JP5268341B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus with a developing device in which a developer layer thickness restricting member is not fixed, the horizontal streak or nonuniform of a developer layer caused by the use of the developer layer thickness restricting member having a cavity in its inside against a surface layer is eliminated, and can be downsized. <P>SOLUTION: The developer layer thickness restricting member 4 is formed from a flexible member 41 that has the cavity in it, and a hold member 42 that holds the flexible member 41. In the flexible member 41, part of the surface of a portion that is not held by the hold member 42 is in contact with a developer carrier 3. The hold member 42 supplies a voltage from a restricting bias means 14 to the flexible member 41. In addition, the hold member 42 has a power supply member that fixes the flexible member 41 to the hold member 42. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic recording system, such as a laser printer, a copying machine, and a facsimile.

  2. Description of the Related Art Conventionally, in a developing device using an electrophotographic system, a toner regulating plate or a cylindrical type is used as a developer layer thickness regulating member (that is, a toner regulating member) for regulating the amount of toner that is a developer (toner) to be supplied. Toner regulating members are known. It is difficult to stably form a thin layer of toner on a developing roller as a developer carrier, and a stable method for forming a thin layer of toner is an essential technology at present when there is a demand for higher image quality. ing.

  In the developing device using the toner regulating plate, the toner layer is formed by the line contact or surface contact with the developing roller, and the developing roller rotates, and the toner is generated by the friction generated between the toner regulating plate and the developing roller. Perform triboelectric charging. In this configuration, the leaf spring is used as a cantilever beam to obtain a pressing force, and the distance between the working point and the fulcrum of the cantilever beam is ensured in order not to apply an excessive load to the toner.

  The developing device using the cylindrical toner regulating member rotates or stops the cylindrical toner regulating member and presses the developing roller so that the toner is caused by friction between the cylindrical toner regulating member and the developing roller. Perform triboelectric charging.

  For example, Patent Document 1 describes a developing device having a structure in which a toner regulating member made of a flexible material having a cylindrical or quadrangular prism shape is fitted in a recess provided on a wall surface of a developing device main body. In the developing device having this structure, it is described that uniform pressure contact force is applied to the developing roller without requiring high accuracy in the mounting position or the like.

Further, in Patent Document 2, a cylindrical toner regulating member is used as a toner regulating member, and the cylindrical toner regulating member uniformly contacts the developing roller by a fixing member parallel to the developing roller to form a toner layer. It is characterized by.
Japanese Patent No. 2973604 JP-A-7-248680

  However, when using the toner regulating plate of the developing device, it is necessary to secure the distance between the working point of the cantilever and the fulcrum in order to obtain a preferable pressure contact force to the developing roller. There are various factors that cause the pressure contact force to change, such as rotational fluctuation of the developing roller, cylindricity, and roundness. To keep the pressure contact force within a predetermined range against these changes, the toner regulating plate The material, thickness, and the distance between the working point of the cantilever and the fulcrum will be selected as appropriate.

  However, among these materials, the material is limited to some extent from the viewpoints of spring constant, durability, rust prevention, cost, and the like. In addition, since the thickness depends on the standard of the distribution material, it is difficult to select an optimum thickness. For this reason, it is preferable to increase the distance between the working point of the cantilever and the fulcrum in order to cope with the change in the pressure contact force. However, increasing the distance between the working point and the fulcrum of the cantilever means that the developing device becomes larger as it is. Therefore, it is difficult to downsize the toner layer regulating member when the toner regulating plate is used.

  Further, when a cylindrical type toner regulating member having a cavity at the center is used, in the conventional configuration, the toner regulating member is sandwiched between the developing roller and the holding member of the toner regulating member, and is pressed by the holding member. . That is, in Patent Document 1, the recess is a holding member, and in Patent Document 2, a cylindrical toner regulating member fixing member is a holding member. Such a configuration reduces the number of parts, thereby reducing the cost. This is a very effective method.

  However, since the toner restricting member is not fixed and is movable, the toner restricting member in contact with the developing roller receives a force by the rotation of the developing roller. In particular, when the developing roller is deviated from the center of rotation or the cylinder is shaken, the force with which the developing roller pushes the toner regulating member also changes. For this reason, the toner regulating member is twisted or the contact state becomes unstable due to vibration caused by rotation.

  Furthermore, in recent years, a voltage different from that of the developing roller may be applied to the toner regulating member in order to stabilize the toner coat by the toner regulating unit.

  However, it is difficult to stably apply a voltage when the toner regulating member is twisted or vibrated as described above, and the path of the current flowing through the toner regulating member is unstable due to the rotation of the developing roller or the vibration caused by the rotation. Tended to be. As a result, the toner coat on the developing roller became unstable, and the toner was coated on the developing roller in the form of a horizontal stripe, or the toner coat was partially shaded.

  An object of the present invention is to prevent lateral streaks and non-uniformity of the developer layer caused by using a developer layer thickness regulating member having a cavity inside the member with respect to the surface layer surface without fixing the developer layer thickness regulating member. An object of the present invention is to provide an image forming apparatus provided with a developing device that can solve the problem and achieve miniaturization.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention comprises an image carrier on which an electrostatic latent image is formed,
A developer carrying body that carries and conveys the developer and makes the electrostatic latent image a visible image with the developer, and development that regulates the layer thickness of the developer carried and carried by the developer carrying body A developing device comprising: a developer layer thickness regulating member; a developing bias means for supplying a voltage to the developer carrying member; and a regulating bias means for supplying a voltage to the developer layer thickness regulating member;
In an image forming apparatus having
The developer layer thickness regulating member is formed by a flexible member having a cavity inside the member and a holding member that holds the flexible member, and the flexible member is held by the holding member. A part of the surface in the part that is not in contact with the developer carrier,
The holding member is to feed a voltage from the regulating bias means to said flexible member, and, have a power supply member for fixing the flexible member to the holding member,
The power supply member is a needle-like electrode member, supplies power by piercing the flexible member, and fixes the flexible member to the holding member.
An image forming apparatus characterized by the above.

  According to the present invention, the horizontal streak and developer generated by using a developer layer thickness regulating member that has been generated in the past, and the developer layer thickness regulating member is not fixed and has a cavity inside the member with respect to the surface layer surface. The non-uniformity of the layers can be eliminated and downsizing can be realized.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
FIG. 1 is a sectional view showing a schematic configuration of a full-color laser printer 100 using an electrophotographic process which is an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a schematic configuration of a process cartridge that contributes to image formation in the image forming apparatus of this embodiment. FIG. 3 is a schematic configuration diagram of the developing device 7 for explaining the developing operation by the developing device 7 as developing means according to the present invention.

  The overall configuration of the image forming apparatus in this embodiment will be described below.

(Overall configuration of image forming apparatus)
In this embodiment, the image forming apparatus 100 includes four process cartridges 9 (9y, 9m, 9m, 9m, 9m, 9m, m), cyan (c), and black (k). 9c, 9k). “Y, m, c, k” shown after the number corresponds to each toner color. For example, the process cartridge 9y is a process cartridge for forming an image of yellow toner.

  As will be described in detail later, each process cartridge 9 includes a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 as an image carrier. In this embodiment, the process cartridge 9 is a unit in which the charging unit 2, the developing unit 4 and the cleaning unit 6 are integrated with the photosensitive drum 1, and is mounted on the image forming apparatus main body 100A (not shown). ) Is detachably mounted. In this embodiment, the four process cartridges 9 are arranged in the vertical direction from the upstream side to the downstream side of the conveyance path of the recording paper P that is a transfer material as a recording medium.

  The toner image formed on the photosensitive drum 1 by the process cartridge 9 of each color is transferred onto an intermediate transfer belt 20 that is an intermediate transfer member constituting the transfer device 8 to form a full color image. That is, the toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt 20 by a primary transfer roller 22 (22y, 22m, 22c, 22k) provided at a position facing the photosensitive drum 1 of each color, It is a color image. The color image is transferred onto the recording paper P all at once by the secondary transfer roller 23 provided on the downstream side in the moving direction of the intermediate transfer belt 20. The untransferred toner on the intermediate transfer belt 20 is collected by the intermediate transfer belt cleaner 21.

  The recording paper P is stacked in a cassette 24 provided in the lower part of the image forming apparatus 100, and is conveyed by a paper feed roller 25 together with a request for a printing operation. At the position of the secondary transfer roller 23, the intermediate transfer belt 20 is transferred. The toner image formed thereon is transferred.

  Thereafter, the toner image on the recording paper P is heated and fixed on the recording paper P by the fixing unit 26, and is discharged from the image forming apparatus 100 to the outside through the paper discharge unit 27.

  In the image forming apparatus 100 of the present embodiment, the life including the toner capacity of the process cartridge 9 is set to be equivalent to 4000 sheets in terms of 5% A4 paper printing rate.

  Next, an image forming process in the process cartridge 9 will be described.

(Process cartridge and image forming process)
FIG. 2 shows a cross section in the vicinity of one of the four process cartridges 9 arranged in parallel.

  In this embodiment, the photosensitive drum 1 which is the center of the image forming process is an organic photosensitive drum 1 in which an outer surface of an aluminum cylinder is coated with a functional undercoat layer, a carrier generation layer, and a carrier transfer layer in this order. ing. In the image forming process, the photosensitive drum 1 is driven in a clockwise direction as indicated by an arrow in the drawing at a speed of 98 mm / sec.

  The charging roller 2 as charging means is driven to rotate by bringing a roller portion 2 b of conductive rubber formed around the core metal 2 a into pressure contact with the photosensitive drum 1. Here, a DC voltage of −1100 V is applied to the core 2a of the charging roller 2 with respect to the photosensitive drum 1 as a charging step. As a result, a uniform dark portion potential (Vd) of about −550 V is formed as the surface potential of the photosensitive drum 1.

  A spot pattern of laser light emitted corresponding to the image data is exposed on the photosensitive drum 1 by the scanner unit 10 serving as an exposure unit on the uniform surface charge distribution surface. In the exposed portion, the charge on the surface is lost by the carrier from the carrier generation layer, and the potential is lowered. As a result, an electrostatic latent image is formed on the photosensitive drum 1 with the light portion potential Vl = −100 V at the exposed portion and the dark portion potential Vd = −550 V at the unexposed portion.

  The electrostatic latent image is developed by developing means 7 having a developing roller 3 as a developer carrying member. On the developing roller 3, a toner coat layer having a predetermined coat amount and charge amount is formed. Although a method for forming the toner layer will be described later, the developing roller 3 rotates in the forward direction (counterclockwise rotation) with respect to the photosensitive drum 1 while being in contact with the photosensitive drum 1. In this embodiment, a DC bias = −350 V is applied to the developing roller 3 by the developing bias means 12 (FIG. 3). As a result, the negatively charged toner due to frictional charging is transferred from the potential difference to only the bright portion potential portion at the developing portion contacting the photosensitive drum 1 to visualize the electrostatic latent image. Image).

  The intermediate transfer belt 20 in contact with the photosensitive drum 1 of each process cartridge 9 is pressed against the photosensitive drum 1 by primary transfer rollers 22 (22y, 22m, 22c, 22k) facing the photosensitive drum 1. Further, a DC voltage is applied to the primary transfer rollers 22y, 22m, 22c, and 22k by a transfer bias unit (not shown), and an electric field is formed between the primary transfer rollers 22y, 22m, 22c, and 22k. As a result, the toner image visualized on the photosensitive drum 1 is transferred from the photosensitive drum 1 to the intermediate transfer belt 20 under the force of the electric field in the pressure contact area. On the other hand, the untransferred toner remaining on the photosensitive drum 1 without being transferred to the intermediate transfer belt 20 is scraped off from the drum surface by a urethane rubber cleaning blade 6a installed in a cleaning device 6 as a cleaning means. Housed in the cleaning device 6.

(Development means)
The details of the developing device 7 which is the developing means used in this embodiment will be described below.

  FIG. 3 shows a schematic configuration of a developing device 7 using a regulating member 4 of Example 1 described later. The developing device 7 includes a developing container 40 in which nonmagnetic one-component toner T that is a developer is accommodated. Further, as described above, the developing device 7 is provided with the developing roller 3 that is a developer carrying member that rotates in the forward direction (counterclockwise) while being in contact with the photosensitive drum 1. Further, the developing device 7 includes a toner supply roller 5 that rotates in the opposite direction (counterclockwise) at the contact portion while being in contact with the developing roller 3, and a stirring member 11 that stirs the toner T. .

  In this embodiment, the rotation speed of the developing roller 3 is 140 mm / sec, and the rotation speed of the toner supply roller 5 is 86 mm / sec.

  Further, the developing device 7 abuts the developing roller 3 on the downstream side of the supply roller 5 with respect to the rotation direction of the developing roller, faces the development, controls the amount of developer, and regulates the developer layer thickness for applying electric charge. A member (hereinafter referred to as “toner regulating member”) 4 is provided.

  The toner regulating member 4 is intended to control the toner on the developing roller 3 to a predetermined coating amount and a predetermined charge amount suitable for development on the photosensitive drum 1.

  Hereinafter, each member in the developing device 7 of the present embodiment will be described.

(Development roller configuration)
As shown in FIG. 3B, the developing roller 3 is a so-called elastic developing roller having an elastic layer 3b on a cored bar 3a. In this embodiment, a first layer (base layer) 3b made of solid rubber in which carbon is dispersed in silicone rubber is formed on a stainless steel core 3a having a diameter of 6 mm with a layer thickness of about 3 mm.

  Further, as the second layer (intermediate layer) 3c, a layer in which a spherical resin of about 20 μm to 60 μm is dispersed in a urethane resin whose resistance is adjusted by a conductive agent is formed with a layer thickness of about 10 μm. The spherical resin serves to adjust the surface roughness of the developing roller.

  A third layer (surface layer) 3d is formed on the second layer. The surface layer 3d is made of a urethane resin whose resistance is adjusted by a conductive agent, and has a layer thickness of about 10 μm. Since the resin of the surface layer 3d has a purpose of charging the toner by being rubbed with the toner, a resin capable of charging the toner to a predetermined polarity is preferably used.

(Development roller material)
As materials for the base layer 3b and the intermediate layer 3c of the developing roller, in addition to the above, butyl rubber, budadiene rubber (BR), natural rubber, acrylic rubber, EPDM (ethylene / propylene copolymer), or a mixed rubber thereof, etc. Generally used rubber can be used.

  A desired resistance value can be obtained by dispersing carbon resin particles, metal particles, an ionic conductive agent, and the like using these rubbers as a base material. As the ionic conductive agent, conductivity can be obtained by dispersing an ionic conductive agent such as lithium perchlorate or a quaternary ammonium salt in a binder.

  As the resin binder for the surface layer 3d, when a negatively chargeable toner is used, a urethane resin, a silicone resin, a polyamide resin, or the like is preferably used. If a positively chargeable toner is used, a fluorine resin or the like is preferably used. A desired resistance value can be obtained by dispersing the aforementioned carbon resin particles, metal particles, ionic conductive agent, and the like in these resins.

  In this embodiment, a three-layer structure is used, but the present invention is not limited to this. In order to form the desired surface roughness, a spherical resin is used for the intermediate layer 3c. However, a two-layer structure may be used by utilizing the surface roughness of the base layer 3a.

The resistance value of the developing roller 3 is desirably 2 × 10 ⁴ Ω to 5 × 10 ⁸ Ω. This is because if it is less than 2 × 10 ⁴ Ω, the current flowing in the elastic layer increases, and the required current capacity increases. Further, if it exceeds 5 × 10 ⁸ Ω, the current flowing during development tends to be hindered. In this embodiment, 5 × 10 ⁵ Ω is used.

(Development roller resistance measurement method)
The resistance measurement will be described with reference to FIG.

  In the figure, a roller 63 to be measured includes a conductive mandrel 62 made of stainless steel, an elastic layer 61 formed on the outer periphery thereof, and a roller surface 60. When the roller 63 is a single layer, the elastic layer 61 and the roller surface 60 are made of the same kind of material. The longitudinal width is about 230 mm.

  The stainless steel cylindrical member 66 having a diameter of 30 mm rotates in the direction of the arrow at a speed of about 48 mm / sec. At this time, the roller 63 rotates following the rotation of the cylindrical member 66. An end roller 69 is fitted to the end of the roller 63 to limit the amount of penetration into the cylindrical member 66 to 50 μm (in order to make the contact area between the roller and the cylindrical member constant). The end roller 69 has a cylindrical shape whose outer diameter is 100 μm smaller than the outer diameter of the roller 63.

  A load 67 is applied to both ends of the roller 63 (62 parts of conductive core metal). As for the load 67, the roller 63 is pressed against the cylindrical member 66 by a load of 1 kg in weight of 500 g on each side.

The measurement circuit 68 includes a power source Ein2, a resistor Ro2, and a voltmeter Eout2. In this measurement, Ein2: 300 V (DC) was performed. For the resistor Ro2, Ro2: 100Ω to 10MΩ can be used. Since the resistance Ro2 is for measuring a weak current, it is preferable to use a resistance value 2 to 4 digits lower than the roller resistance to be measured. That is, if the roller resistance is about 1 × 10 ⁶ Ω, Ro2 may be 1 kΩ.

The roller resistance value Rb is calculated by the following equation.
Rb = Ro2 × (Ein2 / Eout2-1) (Ω)

  In this example, the value of Eout2 10 seconds after applying the voltage was measured and obtained.

(Development roller surface roughness)
The surface roughness of the developing roller 3 is preferably 1 μm to 10 μm in terms of the ten-point average roughness Rz, although it depends on the particle size of the toner used. If the toner particle size to be used is an average volume particle size of 6 μm, a 10-point average roughness Rz of 2 μm to 8 μm can be preferably used. When the toner particle size is smaller, it is preferable to slightly reduce the ten-point average roughness Rz. If the ten-point average roughness Rz is less than 1 μm, a sufficient toner conveying force cannot be obtained, resulting in insufficient density. On the other hand, if the thickness exceeds 10 μm, the toner cannot be sufficiently charged, and so-called “fogging” occurs in which the toner adheres to the non-image area. In the present example, Rz of 3 μm was used.

  The ten-point average roughness Rz was defined according to JIS B0601, and a surface roughness tester “SE-30H” manufactured by Kosaka Laboratory was used for measurement.

(Rubber hardness)
The rubber hardness of the developing roller was an Asker C rubber hardness meter (manufactured by Kobunshi Keiki Co., Ltd.). A rubber hardness of 30 to 75 degrees (Asker C) is preferably used. If it exceeds 75 degrees (Asker C), the toner melts due to the rubbing of the developing roller 3, and blade fusion or roller fusion occurs, which is not preferable. In addition, the contact state between the developing roller 3 and the photosensitive drum 1 is likely to become unstable. If it is less than 30 degrees, it is difficult to use as a developing roller due to permanent deformation due to compression set. More preferably, it is 35 degrees to 60 degrees, and by setting the hardness in this range, triboelectric charging can be performed without applying excessive stress to the toner. In the present example, a 45 degree one was used.

(Development roller manufacturing method)
An example of a developing roller manufacturing method in this embodiment will be described.

  First, an adhesive for securing rubber and ensuring electrical conductivity is applied onto the core metal 3a. Then, a solid rubber in which carbon resin particles and the like are dispersed is wound around the core 3a and placed in a mold. The mold is vulcanized by applying heat and pressure with a press machine, and the surface is polished after vulcanization to obtain a solid elastic roller comprising the base layer 3b. The intermediate layer 3c and the surface layer 3d can be formed by a roll coater method, a spray method, a dipping method, or the like. The coating thickness of the outermost layer 3d is preferably about 3 μm to 50 μm. If it is less than 3 μm, there is a concern about scraping due to rubbing with the photosensitive drum 1, and if it exceeds 50 μm, coating must be repeated many times in order to obtain a desired coating thickness, which is not realistic for production. Because.

  In addition, as shown in FIG. 3B, the supply roller 5 is made of polyurethane foam having a foamed skeleton structure and a relatively low hardness on a core metal 5a having an outer diameter of 5 mm, and a layer thickness of 5.5 mm. An elastic sponge roller having an outer diameter of 16 mm formed with an elastic layer (foamed layer) 5b was used. The supply roller 5 is made of a foam having a continuous foaming property, so that the supply roller 5 is brought into contact with the developing roller 3 without applying excessive pressure, and is consumed during supply of toner onto the developing roller 3 and development with moderate irregularities on the surface of the foam. The remaining image is removed without being removed. The scraping property of the cell structure is not limited to urethane foam, and rubber or the like obtained by foaming silicone rubber or ethylene propylene diene rubber (EPDM rubber) can be used.

  As the resistance adjustment of the foamed layer 5b, a known ionic conductive agent, inorganic fine particles, carbon black, or the like can be dispersed as appropriate.

  A bias is applied to the supply roller 5 in order to assist the toner supply to the developing roller 3. By applying a bias for biasing the negatively charged toner to the developing roller side, it is possible to increase the amount of toner carried on the developing roller 3 before the layer thickness regulation by the toner regulating member 4. Furthermore, the toner density on the developing roller 3 is easily increased by the bias, and a uniform toner density is easily obtained.

  Referring to FIG. 3, the developing roller 3, the toner regulating member 4, and the supply roller 5 are connected to the high-voltage power sources of the developing bias unit 12, the regulating bias unit 13 (-350V), and the supply bias unit 14 (-450V), respectively. The

  The voltage (−450 V) of the regulating bias unit 13 is supplied to the toner regulating member 4, and the voltage of the developing bias unit 12 is supplied to the developing roller 3, whereby the surface of the toner regulating member 4 and the surface of the developing roller 3 where the toner is interposed. An electric field is formed between the two.

(toner)
The one-component developing toner used in this example is substantially spherical and / or in a state where the wax component is not compatible with the binder resin in the tomographic observation of the toner particles using a transmission electron microscope (TEM). It is preferably dispersed in an island shape in a spindle shape.

  By dispersing the wax component as described above and encapsulating it in the toner, it is possible to prevent deterioration of the toner, contamination of the image forming apparatus, etc. An image can be formed over a long period of time. Further, since the wax component acts efficiently during heating, the low-temperature fixability and offset resistance are satisfied.

  As a specific method for observing the tomographic plane of the toner particles, the toner particles are sufficiently dispersed in a room temperature curable epoxy resin and then cured in an atmosphere at a temperature of 40 degrees for 2 days. The obtained cured product was dyed with ruthenium tetroxide and, if necessary, osmium tetroxide, and after that, a flaky sample was cut out using a microtome equipped with diamond teeth, and a transmission electron microscope (TEM) was used. Observe the tomographic morphology of the toner particles.

  As the wax component according to the present embodiment, a wax component having a maximum endothermic peak in a region of 40 to 130 degrees at the time of temperature rise in the DSC curve measured by a differential scanning calorimeter is used. Having a maximum endothermic peak in the above temperature range greatly contributes to low-temperature fixing, and effectively exhibits releasability.

  When this maximum endothermic peak is less than 40 degrees, the self-cohesive force of the wax component becomes weak, resulting in deterioration of high temperature offset resistance and excessive gloss. On the other hand, if the maximum endothermic peak exceeds 130 ° C., the fixing temperature becomes high and it becomes difficult to appropriately smooth the surface of the fixed image. Absent. Further, in the case where granulation and polymerization are carried out in an aqueous medium and a toner is obtained directly by the polymerization method, if the maximum endothermic peak temperature is high, problems such as precipitation of a wax component mainly during granulation are undesirable.

  The maximum endothermic peak temperature of the wax component is measured according to “ASTM D 3418-8”. For the measurement, for example, DSC-7 manufactured by PerkinElmer is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, and an empty pan is set as a control. After the temperature is raised and lowered once to obtain a previous history, the measurement is performed at a rate of temperature rise of 10 degrees / min.

  Specific examples of the wax component include paraffin wax, polyolefin wax, Fischer tropish wax, amide wax, higher fatty acid, ester wax and derivatives thereof, or graft / block compounds thereof.

  The toner according to this embodiment preferably has a shape factor SF-1 value of 100 to 160 and a shape factor SF-2 value of 100 to 140 as measured by the image analysis apparatus. More preferably, the value of the shape factor SF-1 is 100 to 140, and the value of the shape factor SF-2 is 100 to 120. Further, by satisfying the above conditions and setting the value of (SF-2) / (SF-1) to 1.0 or less, not only the characteristics of the toner but also matching with the image analysis apparatus is extremely good. It will be something.

For the shape factors SF-1 and SF-2, 100 toner images enlarged by a magnification of 500 times using FE-SEM (S-800) manufactured by Hitachi, Ltd. are randomly sampled. The image information is a parameter defined by a value obtained by introducing the image information into an image analysis apparatus (Luxex 3) manufactured by Nicole through an interface and performing analysis.
SF-1 = {(MXLNG) 2 / AREA} × (π / 4) × 100
SF-2 = {(PERI) 2 / AREA} × (1 / 4π) × 100
AREA: toner projected area, MXLNG: absolute maximum length, PERI: circumference

  The toner shape factor SF-1 indicates the degree of roundness of the toner particles, and gradually changes from a spherical shape to an irregular shape. SF-2 indicates the degree of unevenness of the toner particles, and the unevenness of the toner surface becomes remarkable.

  When the aforementioned shape factor SF-1 exceeds 160, the torque increases. In addition, since friction increases, frictional heat increases and toner deterioration is likely to occur.

  In order to increase the transfer efficiency of the toner image, the shape factor SF-2 of the toner particles is 100 to 140, and the value of (SF-2) / (SF-1) is preferably 1.0 or less. . When the toner particle shape factor SF-2 is greater than 140 and the value of (SF-2) / (SF-1) exceeds 1.0, the toner particle surface is not smooth, and the toner particles have a large number of irregularities. The transfer efficiency from the photosensitive drum 1 to the transfer material or the like tends to be reduced.

  In particular, when the shape factor SF-1 is 160 or less and the shape factor SF-2 is 140, when a potential difference is provided between the toner regulating member 4 and the developing roller 3, the toner is easily separated from the toner regulating member 4. It is effective in preventing blade fusion.

  The volume average particle diameter of the toner can be measured by various methods. In this embodiment, the toner was measured using a multisizer of a Coulter counter. In other words, a Coulter counter Multisizer II type (manufactured by Coulter Inc.) was used as a measuring apparatus, and an interface (manufactured by Nikkaki Co., Ltd.) for outputting number distribution and volume distribution and a CX-1 personal computer (manufactured by Canon) were connected. For the electrolyte, a 1% NaCl aqueous solution is prepared using special grade or first grade sodium chloride. As a measuring method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added thereto. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and when measuring the toner particle size as an aperture by the multisizer type II of the Coulter counter, a 100 μm aperture is used. taking measurement. The volume and number of toners were measured, and the volume distribution and number distribution were calculated. Then, a weight-based volume average particle diameter obtained from the volume distribution is obtained. In this embodiment, a toner having a volume average particle diameter of 5.6 μm and a toner having a volume average particle diameter of 2 μm or less is less than 5%.

  Further, as the toner particles used in this embodiment, it is preferable to use a toner particle whose surface is coated with an external additive so that the toner has a desired charge amount. In this sense, the external additive coverage on the toner surface is preferably 5% to 99%, more preferably 10% to 99%.

As for the external additive coverage on the toner surface, 100 toner images were randomly sampled using FE-SEM (S-800) manufactured by Hitachi, Ltd., and the image information was sent to the image analysis apparatus (Luxex 3 manufactured by Nicole) via the interface. ) And measure. The obtained image information is binarized since the brightness of the toner particle surface portion and the external additive portion are different, and the area SG of the external additive portion and the area of the toner particle portion (including the area of the external additive portion) are also obtained. Even if it divides into ST, it calculates by the following formula.
External additive coverage (%) = (SG / ST) × 100

  The external additive used in this embodiment preferably has a particle size of 1/10 or less of the weight average diameter of the toner particles from the viewpoint of durability when added to the toner. The particle size of the additive means the average particle size obtained by observing the surface of the toner particles with an electron microscope. As the external additive, for example, the following are used.

  Metal oxide (aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide, etc.), nitride (silicon nitride, etc.), carbide (silicon carbide, etc.), metal salt (sulfuric acid) Calcium, barium sulfate, calcium carbonate, etc.), fatty acid metal salts (zinc stearate, calcium stearate, etc.), carbon black, silica, etc.

  In this embodiment, auxiliary particles were externally added to the toner particles (100 parts by weight). The externally added auxiliary particles added 1 part by weight of silica as a negative-polarity external additive and 0.1 part by weight of titanium oxide as a positive-polarity external additive. In particular, when a positive external additive is added, it is possible to adjust the fluidity of the toner and to impart stable chargeability to the toner.

  These external additives are used in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, based on 100 parts by weight of toner particles. These external additives may be used alone or in combination. Those subjected to hydrophobic treatment are more preferable.

  When the amount of the external additive is less than 0.01 parts by weight, the fluidity of the one-component developer is deteriorated, and the efficiency of transfer and development is lowered. So-called scattering occurs in which toner is scattered.

  On the other hand, when the amount of the external additive exceeds 10 parts by weight, excessive external additive adheres to the photosensitive drum 1 and the developing roller 3 to deteriorate the chargeability of the toner or disturb the image. .

(Developer layer thickness regulating member)
As shown in FIGS. 5A and 5B, the developer layer thickness regulating member in this embodiment, that is, the toner regulating member 4 includes a flexible member 41, a holding member 42, and an electrode as a power feeding member. And a member 43. The flexible member 41 is attached to the holding member 42 by the electrode member 43.

  In this embodiment, the flexible member 41 has a circular cross-sectional shape before deformation, a cylindrical shape having an outer diameter D of 4 to 10 mm and a wall thickness t of 0.4 to 1.2 mm. . If the outer diameter is less than 4 mm, the change in pressure with respect to the deformation of the flexible member 41 becomes large, which requires high accuracy, which is not preferable. On the other hand, if it exceeds 10 mm, the developing device cannot be reduced in size and the developing device is increased in size. The thickness t can be appropriately selected within the outer diameter D so as to satisfy a contact pressure described later.

  As the hardness of the flexible member 41, a member having a hardness of about 55 to 90 degrees according to JIS A can be used. If it is 55 ° or less, the oil and the like from the flexible member will become so severe that it will be difficult to use as a regulating member. If it exceeds 90 degrees, the change in pressure with respect to deformation becomes large, which requires high accuracy, which is not preferable. As a tendency, when a flexible member having a high hardness is used, the above-described thickness t is reduced, and when a flexible member having a low hardness is used, the thickness t is increased.

  A JIS A rubber hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) was used for measuring the rubber hardness of the flexible member.

  In this example, the outer diameter D was 5 mm, and the wall thickness t was 0.5 mm. Thus, in the present embodiment, the flexible member 41 is a flexible cylindrical member, but is not limited to this. In addition, the cross-sectional shape can be various shapes such as an oval and an ellipse.

  The flexible cylindrical member 41 of the present embodiment is formed of a flexible member having a cavity inside the member with respect to the surface layer surface. The flexible member is not particularly limited as long as it exhibits fluidity before curing, and can be appropriately selected from materials known per se. Examples thereof include urethane rubber, silicone rubber, ethylene / propylene rubber (EPM), liquid rubber such as fluorine rubber latex, polymer blend, and the like. Among these, liquid rubber is preferable, urethane rubber and silicone rubber are more preferable in terms of having appropriate polarity and appropriate compatibility with conductive powder, and two-component urethane rubber and one-component silicone rubber are preferable. Particularly preferred. In the present embodiment, as described above, the flexible cylindrical member 41 is a cylindrical member made of silicone rubber having an outer diameter D of 5 mm and a wall thickness t of 0.5 mm.

  Further, in order to obtain the effect when a bias is applied, it is desirable to impart conductivity to the flexible member. The conductivity imparting agent can be appropriately selected from materials known per se. Examples thereof include conductive inorganic powders such as carbon black, carbon beads, carbon filler, potassium titanate, zinc oxide, and titanium oxide, conductive inorganic particles, conductive inorganic filler, and metal oxide. As the ionic conductive agent, conductivity can be obtained by dispersing an ionic conductive agent such as lithium perchlorate or quaternary ammonium salt in the elastic material. Among these, conductive inorganic powder is preferable in terms of easy control of curing conditions, and carbon black is preferable in terms of excellent dispersibility in the elastomer before curing and good balance of density, specific gravity, and the like. preferable. Carbon black having a secondary particle size of several tens to 500 μm and a DBP oil absorption of 50 to 500 g / dl exhibits an appropriate compatibilization in the elastomer before curing, and diffuses during centrifugal molding. This is particularly preferable in that the gradient dispersion can be achieved. In this embodiment, these conductive powders may be used alone or in combination of two or more.

  The resistance value of the toner regulating member 4 includes the type / specific gravity / amount of conductive powder added to the flexible cylindrical member 41, the type / polarity of the elastomer, and molding conditions (for example, the rotational speed and G in the case of centrifugal molding). It is possible to adjust by appropriately changing the above.

(Measurement of resistance of toner regulating member)
To measure the resistance of the toner regulating member 4, the toner regulating member 4 is assembled to the developing device 7, and a SUS304 metal rod having the same outer diameter as the developing roller 3 is disposed instead of the developing roller 3. A current of 5 μA is passed between the metal rod and the electrode member 43 of the toner regulating member 4, and the resistance value of the toner regulating member 4 is measured by reading the applied voltage at that time.

As the resistance value of the toner regulating member, a resistance value of 10 ⁻³ Ω to 10 ⁸ Ω can be used. This is because it is difficult to manufacture a material having a resistance of less than 10 ⁻³ Ω, and an effective electric field cannot be formed between the toner regulating member 4 and the developing roller 3 if it exceeds 10 ⁸ Ω. In this embodiment, the resistance value of the toner regulating member is 3 × 10 ⁴ Ω.

(Configuration of toner regulating member)
FIG. 5 shows a toner regulating member of Example 1. As shown in FIG. 5, in the holding member 42 of the toner regulating member 4, the contact portion (that is, the inner surface portion) 44 with the flexible cylindrical member 41 is formed in a smooth concave shape, and the flexible cylindrical member The outer peripheral surface 45 of 41 and the inner surface 44 of the holding member 42 are in contact with each other. This is because the three-direction surfaces of the outer peripheral portion 45 of the flexible cylindrical member 41, that is, the top portion 45a and both side portions 45b are surrounded by the inner surface portion 44 of the holding member 42 in FIG. This is because 45c comes into contact with the developing roller 3.

  In this embodiment, the inner surface 44 of the holding member 42 has a curved shape that coincides with the outer peripheral surface in a state in which the flexible cylindrical member 41 is deformed so as to surround the flexible cylindrical member 41 pressed by the developing roller 3. It is said that. However, the present invention is not limited to this, and the inner surface 44 of the holding member 42 can have various other cross-sectional shapes according to the cross-sectional shape of the flexible member 41.

  In this embodiment, as shown in FIG. 5B, the flexible cylindrical member 41 is pressed so that Δd is about 0.4 to 1.5 mm. As a result, as will be described in detail later, it is possible to obtain a contact portion (L3) having a predetermined length with the developing roller 3.

  As a material of the holding member 42, an insulating general-purpose plastic can be used. The coupling between the holding member 42 and the electrode member 43 is obtained by aligning the electrode member in the 43 mold and then molding a general-purpose plastic with the mold. Another method is obtained by molding a general-purpose plastic with a mold, then making a hole in the holding member 42, inserting the electrode member 43, and then welding.

  The toner regulating member 4 is assembled by piercing the flexible cylindrical member 41 with an electrode member 43 formed on the holding member 42 and having a needle-like tip in this embodiment. Thus, by sticking the electrode member 43 into the flexible cylindrical member 41, stable posture of the flexible cylindrical member 41 and an uninterrupted electrode contact can be obtained. The assembled toner regulating member 4 is attached to the developing device 7 such that the exposed portion of the flexible cylindrical member 41 is in contact with the developing roller 3. A regulating bias power source 14 (FIG. 3) is connected to the electrode member 43.

  As shown in FIG. 5, the electrode members 43 are arranged at substantially equal intervals in the substantially central portion of the holding member 42, for example, at intervals P = 15 to 40 mm. The regulating bias power supply 14 is connected to the electrode member 43, and a voltage is supplied to the flexible cylindrical member 41 through the electrode member 43.

  The electrode member 43 preferably has a base thickness (d) of 0.5 to 2 mm and a protrusion length (h) from the holding member inner surface 44 of about 0.5 to 2 mm. If the thickness (d) is less than 0.5 mm, the strength tends to be insufficient, and if it exceeds 2 mm, wrinkles are likely to occur when pierced. If the protruding length (h) is less than 0.5 mm, the fixed state tends to be unstable, and if it exceeds 2 mm, the inner surface of the flexible cylindrical member 41 on the developing roller 3 side when the flexible cylindrical member 41 is largely deformed. This is to prevent the electrode from hitting the electrode.

  The flexible cylindrical member 41 is fitted into the curved inner surface shape portion 44 of the holding member 42 as shown in FIG. At this time, the needle-like electrode member 43 is inserted into the flexible cylindrical member 41 to secure an electrical contact, and at the same time, the flexible cylindrical member 41 is fixed to the holding member 42 via the electrode member 43. It becomes.

  Therefore, even if there is vibration or twist due to rotational fluctuation of the developing roller 3, the contact portion to which the voltage from the regulation bias power supply 14 is supplied is stabilized by the needle-like electrode member 43. Will not be interrupted.

  The flexible cylindrical member 41 fixed and fitted by the electrode member 43 comes into contact with the developing roller 3 at a surface substantially opposite to the electrode member 43. The flexible cylindrical member 41 made of a flexible material having a cavity inside the member with respect to the surface layer surface uniformly contacts the developing roller 3 in the longitudinal direction and has a pressure contact force within a predetermined range.

  In order to uniformly charge the toner on the developing roller 3 and to form a thin layer, the setting value of the pressing force of the toner regulating member 4 to the developing roller 3 (linear pressure in the developing roller generating line direction) is 15 g / cm. ˜70 g / cm is preferable, and in this example, 20 g / cm. That is, in this embodiment, the deformation amount Δd of the flexible cylindrical member 41 is about 1.2 mm.

  The linear pressure is measured by stacking three 20 μm thin plates of SUS304H material into the abutting portion of the flexible cylindrical member 41 and the developing roller 3, pulling out the central thin plate with a spring scale, and using the force at that time Linear pressure was converted.

  The surface roughness of the flexible cylindrical member 41 is preferably about 0.02 to 4 μm in Rz. If the thickness is less than 0.02 μm, it is difficult to manufacture, and if it exceeds 4 μm, charging of the toner tends to be insufficient and fogging tends to occur. In this example, Rz of 0.2 μm was used.

  In the configuration of the developing device, a flexible cylindrical member 41 is fixed by an electrode member 43. Therefore, the flexible cylindrical member 41 is not twisted or twisted in the longitudinal direction due to the force received by the rotation of the developing roller 2, and a uniform toner layer can be formed by the regulating bias power source, and a stable image can be obtained. It was. Further, by using the flexible cylindrical member 41 having a cavity inside the member with respect to the surface layer surface, it is not necessary to have a length for adjusting the spring constant as in the case of the cantilever, and the flexible member A preferable pressure contact force can be obtained by adjusting the elastic modulus of the toner, so that the toner regulating member 4 and the developing device 7 can be downsized.

Example 2
FIGS. 6A to 6C are schematic configuration diagrams showing another embodiment of the toner regulating member 4 according to the present invention.

In Example 1, the assembly was performed by piercing the flexible cylindrical member 41 with the electrode member 43 as a power supply member. In the present embodiment, the flexible cylindrical member 41 and the electrode member 43 are formed to fit with each other, as shown in FIGS. A member 43 is formed. A recess 46 is formed in the flexible cylindrical member 41 as shown in FIG. In the embodiment of FIG. 6B, the recess 46 is formed in the flexible cylindrical member 41. However, the recess 46 may be a through hole 47 as shown in FIG. That is, the electrode member 43 has a protruding shape that fits at least partially with the flexible cylindrical member 41.

  For example, in FIG. 6B, the protrusion of the electrode member 43 and the recess 46 of the flexible cylindrical member 41 are fitted. At this time, the hole diameter of the recess 46 is preferably slightly smaller than the outer diameter of the protrusion of the electrode member 43. This is because the flexible cylindrical member 41 comes into close contact with the electrode member 43. Furthermore, it becomes possible to perform fitting easily by tapering each fitting part.

  As shown in FIG. 6A, two or more protrusions of the electrode member 43 and the recesses 46 of the flexible cylindrical member 41 are installed in the longitudinal direction of the holding member 42 to fix the flexible cylindrical member 41. It is desirable to install the fitting portions symmetrically in the longitudinal direction.

  The material of the electrode member 43 may be made of metal, or a conductive resin in which metal powder is dispersed in a resin.

  In this embodiment, the electrode member 43 has a protruding shape, and the flexible cylindrical member 41 has a recess 46 or a hole 47. However, as shown in FIGS. A recess 48 may be formed, and a convex protrusion 49 may be provided on the flexible cylindrical member 41 and fitted. Of course, the recess 48 of the electrode member 43 may be a through hole.

  This embodiment can also achieve the same effect as the first embodiment, and can be easily positioned by fitting the electrode member 43 and the flexible cylindrical member 41 to each other. Can do. Therefore, it can be easily assembled by an automatic machine in a factory.

Example 3
FIG. 8 shows another embodiment of the toner regulating member 4 according to the present invention. The present embodiment is a modification of the flexible cylindrical member 41 of the second embodiment. In the present embodiment, a convex electrode member 43 is formed continuously to the holding member 42 in the longitudinal direction and protruding from the inner surface portion 44 toward the flexible cylindrical member 41 side. On the other hand, a concave groove 50 is formed in the flexible cylindrical member 41 continuously in the longitudinal direction, and is fitted to the convex electrode member 43 of the holding member 42.

  When the groove 50 continuous in the longitudinal direction is formed in the flexible cylindrical member 41, the flexible cylindrical member 41 can be manufactured by extrusion molding at the time of manufacturing, so that it can be manufactured at low cost.

  Moreover, in the said Example, the flexible cylindrical member 41 was made into the single layer of the silicone rubber layer. On the other hand, in the present embodiment, the flexible cylindrical member 41 is made up of a plurality of layers including a flexible member 41a as an inner layer and a surface layer 41b as an outer layer.

  The surface layer 41b is made of a conductive resin and covers the outer peripheral surface of the flexible member 41a. As the resin binder for the surface layer 41b, urethane resin, silicone resin, polyamide resin or the like is preferably used when the developing device 7 uses negatively chargeable toner. If a positively chargeable toner is used, a fluorine resin or the like is preferably used. A desired resistance value can be obtained by dispersing the aforementioned carbon resin particles, metal particles, ionic conductive agent, and the like in these resins.

  The resistance value of the toner regulating member 4 in this embodiment is 20Ω.

  The surface layer 41b can be applied to the surface of the flexible cylindrical member 41 by a spray method, a dipping method, or the like. The coating thickness of the outermost layer 41b is preferably about 3 μm to 50 μm. If it is less than 3 μm, there is a concern about scraping due to rubbing with the photosensitive drum 1, and if it exceeds 50 μm, coating must be repeated many times in order to obtain a desired coating thickness, which is not realistic for production. Because.

  Another advantage of the flexible cylindrical member 41 of the present embodiment is that the resistance of the toner regulating member 4 can be easily adjusted because there is a conductive surface layer 41b in addition to the flexible member 41a. Along with this, the range of selection of the material of the flexible cylindrical member 41 is increased.

Example 4
FIG. 9 shows another embodiment of the toner regulating member 4 according to the present invention. In the present embodiment, the holding member 42 is formed of a conductive resin, and the surfaces of the holding member 42 and the flexible cylindrical member 41 that are in contact with each other are roughened to fix the flexible cylindrical member 41 and supply voltage. Is.

  Similarly to the second embodiment, the electrode member 43 is fitted into a through hole 47 formed in the flexible cylindrical member 41 so that power can be supplied. Furthermore, in this embodiment, it is possible to supply power to the surface of the flexible cylindrical member 41, thereby improving the voltage stability.

  That is, according to the present embodiment, the holding member 42 is formed of a conductive resin in which carbon or metal fine particles are dispersed in general-purpose plastic. The regulating bias power supply 14 is connected to the holding member 42, and the regulating bias power supply 14 is connected to the electrode member 43 via the holding member 42. Of course, the regulation bias power supply 14 can be connected to the electrode member 43.

  The flexible cylindrical member 41 includes a flexible member 41a and a surface layer 41b as in the third embodiment. The flexible cylindrical member 41 has a rough surface portion 51 (a hatched portion in FIG. 9A) that contacts the holding member 42, and the remaining portion that does not contact the holding member 39. Reference numeral 52 denotes a non-rough surface portion where a desired surface roughness is selected as a toner regulating member. As the non-rough surface portion 52, the one having an Rz of 0.2 μm was used as in the above-described embodiment.

  The contact portion of the holding member 42 that contacts the rough surface portion 51 of the flexible cylindrical member 41, that is, the inner surface portion 44 is also roughened. The surface roughness of the mutually roughened portions 51 and 44 is preferably 30 to 500 μm in Rz. This is because if the surface roughness is less than 30 μm, the rough effect cannot be obtained and the contact tends to become unstable, and if the surface roughness exceeds 500 μm, it is difficult to uniformly roughen.

  For the formation of the surface roughness, the surface of the flexible cylindrical member 41 may be roughened, or the surface can be roughened by dispersing conductive resin particles or metal particles in the outermost layer 41b as described above. It is.

  In the above embodiment, the contact portion between the flexible cylindrical member 41 and the holding member 42 is roughened on the entire surface, but the holding member 42 and the flexible cylindrical member 41 are in contact with each other. It is also possible to roughen at least a part of the surface.

  Thus, in this embodiment, the holding member 42 is formed of a conductive resin and the surfaces 51 and 44 of the holding member 42 and the flexible cylindrical member 41 that are in contact with each other are roughened so that the flexible cylindrical member 41 is It is possible to fix and supply voltage. Moreover, since the number of parts can be reduced, it can be manufactured at low cost.

Example 5
FIG. 10 shows another embodiment of the toner regulating member 4 according to the present invention. In the above embodiment, the electrode member 43 is attached to the approximate center of the concave inner surface portion 44 of the holding member 42. However, in this embodiment, the arrangement of the electrode member 43 is shifted to the downstream side in the rotation direction of the developing roller 3 and the holding member. 42.

  In this embodiment, the length of the contact surface along the rotation direction of the developing roller 3 where the toner regulating member 4 and the developing roller 3 are in contact, that is, the contact length (L3) is the same as that of the conventional cantilever beam. It is possible to make the length longer than the contact length between the developing blade and the developing roller.

  In a conventional cantilever developing blade, the contact length is about 0.5 to 1 mm. Increasing the contact length increases the contact pressure of the developing blade, so it is not easy to increase the contact length.

  However, in the toner regulating member 4 according to the present embodiment, as described above, the flexible cylindrical member 41 having an outer diameter of 5 mm and a wall thickness of 0.5 mm is used. The contact length (L3) of the flexible cylindrical member 41 can be 2.5 to 3.5 mm.

  In FIG. 10, the developing roller 3 has moved from right to left in the direction of the arrow in the figure. The toner regulating member 4 is brought into contact with the developing roller 3 with the toner T interposed therebetween. As described above, the electrode member 43 is disposed on the holding member 46 while being shifted downstream in the rotation direction of the developing roller 3.

  That is, in the contact portion L3 between the developing roller 3 and the flexible cylindrical member 41, the most upstream side in the developing roller rotation direction is K1, and the most downstream side is K2. The electrode member 43 is provided along the flexible cylindrical member 41 closer to a position K2 on the most downstream side in the rotation direction of the developing roller 3 than a position K1 on the most upstream side in the rotation direction of the developing roller 3. As described above, the electrode member 43 is arranged so as to be shifted to the downstream side in the rotation direction of the developing roller 3, so that the electric field formed by the developing roller 3 and the toner regulating member 4 can be changed in the contact portion L3. It becomes.

  That is, a voltage is supplied from the regulating bias power supply 14 through the electrode member 43, and a voltage is supplied from the developing bias power supply 12 to the developing roller 3. The voltage of the regulating bias power supply 14 is larger on the charging polarity side of the toner than the voltage of the developing bias power supply 12 (in this embodiment, since the negative polarity toner is used, the voltage on the negative polarity side is larger). ) Is applied. Since the contact portion L3 is in contact via toner, a large current does not flow directly, and an electric field is formed between the surface of the developing roller 3 and the flexible cylindrical member 41. However, as the developing roller 3 rotates, the triboelectric charge is applied to the toner and charge injection occurs, so that a current of several μA flows through the toner regulating member 4.

  Since the flexible cylindrical member 41 has a resistance, a potential drop occurs when a current flows. Since the toner regulating member 4 according to this embodiment has the contact portion L3 long, the voltage at the point K1 is smaller than the voltage at the point K2. This is because the current flow path has a length L2 from the electrode member 43 at the K1 point, whereas L1 is shorter than L2 at the K2 point. In this way, the toner regulating member 4 of the present embodiment can increase the change in electric field in the contact portion L3 as compared with the conventional developing blade.

  Here, since the voltage on the surface of the flexible cylindrical member 41 at the point K1 is low, the electric field applied to the toner is small, frictional charging becomes dominant, and the toner is tightly packed on the developing roller 3. The toner moved with the rotation of the developing roller 3 receives an electric field in the process of moving to the point K2, and the negatively charged toner is pressed to the developing roller 3 side. Conversely, the positively charged toner (so-called reversal toner) is urged toward the flexible cylindrical member 41, and is therefore positively charged by the flexible cylindrical member 41.

  The resistance value of the toner regulating member 4 is desirably larger than the resistance value of the developing roller 3. This is because if it becomes smaller than the developing roller 3, an effective electric field change cannot be formed between the toner regulating member and the developing roller at the contact portion L3.

  As described above, by gradually increasing the electric field formed by the toner regulating member 4 and the developing roller 3 in the contact portion L3, the chargeability of the toner is improved, and the character reproducibility becomes sharp and solid. Image followability is improved.

(Comparative Example 1)
FIG. 11 shows a schematic configuration of the toner regulating member 140 of Comparative Example 1.

  In FIG. 11, the toner regulating member 140 includes a flexible cylindrical member 141 and a holding member 142. The outer diameter of the flexible cylindrical member 140 before deformation was 5 mm, the wall thickness was 0.5 mm, and the contact pressure between the toner regulating member 140 and the developing roller 3 was 20 g / cm. The flexible cylindrical member 141 is insulative.

(Comparative Example 2)
FIG. 12 shows a schematic configuration of the toner regulating member 150 of Comparative Example 2.

  In FIG. 12, the toner regulating member 150 includes a cantilever developing blade 152 supported by a support member 151. A voltage (−450 V) is supplied from the regulation bias power source 153. As the material of the developing blade 152, stainless steel having a thickness of 0.1 mm was used. The contact pressure between the toner regulating member 4 and the developing roller 3 was 20 g / cm. A developing blade 152 having a length L4 of 30 mm was used. The voltage of the developing bias power source 154 was set to −350V.

(Comparative Example 3)
In Comparative Example 3, the voltage of the regulation bias power supply 153 of Comparative Example 2 was set to −350 V, and the same potential as the voltage (−350 V) of the developing bias power supply 154 was used.

(Evaluation)
The following evaluation was performed about the Example and comparative example in this invention.

1) Evaluation of downsizing of regulating member The size of the regulating member itself was evaluated as follows.
×: When the short length of the regulating member is 20 mm or more ○: When the short length of the regulating member is 20 mm or less

2) Evaluation of contact pressure stability of regulating member In order to evaluate the contact stability / disengagement of the regulating member, the ease with which the developing roller was not detached was evaluated. Specifically, the developing roller was incorporated in the developing device in a state where no toner was attached, the developing roller was rotated, and the evaluation was performed 10 times according to the following criteria.
X: Among the 10 evaluations, the toner regulating member is moved or detached even at one time when the developing roller rotation is started. ○: Among the 10 evaluations, the toner regulating member is once when the developing roller is rotated. What does not come off

  When the flexible cylindrical member is detached, toner cannot be regulated, and toner leakage occurs. Furthermore, when the flexible cylindrical member reaches the fixing unit through the transfer unit, it may be clogged at the fixing unit and lead to a failure. In particular, when the amount of toner is low, a state where toner cannot be supplied to a part of the developing roller may occur. At that time, the flexible cylindrical member and the developing roller are in direct contact with each other without toner. Since the frictional force is remarkably increased in the direct contact portion, the flexible cylindrical member is easily detached by the frictional force.

  The purpose of this evaluation is also to evaluate the detachability of the flexible cylindrical member when the frictional force becomes high.

3) Assemblerability evaluation of regulating member The assembling property of the regulating member was evaluated according to the following criteria.
X: The state before assembling the developing roller is unstable, has high precision assembly, and has high precision assembly to obtain a desired contact pressure.
(Triangle | delta): Although the state before incorporating a developing roller is stable, in order to obtain desired contact pressure, it has a highly accurate assembly property.
◯: The state before the development roller is assembled is stable, and high-precision assembly is not required to obtain a desired contact pressure.
A: The state before incorporating the developing roller is stable and very simple. Moreover, in order to obtain a desired contact pressure, high-precision assembly is not required.

4) Image Density Evaluation In the image evaluation, a solid image on which black was printed on the entire surface was output, and the evaluation was performed using a Macbeth densitometer.
×: Image density is less than 1.2 ○: Image density is 1.2 or more Density unevenness evaluation was performed after a 1000-sheet printing test. The printing test was performed by continuously passing a horizontal line of recorded images having an image ratio of 5%.

5) Evaluation of image gradation and character reproducibility Image gradation and character reproducibility were performed by sensory evaluation.
Image gradation ◎: Very gradation exists ○: Gradation is sufficient △: Gradation is insufficient Character reproducibility ◎: Very reproducibility ○: Reproduction is sufficient △: Reproduction is insufficient

  The evaluation results are shown in Table 1.

1) Evaluation of size reduction of regulating member The x in Comparative Example 2 and Comparative Example 3 is a cantilever shape in the conventional developing blade, and the size on the short side is larger than that of the toner regulating member of the present invention. is there.

  In the configuration in which the thin plate elastic member is supported in a cantilever manner, the amount of change in the contact pressure against the toner regulating member increases as the developing roller 3 is pushed in. Conventionally, in order to reduce this change, it is necessary to secure a sufficiently large distance from the fulcrum supporting the thin plate to the contact point with the developing roller 3, that is, the free length, and to reduce the spring constant. However, at the time of downsizing, since the free length is shortened, the spring constant is increased. As a result, even if the setting position of the toner regulating member slightly changes, the contact pressure changes greatly. That is, it becomes difficult to stably obtain a predetermined contact pressure when downsizing.

2) Evaluation of stability of contact pressure of regulating member In Comparative Example 1, as described above, there is no means for fixing against rotation, so that the flexible cylindrical member is twisted or detached.

3) Assemblerability evaluation of restriction member Since Comparative Example 1 has no means for stopping in advance, the flexible cylindrical member is easily swung with the insertion of the developing roller, and the assembly is difficult.

4) Image density evaluation In Comparative Example 1 and Comparative Example 3 in which the regulation bias power source is not connected, the toner amount per unit area on the developing roller is small, and a desired density cannot be obtained. This is particularly noticeable when the toner particle size is small.

As described above, according to the present invention,
(1) The developer layer thickness regulating member is formed of a flexible member having a cavity inside the member with respect to the surface layer surface, and a holding member that holds the flexible member. Since the change in the contact pressure can be dealt with by the change in the shape of the hollow portion, the size of the regulating member can be reduced.
(2) In addition to the above, by having a power supply member that supplies the voltage from the regulation bias means to the flexible member, the power supply member is formed of a needle-like electrode, and the flexible member is fixed. As a result, the contact state does not become unstable due to the rotation of the developer carrier and the vibration caused by the rotation, and it is possible to ensure stable power feeding and contact pressure stability of the regulating member.
(3) Since the power supply member has a shape that fits at least partially with the flexible member, the assemblability is improved.
(4) The surface on which the flexible member is brought into contact with the developer carrying member, and is located between the developer carrying member at a position on the most upstream side in the rotation direction and the most downstream side in the rotation direction of the developer carrying member. When the magnitude of the formed electric field is different, the chargeability of the toner is improved, the character reproducibility is sharpened, and the followability of the solid image is improved.

1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention. It is a schematic block diagram which shows one Example of a process cartridge. FIG. 3A is a schematic configuration diagram showing an embodiment of the developing device, and FIG. 3B is a cross-sectional view for explaining the configuration of the embodiment of the developing roller and the supply roller. It is a figure explaining schematic structure of a resistance measuring device. FIG. 5A is an exploded perspective view illustrating a configuration of an embodiment of the toner regulating member, and FIG. 5B is a cross-sectional view illustrating a use state in which the toner regulating member is attached to the developing device. is there. FIG. 6A is an exploded perspective view illustrating the configuration of another embodiment of the toner regulating member, and FIGS. 6B and 6C illustrate a use state in which the toner regulating member is attached to the developing device. FIG. FIG. 7A is an exploded perspective view illustrating the configuration of another embodiment of the toner regulating member, and FIG. 7B is a cross-sectional view illustrating a use state in which the toner regulating member is attached to the developing device. It is. FIG. 8A is an exploded perspective view illustrating the configuration of another embodiment of the toner restricting member, and FIG. 8B is a cross-sectional view illustrating a use state in which the toner restricting member is attached to the developing device. It is. FIG. 9A is an exploded perspective view illustrating the configuration of another embodiment of the toner regulating member, and FIG. 9B is a cross-sectional view illustrating a use state in which the toner regulating member is attached to the developing device. It is. FIG. 10 is a cross-sectional view illustrating a usage state in which the toner regulating member is attached to the developing device in order to explain the configuration of another embodiment of the toner regulating member. FIG. 6 is a cross-sectional view illustrating a usage state in which a toner regulating member is attached to a developing device in order to describe a configuration of a comparative example of the toner regulating member. FIG. 6 is a cross-sectional view illustrating a usage state in which a toner regulating member is attached to a developing device in order to describe a configuration of a comparative example of the toner regulating member.

Explanation of symbols

1 (1y, 1m, 1c, 1k) Photosensitive drum (photosensitive drum)
2 (2y, 2m, 2c, 2k) Charging roller (charging means)
3 (3y, 3m, 3c, 3k) Development roller (developer carrier)
4 (4y, 4m, 4c, 4k) Toner regulating member (developer layer thickness regulating member)
7 (7y, 7m, 7c, 7k) Developing device (developing means)
9 (9y, 9m, 9c, 9k) Process cartridge 41 Flexible cylindrical member (flexible member)
42 Holding member 43 Electrode member

Claims (5)

An image carrier on which an electrostatic latent image is formed;
A developer carrying body that carries and conveys the developer and makes the electrostatic latent image a visible image with the developer, and development that regulates the layer thickness of the developer carried and carried by the developer carrying body A developing device comprising: a developer layer thickness regulating member; a developing bias means for supplying a voltage to the developer carrying member; and a regulating bias means for supplying a voltage to the developer layer thickness regulating member;
In an image forming apparatus having
The developer layer thickness regulating member is formed by a flexible member having a cavity inside the member and a holding member that holds the flexible member, and the flexible member is held by the holding member. A part of the surface in the part that is not in contact with the developer carrier,
The holding member is to feed a voltage from the regulating bias means to said flexible member, and, have a power supply member for fixing the flexible member to the holding member,
The power supply member is a needle-like electrode member, supplies power by piercing the flexible member, and fixes the flexible member to the holding member.
An image forming apparatus. The image forming apparatus according to claim 1, wherein the flexible member is formed of a single layer or a plurality of layers, and a conductive agent is dispersed at least in part. Wherein at least a portion of the surface of the holding member and the flexible member into contact, the image forming apparatus according to claim 1 or 2, characterized in that it is roughened. The surface on which the flexible member is in contact with the developer carrying member, and is located between the developer carrying member at a position on the most upstream side in the rotation direction and the most downstream side in the rotation direction of the developer carrying member. the image forming apparatus according to any one of claims 1 to 3 in which the magnitude of the electric field formed are different from each other. The power supply member is provided along the flexible member closer to a position on the most downstream side in the rotation direction of the developer carrier than a position on the most upstream side in the rotation direction of the developer carrier. The image forming apparatus according to claim 4 .

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