JP5076357B2 - Developer regulating member and developing device - Google Patents

Description

The present invention relates to a developer regulating member provided in a developing device that develops a latent image on an image carrier with a developer, and a developing device that develops the latent image on the image carrier with a developer.

  The following is mentioned as one form of the developing device of the one-component developing system provided in the image forming apparatus using the electrophotographic system. The developing device uses a roll-shaped toner supply member (developer supply member) having a foam surface layer to attach toner to a development roll (developer holding member), which is a rigid body such as metal, and is made of resin. The toner on the developing roll is scraped off to a predetermined thickness by a plate-like toner regulating member (developer regulating member) having a formed surface layer and pressed against the developing roll to obtain a predetermined thickness and friction. Charges up. Then, the frictionally charged toner is moved onto the latent image based on the potential difference between the developing roll and the latent image on the image carrier.

  In such a developing device, there is a problem that the pressure contact force between the toner regulating member and the developing roll is large and the toner is finely broken. In particular, a toner (chemical toner) produced by a polymerization method has a lower hardness than a toner produced by a pulverization method (pulverized toner), and therefore cracks at the pressure contact portion between the toner regulating member and the developing roll, resulting in a fine powdery state. It may become a fragment and adversely affect the image. This chemical toner is suitable for higher resolution than pulverized toner, and is widely used in two-component developing type developing devices that stir the toner and the carrier without using a toner regulating member to charge the toner. However, in the one-component developing type developing device using the toner regulating member, it is difficult to put it to practical use due to the above-described problem of toner cracking.

  Also, fine particles added for the purpose of modifying the surface of the toner are peeled off from the surface of the toner by the pressure contact force between the toner regulating member and the developing roll, thereby changing the characteristics of the toner and changing the image quality. Defects may occur, for example, toner fluidity may deteriorate, toner circulation in the developing device may be insufficient, and the amount of toner supplied to the developing roll may be insufficient, resulting in insufficient image density. .

  Further, the external additive fine particles peeled off from the toner and the fine powdery crushed pieces due to the cracking of the toner are fused and accumulated on the surface of the developing roll and the toner regulating member to form irregularities, thereby forming the toner on the developing roll. In some cases, streaky unevenness occurs in the layer, and streaky density unevenness occurs in the formed image.

  As means for solving these problems, it has been devised to use a developing roll in which a rubber elastic layer having a thickness of 0.5 to 2 mm is formed on the outer periphery of the metal core in order to reduce the hardness of the surface of the developing roll. The developing roll faces the image carrier through a minute gap of 100 μm or less, and develops a latent image on the image carrier by causing toner to fly to the image carrier.

  Here, when developing the toner by flying it from the developing roll to the image carrier, the developing electric field fluctuates due to the fluctuation of the gap and the density of the image fluctuates. Therefore, the outer diameter of the developing roll is several tens of μm. The error is not allowed.

  However, in the developing roll having the rubber elastic layer on the surface according to the above method, due to restrictions on the manufacturing method, the outer diameter changes due to natural expansion after the rubber elastic layer is taken out from the molding die, and the rubber elastic layer is polished. There is a problem of difficulty in ensuring dimensional accuracy due to deformation. In particular, since the end surface in the axial direction of the developing roll is open and has no restraining force, the outer diameter is larger than the central portion in the axial direction. Further, if the polishing amount is increased only in the axial end portion of the developing roll in anticipation of this, the outer diameter of the axial end portion of the developing roll is smaller than the outer diameter of the central portion in the axial direction as shown in FIG. Sometimes.

  On the other hand, a developing roll is known in which a rubber tube is coated on the outer periphery of a rigid metal core (see, for example, Patent Document 1). When this method is used, a roll with better dimensional accuracy than a roll obtained by vulcanizing and molding a rubber elastic layer using a mold on the outer periphery of the metal core and removing it from the mold is obtained. It seems to be done. However, since the developing tube produced by this rubber tube coating method has a soft rubber tube layer and low tensile strength, the rubber tube layer is scraped by externally added particles on the toner surface, and fine groove-like scratches are formed on the surface of the developing roller. Thus, the problem that streaky unevenness occurs in the toner thin layer formed on the developing roll and streaky density unevenness also occurs in the image cannot be solved.

As another example, a developing roll covered with a tube made only of a resin is known (for example, see Patent Document 2). Although this developing roll has excellent dimensional accuracy, it has a clearly high surface hardness, a large pressure contact force on the toner particles, the toner is destroyed, and the problem that the toner layer formation failure occurs due to agglomeration of crushed pieces is not solved. .
JP 2003-262998 A Japanese Patent Laid-Open No. 9-90735

The present invention has been made in consideration of the above-described facts, and an object thereof is to suppress the occurrence of cracking of the developer and the change in the characteristics of the developer and to ensure the dimensional accuracy of the developer regulating member .

The developer regulating member according to claim 1 is provided in a developing device that develops a latent image on an image carrier with a developer, and holds the developer and moves the developer onto the latent image on the image carrier. a support facing the holding member, wherein on the support is formed only on a surface opposed to the developer holding member, a conductive to bond the resin rubber material is dispersed layer, and the resin layer and the support And an excess of developer held on the developer holding member is scraped off.

The developer regulating member according to claim 1 is provided in the developing device, and applies stress to the developer. However, the surface of the developing device component that contacts the developer is covered with a resin layer in which rubber material is dispersed. Therefore, the contact surface is coated with a resin layer in which rubber material is not dispersed. As a result, the hardness of the contact surface is lowered and the contact pressure between the contact surface and the developer is reduced, so that cracking of the developer, changes in the properties of the developer, and the like are suppressed. Therefore, compared to the conventional case, the development state of the developer layer and the stability of the supply amount of the developer are increased in the developing device, so that development defects such as density unevenness and insufficient density can be suppressed.

  Further, as confirmed in the test described later, the dimensional accuracy of the contact surface can be improved and the development performance can be improved as compared with the conventional case where the contact surface is a rubber material.

Developer regulating member according to claim 2 is the developer regulating member according to claim 1, is the thickness of the resin layer is 30 to 200 [mu] m, and wherein the micro-hardness of 81 ° or less To do .

In the developer regulating member according to claim 2, the resin layer has a thickness of 30 to 200 μm, and the resin layer has a micro hardness of 81 ° or less. As a result, it is possible to suppress the developer cracking to an acceptable level, as well as to maintain the developer formation state above the acceptable level, as well as to ensure the dimensional accuracy of the resin layer. This can be maintained.

A developing device according to a ninth aspect includes the developer regulating member according to the first or second aspect.

In the developing device according to the ninth aspect, as described above, the cracking of the developer and the change in the characteristics of the developer are suppressed as compared with the conventional case. The formation state of the developer layer becomes better, and development defects such as density unevenness and insufficient density can be suppressed. Further, since the dimensional accuracy of the developer regulating member is improved as compared with the conventional case, the developing performance is improved as compared with the conventional case.

Since the present invention is configured as described above, it is possible to suppress the occurrence of cracking of the developer and changes in the characteristics of the developer , and to ensure the dimensional accuracy of the developer regulating member .

  Next, a first embodiment of the present invention will be described with reference to the drawings.

  As illustrated in FIG. 1, the image forming apparatus 12 includes a paper feed tray 14 that stores the recording paper P, a paper feed roll 20 that transports the recording paper P from the paper feed tray 14 to the image forming unit 16, and a transport roll 21. Is provided. The paper feed roll 20 is disposed at the downstream end of the paper feed tray 14 in the transport direction, rotates in contact with the recording paper P set on the top of the paper feed tray 14, and removes the top recording paper P. The paper is fed out from the paper feed tray 14. The transport roll pair 21 is disposed in the transport path of the recording paper P, and sandwiches and transports the recording paper P sent out from the paper feed tray 14 by the paper feed roll 20 to the image forming unit 16.

  The image forming unit 16 includes a photosensitive drum 22 that rotates in a clockwise direction (arrow A direction) in the drawing, a charging roll 24 that is sequentially disposed around the photosensitive drum 22 in the direction of arrow A, and an exposure device. 26, a developing device 28, a transfer roll 30, and a cleaning device 32 are provided. The charging roll 24 rotates in contact with the photosensitive drum 22 to uniformly charge the photosensitive drum 22.

  The exposure device 26 uses a known exposure method such as an optical scanning method for scanning light in the axial direction of the photosensitive drum 22 or a line exposure method for exposing the photosensitive drum 22 in a line shape. An electrostatic latent image is formed on the image 22 based on the image data. This electrostatic latent image is a potential image based on contrast between a portion where the surface potential of the photosensitive drum 22 is hit and the surface potential is lowered and a portion where the surface potential is maintained at a high level without being exposed to light.

  Further, the developing device 28 includes a developing roll 28A and the like that rotate to face the photosensitive drum 22, and the toner is moved from the developing roll 32 to the low potential portion of the electrostatic latent image on the photosensitive drum 22, The electrostatic latent image on the photosensitive drum 22 is developed (visualized).

  As the one-component toner used in the present embodiment, a toner having a volume center particle diameter of about 4.5 to 11 μm may be selected as appropriate. Any toner that satisfies this condition may be a polymerized toner or a pulverized toner. I do not care.

  Further, the transfer roll 30 is in contact with the photosensitive drum 22 across the conveyance path of the recording paper P, and a transfer bias having a polarity that attracts toner on the photosensitive drum 22 is applied to the transfer roll 30 from the bias power source 31. As a result, the toner image is transferred from the photosensitive drum 22 to the recording paper P.

  The cleaning member 32 includes a blade 32A and a waste toner box 32B. The blade 32A is supported by the waste toner box 32B and is in contact with the photosensitive drum 22, and scrapes off the toner (residual toner) remaining on the photosensitive drum 22 without being transferred to the paper P. The waste toner box 32B collects waste toner scraped off from the photosensitive drum 22 by the blade 32A.

  A fixing device 34 is disposed on the downstream side in the transport direction of the image forming unit 16. The fixing device 34 includes a heating roll 34A that is in contact with the transfer surface of the recording paper P, and a pressure roll 34B that is in pressure contact with the heating roll 34A across the conveyance path of the recording paper P. The recording paper P on which the toner is transferred is pressed and heated by the heating roll 34A and the pressure roll 34B, whereby the toner image is fixed on the recording paper P.

  A paper discharge roll pair 36 is disposed on the downstream side in the transport direction of the fixing device 34, and a paper discharge tray 38 is formed on the upper surface of the image forming apparatus 12. The recording sheet P on which the toner image is fixed is discharged to a discharge tray 38.

  Hereinafter, the developing device 28 will be described in detail.

  As shown in FIG. 2, the developing device 28 includes a developing roller 28A, a developing roller 28A that rotatably supports the container 28B that stores one-component toner, a stirring mechanism 28C, a supply roller 28D, and a developing roller. And a toner regulating member 28E that comes into contact with the circumferential surface of 28A. In the developing device 28, the developer accommodated in the accommodating portion 28B is agitated by the agitating mechanism 28C, and the agitated developer is supplied from the supply roll 28D to the developing roll 28A. At this time, the excess toner held on the developing roll 28A is scraped off by the toner regulating member 28E, so that the thickness of the toner held on the developing roll 28A becomes a predetermined value. Then, a developing bias is applied from the bias power source 27 (see FIG. 1) to the developing roll 28A, and the potential of the developing roll 32 is intermediate between the high potential portion and the low potential portion of the electrostatic latent image on the photosensitive drum 22. The charged toner on the developing roller 32 moves to the low potential portion of the electrostatic latent image on the photosensitive drum 22. As a result, the electrostatic latent image on the photosensitive drum 22 is developed (visualized).

  The developing roll 28A is made of a semiconductive resin tube formed in a cylindrical shape by an inflation extrusion molding method or the like and covered with a stainless steel shaft having an outer diameter slightly larger than the inner diameter. It is a roll in which the resin layer J is laminated. As the semiconductive resin, a mixture of polyvinylidene fluoride (PVDF) resin 15 to 70 wt%, fluororubber 25 to 83 wt%, conductive material and other 2 to 20 wt% is used.

Here, the PVDF resin has a high elastic modulus of about 6000 kg / cm ² , and if used alone as it is, the hardness becomes too high and the surface hardness of the roller becomes too high, which is not preferable in consideration of stress on the toner and the photosensitive drum 22. Therefore, the fluororubber having high compatibility with the PVDF resin is mixed and dispersed for use. Further, when the amount of PVDF resin exceeds 70 wt%, the hardness becomes too large, which is not preferable, and when the amount of fluoro rubber exceeds 83 wt%, the film forming property is deteriorated.

  Further, since the developing roll 28A is applied with a developing bias and the counter charge after development must be removed, the surface of the developing roll 28A must have appropriate conductivity. For this reason, in this embodiment, as a conductive agent that adjusts the conductivity of the surface of the developing roll 28A, a perchlorate that is an ion conductive material (for example, lithium perchlorate, sodium perchlorate, ammonium perchlorate, etc.) ) And quaternary ammonium salts such as carbon black and metal oxides which are electronically conductive substances.

Thus, the volume resistivity of the semiconductive resin layer J in which a material exhibiting rubber elasticity is dispersed has a volume resistivity of 1 × 10 ⁴ Ω · cm or more and less than 1 × 10 ¹² Ω · cm. The counter charge after development can be effectively applied, and the ghost phenomenon can be prevented from occurring in the image by instantly removing the counter charge from the development roll 28A, which is preferable.

  The resin layer J may be formed by applying a semiconductive resin solution in which a rubber material is dispersed to a support.

  The toner regulating member 28E is formed by laminating urethane rubber having a thickness of 1.5 mm and Asker C hardness of 40 ° on a phosphor bronze plate, and is pressed against the developing roll 28A with a linear pressure of 200 g / cm. .

The toner supply roll 28D is formed by laminating a conductive polyurethane foam having a thickness of 5.5 mm, an Asker F hardness of 70 °, and a volume resistivity of 1 × 10 ⁷ Ω · cm on a conductive rigid core. The roll is in contact with the developing roll 28A with a biting amount of about 2 mm.

  Here, since the toner regulating member 28E and the toner supply roll 28D are in contact with the developing roll 28A, if the surface hardness of the developing roll 28A is too high, the stress on the toner on the developing roll 28A increases, and the toner Cracks occur. Further, depending on the material and thickness of the surface layer of the developing roll 28A, the straightness of the surface of the developing roll 28A is lowered, and development unevenness occurs. For this reason, it is necessary to appropriately set the material, thickness, hardness and the like of the surface layer of the developing roll 28A. Therefore, the following samples having different surface layer materials, thicknesses, hardnesses, and the like are prepared, and the durability test of the developing device 28 is performed using the samples. Thereafter, the surface of the toner and the developing roll 28A is observed to observe the toner. The amount of occurrence of cracks was evaluated, the quality of the toner layer formed on the developing roll 28A was good and bad, and the dimensional accuracy of the outer diameter of the developing roll 28A was evaluated. The evaluation results are as shown in the table of FIG.

  In the durability test of the developing device 28, the developing roll 28A was rotated for a time required to print 4000 sheets of A4 vertical paper at 300 mm / sec. In this embodiment and second to fourth embodiments to be described later, toner is observed at a magnification of 10,000 using a scanning electron microscope (SEM), and observation of the developing roll 28A and the like is performed at a magnification. The measurement was performed using a 500 × optical microscope. The micro hardness was measured using a micro hardness meter (product name: Micro Durometer MD-1 Asker).

  Further, the toner used in the present embodiment and second to fourth embodiments described later is a toner obtained by agglomerating fine particles obtained by emulsion polymerization. The binder resin is made of styrene acryl, the toner has a volume center particle size of 5.8 μm, the shape factor defined below is 132, titanium oxide and small-diameter silica are externally added, and the toner is negatively charged. It is. The volume center particle diameter of the toner is a value measured with a Coulter counter TAII (manufactured by Beckman-Coulter). The particle size measurement method is as follows. First, 0.5 to 50 mg of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate as a dispersant, and this is added to 100 to 150 ml of an electrolytic solution. Then, the electrolytic solution in which the measurement sample is suspended is subjected to a dispersion treatment for about 1 minute with an ultrasonic disperser, and the particle size distribution is measured using an aperture having an aperture diameter of 100 μm by a Coulter counter TA-II type. That's it.

  In addition, the shape factor is calculated by the following equation by performing image analysis of an enlarged photograph taken with an optical microscope (Microphoto FXA: manufactured by Nikon Corporation) using an image analyzer LUZEX3 (manufactured by NIRECO).

Shape factor = {(absolute maximum length of toner diameter) ² / projection area of toner} × (π / 4) × 100
Here, the shape factor is represented by the ratio of the projected area of the toner and the area of the circle circumscribing the toner, and is 100 for a true sphere, and increases as the shape of the true sphere collapses. It should be noted that the shape factor to be obtained has an average value for a plurality of toner particles as a representative value.

In addition, the evaluation of the amount of occurrence of toner cracking is evaluated as ◯ when the ratio of the broken toner is 10% or more and x is less than 10%. In addition, the evaluation of whether the toner layer formed on the developing roll 28A is good or bad is evaluated as x when streaky unevenness is present in the toner layer, and is evaluated as o when it is not present.
Sample 1: A roll covering a tube having a material of PVDF 65 wt%, fluororubber 30 wt%, conductive material and other 5 wt%, a tube having a thickness of 30 μm and a micro hardness of 81 °.
Sample 2: A roll covering a tube of PVDF 65 wt%, fluorine rubber 30 wt%, conductive material and other 5 wt%, a tube having a thickness of 50 μm and a micro hardness of 59 °.
Sample 3: A roll in which a tube made of PVDF 65 wt%, fluororubber 30 wt%, conductive material and other 5 wt%, a tube having a thickness of 100 μm and a micro hardness of 73 ° is coated.
Sample 4: A roll in which a tube made of PVDF 65 wt%, fluororubber 30 wt%, conductive material and other 5 wt%, coated with a tube having a thickness of 200 μm and a micro hardness of 35 °.
Sample 5: A roll in which a tube made of PVDF 65 wt%, a mixture of fluoro rubber 30 wt%, conductive material and other 5 wt%, a tube having a thickness of 20 μm and a micro hardness of 95 ° is coated.
Sample 6: A roll in which a material is a mixture of PVDF 65 wt%, fluororubber 30 wt%, conductive material and other 5 wt%, a tube having a thickness of 250 μm and a micro hardness of 35 °.
Sample 7: A roll covering a tube having a material of PVDF 95 wt%, a conductive material and other 5 wt%, a thickness of 100 μm, and a micro hardness of 89 °.
Sample 8: A roll covering a tube having a material of PVDF 95 wt%, a conductive material and other 5 wt%, a tube having a thickness of 50 μm and a micro hardness of 95 °.
Sample 9: A roll covering a tube of polyamide (PA) 95 wt%, conductive material and other 5 wt%, a tube having a thickness of 100 μm and a micro hardness of 99 °.

  As can be seen from the table of FIG. 3, in the developing rolls 28A of Samples 7 to 9 in which the fluororubber is not dispersed in the resin layer, the surface micro hardness is as high as 89 ° or more, and the toner is frequently cracked. Further, in the developing roll 28A of Sample 5 having a thickness of 20 μm, the amount of fluororubber was small or toner cracking frequently occurred. On the other hand, in the developing roll 28A of Sample 6 having a thickness of 250 μm, the amount of fluororubber was too much, or the accuracy of the thickness of the resin layer was lowered, and the desired outer diameter dimensional accuracy could not be obtained. Further, streaky unevenness was present in the toner layer on the developing roll 28A.

  On the other hand, in the developing roll 28A of Samples 1 to 4 in which fluororubber is dispersed in the resin layer, the thickness is 30 to 200 μm, and the micro hardness is greater than 0 and equal to or less than 81 °, the occurrence of toner cracking is small No streaky unevenness was present in the toner layer on the developing roll 28A. Further, when the outer diameter of the developing roll 28A was measured three-dimensionally, as shown in FIG. 4, a substantially cylindrical profile was obtained, and dimensional accuracy of a desired outer diameter was obtained.

  Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

  As shown in FIG. 5, in the developing device 102 of the present embodiment, a toner regulating member 102E is provided instead of the toner regulating member 28E of the first embodiment, and a developing roll 102A is provided instead of the developing roll 28A. Has been. As shown in FIG. 6, this toner regulating member 102E is a phosphor bronze plate material, and a 100 μm resin of the same material as the resin layer of the developing roll 28A is formed only on the surface in contact with the toner, that is, the surface facing the developing roll 28A. Layer J is formed. The resin layer J was formed by cutting a tube having a thickness of 100 μm to form a rectangular member, and then bonding the resin layer J to the support S with a conductive double-sided tape T. The resin layer J has a micro hardness of 60 ° and is pressed against the developing roll 102A with a linear pressure of 200 g / cm.

  The developing roll 102A is a roll obtained by sandblasting the surface of an aluminum sleeve.

  Such a developing device 102 is also subjected to a durability test similar to that of the first embodiment, and then the toner and the developing roll 102A are observed to determine whether the amount of toner cracking is large or small, and the toner layer formation state on the developing roll 102A. Evaluation of good or bad. Further, the endurance test was performed in the same manner by changing the developing roll 102A to the developing roll 28A of the sample 3 used in the first embodiment, and similarly, the amount of occurrence of toner cracking was the same, and the formation state of the toner layer on the developing roll 28A Evaluation of good or bad. Further, the endurance test is performed in the same manner by changing the toner restricting member 102E to the toner restricting member 28E used in the first embodiment. Similarly, the amount of occurrence of toner cracking is the same, and the formation state of the toner layer on the developing roll 102A. Evaluation of good or bad. The results are shown in the table of FIG.

  As can be seen from the table of FIG. 7, when the toner regulating member 102E and the developing roll 102A are used, when the toner regulating member 102E and the developing roll 28A are used, evaluation of the amount of occurrence of toner cracking, the developing rolls 102A and 28A are performed. The evaluation of the formation state of the upper toner layer becomes “good”, and when the toner regulating member 28E and the developing roll 102A are used, the evaluation of the amount of toner cracking and the evaluation of the formation state of the toner layer on the developing roll 102A are × I found out that

  That is, by using the toner regulating member 102E having the resin layer J in which the rubber material is dispersed, the amount of occurrence of toner cracking is larger than in the case of using the toner regulating member 28E having the resin layer in which the rubber material is not dispersed. It was found that can be reduced. When the developing roll 28A having the resin layer J in which the rubber material is dispersed is used in addition to the toner regulating member 102E, the amount of toner cracking further decreases.

  Here, the contact surface of the toner regulating member 102E with the toner is a resin material in which a rubber material is dispersed, so that the contact surface is made of the toner and the external additive as compared with the case where the contact surface is a rubber material. It is possible to suppress the deterioration of the contact surface over time, which is polished by the agent and the thickness of the contact surface decreases.

  Next, a third embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 1st, 2nd embodiment, and description is abbreviate | omitted.

  As shown in FIG. 8, in the developing device 104 of the present embodiment, a charging roll 104F that charges the toner on the developing roll 102A is provided in addition to the components of the developing device 102 of the second embodiment. The charging roll 104F is disposed on the downstream side in the rotation direction of the developing roll 102A from the toner regulating member 102E and on the upstream side in the rotational direction of the developing roll 102A from the photosensitive drum 22, and is held by the developing roll 102A and is regulated by the toner. The toner whose thickness is set to a predetermined value by the member 102E is charged.

The charging roll 104F is a roll in which a conductive rigid core is coated with the same material as the resin layer J of the developing roll 28A of the first embodiment or a tube made of the material is coated. The volume resistivity ρ of the resin layer J of the charging roll 104F is preferably 1 × 10 ⁴ Ω · cm ≦ ρ <1 × 10 ¹² Ω · cm. When the volume resistivity ρ of the resin layer J is less than 1 × 10 ⁴ Ω · cm, current leakage occurs between the charging roll 104F and the developing roll 102A, causing unevenness in the discharge and the charge amount of the toner. Will be uneven. On the other hand, when the volume resistivity ρ of the resin layer J is 1 × 10 ¹² Ω · cm or more, an effective discharge cannot be generated between the charging roll 104F and the developing roll 102A, and the charge amount of the toner Is lacking.

  The charging roll 104F is in contact with the developing roll 102A and the toner on the developing roll 102A, and the thickness of the toner on the developing roll 102A can be regulated by the charging roll 104F. Therefore, the toner regulating member 102E can be omitted. is there.

  In such a developing device 104, the same durability test as in the first and second embodiments is performed, and then the toner is observed to check whether the amount of toner cracking is large or small. The quality of the formation was evaluated. In addition, the endurance test was performed in the same manner by changing the charging roll 104F to a charging roll having a resin layer on which the rubber material is not dispersed on the surface. The quality of the layer formation was evaluated.

  As a result, when the charging roll 104F in which the rubber material is dispersed in the resin layer J is used, the amount of occurrence of toner cracking is larger than in the case where the charging roll in which the rubber material is not dispersed in the resin layer is used. And the toner layer was well formed. In this embodiment, the charging roll 104F is used while being in contact with the toner on the developing roll 102A and the developing roll 102A. However, it is not necessary to regulate the thickness of the toner by providing the toner regulating member 102E. Therefore, the charging roll 104F may be used slightly separated from the developing roll 102A and the toner on the developing roll 102A.

  Next, a fourth embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 1st thru | or 3rd embodiment, and description is abbreviate | omitted.

As shown in FIG. 9, in the developing device 106 of the present embodiment, the toner supply roll 106D has a conductive rigid core coated with the same material as the resin layer J of the developing roll 28A or a tube made of the material. The coated roll faces the developing roll 28A in a non-contact manner. The volume resistivity ρ of the resin layer J of the toner supply roll 106D is preferably 1 × 10 ⁴ Ω · cm ≦ ρ <1 × 10 ¹² Ω · cm. When the volume resistivity ρ of the resin layer J is less than 1 × 10 ⁴ Ω · cm, current leakage occurs between the toner supply roll 106D and the developing roll 28A, unevenness in discharge occurs, and toner supply The amount is uneven. On the other hand, when the volume resistivity ρ of the resin layer J is 1 × 10 ¹² Ω · cm or more, an effective electric field cannot be generated between the toner supply roll 106D and the developing roll 28A, and the toner supply amount Is lacking.

  In such a developing device 106, the same durability test as in the first and second embodiments was performed, and then the surface states of the toner supply roll 106D and the developing roll 28A were observed. The toner supply roll 106D was changed to a roll having a urethane foam surface and pressed against the developing roll 28A, and a durability test was performed in the same manner. Thereafter, the surface state of the roll and the developing roll 28A was observed.

  As a result, when the toner supply roll 106D that is not in contact with the developing roll 28A and in which the rubber material is dispersed on the surface layer is used, the toner supply roll 106A that is in pressure contact with the developing roll 28A and whose surface layer is urethane foam is used. In comparison, it was found that the amount of toner fused to the surface of the developing roll 28A is reduced, and the thickness unevenness of the toner layer formed on the developing roll 28A is reduced.

  As described above, by taking the first to fourth embodiments as an example, by forming a resin layer in which a rubber material is dispersed on the contact surface with the toner of the developing device components provided in the developing device, The frequency of occurrence of toner cracking can be reduced. As a result, the external additive particles detached from the toner surface and the crushed fine powder due to toner cracking are fused and accumulated on the surface of the developing roll and the toner regulating member to make the surface uneven, thereby forming a toner layer on the developing roll. As a result, streaky unevenness occurs in the image, and streaky density unevenness occurs in the formed image.

1 is a side view schematically showing an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a side sectional view showing a developing device provided in the image forming apparatus of FIG. 1. 6 is a table summarizing results of tests for evaluating toner cracking, toner layer formation, and outer diameter dimensional accuracy. It is a graph which shows the profile of the outer diameter of a developing roll. FIG. 6 is a side sectional view showing a developing device provided in an image forming apparatus according to a second embodiment of the present invention. FIG. 6 is a cross-sectional view illustrating a toner regulating member provided in the developing device of FIG. 5. 4 is a table summarizing the results of tests for evaluating toner cracking and toner layer formation. FIG. 10 is a side sectional view showing a developing device provided in an image forming apparatus according to a third embodiment of the present invention. It is a sectional side view which shows the image development apparatus with which the image forming apparatus of 4th Embodiment of this invention was equipped. It is a graph which shows the profile of the outer diameter of the conventional image development roll.

Explanation of symbols

12 Image forming apparatus 22 Photosensitive drum (image carrier)
28 Developing Device 28A Developing Roll (Developing Member)
28D supply roll (developer supply member)
28E Toner regulating member (developer regulating member)
102 Developing Device 102A Developing Roll (Developing Member)
102E Toner regulating member (developer regulating member)
104 Developing Device 104F Charging Roll (Charging Member)
106 Developing Device 106D Supply Roll (Developer Supply Member)
J Resin layer

Claims (3)

A support that is provided in a developing device that develops a latent image on the image carrier with a developer, and that faces the developer holding member that holds the developer and moves it onto the latent image of the image carrier;
Wherein on the support is formed only on a surface opposed to the developer holding member, a resin layer rubber material is dispersed,
A conductive double-sided tape that bonds the support and the resin layer;
And a developer regulating member that scrapes off an excess of the developer held by the developer holding member.   The developer regulating member according to claim 1, wherein the resin layer has a thickness of 30 to 200 μm and a micro hardness of 81 ° or less.   A developing device comprising the developer regulating member according to claim 1.

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