JP2020086382A - Image formation device - Google Patents

Abstract

To deal with the case where materials attaching to a photoconductor drum such as transfer residual toner cannot be sufficiently removed from the surface of the photoconductor drum and the materials will cause failures in images in some cases.SOLUTION: An intermediate transfer belt 10 has a plurality of grooves 10a in a surface in contact with a photoconductor drum 1, the grooves being formed in a row with respect to a direction in which the intermediate transfer belt 10 moves and with respect to the width direction perpendicular to the direction of movement of the intermediate transfer belt 10. The grooves 10a are formed obliquely at the angle θ along the direction of movement of the intermediate transfer belt 10, and the interval I among the grooves 10 with respect to the width direction of the intermediate transfer belt 10 is not larger than the peripheral length L of the intermediate transfer belt 10 multiplied by tanθ.SELECTED DRAWING: Figure 3

Description

The present invention relates to a color image forming apparatus using an electrophotographic process or the like.

As an electrophotographic image forming apparatus, a configuration of a tandem type image forming apparatus in which a plurality of image forming units are arranged in the moving direction of an intermediate transfer body such as an intermediate transfer belt is known. The image forming section for each color has a drum-shaped photoconductor (hereinafter referred to as a photoconductor drum) as an image carrier. The toner image of each color carried on the photosensitive drum of each color is transferred to a transfer material such as paper or an OHP sheet conveyed by a transfer material conveying belt, or is transferred to the intermediate transfer belt once and then transferred to the transfer material. After being transferred onto the transfer material, it is fixed on the transfer material by the fixing means.

Japanese Patent Application Laid-Open No. 2004-163242 does not include a cleaning unit that collects toner (transfer residual toner) remaining on the photosensitive drum after the transfer of the toner image from the photosensitive drum of each color to the intermediate transfer belt is completed (hereinafter, a cleanerless configuration. ) Is disclosed. In such a cleanerless configuration, the transfer residual toner is removed from the photosensitive drum and cleaned by moving with the rotation of the photosensitive drum and being collected by the developing means.

JP, 2004-126202, A

However, the following problems may occur in the configuration of Patent Document 1 in which the cleaning unit that contacts the photosensitive drum is not provided. That is, if the adhered matter such as the transfer residual toner that has adhered to the photosensitive drum cannot be sufficiently removed from the surface of the photosensitive drum, an image defect may occur due to the adhered matter.

Therefore, it is an object of the present invention to suppress the occurrence of an image defect due to an adhered matter adhered to a photoconductor in an image forming apparatus having a cleanerless structure.

The present invention relates to a photoconductor, a developing unit that develops a toner image on the photoconductor, an intermediate transfer which is in contact with the photoconductor, and is a primary transfer of a toner image carried by the photoconductor, and which is endlessly movable. And an image forming apparatus capable of collecting the toner remaining on the photoconductor by the developing means after the toner image is primarily transferred from the photoconductor to the intermediate transfer body. Is a groove formed continuously on the surface in contact with the photoconductor in the moving direction of the intermediate transfer body, and the plurality of grooves are provided in the width direction intersecting the moving direction of the intermediate transfer body. The plurality of grooves are formed obliquely with respect to the moving direction at an angle θ along the moving direction, and have a peripheral length L which is a length in the moving direction of the intermediate transfer member. In this case, the interval I between the adjacent grooves in the width direction satisfies the following expression 1.
I≦L×tan θ (Equation 1)

According to the present invention, in an image forming apparatus having a cleanerless configuration, it is possible to suppress the occurrence of an image defect due to an adhered matter adhered to a photoconductor.

3 is a schematic cross-sectional view illustrating the configuration of the image forming apparatus according to the first exemplary embodiment. FIG. FIG. 3 is a schematic diagram illustrating the configuration of an intermediate transfer member according to the first exemplary embodiment. FIG. 3 is a schematic enlarged cross-sectional view of a position where an intermediate transfer member and a photosensitive member are in contact with each other according to the first exemplary embodiment. 5 is a schematic diagram illustrating the configuration of an intermediate transfer member according to Example 2. FIG. FIG. 6 is a schematic enlarged cross-sectional view of a position where an intermediate transfer body and a photoconductor are in contact with each other according to the second exemplary embodiment. FIG. 6 is a schematic enlarged cross-sectional view of a position where an intermediate transfer body and a photoconductor are in contact with each other according to a third embodiment.

Hereinafter, preferred embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the following embodiments should be appropriately changed depending on the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless otherwise specified, the scope of the present invention is not limited.

(Example 1)
[Configuration of image forming apparatus]
FIG. 1 is a schematic cross-sectional view illustrating the configuration of the image forming apparatus 100 of this embodiment. As shown in FIG. 1, the image forming apparatus 100 of the present embodiment is a so-called tandem type image forming apparatus provided with a plurality of image forming units a to d. The first image forming unit a is yellow (Y), the second image forming unit b is magenta (M), the third image forming unit c is cyan (C), and the fourth image forming unit d is black (Bk). ) To form an image with the toner of each color. These four image forming units are arranged in a line at regular intervals, and the configuration of each image forming unit is often substantially the same except for the color of the toner contained therein. Therefore, the image forming apparatus of this embodiment will be described below using the first image forming section a.

The first image forming unit a includes a photosensitive drum 1a that is a drum-shaped photosensitive member, a charging roller 2a that is a charging member, an exposure unit 3a, and a developing unit 4a. The photosensitive drum 1a is an image carrier that carries a toner image, and is rotationally driven at a predetermined peripheral speed (process speed) in a direction indicated by an arrow R1 (counterclockwise) in response to a driving force from a driving source (not shown). To be done. The image forming units a to d in the present embodiment have a so-called cleanerless structure in which a cleaning member that contacts the photosensitive drums 1a to 1d is not provided.

An image forming operation is started when a control unit (not shown) such as a controller receives the image signal, and the photosensitive drum 1a is rotationally driven. In the course of rotation, the photosensitive drum 1a is uniformly charged to a predetermined potential with a predetermined polarity (in this embodiment, negative polarity) by the charging roller 2a, and is exposed by the exposure means 3a according to an image signal. As a result, an electrostatic latent image corresponding to the yellow component image of the target color image is formed. Next, the electrostatic latent image is developed by the developing means 4a at the developing position and visualized as a yellow toner image on the photosensitive drum 1a. In this embodiment, the regular charging polarity of the toner contained in the developing means 4a is negative, and the electrostatic latent image is reversely developed by the toner charged to the same polarity as the charging polarity of the photosensitive drum 1a by the charging roller 2a. is doing. However, the present invention is not limited to this, and the present invention can also be applied to an image forming apparatus that positively develops an electrostatic latent image with toner that is positively charged and has a polarity opposite to that of the photosensitive drum 1a.

The charging roller 2a as a charging member is in contact with the surface of the photosensitive drum 1a, and is rotated by the rotation of the photosensitive drum 1a due to friction with the surface of the photosensitive drum 1a. The charging roller 2a is a roller member in which a core metal having a diameter of 5.5 mm is provided with an elastic layer made of a conductive elastic body having a thickness of 1.5 mm and a volume resistivity of about 1×10 ⁶ Ωcm. .. A predetermined voltage is applied to the charging roller 2a from an unillustrated charging power source according to the image forming operation. The surface potential of the photosensitive drum 1a when a voltage of -1100 [V] is applied to the charging roller 2a from a charging power source (not shown) is about -500 [V] (measured with a surface potential meter Model 344 manufactured by Trek). there were.

The exposure unit 3a includes a laser driver, a laser diode, a polygon mirror, an optical system lens, and the like, and irradiates a laser beam on the basis of image information input from a host computer (not shown) to expose the surface of the photosensitive drum 1a. Form an electrostatic latent image. In the present embodiment, the light amount of the exposure unit 3a was adjusted so that the surface potential Vl of the photosensitive drum 1a when the exposure unit 3a exposed the maximum amount of light to the photosensitive drum 1a was −100 [V].

The developing unit 4a has a developing roller 41a as a developing member and yellow toner, and supplies the toner to the photosensitive drum 1a to develop the electrostatic latent image formed on the photosensitive drum 1a as a toner image. The developing roller 41a can contact and separate from the photosensitive drum 1a, and supplies the toner in a state of contacting the photosensitive drum 1a with a predetermined contact width. The developing roller 41a rotates in a direction (clockwise) opposite to the arrow R1 direction in the figure at a peripheral speed higher than the peripheral speed of the photosensitive drum 1a. A developing power source (not shown) is connected to the developing roller 41a, and a predetermined voltage (-300 [V] in this embodiment) is applied to the developing roller 41a according to an image forming operation.

The toner in this example is a non-magnetic one-component toner produced by the suspension polymerization method, and has a negative polarity in the normal charging polarity, and was measured with a laser diffraction particle size distribution analyzer LS-230 manufactured by Beckman Coulter, Inc. The volume average particle diameter is about 6.0 μm. Further, in order to modify the surface property, about 1.5% of silicon oxide particles with respect to the weight of the toner is attached to the surface of the toner as an external additive, and the volume average particle diameter of the silicon oxide particles is It is about 20 nm. Although the toner manufactured by the suspension polymerization method is used in this embodiment, the toner is not limited to this, and the toner is manufactured by other polymerization method such as pulverization method or emulsion polymerization method. May be

The intermediate transfer belt 10 as an intermediate transfer member is an endlessly movable belt in which a conductive material is added to a resin material to impart conductivity, and is stretched around three axes of tension rollers 11, 12, and 13. , Are driven to rotate at substantially the same peripheral speed as that of each of the photosensitive drums 1a to 1d. The intermediate transfer belt 10 contacts the photosensitive drum 1a to form a primary transfer portion N1a, and the yellow toner image formed on the photosensitive drum 1a is intermediately transferred from the photosensitive drum 1a while passing through the primary transfer portion N1a. The image is primarily transferred onto the belt 10.

On the inner peripheral surface side of the intermediate transfer belt 10, a primary transfer roller 14a as a transfer member is provided at a position facing the photosensitive drum 1a via the intermediate transfer belt 10, and the primary transfer roller 14a has a potential of A primary transfer power source 16 as a forming means is connected. The primary transfer roller 14a is made of a straight nickel-plated SUS round bar having an outer diameter of 6 mm, and contacts the intermediate transfer belt 10 over a predetermined region in the longitudinal direction intersecting the moving direction of the intermediate transfer belt 10. , Is rotated by rotation of the intermediate transfer belt 10.

In accordance with the image forming operation, the primary transfer power supply 16 applies a voltage of 500 [V] to the primary transfer roller 14a. As a result, a potential is formed on the conductive intermediate transfer belt 10, and the yellow toner image is primarily transferred from the photosensitive drum 1a to the intermediate transfer belt 10. In this embodiment, a configuration is used in which a voltage is applied from the common primary transfer power supply 16 to the primary transfer rollers 14a to 14d. However, the present invention is not limited to this, and each of the transfer power sources for applying a voltage to the primary transfer rollers 14a to 14d may be individually provided, or only a part thereof may be shared.

In the same manner, the second, third, and fourth image forming units b, c, and d form a magenta toner image of the second color, a cyan toner image of the third color, and a black toner image of the fourth color. Primary transfer is performed by sequentially superimposing on the transfer belt 10. As a result, four color toner images corresponding to the target color image are formed on the intermediate transfer belt 10. Thereafter, the four color toner images carried on the intermediate transfer belt 10 are fed by the feeding means 50 in the process of passing through the secondary transfer portion N2 formed by the contact between the secondary transfer roller 15 and the intermediate transfer belt 10. Secondary transfer is collectively performed on the surface of the transfer material P such as the fed paper or OHT.

The secondary transfer roller 15 as a secondary transfer member is a nickel-plated steel rod having an outer diameter of 6 mm, a foam sponge body whose main component is NBR and epichlorohydrin rubber adjusted to have a volume resistivity of 10 ⁸ Ω·cm and a thickness of 6 mm. A covered outer diameter of 18 mm is used. The rubber hardness of the foam sponge body is 30° (Asker hardness meter C type). The secondary transfer roller 15 is in contact with the outer peripheral surface of the intermediate transfer belt 10, and presses the opposing roller 13 as an opposing member via the intermediate transfer belt 10 with a pressing force of about 50 N to press the secondary transfer portion N2. Is forming. A secondary transfer power supply 18 is connected to the secondary transfer roller 15, and the secondary transfer power supply 18 applies a voltage to the secondary transfer roller 15 to transfer from the intermediate transfer belt 10 at the secondary transfer portion N2. The toner image is secondarily transferred to the material P. The secondary transfer power source 18 can output a voltage in the range of 100 to 4000 [V], and in the present embodiment, by applying a voltage of 2500 [V], the secondary transfer portion N2. In, the toner image was secondarily transferred from the intermediate transfer belt 10 to the transfer material P.

The transfer material P on which the toner images of four colors carried on the intermediate transfer belt 10 at the secondary transfer portion N2 have been transferred is then introduced into the fixing unit 30 and heated and pressed to apply the toner of four colors. Are melt-mixed and fixed to the transfer material P. The toner remaining on the intermediate transfer belt 10 after the secondary transfer is cleaned and removed by the cleaning unit 17. The cleaning unit 17 is a collection unit that is provided to face the facing roller 13 via the intermediate transfer belt 10 and collects the toner remaining on the intermediate transfer belt 10. Further, the cleaning unit 17 includes a cleaning blade 17a that contacts the outer peripheral surface of the intermediate transfer belt 10 and a waste toner container 17b that stores toner and the like removed from the intermediate transfer belt 10 by the cleaning blade 17a.

In the image forming apparatus 100 of this embodiment, the transfer residual toner remaining on the photosensitive drum 1a after passing the primary transfer portion N1a reaches the charging portion where the charging roller 2a and the photosensitive drum 1a contact each other. No contact member for contacting the photosensitive drum 1a and collecting the toner is provided therebetween. More specifically, with respect to the rotation direction of the photosensitive drum 1a, a so-called cleanerless configuration is used in which a recovery member such as a cleaning blade that contacts the photosensitive drum 1a is not provided between the primary transfer portion N1a and the charging portion. Have Therefore, the transfer residual toner remaining on the photosensitive drum 1a after the toner image is primarily transferred from the photosensitive drum 1a to the intermediate transfer belt 10 is collected by the developing unit 4a after passing through the charging unit.

In the image forming apparatus of this embodiment, a full-color print image is formed by the above operation.

[Intermediate transfer belt 10]
Next, the intermediate transfer belt 10, which is a feature of this embodiment, will be described. The intermediate transfer belt 10 is a cylindrical endless belt, has a peripheral length of 700 mm, and is composed of two layers, a base layer and a surface layer. The material of the base layer is polyimide resin, the material of the surface layer is acrylic resin, the thickness of the base layer is 70 μm, and the thickness of the surface layer is 3 μm. The surface layer of the intermediate transfer belt 10 in this embodiment is a layer formed on the outer peripheral surface side of the intermediate transfer belt 10, that is, a layer that contacts the cleaning blade 17b and the photosensitive drums 1a to 1d. On the other hand, the base layer of the intermediate transfer belt 10 is the thickest layer among the plurality of layers forming the intermediate transfer belt 10 in the thickness direction of the intermediate transfer belt 10.

FIG. 2 is a schematic diagram illustrating the groove 10a formed in the surface layer of the intermediate transfer belt 10 of the present embodiment, and is a schematic diagram in which the endless intermediate transfer belt 10 is developed in a pseudo manner. As shown in FIG. 2, the intermediate transfer belt 10 of this embodiment has a groove 10a on the surface (surface layer) of the intermediate transfer belt 10 that forms an angle θ with respect to a virtual line VL drawn with respect to the moving direction of the intermediate transfer belt 10. Have multiple. Here, θ=1.5°, and the grooves 10a are formed at intervals I of 18 mm in the width direction intersecting the moving direction of the intermediate transfer belt 10. In this embodiment, the interval I between the adjacent grooves is set so as to satisfy the following formula 1 by using the circumferential length L of the intermediate transfer belt 10 and the angle θ.
I≦L×tan θ (Equation 1)
FIG. 3 is a schematic enlarged cross-sectional view of the contact portion between the photosensitive drum 1a and the intermediate transfer belt 10 in the primary transfer portion N1a when viewed from the moving direction of the intermediate transfer belt 10. As shown in FIG. 3, in this embodiment, a groove 10a having a width of 1 μm and a depth of 2 μm is formed on the surface of the intermediate transfer belt 10. Here, the width and depth of the groove 10a are not limited to the values described above for obtaining the effect of the present embodiment, but are set to be equal to or smaller than the average particle diameter of the toner in consideration of the primary transferability of the toner. Is more preferable.

[Removal of Adhesion on Photosensitive Drum 1]
The image forming apparatus 100 according to the present exemplary embodiment has a cleanerless configuration that does not include a cleaning unit that contacts the photosensitive drums 1a to 1d to collect the transfer residual toner. Then, when the transfer residual toner is not sufficiently collected in the developing units 4a to 4d, that is, when a part of the transfer residual toner and external additives are accumulated as adhered substances on the surfaces of the photosensitive drums 1a to 1d, There is a risk that the transfer material P may become apparent as an image defect. Here, in the following description, when the same control and operation are performed for each member of the image forming units a to d, reference numerals a to d for indicating which member of the image forming unit is used. The description will be omitted.

FIG. 3 is an enlarged schematic cross-sectional view of a position where the intermediate transfer belt 10 and the photosensitive drum 1 are in contact with each other in this embodiment. As shown in FIG. 3, in this embodiment, by forming the groove 10a on the surface of the intermediate transfer belt 10, the adhered matter W adhering to the photosensitive drum 1 is easily scraped off from the photosensitive drum 1. More specifically, as the intermediate transfer belt 10 moves, the edge portion of the groove 10 a moves while being in contact with the surface of the photosensitive drum 1, so that the deposit W can be scraped off from the photosensitive drum 1. ..

Further, as shown in FIG. 2, in this embodiment, an angle θ is provided between the groove 10a and the moving direction of the intermediate transfer belt 10, and an interval I between the grooves 10a in the width direction of the intermediate transfer belt 10 is The circumferential length of the intermediate transfer belt 10 is set to L×tan θ or less. As a result, while the intermediate transfer belt 10 and the photosensitive drum 1 are overlapped with each other, the groove 10a passes at any position of the photosensitive drum 1 in the width direction of the intermediate transfer belt 10, that is, the longitudinal direction of the photosensitive drum 1. As a result, according to the configuration of this embodiment, it is possible to scrape off the adhered matter W adhering to the surface of the photosensitive drum 1 by the groove 10a.

Hereinafter, the effect of this embodiment will be described in detail by comparison with Comparative Example 1. Here, as Comparative Example 1, an intermediate transfer belt having no groove-shaped recess was used. The comparative example 1 is substantially the same as the present example in the other configuration except that no groove is formed on the surface of the intermediate transfer belt. Therefore, in the following description, the elements common to the present example and the comparative example 1 are designated by the same reference numerals and the description thereof will be omitted.

[Image evaluation]
As an evaluation of whether or not an image defect occurred, an A4 size paper having a basis weight of 80 g/m ² (manufactured by Red Label/Oce) was used and an image having a printing rate of 5% was continuously applied to 1000 transfer materials P. An image was formed, and then a test image was formed to confirm whether or not an image defect occurred. Here, the test image is formed at a position of 5 mm to 55 mm from the front end of the transfer material P in the transport direction of the transfer material P and in the entire image forming area in the width direction of the transfer material P, and has a printing rate of 100%. It is a toner image (solid black image). Such a test image is formed on the transfer material P, and in the conveyance direction of the transfer material P, an area (solid area) where a toner image is not formed, which is upstream of an area (solid black area) where a solid black image is formed. Image evaluation was performed by confirming whether or not an image defect occurred in the white part).

As a result of the above-described image evaluation, in the configuration of this example, no image defect was observed, but in the configuration of Comparative Example 1, an image defect in which toner derived from a solid black part adheres to a solid white part ( Hereinafter, it will be referred to as a transfer residual ghost). More specifically, the transfer residual ghost is generated when the photosensitive drum 1 makes one revolution while the transfer residual toner remains on the photosensitive drum 1 and is transferred to the intermediate transfer belt 10 at the next primary transfer. The image is defective.

According to the configuration of this embodiment, the groove 10a is provided in the intermediate transfer belt 10, so that it is possible to scrape off the toner, the external additive, and the like attached to the photosensitive drum 1 as the intermediate transfer belt 10 moves. is there. As a result, it is possible to suppress the accumulation of toner, external additives, and the like on the photosensitive drum 1 as the adherent W, and to suppress the occurrence of image defects such as transfer residual ghost.

On the other hand, in the configuration of Comparative Example 1, since the groove is not formed in the intermediate transfer belt, a part of the transfer residual toner and an adhering matter W such as an external additive is accumulated on the surface of the photosensitive drum 1, and As a result, a transfer residual ghost was generated due to an increase in the transfer residual toner. This is because when remnant toner such as transfer residual toner or external additive W accumulates on the photosensitive drum 1, the releasability of the toner on the photosensitive drum 1 decreases, so that the transfer remaining on the photosensitive drum 1 after the primary transfer. This is because the amount of residual toner increases and transfer residual ghost is likely to occur.

As described above, according to the configuration of this embodiment, the groove 10a forming an angle θ with the moving direction of the intermediate transfer belt 10 is formed on the surface of the intermediate transfer belt 10, and the interval I between the grooves 10a is set to the intermediate value. The peripheral length of the transfer belt 10 is set to L×Tan θ or less. As a result, the adhering matter W adhering to the photosensitive drum 1 can be removed from the surface of the photosensitive drum 1, and the occurrence of image defects due to the adhering matter W can be suppressed.

In this embodiment, the intermediate transfer belt 10 including the two layers of the base layer and the surface layer has been described. However, if the groove 10a is formed on the surface contacting the photosensitive drum 1, the layer of the intermediate transfer belt 10 is formed. The configuration is not limited to this. For example, it may be a single-layer belt having only a base layer or a multi-layer belt composed of three or more layers.

(Example 2)
In the first embodiment, the configuration in which the groove 10a forming an angle θ with the moving direction of the intermediate transfer belt 10 is formed on the surface of the intermediate transfer belt 10 has been described. On the other hand, in the second embodiment, a configuration in which a streak-shaped convex portion 110b forming an angle θ with the moving direction of the intermediate transfer belt 110 is formed on the surface of the intermediate transfer belt 110 will be described. The configuration of the second embodiment is substantially the same as that of the first embodiment except that the intermediate transfer belt 110 provided with the streak-shaped convex portions 110b is used. Therefore, in the following description, the same components and controls as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

[Intermediate transfer belt 110]
FIG. 4 is a schematic diagram illustrating the convex portion 110b formed on the surface layer of the intermediate transfer belt 110 of the present embodiment, and is a schematic diagram in which the endless intermediate transfer belt 110 is pseudo-developed. As shown in FIG. 4, the intermediate transfer belt 110 according to the present exemplary embodiment has a plurality of convex portions 110b formed on the surface of the intermediate transfer belt 110 and forming an angle θ with respect to the virtual line VL drawn with respect to the moving direction of the intermediate transfer belt 110. Have. Here, θ=1.5°, and the convex portions 110b are formed at intervals I of 18 mm in the width direction intersecting the moving direction of the intermediate transfer belt 110. Also in this embodiment, the interval I between the adjacent convex portions is set so as to satisfy the expression 1 of the first embodiment.

FIG. 5 is a schematic enlarged cross-sectional view of the contact portion between the photosensitive drum 1a and the intermediate transfer belt 110 in the primary transfer portion N1a when viewed from the moving direction of the intermediate transfer belt 110. As shown in FIG. 5, in this embodiment, the intermediate transfer belt 110 is provided with a convex portion 110b having a width of 1 μm and a height of 2 μm on the surface thereof. Here, the width and height of the convex portion 110b are not limited to the values described above in obtaining the effect of the present embodiment, but are set to be equal to or smaller than the average particle diameter of the toner in consideration of the primary transferability of the toner. Is more preferable.

[Removal of Adhesion on Photosensitive Drum 1]
In addition to the transfer residual toner and the external additive described in the first embodiment, discharge products such as nitride oxides may adhere to the surface of the photosensitive drum 1. Such a discharge product is generated by discharge generated in the vicinity of the charging portion where the charging roller 2a and the photosensitive drum 1a are in contact with each other, and gradually accumulates on the photosensitive drum 1 by repeating the image forming operation. When the amount of the discharge product accumulated on the photosensitive drum 1 becomes large, the discharge product adsorbs water in a high humidity environment to reduce the resistance, and disturbs the charges in the latent image formed on the photosensitive drum 1. Therefore, there is a possibility that an image defect may occur in which the image density becomes low.

Therefore, as shown in FIG. 5, in this embodiment, by forming the convex portion 110b on the surface of the intermediate transfer belt 110, the adhered substances W such as the discharge products adhered to the photosensitive drum 1 are removed from the photosensitive drum 1. It is designed to be easily scraped. More specifically, as the intermediate transfer belt 110 moves, the protrusions 110b move while contacting the surface of the photosensitive drum 1, so that the adhered matter W can be scraped off from the photosensitive drum 1.

Further, as shown in FIG. 4, in this embodiment, an angle θ is provided between the convex portion 110b and the moving direction of the intermediate transfer belt 110, and an interval I between the convex portions 110b in the width direction of the intermediate transfer belt 110 is provided. Is set to be equal to or less than the peripheral length L×tan θ of the intermediate transfer belt 110. As a result, while the intermediate transfer belt 110 and the photosensitive drum 1 are overlapped with each other, the convex portion 110b passes at any position of the photosensitive drum 1 in the width direction of the intermediate transfer belt 110, that is, the longitudinal direction of the photosensitive drum 1. .. As a result, according to the configuration of the present embodiment, it becomes possible to scrape off the adhered matter W adhering to the surface of the photosensitive drum 1 by the convex portion 110b.

Hereinafter, the effect of the present embodiment will be described in detail by comparison with Comparative Example 2. Here, as Comparative Example 2, an intermediate transfer belt having no convex portion formed on its surface was used. Comparative Example 2 is substantially the same as the present Example in other configurations except that no convex portion is formed on the surface of the intermediate transfer belt. Therefore, in the following description, elements common to the present example and the comparative example 2 are designated by the same reference numerals and the description thereof will be omitted.

[Image evaluation]
In order to evaluate whether or not an image defect has occurred, two types of test images are formed using a transfer material P which is a sheet of A4 size and a basis weight of 80 g/m ² (manufactured by Red Label/Oce). The occurrence was confirmed. First, as the first image evaluation, similarly to the image evaluation performed in Example 1, images with a print ratio of 5% are continuously formed on 1000 sheets of the transfer material P, and then a transfer residual ghost occurs. A test image was formed to confirm the presence or absence of Here, as described above, the test image is formed from the tip 5 mm to 55 mm of the transfer material P in the transport direction of the transfer material P and in the entire image forming area in the width direction of the transfer material P. The toner image (solid black image) has a printing rate of 100%.

Then, as a second image evaluation, after the image forming apparatus 100 was left in a high temperature and high humidity environment of a temperature of 30° C. and a humidity of 90% for 3 days, images having a printing rate of 5% were continuously printed on 1000 transfer materials P. Then, an image was formed, and then a test image was formed to confirm whether or not an image defect occurred. Here, the test image is a halftone image formed on the entire image forming area of the transfer material P and having a printing rate of 20%. Such a test image was formed on the transfer material P, and it was confirmed whether or not there was an image defect due to a discharge product in which the image density was reduced.

As a result of performing the above-described image evaluation, in the configuration of the present embodiment, neither the transfer residual ghost nor the image defect in which the image density becomes low occurred. On the other hand, in the configuration of Comparative Example 2, both a transfer residual ghost and an image defect in which the density of a halftone image with a print ratio of 20% is reduced were confirmed.

As described above, according to the configuration of the present embodiment, by providing the convex portion 110b on the intermediate transfer belt 110, the toner and the external additive attached to the photosensitive drum 1 along with the movement of the intermediate transfer belt 110, and the discharge It is possible to scrape off products and the like. As a result, it is possible to suppress the accumulation of toner, external additives, discharge products, etc. on the photosensitive drum 1 as the adherent W, and to suppress the occurrence of transfer residual ghost and image defects in which the image density becomes low. Is.

On the other hand, in the configuration of Comparative Example 2, since no protrusion is formed on the intermediate transfer belt, a part of the transfer residual toner, the external additive, and the adhered substances such as discharge products are formed on the surface of the photosensitive drum 1. Accumulation of W easily occurs. As a result, a transfer residual ghost and an image defect in which the image density becomes low occur. When the adhered material W such as the transfer residual toner and the external additive is accumulated on the photosensitive drum 1, the releasability of the toner on the photosensitive drum 1 is reduced, and the transfer residual toner remaining on the photosensitive drum 1 after the primary transfer is reduced. The amount increases, and a transfer residual ghost easily occurs. Further, when the attached product W such as a discharge product accumulates on the photosensitive drum 1, the discharge product adsorbs water to reduce the resistance, and disturbs the electric charge in the latent image formed on the photosensitive drum 1. Therefore, an image defect in which the density of the halftone image becomes light is likely to occur.

As described above, according to the configuration of the present exemplary embodiment, the convex portion 110b forming an angle θ with the moving direction of the intermediate transfer belt 110 is formed on the surface of the intermediate transfer belt 110, and the interval I between the convex portions 110b is further reduced. The peripheral length of the intermediate transfer belt 110 is set to L×tan θ or less. As a result, it is possible to remove the adhering matter W adhering to the photosensitive drum 1 from the surface of the photosensitive drum 1, and it is possible to suppress the occurrence of image defects due to the adhering matter W.

(Example 3)
In the first embodiment, the configuration in which the groove 10a forming an angle θ with the moving direction of the intermediate transfer belt 10 is formed on the surface of the intermediate transfer belt 10 has been described. On the other hand, in the third embodiment, a groove 210a forming an angle θ with the moving direction of the intermediate transfer belt 210 and streak-shaped convex portions 210b on both sides of the groove 210a are formed on the surface of the intermediate transfer belt 210. The configured configuration will be described. The configuration of the third embodiment is substantially the same as that of the first embodiment except that the intermediate transfer belt 210 having the groove-shaped protrusions 210b on both sides of the groove 210a is used. Therefore, in the following description, the same components and controls as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

[Intermediate transfer belt 210]
The intermediate transfer belt 210 in this embodiment is similar to the intermediate transfer belt 10 described with reference to FIG. 2 in the first embodiment, and a virtual line VL drawn on the surface of the intermediate transfer belt 210 in the moving direction of the intermediate transfer belt 210. There are a plurality of grooves 210a forming an angle θ with respect to. Here, θ=1.5°, and the grooves 210a are formed at intervals I of 18 mm in the width direction intersecting the moving direction of the intermediate transfer belt 110. Also in this embodiment, the interval I between the adjacent grooves is set so as to satisfy the expression 1 of the first embodiment.

FIG. 6 is a schematic enlarged cross-sectional view of the contact portion between the photosensitive drum 1a and the intermediate transfer belt 210 in the primary transfer portion N1a when viewed from the moving direction of the intermediate transfer belt 210. As shown in FIG. 6, in this embodiment, a groove 210a having a width of 1 μm and a depth of 2 μm is formed on the surface of the intermediate transfer belt 210. Further, in this embodiment, the convex portions 210b are formed on both sides of the groove 210a in the width direction of the intermediate transfer belt 210. Here, the width and depth of the groove 210a are not limited to the values described above in obtaining the effect of the present embodiment, but are set to be equal to or smaller than the average particle diameter of the toner in consideration of the primary transferability of the toner. Is more preferable. More specifically, the sum of the depth of one groove 210a and the height of the convex portions 210b formed on both sides of the one groove 210a is preferably set to be equal to or less than the average particle diameter of the toner. Similarly, the sum of the width of one groove 210a and the width of the convex portions 210b formed on both sides of the one groove 210a is preferably set to be equal to or less than the average particle diameter of the toner.

[Image evaluation]
In order to evaluate whether or not an image defect has occurred, two types of test images are formed using a transfer material P which is a sheet of A4 size and a basis weight of 80 g/m ² (manufactured by Red Label/Oce). The occurrence was confirmed. First, as the first image evaluation, similarly to the image evaluation performed in Example 1, images with a print ratio of 5% are continuously formed on 1000 sheets of the transfer material P, and then a transfer residual ghost occurs. A test image was formed to confirm the presence or absence of Here, as described above, the test image is formed from the tip 5 mm to 55 mm of the transfer material P in the transport direction of the transfer material P and in the entire image forming area in the width direction of the transfer material P. The toner image (solid black image) has a printing rate of 100%.

Then, as a second image evaluation, after the image forming apparatus 100 was left in a high temperature and high humidity environment of a temperature of 30° C. and a humidity of 90% for 3 days, images having a printing rate of 5% were continuously printed on 1000 transfer materials P. Then, an image was formed, and then a test image was formed to confirm whether or not an image defect occurred. Here, the test image is a halftone image formed on the entire image forming area of the transfer material P and having a printing rate of 20%. Such a test image was formed on the transfer material P, and it was confirmed whether or not there was an image defect due to a discharge product in which the image density was reduced.

Furthermore, in this example, the dynamic friction coefficient of the surface of the intermediate transfer belt 210 was measured before and after the second image evaluation, and changes in the dynamic friction coefficient of the intermediate transfer belt 210 before and after the image evaluation were confirmed. Here, the dynamic friction coefficient is measured by using a surface tester (Haydon 14FW manufactured by Shinto Scientific Co., Ltd.) and a urethane rubber ball indenter (outer diameter 3/8 inch, rubber hardness 90 degrees) as a measurement indenter. did. The measurement conditions were a test load of 50 gf, a speed of 10 mm/sec, and a measurement distance of 50 mm. Then, a value obtained by dividing the average value of the friction force (gf) measured from 1 second to 4 seconds from the start of measurement by the test load (gf) was obtained as the value of the dynamic friction coefficient.

As a result of performing the above-described image evaluation, in the configuration of the present embodiment as well, similarly to the first and second embodiments, neither the transfer residual ghost nor the image defect in which the image density is reduced occurs. As described above, according to the configuration of the present embodiment, by providing the convex portion 210b on the intermediate transfer belt 210, the toner and the external additive attached to the photosensitive drum 1 as the intermediate transfer belt 210 moves, and the discharge It is possible to scrape off products and the like. As a result, it is possible to suppress the accumulation of toner, external additives, discharge products, etc. on the photosensitive drum 1 as the adherent W, and to suppress the occurrence of transfer residual ghost and image defects in which the image density becomes low. Is.

In the configuration of this embodiment, the dynamic friction coefficient of the intermediate transfer belt 210 before the second image evaluation is 0.42, and the dynamic friction coefficient of the intermediate transfer belt 210 after the second image evaluation is 0. It was almost unchanged at 0.45. This is because the groove 210a is formed in the vicinity of the convex portion 210b of the intermediate transfer belt 210, so that the deposit W such as the discharge product scraped off the photosensitive drum 1 by the intermediate transfer belt 210 is collected in the groove 210a. It is thought to be a tame. That is, it is considered that the change in the dynamic friction coefficient was small because it was difficult for the discharge products scraped off from the photosensitive drum 1 and other deposits W to adhere to the surface of the intermediate transfer belt 210.

If the friction coefficient of the intermediate transfer belt 210 changes significantly, the contact between the cleaning blade 17a that collects the toner remaining on the intermediate transfer belt 210 and the intermediate transfer belt 210 may become unstable. In this case, there is a possibility that abnormal cleaning may occur or abnormal noise may occur due to the vibration of the cleaning blade 17a. Therefore, as in the present embodiment, the smaller the change in the dynamic friction coefficient of the intermediate transfer belt 210, the longer the time. Easy to achieve stable cleaning performance across.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 4 Developing means 10 Intermediate transfer belt 10a Groove 110 Intermediate transfer belt 110b Convex portion

Claims (8)

A photosensitive member; a developing unit for developing a toner image on the photosensitive member; and an endlessly movable intermediate transfer member which is in contact with the photosensitive member and on which the toner image carried by the photosensitive member is primarily transferred. In the image forming apparatus, which is capable of collecting the toner remaining on the photoconductor by the developing means after the toner image is primarily transferred from the photoconductor to the intermediate transfer body,
The intermediate transfer member is a groove formed continuously on the surface in contact with the photosensitive member in the moving direction of the intermediate transfer member, and a plurality of grooves are provided in the width direction crossing the moving direction of the intermediate transfer member. With the groove,
When the plurality of grooves are formed obliquely with respect to the moving direction at an angle θ along the moving direction, and the circumferential length, which is the length of the intermediate transfer member in the moving direction, is L. In the image forming apparatus, the distance I between the adjacent grooves in the width direction satisfies the following expression 1.
I≦L×tan θ (Equation 1) 2. The image according to claim 1, wherein the intermediate transfer member has convex portions continuously formed in the moving direction of the intermediate transfer member on both sides of the groove in the width direction. Forming equipment. The sum of the depth of one of the grooves and the height of one of the protrusions, and the sum of the width of the one of the groove and the protrusion when viewed in the width direction are each equal to or less than the average particle diameter of the toner. The image forming apparatus according to claim 2, wherein the image forming apparatus is provided. The image forming apparatus according to claim 1, wherein the depth and the width of the groove when viewed from the width direction are equal to or less than the average particle diameter of the toner. A photosensitive member; a developing unit for developing a toner image on the photosensitive member; and an endlessly movable intermediate transfer member which is in contact with the photosensitive member and on which the toner image carried by the photosensitive member is primarily transferred. In the image forming apparatus, which is capable of collecting the toner remaining on the photoconductor by the developing means after the toner image is primarily transferred from the photoconductor to the intermediate transfer body,
The intermediate transfer member is a convex portion formed continuously on the surface in contact with the photosensitive member in the moving direction of the intermediate transfer member, and a plurality of protrusions are provided in the width direction intersecting the moving direction of the intermediate transfer member. Having the above-mentioned convex portion,
The plurality of convex portions are formed obliquely with respect to the moving direction at an angle θ along the moving direction, and the circumferential length, which is the length of the intermediate transfer member in the moving direction, is L. At times, in the widthwise direction, the interval I between the adjacent convex portions satisfies the following expression (1).
I≦L×tan θ (Equation 1) The image forming apparatus according to claim 5, wherein the height and the width of the convex portion when viewed from the width direction are equal to or less than the average particle diameter of the toner. A charging member that contacts the photoconductor to charge the photoconductor is provided, and the photoconductor and the charging member come into contact with each other from a position where the photoconductor and the intermediate transfer body come into contact with each other in a rotation direction of the photoconductor. The image forming apparatus according to any one of claims 1 to 6, wherein a blade that abuts on the photoconductor is not provided up to a position where the image forming apparatus is formed. The intermediate transfer member is composed of a plurality of layers, and has a base layer which is the thickest layer of the plurality of layers, and a surface layer formed on the surface of the intermediate transfer member in contact with the photoconductor. The image forming apparatus according to any one of claims 1 to 7, which is characterized in that.

Images