JP2007240717A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device by which density unevenness caused in an image edge area is suppressed and a satisfactory image is obtained in a state satisfactory leak prevention capability of toner is held at all times. <P>SOLUTION: In the development device having a developer container which stores developer, a developer carrier which carries the developer and a toner leak prevention sheet member which abuts on the outer peripheral surface of the developer carrier and prevents leakage of the developer from the developer container, surface roughness of a longitudinal edge area of the toner leak prevention sheet member is larger than surface roughness of a longitudinal center part area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device, a process cartridge, and an image forming apparatus to which the process cartridge can be attached and detached, which are used for electrophotographic image formation.

  Currently, electrophotographic copying machines and laser beam printers are widely used as office equipment. Hereinafter, an example of an image forming apparatus provided with a conventional developing device will be shown, and an outline of image formation will be described.

  In an image forming apparatus such as an electrophotographic printer, a latent image carrier that is uniformly charged is selectively exposed to form a latent image, and the latent image is visualized with a developer (toner). At the same time, the toner image is transferred to a recording material to form an image.

  In order to visualize the latent image formed on the latent image carrier, a fine powder called a dry developer is used as the developer. The developer is accommodated in a developer container of the developing device, conveyed to a developing sleeve which is a rotatable developer carrier by a stirring unit in the developer container, and is carried on the developing sleeve.

  In the vicinity of the developing sleeve, a developer layer thickness regulating member (elastic blade) is disposed to regulate the developer layer thickness on the developing sleeve to a predetermined thickness. Thereafter, the developer is conveyed to a position facing the toner image forming portion on the latent image carrier by the rotation of the developing sleeve, and a toner image is formed on the latent image carrier by the potential difference between the developing sleeve and the latent image carrier. Fly to the club. Thereby, the latent image on the latent image carrier is visualized.

<1. Seals at both ends of developer layer thickness regulating member>
Further, in order to prevent the developer from leaking out of the developing device, end seal members (hereinafter referred to as “toner leakage preventing members”) are provided at both ends of the developing sleeve and the developer layer thickness regulating member. Is provided. When the sealing property of the toner leakage preventing member is insufficient, the following problems occur.

  For example, if the developer leaks from the developing device in the image forming apparatus, the image on the recording material is soiled with the developer, or if it adheres to the transfer roller, it becomes a defective transfer image. In addition, when removing the developing device for maintenance, the developer may leak from the developing device and spill onto the floor, or may cause inconveniences such as dirtying the clothes and hands of the person who performed the maintenance. is there.

  Accordingly, the developer should not leak from the developing device or the developer container, and various measures are taken to prevent the developer from leaking.

<1.1 Sealing method with elastic body or foam>
In order to solve these problems, in general, a fiber material such as wool felt and Teflon (registered trademark) pile, a foam such as polyurethane foam and sponge rubber, or the like is provided in the gap between both ends of the developing sleeve and the opening of the developing device. There is a method in which a “toner leakage preventing member” made of a material is provided to eliminate a gap through which toner leaks to the outside of the developing device. Both ends of the developing sleeve are prevented by preventing leakage of toner from both ends in the longitudinal direction of the developing device and the developing sleeve, and sandwiching both ends of the developer layer thickness regulating member between the developing sleeve and the toner leakage preventing member. This prevents toner from leaking out. This method has the advantage that the structure is simple and the elastic material such as fiber material or foam is inexpensive, and the toner can pass through both ends of the developing sleeve by contacting the toner leakage prevention member. Since there is no gap, the effect of preventing toner leakage is high, and it is widely used.

<1.2 Magnetic seal method>
Further, in a developing device having a magnet roller inside the developing sleeve, a magnetic material or a magnet is provided as a toner leakage preventing member at a predetermined interval at both ends of the developing sleeve, and a magnetic field is applied to the gap between the toner leakage preventing member and the developing sleeve. Concentrate and form a magnetic circuit. This system is called a so-called magnetic seal system in which a dense magnetic brush is formed by a developer to prevent toner leakage from the longitudinal end.

  In the magnetic seal system, since the toner leakage preventing member does not contact the developing sleeve, all the problems related to wear and the like considered when using the toner leakage preventing member made of an elastic body or foam can be avoided in principle. In addition, a magnetic material having an appropriate magnetic permeability or a magnet having an appropriate magnetic density is used as a toner leakage prevention member, and the magnetic material or the magnet is arranged at an appropriate interval with respect to the developing sleeve to maintain a good sealing performance. can do. In addition, since the magnetic body or magnet is not in contact with the developing sleeve, the member is not worn and damaged, so that its lifetime is semi-permanent and is very suitable for recycling.

  Further, when a developer layer thickness regulating member having a strong regulating force against the developer such as urethane rubber is adopted for the developing sleeve, the amount of the developer moving to the end portion in the longitudinal direction of the developing sleeve increases. Therefore, in the non-image area at both ends of the developing sleeve, the developer stays in the developing chamber, and the force that the developer applies to the toner leakage preventing member (magnetic seal) increases. Therefore, leakage can be prevented by optimizing the gap between the developer carrier and the position of the magnetic seal (see Patent Document 1).

<2. Toner Leakage Prevention Sheet Member>
Further, in the developing device, a “toner leakage preventing sheet member” is disposed under the developing sleeve over the entire longitudinal direction of the developing device in order to prevent toner leakage to the outside. As a method for attaching the toner leakage prevention sheet member, the following method is performed (see Patent Document 2).

  (1) A method in which the sheet is deformed and attached so as not to be wavy over the entire length direction, that is, a method in which the sheet is attached to the attaching surface of the developer container while being pulled in the length direction.

  (2) A method of pasting the sheet by deforming the seating surface of the container to which the sheet is pasted, that is, pasting the sheet horizontally with the sheet pasting surface deformed, and then releasing the deformation of the sheet pasting surface Then, a sheet attaching method for obtaining tension in the longitudinal direction of the sheet (hereinafter referred to as affixing).

As described above, the developer layer thickness regulating members at both ends of the developing sleeve use a magnetic seal method, or a sponge-like or felt-like elastic body or fiber material. Toner leakage from the opening of the developing device has been prevented by sticking a toner leakage prevention sheet member over the entire longitudinal direction.
JP-A-8-202152 JP 2003-173127 A

However, in recent years, further improvement in image quality and cost reduction and miniaturization of the apparatus are desired. In order to reduce the cost and size of the apparatus, the number of parts and material costs are reduced, and the container is made compact and the length of the longitudinal region is reduced with a simple configuration. In addition, in order to improve the image quality, the developer layer thickness on the developer carrying member is further thinned to efficiently and uniformly charge the developer. Therefore, a developer having a high average circularity is used. On the other hand, in the developing device in which such a developer is combined with the above configuration, the following problems may occur. An immediate solution was desired.

The developer having a high average circularity is a one-component magnetic developer having at least a binder resin and a magnetic material and having an average circularity of 0.960 or more. Therefore, the charge imparting power to the developer tends to be higher than that of the conventional developer due to the high sphericity and the effect of the external additive.

  By using the above developer, the charge imparting power to the developer becomes higher than before, and it becomes possible to provide a high-quality image by improving selective developability.

<2. Toner Leakage Prevention Sheet Member>
<2.1 Issues in magnetic seal system>
At both ends of the conventional developing sleeve, the “toner leakage preventing sheet member” is deformed by the developing sleeve itself or by the weight of the developer, and a gap is created between the “toner leakage preventing member” and the developing sleeve. As a result, the developer sometimes leaked sideways.

  As a countermeasure, a “toner side leakage preventing member” made of a sponge-like elastic body or the like is disposed along the side of the toner leakage preventing member such as a magnetic body or a magnet. The toner leakage prevention member is prevented from being deformed by pressing the “toner leakage prevention sheet member” against the developing sleeve from below using the toner lateral leakage prevention member. That is, with this configuration, the toner leakage preventing sheet member is always in contact with the developing sleeve, thereby filling the gap and preventing the toner from leaking out of the developer container by improving the sealing performance.

  That is, in both end regions of the developing sleeve, a “toner leakage preventing member” such as a magnetic body or a magnet and a “toner side leakage preventing member” such as a sponge-like elastic body so that the toner does not leak outside the developer container. In addition, a “toner leakage prevention sheet member” or the like is used.

  Here, due to the configuration of the developer container, the “toner side leakage preventing member” is in the form of abutting the toner leakage preventing sheet member against the developing sleeve while lifting from the lower part. Therefore, inevitably, the contact pressure of the toner leakage preventing sheet member in the both end region of the developing sleeve tends to be higher than that in the central region of the developing sleeve.

  As a result, the layer thickness of the developer having a high average circularity becomes non-uniform on the developing sleeve, or the developers partially cause electrostatic aggregation. In particular, in a low-temperature and low-humidity environment, the developer tends to be in an excessively charged state (charge-up state), and the developers are partially electrostatically aggregated while being in a high charge state. As a result, “density unevenness” may occur at the end (image end) of the image formed at the end of the developing sleeve, and various countermeasures have been desired.

<2.2 Problems in sealing methods with elastic bodies and foams>
In addition, there is a problem similar to that of the magnetic seal method in the case of preventing lateral leakage from the toner leakage prevention sheet member by a sealing method using an elastic body or foam. That is, the developer may partially electrostatically aggregate at both ends of the developing sleeve while being in a high charge state, and “density unevenness” may occur at the edge of the formed image (image edge).

<Problems in 2.3 Dispensing>
Further, in a developer container attached by using a method of sticking to the toner leakage prevention sheet member in order to prevent leakage of toner to the outside (a method of deforming and sticking the sheet so that there is no waviness over the entire longitudinal direction). However, the same problem occurs. In the region overlapping with the “toner leakage preventing member” at the longitudinal end portion due to the attachment method, the contact pressure of the “toner leakage preventing sheet member” at the both end region of the developing sleeve tends to increase. Then, as described above, when a developer having a high average circularity is used, the toner layer coated on the developing sleeve becomes non-uniform, causing electrostatic unevenness, resulting in density unevenness. was there.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a developing device capable of suppressing density unevenness occurring in an image end region and obtaining a good image while maintaining a good toner leakage prevention capability. With the goal.

  In order to achieve the above object, the present invention provides a developer container that contains a developer, a developer carrier that carries the developer, and a developer carrier that abuts along the outer peripheral surface of the developer container to develop the developer from the developer container. In the developing device having the toner leakage preventing sheet member for preventing the leakage of the agent, at least the surface roughness of the toner leakage preventing sheet member in contact with the developer carrying member is the surface roughness of the longitudinal center region in the longitudinal end region. It is larger than this.

  According to the present invention, it is possible to suppress the density unevenness generated in the image edge region and to obtain a good image while maintaining a good toner leakage prevention capability.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A laser beam printer will be described as an example of the image forming apparatus.
<First embodiment>
A first embodiment of a representative invention of the present invention is shown below.

  FIG. 8 is a side sectional view of the process cartridge, and FIG. 9 is a side sectional view of the image forming apparatus equipped with the process cartridge.

<Image forming apparatus>
First, the image forming apparatus will be described. The image forming apparatus includes (1) an image forming unit that forms a toner image, (2) a transfer unit that transfers the toner image onto the conveyed recording material 7, and (3) fixing the toner image to the recording material 7. And a fixing unit.

  In the image forming apparatus shown in FIG. 9, a laser beam modulated in accordance with an image signal is output from a scanner unit 1 including a laser and a polygon mirror correction system lens. Then, the laser beam is reflected by the folding mirror 11 and irradiated onto the photosensitive drum 2 which is an image carrier. The photosensitive drum 2 is uniformly charged in advance by a charging roller 3 that is a primary charger, and an electrostatic latent image is formed on the surface in response to the irradiation of the laser beam.

(1) On the other hand, the one-component magnetic toner 40 is stored in a toner hopper 41 which is a developer container of the developing unit 4. The one-component magnetic toner 40 is supplied to the developer carrier 43 by the developer conveying member 42, and a developer regulating member 45 that is in contact with the outer peripheral surface of the developer carrier 43 by the rotation of the developer carrier 43. Charged by friction. The charged one-component magnetic toner 40 is held and conveyed by a magnet in the developing sleeve 43, and a developable toner layer is formed on the developer carrier 43. The electrostatic latent image is developed by the toner layer and visualized as a toner image on the photosensitive drum 2 (corresponding to the “image forming portion” of the present invention).

  A thin plate member such as polyethylene terephthalate is referred to as “toner leakage preventing sheet member A” under the developer carrying member 43 and is brought into contact with the entire region of the developer carrying member 43 in the rotational axis direction with very light pressure. At both ends of the developer carrier 43, toner leakage prevention members B made of a magnetic material are arranged with a certain distance from the outer peripheral surface of the developer carrier 43.

  (2) On the other hand, the recording material 7 accommodated in the cassette 71 is supplied by the paper feed roller 72 in synchronization with the formation of the latent image on the photosensitive drum 2 and is conveyed to the roller-shaped transfer device 6. The toner image is transferred onto the recording material 7 by the transfer device 6 (corresponding to the “transfer portion” of the present invention).

  (3) The recording material 7 to which the toner image has been transferred is conveyed to a fixing device 8 (corresponding to the “fixing portion” of the present invention), where the toner image is fixed to form a permanent image, and then discharged. The one-component magnetic toner 40 remaining on the photosensitive drum 2 is removed by the cleaning unit 5.

<Process cartridge>
The process cartridge 10 shown in FIG. 8 has the photosensitive drum 2, the charging roller 3, the developing unit 4 in which the developer carrying member 43 and the toner hopper 41 are integrated, the cleaning unit 5, and the cover as a unit. ing. These photosensitive drums 2 and the like are assembled in the process cartridge 10 with a predetermined mutual relationship, and the process cartridge 10 is inserted and mounted in a predetermined manner with respect to a predetermined portion in the main body of the image forming apparatus. It can be removed from the main unit.

  Further, since the user can replace the process cartridge 10 with a new process cartridge, maintenance-free operation free from contamination due to toner replenishment work can be realized. For example, when the one-component magnetic toner 40 stored in the developing unit 4 is consumed, or when the collected toner is filled in the waste toner container of the cleaning unit 5, the process cartridge 10 is processed depending on the drum life. It is replaced when the cartridge reaches the end of its life.

  Next, the relationship and configuration of the toner leakage prevention sheet member A, the toner leakage prevention member B, and the developer container 4 will be described in detail with reference to FIGS.

  FIG. 4 is a perspective view showing the attachment positions of the toner leakage prevention member B, which is a magnetic seal member, and the frame of the developer container.

  As shown in FIG. 4, the toner leakage preventing member B has a shape along the arc of the developing sleeve 43 and is attached to the opening end of the developer container 4.

  FIG. 5 is a perspective view of the toner leakage preventing member B and the developing sleeve 43. As shown in the drawing, toner leakage prevention members B are arranged at both ends of the developing sleeve 43 with a gap g from the outer peripheral surface of the developing sleeve 43. Magnetic poles are arranged in the circumferential direction of the developing sleeve 43 on the inner peripheral surface of the toner leakage preventing member B (the surface facing the outer peripheral surface of the developing sleeve 43), and a magnetic brush is formed in the gap g by the one-component magnetic toner 40. To do. Thereby, the outflow of the one-component magnetic toner 40 from the end of the developing sleeve 43 is prevented.

In the first embodiment, the developing sleeve 43 uses a hollow cylindrical nonmagnetic metal such as aluminum. Then, the surface of the developing sleeve 43 is subjected to a blasting treatment, or a phenol resin solution (coating agent) in which rough particles such as carbon, graphite, and spherical carbon particles are dispersed is spray-coated to obtain roughness (for example, average (Roughness Ra = 1.2 μm).

  FIG. 6 is a cross-sectional view when the toner leakage preventing member B and the developing sleeve 43 are attached to the developer container 4. As illustrated, the plurality of magnetic poles of the toner leakage preventing member B are disposed along the circumferential direction. The number of magnetic poles is appropriately selected according to the diameter of the developing sleeve 43 and the magnetic force of the magnet. In FIG. 6, the case of 6 poles is shown. As described above, the toner sealing property is secured by the magnetic brush formed in the gap g between the toner leakage preventing member B and the developing sleeve 43.

In addition, the toner leakage prevention sheet member A is disposed in the developer container 4, and prevents the toner from leaking against sudden impact by contacting the entire area of the developing sleeve 43 in the rotation axis direction. Can do. The material of the toner leakage prevention sheet member A is polyethylene terephthalate (PET) having a thickness of 50 μm. The toner leakage prevention sheet member A is in contact with the developing sleeve 43 in order to prevent toner leakage due to an impact when the process cartridge is mounted. However, the passage of the one-component magnetic toner 40 on the developing sleeve 43 is allowed. The toner leakage preventing sheet member A is disposed so as to substantially uniformly contact at least the toner leakage preventing member B made of a magnetic material in the longitudinal direction. A toner leakage preventing member B is provided below the toner leakage preventing sheet member A.

  By arranging the toner side leakage preventing member C next to the toner leakage preventing member B so as to contact the lower portion of the toner leakage preventing sheet member A, the toner leakage preventing member B can be made to contact the developing sleeve 43 more strongly. The side leakage of the magnetic toner 40 is reliably prevented.

  FIG. 7 is a perspective view of FIG. Actually, the toner leakage prevention sheet member A is configured to cover the toner lateral leakage prevention member C and the toner leakage prevention member B, and extends to the longitudinal end portion.

  Next, FIG. 1 is a view showing the positional relationship in the longitudinal direction of the developing sleeve 43, the toner leakage prevention sheet member A, the toner leakage prevention member B, and the toner lateral leakage prevention member C and the roughened region X. The roughening area X is formed as an area having a roughness on the surface of the toner leakage prevention sheet member A that is in contact with the developing sleeve 43 at both end areas.

  As shown in FIG. 1, by providing the roughened regions X in the longitudinal end regions of the toner leakage preventing sheet member A, the surface roughness of the surface of the end portion in contact with the developing sleeve is larger than the longitudinal central portion. It was made to become.

  The roughening region X preferably includes at least a region where the toner leakage prevention sheet member A overlaps the toner leakage prevention member B and the toner lateral leakage prevention member C. This is because the contact pressure applied to the toner layer on the developing sleeve 43 by the toner leakage preventing sheet member A is highest in the overlapping region. FIG. 2 shows an example of the rough area X formed on the toner leakage preventing sheet member A. FIG. 2A shows an example in which a magnetic seal member or magnetic body is used as the toner leakage preventing member B, and a sponge-like elastic body is used as the toner side leakage preventing member C. FIG. 2B shows an example in which a fiber material such as wool felt / Teflon (registered trademark) pile is used as the toner leakage preventing member B.

Since the toner leakage prevention member B and the toner lateral leakage prevention member C are arranged in the non-image formation area in the longitudinal arrangement relationship in the developer container 4, image formation is performed in the image formation area and the image end portion on the transfer paper. It seems that it will not adversely affect However, the contact pressure of the end portion of the toner leakage preventing sheet member A that is actually in contact with the developing sleeve tends to be higher than the central portion of the developing sleeve 43 in the image forming region inside the toner leakage preventing member B. It is in. Therefore, the coat state and charge distribution of the toner layer are also nonuniform at the edge of the image forming area,
Density unevenness may occur.

  FIG. 3 is a diagram showing the relationship between the position in the longitudinal direction of the toner leakage preventing sheet member A and the contact pressure applied to the surface of the developing sleeve 43. As shown in FIG. The toner leakage prevention sheet member A itself is attached to the developer container 4 using a double-sided tape, an adhesive, or the like. However, as described above, the contact pressure rapidly increases as it goes to the longitudinal end regions.

  Therefore, the contact pressure with respect to a certain point in the longitudinal direction of the toner leakage preventing sheet member A was modeled, and the change in the contact pressure at a plurality of points was measured.

First, the toner leakage preventing sheet member A (for example, polyethylene terephthalate having a thickness of 38 μm) was fixed together with the toner leakage preventing member B and the toner side leakage preventing member C on a flat surface. A force gauge (FGC-0.2 manufactured by SHIMPO) was attached to a height gauge (Model: manufactured by 192-601 Mitutoyo), and the point where the tip of the force gauge touched the toner leakage prevention sheet member A was used as a reference for the height gauge. A pressure gauge is used to measure the pressure when 1.0 mm is inserted below the toner leakage preventing sheet member A vertically with a height gauge. The range in which the intrusion measurement into the toner leakage prevention sheet member A was performed was substantially the same as the range in which the developing sleeve 43 actually contacts the toner leakage prevention sheet member A when attached to the developer container 4. The measurement range is a range where the developing sleeve 43 is considered to be rubbed, and is a range from 1.0 mm to 5.0 mm in the short direction from the front end of the toner leakage prevention sheet member A. The amount of backup was changed within the range, and the reaction force was measured at 10 points for each of the central region and the both end regions.

As a result, the pressure in the central region of the toner leakage preventing sheet member A is in the range of about 0.5 to 2 gf, and the pressure in the end region of the toner leakage preventing sheet member A is in the range of about 5 to 20 gf. there were. This is the case where a magnetic seal member or magnetic body is used as the toner leakage prevention member B, and a sponge-like elastic body is used as the toner side leakage prevention member C. However, a fiber material such as wool felt, Teflon (registered trademark) pile, etc. Similar results were obtained when using.

  Therefore, the surface of the developing sleeve 43 having roughness and the one-component magnetic toner 40 are rubbed with each other by providing roughness at both ends of the longitudinal end regions in order to reduce the pressure on the toner. The reason why the pressure on the toner is decreased is that the surface area is increased and the pressure is dispersed by giving the roughness. As a result, it is possible to prevent the charge of the toner layer from rising too much. Since the charge does not increase excessively, it is possible to prevent the one-component magnetic toners 40 from being in an excessive charge state and electrostatic aggregation, and the toner layer at the end of the developing sleeve 43 can be well regulated.

  Here, the arithmetic mean roughness Ra (μm) of the longitudinal central portion in a smooth state before the roughness is provided to the toner leakage preventing sheet member A is in the range of 0.5 μm ≦ Ra ≦ 1 μm. Then, in the roughened region X of the longitudinal end portion region of the toner leakage preventing sheet member A, a rough member such as sandpaper was used to set an appropriate roughness. Details will be described later.

Therefore, by providing roughness at both ends of the toner leakage preventing sheet member A, the toner layer coating can be applied even if the contact pressure of the toner leakage preventing sheet member A contacting the developing sleeve is high at both longitudinal ends. The state and charge distribution can be made uniform. That is, the coating state and the charge distribution on the toner layer held at both longitudinal ends on the developing sleeve 43 can be made uniform. As a result, it is possible to prevent the one-component magnetic toner 40 from being excessively charged at the end of the developing sleeve and electrostatic aggregation of the one-component magnetic toners 40 while remaining in an excessively charged state. That is, it is possible to reliably prevent an image defect such as density unevenness in the image end region due to an abnormal toner layer thickness at the end of the developing sleeve 43 or an unstable charge state.

In order to verify the effect of the present invention using the developing device of this embodiment, a verification experiment was performed under the following conditions.
・ Process speed (photosensitive drum peripheral speed) = 126.16 mm / sec
-Durable number: 6000 sheets-Image printing rate: 2%

Under the above conditions, an intermittent durability experiment was performed in a low-temperature and low-humidity environment (15 ° C., 10%), and sample images were confirmed every 2000 sheets. Table 1 shows an evaluation of image defects appearing in a halftone image when a sheet of 2000 sheets is passed through an intermittent endurance experiment using a developing device in which both ends of the toner leakage prevention sheet member A are appropriately roughened with sandpaper. Results are shown. In Table 1, “◎”, “◯”, and “X” are ranked in stages with respect to the uniformity of the toner layer and the generation level and frequency of the streaks appearing in the halftone image. A indicates that no image defect occurred. ○ indicates occurrence of minor image defects, but a level at which there is no problem in actual use. × indicates that image defects (streaks) have been confirmed.

Here, the surface roughness in this example refers to the arithmetic average roughness Ra measured according to JIS B 601 (2001), and is cut off using a surface roughness meter Surfcoder SE-3300 manufactured by Kosaka Laboratory. Measurement was carried out with a value of 0.8 mm and a measurement length of 8 mm.

From these experimental results, the arithmetic average roughness Ra (μm) in the roughened region X of the toner leakage preventing sheet member A was in the range of 3 μm ≦ Ra ≦ 25 μm, and a good result was obtained. When the surface roughness (Ra) of the toner leakage prevention sheet member A was 3 μm, a very slight density unevenness could be confirmed in the image edge area of the halftone image. However, the image quality was at a level at which there is no problem in practical use. When the surface roughness was 25 μm, slight slight streaks in the vertical direction could be confirmed in the image edge area of the halftone image, but the image quality was at a level of no problem in practical use.

The arithmetic average roughness Ra (μm) of the roughened region X is more preferably in the range of 7 μm ≦ Ra ≦ 15 μm. Within this range, the best results are obtained with no image defects at all.

  Next, the width (length in the longitudinal direction) of the roughened region X of the toner leakage preventing sheet member A was examined. The conditions for the verification experiment were the same as those described above. By providing the toner leakage prevention sheet member A with a rough surface on the surface of the developing sleeve 43, it is possible to prevent density unevenness from occurring at the image edge. However, if the entire surface of the toner leakage prevention sheet A is roughened, it is conceivable that vertical stripes are generated in the halftone image in the central portion of the developing sleeve, which has no problem.

Table 2 shows intermittent endurance with a developing device in which both end regions of the toner leakage preventing sheet member are moderately roughened with sandpaper and the average roughness Ra is set to fall within a range of 5 μm ≦ Ra ≦ 25 μm. The evaluation result of the image defect at the time of experiment is shown. As an evaluation result, for each width (mm) of the rough region X shown in Table 2, an evaluation of an image defect appearing in a halftone image when 2000 sheets are passed is shown. In Table 2, “◎”, “×”, and “x” are ranked in stages with respect to the uniformity of the toner layer and the generation level and occurrence frequency of vertical stripes appearing in the halftone image. A indicates that no image defect occurred. A circle indicates that a minor image defect was confirmed very rarely, but there was no problem at all in actual use, and X represents an image defect (vertical stripe) confirmed.

From these experimental results, the width (mm) of the roughened area X at both ends of the toner leakage prevention sheet member A was in the range of 2 mm <X ≦ 30 mm, and a good result was obtained. When the roughened area X at both ends was 2 mm, an effect was obtained as compared with the case where the roughened area X was not rough at all, but the occurrence of density unevenness at a very slight level was confirmed. However, the image quality was at a level at which there is no problem in practical use. On the contrary, when the rough area X at both ends is 30 mm, a slight level streak in the vertical direction can be confirmed slightly in the image end area of the halftone image, but there is no problem in practical use as the image quality. It was a level.

  Further, it is more preferable if the width of the roughened region X at both ends is in the range of 5 mm ≦ X ≦ 20 mm. Within this range, the best results were obtained with no image defects at all conditions.

  In particular, a developing device in which a toner leakage prevention member B made of a magnetic material and a sponge-like elastic body as a toner lateral leakage prevention member C are provided below the toner leakage prevention sheet member A along the side of the toner leakage prevention member B. In this case, it is important that at least the region where the toner leakage preventing sheet member A, the toner leakage preventing member B, and the toner lateral leakage preventing member C overlap has roughness.

  As described above, according to the present embodiment, only the longitudinal end region of the surface of the toner leakage preventing sheet member that contacts the developing sleeve has a configuration that is rougher than the longitudinal central region. As a result, even if the contact pressure against the developing sleeve is high at both ends of the toner leakage preventing sheet member, the toner layer on the developing sleeve is made uniform and density unevenness does not occur. In addition, by setting the surface roughness and width of the roughened area of the toner leakage preventing sheet member to the appropriate ranges described above, vertical stripes at the image edge can be prevented.

<Second embodiment>
FIG. 10 is a diagram showing a second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member similar to 1st Example, and description is abbreviate | omitted.

  The second embodiment is characterized in that the toner layer and the charge distribution at both ends of the developing sleeve 43 are made uniform by coating the surface of both ends of the toner leakage prevention sheet member A to provide roughness. Is to plan.

  In this embodiment, since only the both end regions X ′ of the toner leakage prevention sheet member A need only be coated, as shown in FIG. 10, the configuration is simple and inexpensive without any major changes in configuration. Can be realized.

  In the second embodiment, a sheet made of polyethylene terephthalate (PET) having a thickness of 38 μm is used as the toner leakage preventing sheet member A.

Only a predetermined region X ′ (for example, the roughened region X = 7 mm) at both ends of the toner leakage prevention sheet member A is spray-coated with a phenol resin solution (coating agent) in which rough particles such as spherical carbon particles are dispersed. To a predetermined roughness (for example, arithmetic average roughness Ra = 7 μm).

  FIG. 11 is an enlarged cross-sectional view of the toner leakage prevention sheet member A of the present embodiment cut in the longitudinal direction. As shown in the drawing, since the rough particles are uniformly applied to the rough region X ′ of the longitudinal end portion of the toner leakage prevention sheet member A, the toner leakage prevention sheet member A is uniformly roughened. Can be provided. By doing so, the toner layer on the developing sleeve 43 and the charge distribution of the toner can be easily set to predetermined values.

  In this embodiment, as a roughening method, the toner leakage prevention sheet member A is not roughened by a roughing member such as sandpaper, but the toner leakage prevention sheet member A is roughened by spray coating. Explained the method. According to this method, it is possible to set the arithmetic average roughness Ra and the range (width) of the roughened region X ′ at both ends with high accuracy, and to reduce assembly tolerances. Further, since the roughness can be provided without cutting the toner leakage preventing sheet member A, the material cost can be reduced by thinning the toner leakage preventing sheet member A itself.

  As described above, according to the present embodiment, the surface of the toner leakage prevention sheet member is roughened by coating only both end regions. With this configuration, the contact pressure in the longitudinal direction of the toner leakage preventing sheet member, the toner layer on the developing sleeve, and the charge distribution can be made uniform. As a result, it is possible to suppress the occurrence of density unevenness while preventing toner leakage by attaching a toner leakage preventing member or a toner lateral leakage preventing member to both ends.

  In addition, since the surface of both end regions of the toner leakage prevention sheet member can be provided with a coating process by spray coating, the arithmetic average roughness Ra and the range of the rough regions X at both ends can be set with high accuracy. And assembly tolerances can be reduced. For this reason, it is possible to reliably prevent vertical stripes at the edge of the image.

  In the above-described embodiment, an example in which the contact pressure to the developing sleeve 43 at both ends of the toner leakage preventing sheet A increases when the toner leakage preventing member B is used has been described. However, the application example of the present invention is not limited to this. The present invention is applicable if the contact pressure against the developing sleeve 43 at both ends of the toner leakage preventing sheet A is high. For example, even in a sheet attaching method for obtaining tension in the longitudinal direction of the toner leakage preventing sheet A (straining attachment), the roughening regions (X, X ′) are provided at both ends of the toner leakage preventing sheet A, thereby implementing the above-described implementation. The same effect as the example can be obtained.

FIG. 3 is a diagram illustrating a longitudinal relationship and a roughened region X of a toner leakage prevention sheet member according to the first exemplary embodiment of the present invention. FIG. 4 is a diagram illustrating an arrangement with a toner leakage preventing member according to the first exemplary embodiment of the present invention. The figure which showed the contact pressure with respect to the longitudinal direction in 1st Example of this invention. FIG. 6 is a perspective view showing the attachment position of the toner leakage prevention member B and the frame of the developer container. FIG. 3 is a perspective view of a toner leakage preventing member B and a developing sleeve. FIG. 3 is a cross-sectional view of the toner leakage prevention member B and a developing sleeve attached to a developer container. FIG. 3 is a perspective view in which a toner leakage preventing member B and a developing sleeve are attached to a developer container. The side sectional view of a process cartridge. FIG. 3 is a side sectional view of the image forming apparatus equipped with a process cartridge. FIG. 6 is a diagram illustrating a relationship between a toner leakage prevention sheet member longitudinal direction and a roughened region X in a second embodiment of the present invention. FIG. 4 is a cross-sectional view of a toner leakage prevention sheet member that is cut in the longitudinal direction and enlarged.

Explanation of symbols

A ... toner leakage prevention sheet member B ... toner leakage prevention member C ... toner side leakage prevention member 43 ... development sleeve 1 ... laser scanner 2 ... photosensitive drum 3 ... charging Roller 4 ... Developer container 5 ... Cleaning container 6 ... Transfer roller 7 ... Transfer paper 8 ... Fixing device 10 ... Process cartridge

Claims (7)

A developer container containing the developer;
A developer carrying member carrying the developer;
In a developing device having a toner leakage preventing sheet member that contacts an outer peripheral surface of the developer carrying member and prevents leakage of the developer from the developer container,
The developing device according to claim 1, wherein the surface roughness of the longitudinal end region of the toner leakage preventing sheet member is larger than the surface roughness of the longitudinal central region. A toner leakage preventing member disposed at an end of the developer carrying member;
Further comprising
2. The development according to claim 1, wherein the surface roughness of the toner leakage preventing sheet member is larger than the surface roughness of the longitudinal center region at least in a range where the toner leakage preventing member and the toner leakage preventing sheet member overlap each other. apparatus.   2. The toner leakage prevention sheet member according to claim 1, wherein an arithmetic average roughness (Ra) of a longitudinal end region of a surface in contact with the developer carrying member satisfies a range of 3 μm ≦ Ra ≦ 25 μm. Item 3. The developing device according to Item 2. 4. The developer according to claim 1, wherein the developer is a one-component magnetic developer having at least a binder resin and a magnetic material and having an average circularity of 0.960 or more. Development device. The toner leakage prevention member is made of a magnetic material or a magnet, and is disposed at both ends of the developer carrier so as to face the outer peripheral surface of the developer carrier with a predetermined gap from the developer carrier. ,
5. The developing device according to claim 2, wherein a magnetic circuit is formed in a gap between the toner leakage preventing member and the developer carrying member.   A process cartridge comprising the developing device according to claim 1, wherein the process cartridge is detachable from an image forming apparatus main body. An image forming unit for forming a toner image;
A transfer portion for transferring a toner image onto a recording material;
In an image forming apparatus comprising a fixing unit that fixes a toner image to a recording material,
The image forming apparatus according to claim 6, wherein the image forming unit is the process cartridge according to claim 6.

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