a high-quality color image without using a technique for preventing a complicated image from being misaligned has already been proposed.
[0005]
(Prior art described in JP-A-10-78686)
FIG. 10 is an explanatory diagram of a conventional technique disclosed in Japanese Patent Application Laid-Open No. 10-78686.
As shown in FIG. 10, in the conventional image forming apparatus, a unit structure including two photoconductors 101 and 102 and one transfer intermediate 151, two photoconductors 103 and 104 and one transfer intermediate 152, And the two transfer intermediates 151 and 152 are configured to be in contact with another transfer intermediate 153. The four photoconductors 101, 102, 103, 104 shown here have a common tangent line 100, and therefore a charging device arranged around these four photoconductors 101, 102, 103, 104 111, 121, 131, 141, exposure devices 112, 122, 132, 142, developing devices 113, 123, 133, 143, and cleaning devices 114, 124, 134, 144 are respectively photosensitive members 101, 102, 103, 104. Are arranged at the same position, and devices are shared for each device type.
[0006]
In the case of the image forming apparatus shown in FIG. 10, each toner image formed on the photoconductors 101 and 102 is transferred to the transfer intermediate body 153 after being transferred to the transfer intermediate body 151, and is transferred to the photoconductors 103 and 104. Each of the formed toner images is transferred to the transfer intermediate member 153 after being transferred to the transfer intermediate member 152, and the toner images transferred to the intermediate transfer member 153 are collectively transferred onto the conveyed paper P. The toner image transferred onto the paper P is fixed on the paper P by a fixing device (not shown). Since the transfer intermediates 151, 152, and 153 are of a drum type and are made of a rigid body, misregistration between toner images hardly occurs.
[0007]
When the cleaning devices 114, 124, 134, 144 for removing the transfer residual toner after the primary transfer are attached to the photoconductors 101, 102, 103, 104, the surfaces of the photoconductors 101, 102, 103, 104 are cleaned. The photoconductors 101, 102, 103, and 104 are scraped by the rubbing of the devices 114, 124, 134, and 144, and the thickness of the photoconductors 101, 102, 103, and 104 is shortened.
[0008]
Therefore, in order to extend the life of the photoconductors 101, 102, 103, and 104, the cleaning devices 114, 124, 134, and 144 are eliminated, and the intermediate transfer bodies 151, 152, and 153, and the photoconductors 101, 102, 103, and 104 are removed. There has been proposed an image forming apparatus of a type in which toner on other members is collected on a final transfer roll 161 using a potential gradient and collected by a cleaning device 171 attached to the final transfer roll 161.
[0009]
In an image forming apparatus of the type shown in FIG. 10 (the arrow in the figure indicates the direction of rotation of the roll), the surfaces of the rotating photoconductors 101, 102, 103, 104 are contact charging members 111, 121, 131, For example, by applying a voltage of about −1000 V to the memory 141, it is charged to about −500 V. Next, image exposure is performed on the surfaces of the photoconductors 101, 102, 103, and 104 by the exposure devices 112, 122, 132, and 142 to form electrostatic latent images. In this manner, the surface potential of the latent image portion on which the images of the photoconductors 101, 102, 103, and 104 are exposed is eliminated to about -100 V or less. Next, the electrostatic latent images on the surfaces of the photoconductors 101, 102, 103, and 104 are developed with negatively (-) charged toner by developing devices 113, 123, 133, and 143, respectively. , 104 are formed with toner images. The toner image formed on the surface of each of the photoconductors 101, 102, 103, and 104 has a surface of about +300 V (this surface potential is optimally set depending on the toner charging state, ambient temperature, and humidity). The image is electrostatically transferred onto the charged intermediate transfer members 151 and 152.
[0010]
On the intermediate transfer member 151 in contact with the photoconductors 101 and 102 and the intermediate transfer member 152 in contact with the photoconductors 103 and 104, a single color or two color toner image is superimposed. The surface of the toner images on the intermediate transfer members 151 and 152 is then charged to about +800 V (the surface potential is optimally set depending on the charged state of the toner, the ambient temperature, and the humidity). 153 is electrostatically transferred onto As a result, the toner image is superimposed on the intermediate transfer member 153. This toner image is transferred onto the sheet P by the final transfer roll 161 at the transfer portion.
[0011]
When the toner image passes through a transfer portion formed by the intermediate transfer members 151 and 152 and the photoconductors 101, 102, 103, and 104, a part of the negatively charged toner due to Paschen discharge or charge injection has an opposite polarity. The toner is charged and becomes a positively charged toner. This + charged toner is electrostatically attached to the photoconductors 101, 102, 103, and 104 without being transferred to the intermediate transfer bodies 151 and 152. The + charged toner adhered to the surfaces of the photoconductors 101, 102, 103, and 104 moves to the charged portions that come into contact with the contact charging members 111, 121, 131, and 141 together with the surfaces of the photoconductors 101, 102, 103, and 104. At this time, since the contact charging members 111, 121, 131, and 141 are more negatively charged than the surfaces of the photoconductors 101, 102, 103, and 104, the + toner is not charged. 141 electrostatically adheres to the surface.
In the portion where the toner adheres, the discharge becomes active, and the surface potential of the photoconductors 101, 102, 103, and 104 tends to increase (in the case of a charged photoconductor, it tends to be more strongly charged). Therefore, the surface potential of the photoconductors 101, 102, 103, and 104 becomes uneven at portions where the amount of toner adhered is large, small, and no. When the surface potential becomes uneven, even if the surfaces of the photoconductors 101, 102, 103, and 104 are exposed to form an electrostatic latent image, the latent image potential becomes uneven, resulting in a difference in the development amount. Therefore, when a halftone image is developed, density unevenness becomes conspicuous.
[0012]
Therefore, in the image forming apparatus configured as described above, the following operation is performed before or after the printing operation in order to remove the + charged toner attached to the contact charging members 111, 121, 131, and 141. Is done.
[0013]
A cleaning device 171 is attached to the final transfer roll 161 to electrically float the intermediate transfer member 153, the intermediate transfer member 152, and the intermediate transfer member 151, apply a negative polarity voltage to the final transfer roll 161, The surface of the transfer body 153 is negatively charged, and at the same time, the surfaces of the intermediate transfer body 152 and the intermediate transfer body 151 are negatively charged by the intermediate transfer body 153, thereby providing an electrical gradient to the photosensitive bodies 101 and 102. , 103, 104 plus the positive polarity toner adhered to the surfaces of the contact charging members 111, 121, 131, 141, and the + polar residue adhered to the surfaces of the photoconductors 101, 102, 103, 104 and the intermediate transfer bodies 151, 152, 153 The toner is attached to the final transfer roll 161 by electrostatically transferring and moving the toner to the final transfer roll 161. The cleaning device 171 collects these + charged toner.
[0014]
As the cleaning device 171, a blade cleaning device or a brush cleaning device is preferably used. A collection box or the like in which toner can be stored is attached to the cleaning device 171. In the same manner, the remaining negatively charged toner is collected.
[0015]
As the final transfer roll described above, a foamed roll provided with conductivity to a conductive tube made of polyimide disclosed in Japanese Patent Application Laid-Open No. 2002-182497 (a semiconductive cylindrical foam on the surface of a metal roll). A transfer roll of a type configured by inserting a roll on which a resin layer is formed, a semiconductive resin roll) is preferably used. This is because a guard resin (cylindrical resin) whose surface microhardness (surface hardness measured by pressing a micropart such as the tip of a needle) on the surface of the transfer roll is equal to or higher than a value corresponding to polyimide resin or polyetherimide resin. And a semiconductive resin layer that suppresses charge accumulation in the surface layer is provided as an underlayer of the surface layer (guard resin layer).
Furthermore, since there is a concern that image forming particles such as toner and its external additives may adhere to the surface of the transfer roll, from the viewpoint of cleaning the surface of the transfer roll, the surface layer (guard resin layer) of the transfer roll may be used. A mode in which a scraper (cleaning blade) for cleaning is arranged in contact is usually adopted.
[0016]
[Problems to be solved by the invention]
Prior art: Among transfer rolls disclosed in JP-A-2002-182497, there is a transfer roll of a type in which the surface of a semiconductive resin layer is covered with a conductive tube (cylindrical surface layer) made of polyimide. Hereinafter, the tubing BTR (BTR is also referred to as a bias transfer roll, that is, a transfer roll).
In the tubing BTR (transfer roll having a cylindrical surface layer), since both ends of the tube are open, both ends of the foam roll are more susceptible to the environment in which the apparatus is placed than the center of the foam roll. For example, when the device is placed in a high-humidity environment, the foam roll at the end absorbs moisture and lowers resistance, but since the center of the foam roll is less susceptible to outside air, the resistance is relatively higher than at the end. Would. Conversely, if the device is placed in a low-humidity environment, the foam roll at the end dehumidifies and increases resistance, but the center of the foam roll is less susceptible to outside air, so the resistance is relatively lower than at the end. turn into.
[0017]
As described above, the volume resistivity of the semiconductive resin layer of the tubing BTR (transfer roll in which the semiconductive resin layer is covered with the cylindrical surface layer) changes depending on the environment where the apparatus is placed. If the volume resistivity of the semiconductive resin layer varies in the axial direction of the tubing BTR, the following problem will occur.
Heretofore, it has been known that the transfer rate is reduced even when the transfer current is larger or smaller than the transfer current value (transfer current optimum value) at which the transfer rate of the toner is highest.
For example, if the volume resistivity at the end of the semiconductive resin layer of the tubing BTR decreases in a high humidity environment, the transfer current concentrates on the end of the BTR. If the transfer current is concentrated at the end of the BTR, the transfer current at the center of the BTR becomes insufficient. At this time, a transfer failure or the like occurs in an image portion corresponding to the central portion of the BTR having a relatively high volume resistivity. If the transfer current is increased in order to prevent this transfer failure, the transfer current at the end of the BTR becomes an overcurrent, and a transfer failure such as missing transfer occurs.
[0018]
Further, if the volume resistivity at the end of the BTR is increased in a low humidity environment, the transfer current is concentrated on the central portion of the BTR having a relatively low volume resistivity. If the transfer current is concentrated at the center of the BTR, the transfer current at the end of the BTR becomes insufficient. At this time, a transfer failure or the like occurs in an image portion corresponding to an end portion of the BTR having a relatively high volume resistivity. If the transfer current is increased in order to prevent this transfer failure, the transfer current becomes excessive at the center of the BTR, and transfer failures such as missing transfer and white spots occur.
[0019]
A transfer roll provided with a cylindrical surface layer (guard resin layer) whose surface microhardness is equal to or greater than that of a polyimide resin or a polyetherimide resin, abuts the blade tip of a metal cleaning blade on the transfer roll surface. Then, cleaning can be performed. A cleaning blade using a metal blade has high cleaning performance and a long life. For this reason, the transfer device in which the transfer roll provided with the cylindrical surface layer (guard resin layer) and the metal cleaning blade have a long service life and can reduce the manufacturing cost.
[0020]
The present invention has been made in view of the above circumstances and examination results, and has an object to be described in the following (O01) and (O02).
(O01) To prevent a variation in the volume resistivity of the transfer roll in the axial direction with respect to an environmental change, thereby preventing a transfer failure from occurring.
(O02) To provide a long-life transfer device capable of preventing occurrence of transfer failure due to an environmental change.
[0021]
[Means for Solving the Problems]
Next, the present invention devised to solve the above problem will be described. Elements of the present invention are indicated by parentheses in the elements of the embodiment in order to facilitate correspondence with the elements of the embodiments described later. Add the items enclosed in.
The reason why the present invention is described in correspondence with the reference numerals of the embodiments described below is to facilitate understanding of the present invention, and not to limit the scope of the present invention to the embodiments.
[0022]
The cause of the problem described in the problem to be solved by the invention is that the volume resistivity in the axial direction of the transfer roll (BTR) varies. This variation occurs because only the end of the semiconductive resin layer (2) is easily affected by the environment (humidity) and the volume resistivity of the end relatively increases or decreases. The following three configurations (A) to (C) are used to prevent variations in the volume resistivity of the transfer roll (BTR) in the axial direction.
(A) A transfer roll (BTR) in which a cylindrical semiconductive resin layer (2) formed on the surface of a core metal (1) is coated with a watertight and semiconductive surface layer (3) has a central portion in the axial direction. The structure is easily affected by outside air.
(B) An axial end of a transfer roll (BTR) in which a cylindrical semiconductive resin layer (2) formed on the surface of a core metal (1) is covered with a watertight and semiconductive surface layer (3). A configuration that is not easily affected by outside air.
(C) The resistance environment dependence of a transfer roll (BTR) in which a cylindrical semiconductive resin layer (2) formed on the surface of a core metal (1) is covered with a watertight and semiconductive surface layer (3). The configuration is less than a certain value.
[0023]
In addition, the transfer roller (BTR) having the above-described configuration (A) to (C) and the tip of the blade (CLb) abutting on the surface of the transfer roll (BTR) remove the toner adhered to the surface of the transfer roll (BTR). Transfer device provided with a transfer roll cleaner (CL) having a metallic cleaning blade (CLb), which is capable of obtaining a transfer device (T) having a simple structure and a long life. The configuration of (BTR) is the following configuration (D).
(D) A configuration in which a cylindrical surface layer (guard resin layer) having a surface microhardness not less than a value corresponding to a polyimide resin or a polyetherimide resin is provided as a surface layer (3) of the transfer roll (BTR).
[0024]
(Transfer Roll Having Configuration (A))
As the transfer roll BTR having the configuration (A), there are transfer rolls (A1) to (A5) having the following configurations (A1) to (A5).
(A1) A core bar (1), a semiconductive resin layer (2) formed on the outer peripheral surface of the core bar (1), and a watertightness covering the outer peripheral surface of the semiconductive resin layer (2). And a transfer roll (BTR) having a semiconductive surface layer (3),
Resistance environment dependence of the end portion of the semiconductive resin layer (2) (volume resistivity when applying 1000 V at 28 ° C./85% RH at high temperature and high humidity and 1000 V at 10 ° C./15% RH at low temperature and low humidity). A transfer roll (BTR) having a smaller volume resistivity (ratio of volume resistivity) than a central portion.
(A2) A core bar (1), a semiconductive resin layer (2) formed on the outer peripheral surface of the core bar (1), and a watertightness covering the outer peripheral surface of the semiconductive resin layer (2). And a transfer roll (BTR) having a semiconductive surface layer (3),
A groove (1a) extending in the axial direction of the transfer roll (BTR) is formed on the surface of the core metal (1), and moisture easily passes through the groove (1a) to the center of the semiconductive resin layer (2). A transfer roll (BTR) characterized in that the transfer roll (BTR) is configured to be able to enter.
[0025]
(A3) A core metal (1), a semiconductive resin layer (2) formed on the outer peripheral surface of the core metal (1), and a watertightness covering the outer peripheral surface of the semiconductive resin layer (2). And a transfer roll (BTR) having a semiconductive surface layer (3),
Micro holes (3a) are provided in the surface layer (3) at the center in the axial direction of the transfer roll (BTR), and moisture easily passes through the micro holes (3a) to the center of the semiconductive resin layer (2). A transfer roll (BTR) characterized in that the transfer roll (BTR) is configured so as to be able to penetrate into a transfer roller.
(A4) A core metal (1), a semiconductive resin layer (2) formed on the outer peripheral surface of the core metal (1), and a watertightness covering the outer peripheral surface of the semiconductive resin layer (2). And a transfer roll (BTR) having a semiconductive surface layer (3),
A thin tunnel-shaped hole (2d) extending in the axial direction of the transfer roll (BTR) is provided in the semiconductive resin layer (2), and moisture passes through the tunnel-shaped hole to allow moisture to pass through the semiconductive resin layer (2). B) a transfer roll (BTR) characterized in that the transfer roll (BTR) is configured to easily enter the central portion of (b).
(A5) A core bar (1), a semiconductive resin layer (2) formed on the outer peripheral surface of the core bar (1), and a watertightness covering the outer peripheral surface of the semiconductive resin layer (2). And a transfer roll (BTR) having a semiconductive surface layer (3),
The metal core (1) is formed in a pipe shape, and an air hole (1c) is provided in the axial center portion of the metal core (1), and moisture passes through the air hole (1c) and the semiconductive resin layer (2). A transfer roll (BTR) characterized in that the transfer roll (BTR) is configured so as to be easily penetrated into a central portion of the transfer roller.
[0026]
The transfer roll (BTR) having the above-mentioned constitutions (A1) to (A5) comprises a cylindrical semiconductive resin layer (2) formed on the surface of a cored bar (1) and a watertight and semiconductive surface layer ( Since the central portion in the axial direction of the transfer roll (BTR) covered with 3) is easily affected by the outside air, the core metal (1) and the surface layer (3) between the end portion and the central portion of the transfer roll (BTR) when the environment changes. ) Can be prevented from occurring.
Therefore, it is possible to prevent the variation of the volume resistivity in the axial direction of the transfer roll (BTR) due to the environmental change, and to prevent the occurrence of transfer failure.
[0027]
(Transfer Roll Having Configuration (B))
The transfer roll (BTR) having the configuration (B) includes a metal core (1), a semiconductive resin layer (2) formed on an outer peripheral surface of the metal core (1), and the semiconductive resin. A transfer roll (BTR) including a watertight and semiconductive surface layer (3) covering the outer peripheral surface of the resin layer (2),
The end portion of the semiconductive resin layer (2) is made of a material having a small change in volume resistivity due to an environmental change.
[0028]
The transfer roll (BTR) having the configuration (B) can have, for example, the following specific configurations (B1) to (B3).
(B1) A sealant or the like is injected into the end of the transfer roll (BTR) so that the semiconductive resin layer (2) at the end of the transfer roll (BTR) does not come into contact with the outside air.
(B2) The semiconductive resin layer (2) is divided into three or five or more in the axial direction, and only the semiconductive resin layer (2b) near the end has less resistance variation due to an environment such as a carbon conductive type. It consists of the following types of materials.
(B3) The central portion is formed of a foam type resin layer (2a), and the end portion is formed of a solid type resin layer (2b).
(Operation of Transfer Roll Having (B))
In the transfer roll (BTR) having the above-described configurations (B1) to (B3), since the end of the transfer roll (BTR) is hardly affected by the environment, the end of the semi-conductive resin layer (2) due to the environment. Variations in the volume resistivity in the radial direction between the portion and the central portion or in the radial direction can be prevented.
[0029]
(Transfer Roll Having Configuration (C))
The transfer roll (BTR) having the configuration (C) includes a metal core (1), a semiconductive resin layer (2) formed on the outer periphery of the metal core (1), and the semiconductive resin. A water-tight and semiconductive surface layer (3) for covering the outer peripheral surface of the layer (2), and the environment dependency of the volume resistivity of the semiconductive resin layer (2) (high temperature and high humidity of 28 ° C.) / 85% RH at a voltage of 1000 V and a low temperature and low humidity of 10 ° C./volume resistivity at a voltage of 1000 V at 15% RH within 1 digit), and the surface layer (3) is a polyimide resin. Alternatively, it has a surface microhardness not less than a value corresponding to a polyetherimide resin.
[0030]
(Operation of Transfer Roll Having Configuration (C))
Watertight and semiconductive covering the core metal (1), the semiconductive resin layer (2) formed on the outer periphery of the core metal (1), and the outer peripheral surface of the semiconductive resin layer (2) The normal transfer roll (BTR) provided with the surface layer (3) has a semiconductive resin layer (2) formed of a foamed resin and has a resistance in a normal temperature environment (22 ° C./55% RH). It is adjusted to about 0 log Ω (1000 V applied / plate pressing method). In general, the environment dependency of the semiconductive resin layer (2) made of the foamed resin of the transfer roll (BTR) (resistance at 28 ° C / 85% RH in a high temperature and high humidity environment and 10 ° C / 15% RH at a low temperature and low humidity environment) Is less than about 2.5 digits (when applying 1000 V / plate pressing method). In particular, the environmental dependence of the semiconductive resin layer (2) made of an ion conductive foamed resin is adjusted to about two digits. When such a semiconductive resin layer (2) is used, variation in the axial resistance of the BTR becomes remarkable, and the above-described problem occurs.
In order to prevent this, the resistance of the semiconductive resin layer (2) is adjusted to use a material having environmental dependency of about 1.0 digit or less. By using this type of semiconductive resin layer (2), it is possible to prevent variations in the volume resistivity or resistance value in the radial direction of the central portion and the end portion of the transfer roll (BTR) in the axial direction.
[0031]
The above configuration (D) can be provided in the transfer roll (BTR) having the above configurations (A) to (C). A transfer roller (BTR) having the configuration (D) and a metallic cleaning blade (BTR) for removing toner adhered to the surface of the transfer roll (BTR) by a tip of a blade (CLb) contacting the surface of the transfer roll (BTR) It is possible to configure a transfer device (T) including a transfer roll cleaner (CL) having CLb).
The transfer device (T) having the above configuration has a simple configuration and a long life.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments.
(Embodiment 1)
FIG. 1 is an explanatory view of a transfer device according to Embodiment 1 of the present invention. FIG. 1A is a front view of a transfer roll used in the transfer device. FIG. 1B is a front sectional view of the transfer roll. 1C is an explanatory view of a transfer device having a transfer roll and a cleaner for removing toner on the surface of the transfer roll as viewed from an arrow IC in FIG. 1A.
FIG. 2 is a view showing the difference between the characteristics of the transfer roll shown in FIG. 1 and a conventional transfer roll, and FIG. FIG. 2B is a diagram showing a change in the resistance value in the radial direction at the central portion and the end portion in the axial direction of the transfer roll with respect to an environmental change.
[0033]
In FIG. 1, a transfer roll BTR includes a core 1 having a cylindrical outer peripheral surface, a cylindrical semiconductive resin layer 2 formed on the outer peripheral surface of the core 1, and a conductive semiconductive resin layer 2. And a surface layer 3 covering the surface. The semiconductive resin layer 2 is a foamed resin having a resistance environment dependency (ratio of resistance at 1000C applied at 10 ° C / 15% RH environment and resistance at 1000V applied at 28 ° C / 85 environment) of 1.0 digit or less. It is composed of layers. The surface layer 3 is constituted by a tube made of a polyimide resin (or a polyetherimide resin). The transfer roll BTR is obtained by inserting a foaming roll having the cored bar 1 and the foamed resin layer (semi-electrostatic resin layer) 2 formed on the surface thereof into the resin tube (surface layer) 3. It is configured. The use of the foam roll reduces the occurrence of resistance variation in the axial direction of the transfer roll BTR.
[0034]
As the semiconductive resin layer 2 constituting the foam roll, for example, a foam roll of the type disclosed in JP-A-10-254215 is used. In the foam roll of the type disclosed in the above-mentioned JP-A-10-254215, the semiconductive resin layer (foam resin layer) 2 has a sea-island structure of three types of rubber having different solubility parameter values, and has different characteristics. Types of carbon black are dispersed. The solubility parameter value δ can be expressed as δ = ΔE / V, where ΔE is the evaporation energy of the polymer or its solvent molecule, and V is the molar volume. Then, the closer the δ value of the polymer and the solvent molecule is, the higher the solubility becomes in principle.
Furthermore, it is composed of three kinds of rubbers having different solubility parameter values. By selecting the solubility parameter value of each rubber, the compatibility between the rubbers can be enhanced, and the carbon black having different properties is located near the interface of the sea-island structure. Since the carbon black is widely distributed, the concentrated uneven distribution of carbon black is reduced, the dispersibility of carbon black as conductive particles is improved, and uniform charging and transfer can be performed.
Furthermore, carbon black is composed of two types having different characteristics, and conductivity with less resistance variation can be obtained. Also, since it is not necessary to use a plasticizer such as process oil, there is no bleeding of the plasticizer, and there is no need to use an antistatic agent or other electrolytes. The variation of the resistance value with respect to the change can be reduced, and the adjustment of the hardness and the resistance value is easy.
[0035]
FIG. 2 shows resistance measurement data of the roll resistance (1000 V applied / plate pressing method) of the foam roll as described above. The environmental dependency of a general foaming roll (tentatively called a current product) is two orders of magnitude, and the environmental dependency of a foam roll of the type described above (tentatively called an improved product) is about one digit. This improved product roll is inserted into a tube to manufacture a transfer roll BTR (tentatively called an improved BTR). The foam roll has an outer diameter of 20.4 mm, a core metal outer diameter of 12 mm, and a foam roll width of 230 mm. This foam roll is inserted into a semiconductive polyimide tube having an inner diameter of 20.3 mm, a film thickness of 50 μm, and a length of 230 mm.
The resistance of the tube is 6.5 log Ω (= 10 ^6.5 Ω) (100 V applied). A tube resistance is measured by inserting a metal shaft into a tube and applying a roll resistance of 2 log Ω (= 10 ² Ω) With a load of 500 gf applied to both ends of the core, a current is applied when a voltage of 100 V is applied between the metal shaft and the core of the rubber roll, and the resistance is calculated. are doing. The roll resistance 2 log Ω is a value measured by applying 100 V between the rubber roll core and the metal plate while the rubber roll is pressed against the conductive metal plate.
In addition, the roll resistance of the rubber roll is 2 logΩ (= 10 ² Ω) is a resistance value calculated from a current value when 1000 V is applied by pressing the rubber roll against a metal shaft of about Φ = 30 mm and pressing both ends of the shaft with a pressing force of about 500 gf.
[0036]
FIG. 2 shows the measurement results of the resistance variation at each axial position of the current BTR and the improved BTR thus completed. The improved BTR has a smaller variation in the axial direction in each environment than the current BTR. At this time, the resistance was measured by pressing a terminal having a width of 5 mm against the surface of the BTR, and measuring the resistance from a current value when 1000 V was applied between the terminal and the foam roll core.
By using the improved BTR (transfer roll) having such an environment dependency of about one digit or less, the resistance difference between the BTR edge and the center can be made within 0.1 digit in each environment, Poor transfer / fringe contamination (stain caused by an enhanced electric field (fringe electric field) at the boundary of the electric field) in a range corresponding to the center of the BTR in a high-humidity environment can be suppressed. Transfer failure / fringe contamination in a corresponding range can be suppressed.
[0037]
As shown in FIG. 1C, the transfer roll BTR is used in a transfer device T of an image forming apparatus such as an electrophotographic copying machine. In FIG. 1C, the transfer roll BTR is disposed in contact with the surface of a toner image carrier TT such as a photoconductor or an intermediate transfer belt of an image forming apparatus, and a transfer area Q between the transfer roll BTR and the toner image carrier TT. The toner image formed on the surface of the toner image carrier TT is transferred to a sheet (recording sheet) passing through the sheet.
Since the surface layer 3 made of polyimide resin of the transfer roll BTR has a high surface microhardness (surface hardness measured by pressing a small portion such as the tip of a needle), cleaning with a thin metal such as stainless steel or phosphor bronze is performed. By contacting the tip of the blade, toner adhered to the surface can be removed.
[0038]
Therefore, the transfer device T according to the first embodiment includes the improved transfer roll BTR and a cleaner CL, and the cleaner CL is made of a metal (made of SUS) that scrapes toner adhered to the surface of the transfer roll BTR. And a cleaner container CLv for collecting the scraped toner.
In the transfer device T of the first embodiment, the toner adhered to the surface of the transfer roll BTR is scraped off by the metal (SUS) cleaning blade CLb, so that the configuration of the cleaner CL is simplified. Therefore, the configuration of the transfer device T having the transfer roll BTR and the cleaner CL is simplified, and the manufacturing cost can be reduced. Further, in the transfer device of the first embodiment, since the improved transfer roll BTR is used, a long-life transfer device capable of preventing occurrence of transfer failure due to environmental change is provided. Can be.
[0039]
(Embodiment 2)
FIG. 3 is an explanatory view of a transfer device according to Embodiment 2 of the present invention, FIG. 3A is a front view of a portion of a transfer roll used in the transfer device from which a surface layer has been removed, FIG. 3B is a front sectional view of the transfer roll, FIG. 3C is an explanatory diagram of a transfer device including a transfer roll viewed from an arrow IIIC in FIG. 3B and a cleaner that removes toner from the surface of the transfer roll.
In the description of the second embodiment, the same reference numerals are given to the components corresponding to the components of the first embodiment, and the detailed description thereof will be omitted.
In the following description of the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The second embodiment is different from the first embodiment in the following points, but is configured in the same manner as the first embodiment in other points.
[0040]
The semiconductive resin layer 2 inserted into the surface layer (resin tube) 3 of the transfer roll BTR according to the second embodiment includes a central member 2a made of foamed resin and end members made of foamed resin on both sides thereof. 2b and 2b. The end members 2b, 2b are made of a material whose resistance environment dependency is smaller than that of the center member 2a. With such a configuration, it is possible to suppress an axial variation in the resistance (or volume resistivity) of the transfer roll BTR in the radial direction.
By lowering the foam density of the end member 2b of the semiconductive resin layer 2 than that of the center member 2a, it is possible to reduce the influence of the environment by reducing the ventilation between the bubbles. In addition, the center member 2a and the end members 2b, 2b of the semiconductive resin layer 2 can be integrally formed, or the core metal 1 can be inserted into three parts.
[0041]
In the transfer device T using the transfer roll BTR according to the second embodiment, the toner adhered to the surface of the transfer roll BTR is scraped off by a metal (SUS) cleaning blade CLb, so that the configuration of the cleaner CL is simplified. . Therefore, the configuration of the transfer device T having the transfer roll BTR and the cleaner CL is simplified, and the manufacturing cost can be reduced. Further, in the transfer device of the first embodiment, since the above-described transfer roll BTR is used, it is possible to provide a long-life transfer device capable of preventing the occurrence of transfer failure due to an environmental change. it can.
[0042]
(Embodiment 3)
FIG. 4 is an explanatory view of a transfer roll according to Embodiment 3 of the present invention. FIG. 4A is a side view of a portion excluding a surface layer of the transfer roll, and FIG. 4B is a side sectional view of the transfer roll.
In the following description of the third to eighth embodiments of the present invention, elements corresponding to the elements of the first embodiment are denoted by the same reference numerals, and redundant detailed description will be omitted. The transfer roll BTR according to the following third to eighth embodiments uses a polyimide resin or a polyetherimide resin for its surface layer 3 so that the surface of the transfer roll BTR can be cleaned with a metal cleaning blade. Become. In that case, the configurations of the cleaner having the cleaning blade and the transfer device having the transfer roll can be simplified, and the manufacturing cost can be reduced.
The semiconductive resin layer 2 inserted into the surface layer (resin tube) 3 of the transfer roll BTR according to the third embodiment includes a central member 2a made of foamed resin and solid resin (non-foamed resin) on both sides thereof. ) End members 2b, 2b.
By forming the end members 2b and 2b as solid members, it is possible to prevent moisture from entering the end member 2b and reduce the influence of the environment of the semiconductive resin layer 2.
[0043]
(Embodiment 4)
5A and 5B are explanatory views of a transfer roll according to a fourth embodiment of the present invention. FIG. 5A is a side view, FIG. 5B is a view from the arrow VB-VB in FIG. 5A, and FIG. FIG. 5 is a sectional view taken along line VC-VC of FIG.
The semiconductive resin layer 2 inserted into the surface layer (resin tube) 3 of the transfer roll BTR according to the fourth embodiment is made of a foamed resin, and has both ends to prevent moisture intrusion and dehumidification. The intended ring-shaped moisture-impermeable end member 4 is attached by bonding. The transfer roll BTR according to the fourth embodiment can also prevent moisture from entering the end member 4 and reduce the influence of the environment of the semiconductive resin layer 2.
[0044]
(Embodiment 5)
FIG. 6 is an explanatory view of a transfer roll according to a fifth embodiment of the present invention. FIG. 6A is a side view of a core metal of the transfer roll, FIG. 6B is a view seen from the arrow VIB-VIB in FIG. 6A, and FIG. 6D is a side view of the transfer roll, FIG. 6D is a view from the arrow VID-VID of FIG. 6C, FIG. 6E is a side cross-sectional view of the transfer roll, and FIG. 6F is a VIF-VIE of FIG. 6E. It is a VIF line sectional view.
In FIG. 6, four grooves 1a are formed in the outer peripheral surface of the cored bar 1 in the axial direction at intervals of 90 degrees in the circumferential direction. When the outside air passes through the groove 1a, the center member 2a of the semiconductive resin layer 2 of the transfer roll BTR is easily affected by the temperature and humidity of the outside air, like the end member 2b.
By making it easier for the influence of the temperature and humidity of the outside air to be transmitted to the central portion of the transfer roll BTR, it is possible to reduce variations in the BTR resistance in the axial direction. For example, in a high-temperature and high-humidity environment, moisture enters the center of the BTR through the groove 1a, thereby lowering the BTR resistance at the center as well as at the end. Eliminates variations in directional resistance. In a low-temperature and low-quality environment, the moisture in the central portion of the BTR goes out through the groove to the outside air, and the resistance at the central portion of the BTR rises and shakes with the end portion according to the environment, thereby reducing the variation in resistance in the axial direction.
[0045]
The depth and width of the groove 1a may be such that moisture can pass therethrough, and may be about 2 mm in depth and about 0.5 mm in width. Further, the length of the groove 1a in the axial direction needs to be longer than the semiconductive resin layer (foamed resin layer) 2. It is necessary to form a range in which the semiconductive resin layer 2 does not cover the groove 1a, and to allow the outside air to enter and exit from this range. The number of the grooves 1a must be three or more at the same width in the circumferential direction. For example, if they are located at one location, the variation in resistance in the circumferential direction increases, and a defect in image quality (transfer failure / fringe stain) occurs at the BTR circumferential pitch.
[0046]
(Embodiment 6)
FIG. 7 is an explanatory view of Embodiment 6 of the transfer roll of the present invention, and is a perspective view of a surface layer which is a main part of Embodiment 6 of the present invention.
In FIG. 7, minute holes 3a are provided in a surface layer 3 formed by a resin tube, and the outside air can easily contact a semiconductive resin layer (not shown) 2 through the minute holes 3a. As a result, the central portion of the BTR is easily affected by the temperature and humidity of the outside air. By making it easier for the influence of the temperature and humidity of the outside air to be transmitted to the central portion of the BTR, the variation in the BTR resistance in the axial direction can be reduced.
The size of the fine holes 3a needs to be smaller than the toner particle size. If the diameter is larger than the toner particle diameter, toner clogging occurs, and moisture does not sufficiently enter and exit. If a hole smaller than the toner particle diameter is formed in the surface layer (resin tube) 3, the minute hole 3a is not clogged with the toner, and even if it is clogged, it can be easily scraped off by the cleaning blade (scraper). The toner used in the present invention is a spherical toner having a particle diameter of about 7 μm. Therefore, the hole diameter is set to about 6 μm or less. A method for forming micropores in the surface layer 3 made of a polyimide resin is to mix a raw material of the polyimide resin with a salt having a particle size of 6 μm or less, bake the tube, and wash with water to wash off the salt.
The density of the micro holes 3a may be absent or small in the range of about 50 mm from the end of the BTR which is easily affected by the environment. However, in the range corresponding to the center of the BTR, 0.01 pieces / mm ² It is desirable that there be.
[0047]
(Embodiment 7)
8 is an explanatory view of a transfer roll according to a seventh embodiment of the present invention and a modified example thereof, FIG. 8A is a side view of the seventh embodiment, FIG. 8B is a view seen from the arrow VIIIB of FIG. 8A, and FIG. 8D is a sectional view taken along the line VIIIC-VIIIC of FIG. 8A, FIG. 8D is a sectional view taken along the line VIIID-VIIID of FIG. 8C, FIG. 8E is an explanatory view of Modification Example 1 of the transfer roll of Embodiment 7, and FIG. FIG. 18 is an explanatory diagram of a second modification of the transfer roll according to the seventh embodiment.
8A to 8D, the semiconductive resin layer (foamed resin layer) 2 of the transfer roll BTR according to the seventh embodiment has a plurality of tunnel-shaped holes 2d extending in the axial direction at intervals in the circumferential direction. Have been. When the outside air passes through the hole 2d, the central portion of the semiconductive resin layer 2 is easily affected by the temperature and humidity of the outside air similarly to the end portions. In this way, the influence of the temperature and humidity of the outside air is easily transmitted to the central portion of the BTR, whereby the variation in the BTR resistance in the axial direction can be reduced.
The tunnel-shaped hole 2d needs to pass from the end to the center of the semiconductive resin layer 2. As a result, the outside air entering from the end can easily pass to the center of the BTR. This makes it easier for the influence of the temperature and humidity of the outside air to be transmitted to the central portion of the BTR, so that variations in the BTR resistance in the axial direction can be reduced. For example, in a high-temperature and high-humidity environment, when moisture enters the center of the BTR, the resistance at the center as well as at the ends is reduced according to the environment, and the variation in axial resistance is reduced. Further, in a low-temperature and low-quality environment, the moisture in the central portion of the BTR exits to the outside through the groove, and the resistance in the central portion of the BTR increases in the same manner as at the end portions in accordance with the environment, thereby reducing the variation in the axial resistance.
[0048]
The diameter of the hole 2d only needs to pass moisture, and may be about 0.5 mm. The number of holes in the circumferential direction should be at least three places with approximately equal width. For example, if it is located at one location, the variation in resistance in the circumferential direction increases, and a defect in image quality (transfer failure / fringe stain) occurs at the BTR circumferential pitch. It is sufficient that the position of the hole 2d is open to at least one axial end of the semiconductive resin layer 2. Further, the position of the tunnel-shaped hole 2d is arranged at the center (middle) in the radial direction.
(Modifications 1 and 2 of Embodiment 7)
8E and 8F, the positions of the tunnel-shaped holes 2d in the first and second modifications are near the surface layer in the radial direction as shown in FIGS. 8E and 8F (see FIG. 8E) or near the core metal (see FIG. 8F). ) Is also possible.
[0049]
(Embodiment 8)
9 is an explanatory view of Embodiment 8 of the transfer roll of the present invention, FIG. 9A is a side view of the core material, FIG. 9B is a view from the arrow IXB of FIG. 9A, FIG. 9C is a side view, and FIG. FIG. 10C is a side sectional view taken along the line IXD-IXD of FIG. 9C.
The metal core 1 is constituted by a pipe having a through hole 1b in the axial direction. A plurality of ventilation holes 1c extending in the radial direction are formed in the central portion in the axial direction of the through hole 1b. A plurality of the ventilation holes 1c are arranged at intervals in the axial direction, and are arranged at 90 ° intervals in the circumferential direction. The central portion of the BTR comes into contact with the outside air through the through hole 1b and the plurality of ventilation holes 1c. Therefore, when the outside air passes through the ventilation hole 1c, the central portion of the BTR is easily affected by the temperature and humidity of the outside air. In this way, the influence of the temperature and humidity of the outside air is easily transmitted to the central portion of the BTR, whereby the variation in the BTR resistance in the axial direction can be reduced.
The number of the ventilation holes may not be within the range of about 50 mm from the end of the BTR which is easily affected by the environment, or may be small. However, it is necessary to form the ventilation hole 1c in a range corresponding to the center of the BTR. Further, the number of the ventilation holes 1c in the circumferential direction must be equal to or more than three at equal places. For example, if it is located at one location, the variation in resistance in the circumferential direction increases, and a defect in image quality (transfer failure / fringe stain) occurs at the BTR circumferential pitch.
[0050]
【The invention's effect】
The above-described transfer roll of the present invention has the following effects (E01) to (E03).
(E01) Variations in the volume resistivity of the transfer roll in the axial direction with respect to environmental changes can be suppressed, and transfer failure can be prevented.
(E02) It is possible to provide a long-life transfer device capable of preventing occurrence of transfer failure due to an environmental change.
(E03) Poor transfer / fringe contamination at a BTR edge in a low temperature environment and poor transfer / fringe contamination at a BTR center in a high temperature and high humidity environment can be suppressed. Thereby, the transfer current can be set low. Further, since the transfer current can be set low, the increase in the current-carrying resistance of the BTR can be suppressed low, and the life of the transfer roll and the transfer device can be extended.
[Brief description of the drawings]
1 is an explanatory view of a transfer device according to a first embodiment of the present invention; FIG. 1A is a front view of a transfer roll used in the transfer device; FIG. 1B is a front sectional view of the transfer roll; 1C is an explanatory view of a transfer device having a transfer roll and a cleaner for removing toner on the surface of the transfer roll as viewed from an arrow IC in FIG. 1A.
FIG. 2 is a diagram showing a difference between the characteristics of the transfer roll shown in FIG. 1 and a conventional transfer roll. FIG. 2A shows a change in volume resistivity of a semiconductive resin layer of the transfer roll with respect to an environmental change. FIG. 2B is a diagram showing a change in the resistance value in the radial direction at the central portion and the end portion in the axial direction of the transfer roll with respect to an environmental change.
FIG. 3 is an explanatory view of a transfer device according to a second embodiment of the present invention. FIG. 3A is a front view of a portion of a transfer roll used in the transfer device from which a surface layer is removed, and FIG. FIG. 3C is an explanatory view of a transfer device having a transfer roll and a cleaner for removing toner from the surface of the transfer roll as viewed from an arrow IIIC in FIG. 3B.
FIG. 4 is an explanatory view of a transfer roll according to a third embodiment of the present invention. FIG. 4A is a side view of a portion of the transfer roll excluding a surface layer, and FIG. 4B is a side cross-sectional view of the transfer roll.
5 is an explanatory view of a transfer roll according to a fourth embodiment of the present invention. FIG. 5A is a side view, FIG. 5B is a view seen from arrow VB-VB in FIG. 5A, and FIG. FIG. 5B is a sectional view taken along line VC-VC of FIG. 5A.
6 is an explanatory view of a transfer roll according to a fifth embodiment of the present invention, FIG. 6A is a side view of a core metal of the transfer roll, FIG. 6B is a view seen from the arrow VIB-VIB in FIG. 6A, 6C is a side view of the transfer roll, FIG. 6D is a view from the arrow VID-VID of FIG. 6C, FIG. 6E is a side cross-sectional view of the transfer roll, a cross-sectional view taken along the line VIE-VIE of FIG. 6C, and FIG. FIG. 6B is a sectional view taken along line VIF-VIF of FIG. 6E.
FIG. 7 is an explanatory view of Embodiment 6 of the transfer roll of the present invention, and is a perspective view of a surface layer which is a main part of the present invention.
FIG. 8 is an explanatory view of a transfer roll according to a seventh embodiment of the present invention and a modified example thereof. FIG. 8A is a side view of the seventh embodiment, and FIG. 8B is a view seen from the arrow VIIIB of FIG. 8A. 8C is a sectional side view taken along the line VIIIC-VIIIC of FIG. 8A, FIG. 8D is a sectional view taken along the line VIIID-VIIID of FIG. 8C, and FIG. FIG. 8F is an explanatory view of a second modification of the transfer roll according to the seventh embodiment.
9 is an explanatory view of Embodiment 8 of the transfer roll of the present invention, FIG. 9A is a side view of a core material, FIG. 9B is a view from the arrow IXB of FIG. 9A, and FIG. 9C is a side view FIG. 9D is a side sectional view taken along the line IXD-IXD of FIG. 9C.
FIG. 10 is an explanatory diagram of a conventional technique disclosed in Japanese Patent Application Laid-Open No. 10-78686.
[Explanation of symbols]
BTR: transfer roll,
CL: Transfer roll cleaner,
CLb: metallic cleaning blade,
T: transfer device,
1 ... core metal,
1a ... groove,
1c ... vent,
2 ... Semiconductive resin layer,
2a: Central part member of semiconductive resin layer (semiconductive resin layer near central part in axial direction)
2b: End member of semiconductive resin layer (semiconductive resin layer near the end)
2d: tunnel-shaped hole,
3: Surface layer.

Claims (9)

Core, a semiconductive resin layer formed on the outer peripheral surface of the core, and a transfer roll including a watertight and semiconductive surface layer covering the outer peripheral surface of the semiconductive resin layer,
Resistance environment dependence of the end portion of the semiconductive resin layer (volume resistivity when applying 1000 V at high temperature and high humidity of 28 ° C./85% RH and volume resistivity when applying 1000 V at low temperature and low humidity of 10 ° C./15% RH) (Transfer roll) having a smaller ratio than that of the center portion. Core, a semiconductive resin layer formed on the outer peripheral surface of the core, and a transfer roll including a watertight and semiconductive surface layer covering the outer peripheral surface of the semiconductive resin layer,
A transfer roll, characterized in that a groove extending in the axial direction of the transfer roll is formed on the surface of the cored bar, so that moisture can easily enter the central portion of the semiconductive resin layer through the groove. Core, a semiconductive resin layer formed on the outer peripheral surface of the core, and a transfer roll including a watertight and semiconductive surface layer covering the outer peripheral surface of the semiconductive resin layer,
A transfer roll, characterized in that a fine hole is provided in a surface layer at a central portion in the axial direction of the transfer roll so that moisture can easily enter the central portion of the semiconductive resin layer through the fine hole. Core, a semiconductive resin layer formed on the outer peripheral surface of the core, and a transfer roll including a watertight and semiconductive surface layer covering the outer peripheral surface of the semiconductive resin layer,
A thin tunnel-shaped hole extending in the axial direction of the transfer roll is provided in the semiconductive resin layer so that moisture can easily enter the central portion of the semiconductive resin layer through the tunnel-shaped hole. A transfer roll characterized in that: Core, a semiconductive resin layer formed on the outer peripheral surface of the core, and a transfer roll including a watertight and semiconductive surface layer covering the outer peripheral surface of the semiconductive resin layer,
The cored bar is formed in a pipe shape, and a vent is provided at a central portion in the axial direction of the cored bar, so that moisture can easily enter the central portion of the semiconductive resin layer through the vent. And a transfer roll. Core, a semiconductive resin layer formed on the outer peripheral surface of the core, and a transfer roll including a watertight and semiconductive surface layer covering the outer peripheral surface of the semiconductive resin layer,
A transfer roll, wherein an end portion of the semiconductive resin layer is made of a material having a small change in volume resistivity due to an environmental change. The transfer roll according to claim 1, wherein the surface layer has the surface layer having a surface microhardness not less than a value corresponding to a polyimide resin or a polyetherimide resin. 8. A transfer device comprising: the transfer roll according to claim 7; and a transfer roll cleaner including a metallic cleaning blade having a blade tip that contacts the surface of the transfer roll. A core, a semiconductive resin layer formed on the outer periphery of the core, and a watertight and semiconductive surface layer covering an outer peripheral surface of the semiconductive resin layer; The environmental dependence of the volume resistivity of the layer (the ratio of the volume resistivity when applying 1000 V at high temperature and high humidity of 28 ° C./85% RH to the volume resistivity when applying 1000 V at low temperature and low humidity of 10 ° C./15% RH) A transfer roller having a surface microhardness not less than a value corresponding to a polyimide resin or a polyetherimide resin, and a toner adhering to the surface of the transfer roll by a blade tip contacting the surface of the transfer roll. And a transfer roll cleaner having a metallic cleaning blade for removing the toner.

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