JP2006301092A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can keep a stable cleaning performance for a long period of time while using a photoreceptor with high durability (high strength and high wear resistance) and is extensive in service life, high in image quality and low in running cost without causing preventing any image deletion. <P>SOLUTION: The image forming apparatus has a cleaning step of removing a transfer residual toner from an image carrier, and is characterized in that: the image carrier shows HU (universal hardness) of 150 N/mm<SP>2</SP>to 220 N/mm<SP>2</SP>, an elastic deformation rate We of 40% to 65%, surface roughness Rz of 0.2 to 3.0 μm, an average interval Sm of the surface rugged pattern of 10 to 100 μm, and an acuteness degree Rku of the surface in the range of 3<Rku<20; and inorganic fine powder having 30 to 300 nm particle diameter of primary particles and having a cubic and/or parallelepiped particle form is supplied onto the surface of the image carrier. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  In general, in an image forming apparatus that records an image on a recording medium such as paper such as a copying machine, a printer, and a facsimile, an electrophotographic system is employed as a system for recording the image on the recording medium. In an electrophotographic system, a photosensitive drum having a surface coated with a photosensitive material is used as an image carrier. First, after the surface of the photosensitive drum is uniformly charged, the surface of the photosensitive drum is irradiated with laser light, and a potential difference is given between the irradiated portion and the non-irradiated portion. Next, the charged toner contained in the developer adheres to the surface of the photosensitive drum, whereby a toner image is formed on the surface of the photosensitive drum. Thereafter, the toner image is transferred to a recording medium, and an image is formed on the recording medium.

  Recently, demands such as higher image quality and lower running cost of output devices have increased, and the photosensitive drum as an image carrier used in the electrophotographic system has a higher photosensitive layer thickness because of the necessity of high resolution. Thin ones are used, and in addition, in order to reduce the running cost, it is necessary to extend the life of the photosensitive drum itself, so that the electrical, mechanical strength and abrasion resistance of the photosensitive member surface can be improved. It has been.

  However, an image forming apparatus using such a photosensitive drum has the following problems.

  High-strength, high-abrasion photosensitive drums with high durability are now used, so the surface of the photosensitive drum is not refreshed due to scraping, electrical damage due to charging, etc., surface due to adhesion of discharge products, etc. Deterioration, mechanical damage due to rubbing with the cleaning blade, etc. accumulates over the long term, reducing the slipperiness of the photosensitive drum surface (especially the cleaning blade) and making the cleaning blade more susceptible to chatter, squealing, and wobbling. Come. Further, since the surface of the photosensitive member cannot be scraped, the discharge product is not removed, and there is a problem in that image flow occurs. Therefore, various methods have been considered so far to solve this problem.

  For example, there is a method of preventing image flow by preventing a reduction in resistance of the surface of the photoreceptor due to moisture adsorption by heating with a heater (see Patent Document 1). However, the provision of a heater not only requires a heat control means and the configuration thereof becomes complicated, but also the system becomes complicated when the heater is used especially in the miniaturization and personalization of copying machines and printers. . In addition, it takes a certain time to raise the temperature of the heater, and the time (warm-up time) from when the power is turned on until printing is long, and power consumption for that is required. Further, when the photosensitive member is heated to a temperature close to the TG temperature (glass transition temperature) of the toner, the toner adheres to the surface of the photosensitive member. Various problems occur. As another method, a method of removing the corona product by rubbing the surface of the photoreceptor with an elastic roller is considered (see Patent Document 2). In this method, the rubbing force is sufficiently exerted, but since the toner scraped off from the surface of the photosensitive drum and adhering to itself is not further scraped off by other means, it is adhered to the roller forever. Repeated rubbing between them causes fusion. Conversely, if the roller surface is sufficiently scraped and there is too little transfer residual toner, the roller surface may directly contact and rub against the surface of the photosensitive drum, which may damage the surface of the photosensitive drum. It was.

No. 1-334205 JP-A-61-100780

  The present invention solves the above-mentioned problems, and maintains a stable cleaning performance for a long period of time while using a highly durable (high strength, high wear resistance) photosensitive member, and does not cause image flow, and has a high An object of the present invention is to provide an image forming apparatus having a long life, high image quality and low running cost.

  The above object is achieved by an image forming apparatus having the following configuration according to the present invention.

(1) At least a step of charging an image carrier having a photosensitive layer on a conductive support, an electrostatic latent image forming step of forming an electrostatic latent image on the charged image carrier, and a toner on the electrostatic latent image In an image forming apparatus having a developing step for transferring and visualizing a toner, a step for transferring a toner image formed on an image carrier to a transfer material, and a cleaning step for removing transfer residual toner from the image carrier,
The image carrier was subjected to a hardness test using a Vickers square pyramid diamond indenter in an environment of 25 ° C. and 50% humidity, and the HU (universal hardness value) when pressed at a maximum load of 6 mN was 150 N / mm ² or more and 220 N / an image bearing member having an elastic deformation rate We of 40% or more and 65% or less, which is equal to or less than mm ² ,
The image carrier has a surface roughness Rz of 0.2 to 3.0 μm, a surface irregularity average interval Sm of 10 to 100 μm, and a surface sharpness Rku in the range of 3 <Rku <20,
An image forming apparatus, characterized in that an inorganic fine powder having primary particles having a cubic shape and / or a rectangular parallelepiped shape having a particle size of 30 to 300 nm is supplied on the surface of the image carrier.

  (2) A member for rubbing the surface of the image carrier is provided, and the member is a fur brush. When the fiber diameter of the fur brush is A (μm), Sm> A, and the fur brush is driven to rotate. Alternatively, the image forming apparatus according to (1), which is reciprocally driven.

  (3) The image forming apparatus according to (1), wherein a member for rubbing the surface of the image carrier is provided, and the member is an elastic roller.

  (4) A member for rubbing the surface of the image carrier is provided, the member is a magnetic brush, and Sm> D, where D (μm) is a carrier particle size used for the magnetic brush. The image forming apparatus according to (1).

  (5) The charging step is performed by a contact roller member, and the rotation axis of the contact roller member and the rotation axis of the image carrier are arranged so as to intersect each other. The image forming apparatus according to 4).

(6) The cleaning step is performed by a cleaning blade that contacts the image carrier. The cleaning blade has a hardness of 60 to 85 (Shore hardness HS), a 100% modulus of 20 to 80 (kgf / cm ² ), and repulsion. The image forming apparatus according to any one of (1) to (5), wherein the elasticity is in the range of 5 to 50%.

  (7) The image forming apparatus according to (6), wherein a coefficient of dynamic friction μ between the surface of the image carrier and the cleaning blade is 0.1 ≦ μ ≦ 3.

  According to the present invention, by adopting a configuration in which a specific inorganic fine powder is supplied onto the surface of a specific image carrier, stable image formation that does not cause image flow, cleaning blade chatter, squealing, or blurring over a long period of time is achieved. Has the effect of being able to do.

  The configuration and operation of an image forming apparatus according to an embodiment of the present invention and examples will be described below with reference to the drawings.

  FIG. 1 is a schematic view of a copying machine as an embodiment of an image forming apparatus according to the present invention. First, the outline of the entire copying machine will be described. A so-called reversal developing system is used in which a negatively charged organic photoreceptor is used for the photosensitive drum 1 as an image carrier and a negatively charged toner is used as a developer. Is. As a method for uniformly charging the photosensitive member, a roller charging method, which is one of low-cost contact charging methods, is used, but there is no problem even if a corona charging method is used.

  The image forming process of this copying machine will be described. First, the photosensitive drum 1 is charged to a uniform potential by a charging roller 2 constituting a charging device, and a laser beam L corresponding to image information is main-scanned in the axial direction of the photosensitive drum 1 by an exposure optical system (not shown). Sub-scanning is performed by the rotation of the photosensitive drum 1. As a result, an electrostatic latent image corresponding to the image information is formed on the photosensitive drum 1. This electrostatic latent image is developed by the developing device 3 to become a toner image. The toner image is transferred to the recording medium P by the transfer device 4. The recording medium to which the image has been transferred is separated from the photosensitive drum 1 and conveyed, and then the image is fixed by pressurizing and heating the fixing device 5 to complete printing. On the other hand, the toner remaining on the photosensitive drum 1 after the transfer is removed from the photosensitive drum 1 by the cleaning device 6. Thereafter, the charge remaining on the photosensitive drum 1 is neutralized by the neutralizing light from the neutralizing lamp 7, and the photosensitive drum 1 is prepared for the next image formation.

[Image carrier]
A photoconductor that is an image carrier in the invention will be described below (hereinafter, the image carrier is referred to as a photoconductor or a photosensitive drum).

  The photoconductor used in the present invention is an electrophotographic photoconductor containing a compound in which at least the surface layer is polymerized or crosslinked and cured, and the curing means is light such as heat, visible light, ultraviolet light, Furthermore, radiation can be used. Therefore, the hand for forming the surface layer in the present invention uses a coating solution that melts and contains a compound that can be polymerized or crosslinked and cured for the surface layer, dip coating method, spray coating method, curtain coating method, The procedure is such that coating is performed by spin coating or the like, and this is cured by the above-described curing means. The impregnation coating method is the best for efficient mass production of the photoreceptor, and the dip coating method is also possible in the present invention.

  The structure of the photoconductor of the present invention is a single layer type in which both a charge generation material and a charge transport material are contained in the same layer on a conductive substrate having an outer diameter of about 30 mm, or a charge containing a charge generation material. The charge transport layer containing the generation layer and the charge transport material is either of the stacked type in which the layers are stacked in this order or in the reverse order. Furthermore, a surface protective layer can be formed on the photosensitive layer. In the present invention, at least the surface layer of the photoreceptor should contain a compound that can be polymerized or crosslinked and cured by heat, light such as visible light, ultraviolet light, and radiation. However, from the viewpoint of characteristics as a photoreceptor, particularly electrical characteristics such as residual potential and durability, a charge generation layer / charge transport layer is laminated in this order, or a functionally separated photoreceptor structure is laminated. A configuration in which a surface protective layer is formed on the photosensitive layer is preferable.

  In the present invention, it is preferable to use radiation in the method of curing the compound for crosslinking or crosslinking the surface layer, since the residual potential does not increase without deterioration of the photoreceptor characteristics and sufficient hardness can be exhibited. .

  At this time, the radiation used is an electron beam and a gamma ray. When irradiating with an electron beam, any of a scanning type, an electron curtain type, a broad beam type, a pulse type, and a minor type can be used as an accelerator. In the case of irradiating an electron beam, the acceleration voltage is preferably 250 kV or less and optimally 150 kV or less, in order to develop the electrical characteristics and durability of the photoreceptor of the present invention. The irradiation dose is preferably in the range of 10 KGy to 1000 KGy, more preferably in the range of 30 KGy to 500 KGy. If the accelerating voltage exceeds the above, the electron beam irradiation damage tends to increase on the characteristics of the photoreceptor. In addition, it is necessary to be careful since curing is likely to be insufficient when the irradiation dose is less than the above range, and deterioration of the photoreceptor characteristics is likely to occur when the dose is large.

  As the surface layer compound that can be polymerized or crosslinked and cured, the unsaturated polymerizable functional group in the molecule has high reactivity, high reaction rate, and high hardness achieved after curing. Among them, compounds having an acrylic group, a methacryl group, and a styrene group are particularly preferable.

  The film thickness of the surface protective layer used in the present invention is preferably in the range of 0.2 to 10 μm, more preferably in the range of 0.5 to 6 μm.

  In addition, the HU (universal hardness value) and elastic deformation rate in the present invention are the microhardness measuring device Fischerscope in which the indenter is continuously loaded and the indentation depth under the load is directly read to obtain the continuous hardness. Measurement was performed using H100V (Fischer). The indenter used was a Vickers square pyramid diamond indenter with a face angle of 136 °. The load conditions were measured stepwise up to a final load of 6 mN (273 points with a holding time of 0.1 s for each point).

  HU (universal hardness value: hereinafter referred to as HU) is defined by the following formula (1) from the indentation depth under the same load when indented at 6 mN.

The elastic deformation rate is obtained from the work (energy) performed by the indenter on the membrane, that is, the change in energy due to the increase or decrease of the load of the indenter on the membrane, and the value can be obtained from the following equation (2). Here, Wt (nW) is the total work, and Wo (nW) is the work of elastic deformation.
Elastic deformation rate We = Wo / Wt × 100 (%) (2)

  As described above, the performance required for the organic electrophotographic photosensitive member includes improved durability against mechanical deterioration. In general, the hardness of the film is higher as the amount of deformation with respect to external stress is smaller, and it is considered that the electrophotographic photosensitive member having higher pencil hardness or Vickers hardness naturally improves durability against mechanical deterioration. However, the high hardness obtained by these measurements has not always been expected to improve durability.

As a result of intensive studies, we found that mechanical deterioration of the surface layer of the photoconductor hardly occurs when the values of HU and elastic deformation ratio are within a certain range, and the present invention has been achieved. That is, a hardness test is performed using a Vickers square pyramid diamond indenter, the HU when pressed at a maximum load of 6 mN is 150 N / mm ² or more and 220 N / mm ² or less, and the elastic deformation rate is 40% or more and 65% or less. By using the electrophotographic photosensitive member, which is

  The amount of wear on the surface of the photoreceptor, which is the image carrier used in this embodiment, is 2 mg or less in the Taber abrasion tester. The test method for the Taber abrasion test is to mount the sample on the sample stand of the Taber abrasion tester (YSS Taber Yasuda Seisakusho) and attach the wrapping tape (Fuji Film product name: C2000) to the two surfaces. This is a method of applying a load of 500 gr to each rubber worn wheel (CS-0) and measuring the decrease in mass of the sample after 1000 revolutions with a precision balance.

  In the present invention, the surface shape of the electrophotographic photosensitive member is such that the surface roughness Rz (10-point average surface roughness) is 0.2 μm or more and 3.0 μm or less, the surface unevenness average interval Sm is 10 to 100 μm, and the surface The sharpness RKu is in the range of 3 <Rku <20. When Rz is smaller than 0.2 μm, the contact area between the cleaning blade and the photoreceptor surface becomes too large, and problems such as blade chatter, blade wear, and chipping occur, and good cleaning properties cannot be obtained. Similarly, even when Sm is larger than 100 μm, the adhesion between the blade and the surface of the photoconductor becomes too high to perform good cleaning. On the other hand, when Rz is larger than 3 μm or Sm is smaller than 10 μm, the cleaning blade cannot follow the surface shape of the photosensitive member, the contact area is too low, and the remaining toner cannot be blocked. Defects occur.

  Next, the parameter Rku representing the surface shape will be described. Rku (or Kurtosis) is a measurement of the sharpness of the ADF (Modulation Density Function) curve and the “Spikness” of the surface, as shown in FIG. In the state, Rku = 3, and the value becomes farther from 3 as the sharpness is biased in either the upper or lower direction. Rku is calculated from the following equation. Here, n is the number of elements Yi in the profile, and Rq is the root mean square roughness.

  When Rku is 3 or less, the contact area with the cleaning blade is reduced because the convex portions of the surface shape of the photoreceptor have a sharp shape. For this reason, even if Rz and Sm are within the above ranges, there may be a situation in which slipping-out occurs due to the weak blocking force of the transfer residual toner by the cleaning blade. In addition, since the contact area is small, it is difficult to remove the discharge products by the cleaning blade, and image flow is likely to occur. Further, since the surface shape of the photosensitive member is maintained even after the endurance, the edge of the cleaning blade is severely worn at a portion having a high kurtosis on the surface of the photosensitive member, which may cause a problem in cleaning performance after the endurance.

  On the other hand, when Rku is larger than 3, the contact area between the blade and the surface of the photoreceptor becomes appropriate, and good cleaning properties are obtained.

  As described above, it is important to appropriately set the ranges of Rz, Sm, and Rku in order to make full use of a drum having a low wear rate as in the present invention. Those having a large wear rate on the surface of the photosensitive member are not significantly involved in the cleaning performance after endurance because the shape cannot be maintained even if the surface shape is determined in the initial stage. Since the surface is always refreshed, discharge products and the like do not accumulate, and the friction coefficient between the cleaning blade and the photoreceptor surface does not increase so much. On the other hand, in the photoconductor having high durability as in the present invention, discharge products or the like are accumulated, or they must be removed by the blade, and the load on the blade is increased, causing problems such as blade wear, chattering, and sag. Let Therefore, since the surface shape of a photosensitive drum having a very low wear rate is maintained even after long-term durability, the first surface shape determination is important.

  In the present invention, the surface roughness of the surface of the electrophotographic photosensitive member is measured as follows using a contact type surface roughness measuring machine (trade name: Surfcorder SE3500, manufactured by Kosaka Laboratory Ltd.).

  Detector: R2 μm, 0.7 mN diamond needle, filter: 2CR, cutoff value: 0.8 mm, measurement length: 2.5 mm, feed rate: 0.1 mm, 10 points defined by JIS standard B0601 Data of average surface roughness Rz was processed. The average spacing Sm of the surface irregularities is an arithmetic average value obtained from the following equation measured under the same conditions.

Ｓｍｉ：凹凸の間隔
ｎ：基準長さ内で凹凸の間隔の個数

Smi: spacing of irregularities n: number of irregularities within the reference length

  Rku is a value measured by a Newview 5000 system of Zygo and analyzed by Metropro. During the measurement, a 10X Mirau interference objective lens was used.

  Next, FIG. 3 shows an example of a polishing machine including a polishing sheet as roughening means for controlling the surface shape of the electrophotographic photosensitive member of the present invention. The abrasive sheet is a sheet in which abrasive grains are dispersed in a binder resin and applied to a substrate. The polishing sheet 8 is wound around a hollow shaft a, and a motor (not shown) is disposed so that tension is applied to the polishing sheet 8 in a direction opposite to the direction in which the sheet is fed to the shaft a. The polishing sheet 8 is fed in the direction of the arrow, passes through the backup roller 11 through the guide rollers 2-1 and 2-2, and the polished sheet is wound by a motor (not shown) through the guide rollers 2-3 and 2-4. The take-up means 12 is wound up. The polishing is basically performed by constantly pressing an untreated polishing sheet against the surface of the photoconductor to roughen the surface of the photoconductor.

  FIG. 4 shows a schematic view of abrasive grain discharging means for controlling the surface shape by another method. It comprises an abrasive discharge device 9, driving means (not shown) for rotating the electrophotographic photosensitive member 10 in the direction of arrow c, and an exhaust device (not shown). The abrasive grains are sprayed from the discharge device 9 onto the surface of the electrophotographic photosensitive member 10 rotated at a desired number of revolutions, and the discharge device 9 or the electrophotographic photosensitive member 10 moves in the thrust direction, whereby the electrophotographic photosensitive member. The entire surface of is roughened. At that time, the abrasive grains discharged from the discharge device 9 are sucked by an exhaust device (not shown). The abrasive grains may be reused. The abrasive grains used in the roughening step are preferably metal, glass, resin or the like. Among them, the electrophotographic photosensitive member surface shape that can obtain the desired shape as described above may be selected. In the case of metal, the abrasive grain size is preferably 1 to 100 μm, and more preferably 5 to 60 μm. In the case of resin, 30-200 micrometers is preferable. The shape of the abrasive grains is preferably spherical if it is indeterminate because deep recesses are likely to occur on the surface of the photoreceptor. In roughening, a plurality of particles having different particle diameters, shapes, and materials may be used.

  The surface shape control means described above has described a method for obtaining a desired surface shape by forming a film on the surface of the photoconductor and performing a roughening treatment after curing. There is no problem even if a means for curing is formed after forming the film.

[developing]
As a developing method used in the image forming apparatus of the present invention, a method of developing in a non-contact state with respect to the photosensitive drum (one-component non-contact development), a method of developing in a state of contact with the photosensitive drum (one-component contact development) ), A method in which toner particles are mixed with a magnetic carrier as a developer, the developer is conveyed by magnetic force, and developed in contact with a photosensitive drum (two-component contact development), the above two components Any of the methods for developing the developer in a non-contact state with respect to the photosensitive drum (two-component non-contact development method) can be suitably used. In this embodiment, since the developing device can be simplified and low running cost can be achieved, the one-component non-contact development using the magnetic toner is adopted.

[Inorganic fine powder]
In the present invention, an inorganic fine powder having a particle size of 30 to 300 nm of primary particles having a cubic shape and / or a rectangular parallelepiped shape on the surface of the photoreceptor is supplied. Inorganic fine powder has high hardness and excellent polishing performance. As the inorganic fine powder, for example, strontium titanate, barium titanate, calcium titanate and the like are used. In the embodiment of the present invention, the perovskite crystal form having a cubic and / or rectangular parallelepiped shape is effective. The photoconductor used in the present invention needs to set Rz, Sm, and Rku in appropriate ranges as described above due to its high durability. However, in the above range, there is no problem with phenomena such as chattering, wobbling and slipping of the cleaning blade, but problems such as image flow and fusion may occur. This is considered to be a phenomenon that occurs because discharge products, external additives, toner, and the like accumulate in the recesses on the surface of the photoconductor because the surface shape of the photoconductor is maintained. In this recess, a portion where the rubbing force by the cleaning blade is insufficient is generated, and discharge products, external additives, and the like accumulate therein. In particular, in the present invention, since the concave portion is pointed to satisfy Rku> 3, the details cannot be scraped by the cleaning blade. However, if an inorganic fine powder having a cubic and / or cuboidal perovskite crystal form is supplied onto the surface of the photoreceptor, the charged products and external additives accumulated in the recesses can be efficiently removed. Yes (Fig. 9). This is because the particle shape is cubic and / or rectangular parallelepiped, so that the contact area with the surface of the photoconductor can be increased, and the ridge line of the cube or cuboid is in contact with the surface of the photoconductor. It is thought that it is because it is possible to obtain a take-off. This scraping action is considered to be performed mainly when the inorganic fine powder is pressed against the surface of the photoreceptor at the cleaning blade nip.

  On the other hand, when an amorphous or spherical inorganic fine powder is used, the polishing ability cannot be effectively exhibited and the image flow cannot be prevented.

  The strontium titanate of the perovskite crystal used in the present invention preferably has an average primary particle size of 30 nm to 300 nm. If the average particle size is less than 30 nm, the polishing effect of the particles is insufficient. On the other hand, if the average particle size exceeds 300 nm, the polishing effect is too strong, so that the photoconductor scratches and charging roller damage may occur. The polishing performance is greatly related to the particle size of the inorganic fine powder, and the larger the particle size, the greater the polishing effect.

  Examples of means for supplying the inorganic fine powder to the surface of the photoreceptor include a method of externally adding to the developing toner and a method of providing an inorganic fine powder supply member in the cleaning device, but are not particularly limited.

[Cleaning device]
As cleaning in the electrophotographic system, the surface of the photosensitive drum is repeatedly used for forming a toner image. Therefore, after the toner image is transferred to the recording medium, it remains on the surface of the photosensitive drum without being transferred to the recording medium. It is necessary to sufficiently remove the residual toner. Many methods have been proposed for removing residual toner, but a method of scraping residual toner by contacting a cleaning blade, which is a counter blade made of an elastic material, with the surface of the photosensitive drum is low cost. Since the entire electrophotographic system can be made simple and compact and has excellent toner removal efficiency, it has been widely put into practical use. As a material for the cleaning blade, urethane rubber is generally used that has high hardness and high elasticity, and is excellent in wear resistance, mechanical strength, oil resistance, ozone resistance, and the like.

FIG. 5 shows a diagram relating to the cleaning blade. The cleaning blade 8a is made of polyurethane rubber that is integrally held at the front end of the sheet metal, and is in contact with the photoreceptor 1 under conditions of a predetermined penetration amount δ and a set angle θ. As a result of repeating trial and error in this embodiment and finding optimum conditions, the hardness is in the range of 60 to 85 (Shore hardness HS), the 100% modulus is 20 to 80 (kgf / cm ² ), and the resilience is 5 to 50%. It was found that it can be cleaned stably.

  Next, a method for measuring the dynamic friction coefficient μ will be described.

  When the photoconductor is in the form of a sheet, flat plate, or endless (endless) belt, the coefficient of dynamic friction μ between the cleaning blade and the surface of the photoconductor is usually a surface property test apparatus (type) manufactured by HEIDON. Measured by HEIDON-14). The cleaning blade is pressed against the photoreceptor with a constant load (gf), and the force (gf) applied when the cleaning blade is moved in parallel with the surface of the photoreceptor in this state is measured. The coefficient of dynamic friction μ is obtained by [force applied to the photoreceptor (gf)] / [load applied to the blade (gf)].

However, the photoreceptor incorporated in the electrophotographic image forming apparatus is a drum-shaped photoreceptor drum mainstream, and the dynamic friction coefficient μ in this case is the rotational torque T1 (kgf · cm) of the photoreceptor drum itself and the cleaning blade. Is obtained by measuring the rotational torque T2 (kgf · cm) in a system in which residual toner after the transfer step is interposed on the photosensitive drum in a state where the toner is pressed with a load F (kgf), and calculating by the following formula. Where γ is the radius (cm) of the photosensitive drum.
μ = (T2−T1) / (F · γ)

  When the value of the dynamic friction coefficient μ was in the range of 0.1 to 3, it was possible to clean well. If μ is less than 0.1, the toner may slip through. On the other hand, if it exceeds 3, problems such as chattering and squeezing of the cleaning blade and severe wear of the cleaning blade may occur. The adjustment of the dynamic friction coefficient μ can be made according to the surface shape of the photosensitive member described above, and can also be made by the contact condition of the cleaning blade to the photosensitive member.

  Hereinafter, the present invention will be described more specifically with reference to examples. These examples are examples of the best mode of the present invention, but the present invention is not limited to these examples.

[Example 1]
In this embodiment, a photoconductor having a universal hardness value of 200 N / mm ² and an elastic deformation rate We of 50% was used. Further, the surface roughening was performed by using the apparatus shown in FIG. 3 with a polishing sheet (trade name: AX-3000 (manufactured by Fuji Photo Film Co., Ltd.)), polishing abrasive grains: alumina (average particle diameter: 5 μm), and substrate: polyester. Using a film (thickness: 75 μm), polishing sheet feed speed: 150 mm / sec, photoreceptor rotation speed: 15 rpm, pressing pressure: 7.5 N / m ² , the rotation direction of the sheet and the electrophotographic photoreceptor is the same direction, A backup roller having an outer diameter of 40 cm and an Asker C hardness of 40 was used and roughened for 300 sec.Rz, Sm, and Rku on the surface of the photoreceptor were Rz = 0.33 μm, Sm = 15 μm, and Rku, respectively. = 4.

  The inorganic fine powder was supplied onto the photoreceptor by externally adding it to the developing toner. In this example, a strontium titanate perovskite crystal having an average primary particle diameter of 100 nm (shown in FIG. 6) is externally added by 1.5 parts by mass to 100 parts by mass of the developing toner with a Henschel mixer FM10B. Using.

In this embodiment, urethane rubber having a hardness of 70 (Shore hardness HS), a 100% modulus of 25 kgf / cm ² and a rebound resilience of 11% is used as a cleaning blade, a set angle θ = 25 °, an intrusion amount δ = 0.7 mm, and a photosensitivity. The contact pressure to the body 2 was set to about 25 g / cm.

  As a result of the endurance evaluation of 100,000 sheets under high temperature and high humidity (30 ° C., 80%) with the above configuration, good results were obtained in terms of image flow, fusion, and cleaning properties. Although the cleaning blade was worn, it was at a level causing no problem in practical use. If the discharge products and the like attached to the surface of the photosensitive member are not removed, the frictional force between the surface of the photosensitive member and the cleaning blade increases, and blade wear increases. Therefore, it is possible to determine whether the surface of the photoreceptor is effectively refreshed by looking at the blade wear amount. Further, as the blade wear progresses, the force to block the transfer residual toner becomes weak, which leads to cleaning failure such as slipping through. The dynamic friction coefficient μ between the photoreceptor surface and the cleaning blade was 0.9.

[Comparative Example 1]
In this comparative example, amorphous strontium titanate (shown in FIG. 7) having an average primary particle size of 500 nm was used as the inorganic fine powder supplied onto the photoreceptor. Other configurations were the same as those in Example 1. As a result of the endurance evaluation of 100,000 sheets under high temperature and high humidity (80 ° C. at 30 ° C.), an image flow occurred from the beginning of the endurance. The blade was severely damaged as compared with Example 1, and toner slipping was observed in the second half of the durability.

[Example 2]
In this embodiment, a photoconductor having a universal hardness value of 200 N / mm ² and an elastic deformation rate We of 50% was used. For the roughening treatment, the surface of the surface was roughened by dry blasting using the apparatus shown in FIG. 4 at a rotational speed of the photosensitive member of 30 rpm and using abrasive grains: shaped glass beads (average particle size: 40 μm). The surface shape was Rz = 0.8 μm, Sm = 45 μm, and Rku = 6.5. The other configurations were the same as in Example 1.

  As a result of the endurance evaluation of 100,000 sheets under high temperature and high humidity (30 ° C., 80%) with the above configuration, good results were obtained in terms of image flow, fusion, and cleaning properties. Although the cleaning blade was worn, it was at a level causing no problem in practical use. The dynamic friction coefficient μ between the photoreceptor surface and the cleaning blade was 1.1.

[Example 3]
In this embodiment, a fur brush that is rotationally driven is provided upstream of the cleaning blade in the photosensitive drum rotation direction. The fur brush moved in the same direction as the photoconductor at the contact portion with the photoconductor, and was driven so that the peripheral speed of the photoconductor was 110%. The fur brush was made of an acrylic material having a fiber diameter of 30 μm, a fiber density of 100 fibers / mm ² , and an amount of entry to the photoreceptor of 1 mm. Other configurations were the same as those in Example 2.

  As a result of the endurance evaluation of 100,000 sheets under high temperature and high humidity (30 ° C., 80%) with the above configuration, good results were obtained in terms of image flow, fusion, and cleaning properties. The cleaning blade wear was better than that in Example 1. This is considered to be because the surface of the photoreceptor is rubbed with the fur brush and the fur brush carries the inorganic fine powder, and the polishing performance of the inorganic fine powder is further extracted. Further, it is considered that the effect of scraping off the discharge products and the like that have entered the recesses more reliably and accumulated in the recesses can be obtained by setting the fur brush fiber diameter to be smaller than the photoreceptor surface irregularity interval: Sm. The dynamic friction coefficient μ between the surface of the photoreceptor and the cleaning blade was 0.8.

[Example 4]
In this embodiment, an elastic roller that is rotationally driven is provided upstream of the cleaning blade in the photosensitive drum rotation direction. As the elastic roller, a sponge roller such as foamed polyurethane, foamed silicon, foamed EPDM or the like is preferably used. In this embodiment, foamed polyurethane is used. The outer diameter of the sponge roller is 15.4 mm, and its hardness is 30 ° (Asker C). The roller hardness is preferably 10 to 50 ° (Asker C). If the roller hardness is 10 ° or less, the expected effect cannot be obtained due to insufficient rubbing force. If the roller hardness is 50 ° or more, the photosensitive member may be damaged. is there. An intrusion amount of 0.6 mm is in contact with the photosensitive member at a linear pressure of 40 g / cm, and is rotatably disposed upstream of the cleaning blade 8a in the rotational direction of the photosensitive member. The contact portion was moved in the same direction as the photoconductor, and was driven so that the peripheral speed of the photoconductor was 110%. Other configurations were the same as those in Example 1.

  As a result of the endurance evaluation of 100,000 sheets under high temperature and high humidity (30 ° C., 80%) with the above configuration, good results were obtained in terms of image flow, fusion, and cleaning properties. The cleaning blade wear was better than that in Example 1. This is presumably because the surface of the photoconductor is rubbed by the elastic roller and the surface of the photoconductor is effectively rubbed by the inorganic fine powder supported on the surface of the sponge roller or sponge cell. Further, it is considered that when the elastic roller is in pressure contact with the photosensitive member, the inorganic fine powder existing in the concave portion acts more in the direction of scraping out the discharge products and the like. The coefficient of dynamic friction μ between the photoreceptor surface and the cleaning blade was 0.6.

[Example 5]
In this embodiment, a mag roller that is rotationally driven is provided upstream of the cleaning blade in the photosensitive drum rotation direction. The mag roller moved in the same direction as the photosensitive member at the contact portion with the photosensitive member, and was driven so that the peripheral speed of the photosensitive member was 110%. The magnetic roller carries the same magnetic toner as the developing toner to form a magnetic brush. Other configurations were the same as those in Example 1.

  As a result of the endurance evaluation of 100,000 sheets under high temperature and high humidity (30 ° C., 80%) with the above configuration, good results were obtained in terms of image flow, fusion, and cleaning properties. The cleaning blade wear was better than that in Example 1. This is considered to be because the surface of the photoreceptor is rubbed by the magnetic brush and the magnetic brush carries the inorganic fine powder, and the polishing performance of the inorganic fine powder is more effectively extracted. Further, since the magnetic toner having a particle diameter of 7 μm is used, it is considered that the magnetic brush enters the concave portion on the surface of the photoreceptor and the effect of scraping the discharge product and the like accumulated in the concave portion more reliably can be obtained.

  In this embodiment, since magnetic toner is used as the developing toner, the magnetic toner is used as the magnetic brush. However, when the carrier is used in the two-component developing system, the carrier may be used as the magnetic brush. The coefficient of dynamic friction μ between the photoreceptor surface and the cleaning blade was 0.6.

[Example 6]
In this embodiment, a crossing angle of 0.2 ° is provided between the rotating shaft of the charging roller and the rotating shaft of the photosensitive member (shown in FIG. 8). The purpose of providing the crossing angle is to diffuse the contamination of the charging roller from external additives as much as possible to prevent local charging failure, but in the case of this embodiment, the frictional force is expected. is doing. That is, since the vectors in the rotation direction of the charging roller and the photosensitive drum are different, a rubbing force is generated at the nip portion. Other configurations were the same as those in Example 1.

  As a result of the endurance evaluation of 100,000 sheets under high temperature and high humidity (30 ° C., 80%) with the above configuration, good results were obtained in terms of image flow, fusion, and cleaning properties. The cleaning blade wear was better than that in Example 1. This is considered to be because the surface of the photosensitive member is effectively rubbed at the nip portion by providing a crossing angle on the charging roller. In addition, it is considered that the inorganic fine powder existing in the concave portion at the charging roller nip portion acts more in the direction of scraping discharge products and the like. The dynamic friction coefficient μ between the photoreceptor surface and the cleaning blade was 0.75.

1 is a schematic cross-sectional view of an image forming apparatus suitable for the present invention. It is explanatory drawing of Rku. It is explanatory drawing of a grinder. It is explanatory drawing of an abrasive-grain discharge apparatus. It is the elements on larger scale explaining a cleaning blade. It is a figure based on the photograph of the strontium titanate of a perovskite type crystal. It is a figure based on the photograph of amorphous strontium titanate. It is a crossing angle view of a charging roller. It is a photoreceptor surface recessed part figure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Developing device 4 Transfer device 5 Fixing device 6 Cleaning device 8 Polishing sheet 8-a Cleaning blade 9 Discharge device 10 Electrophotographic photosensitive member 11 Backup roller 12 Polishing sheet winding means 13 Photosensitive member surface concave portion 14 Discharge Products and external additives 15 Inorganic fine powders of perovskite crystals 16 Cleaning blades 17 External additives

Claims (7)

At least a step of charging an image carrier having a photosensitive layer on a conductive support, an electrostatic latent image forming step of forming an electrostatic latent image on the charged image carrier, and transferring toner to the electrostatic latent image In an image forming apparatus having a visualizing development step, a step of transferring a toner image formed on an image carrier onto a transfer material, and a cleaning step of removing transfer residual toner from the image carrier.
The image carrier is subjected to a hardness test using a Vickers square pyramid diamond indenter in an environment of 25 ° C. and 50% humidity, and the HU (Universal Hardness Value) when pressed at a maximum load of 6 mN is 150 N / mm ² or more and 220 N / an image bearing member having an elastic deformation rate We of 40% or more and 65% or less, which is equal to or less than mm ² ,
The image carrier has a surface roughness Rz of 0.2 to 3.0 μm, a surface irregularity average interval Sm of 10 to 100 μm, and a surface sharpness Rku in the range of 3 <Rku <20,
An image forming apparatus, wherein an inorganic fine powder having a primary particle size of 30 to 300 nm and a cubic shape and / or a rectangular parallelepiped shape is supplied onto the surface of the image carrier.   A member for rubbing the surface of the image carrier is provided, and the member is a fur brush. When the fiber diameter of the fur brush is A (μm), Sm> A, and the fur brush is driven to rotate or reciprocate. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein a member that slides on the surface of the image carrier is provided, and the member is an elastic roller.   A member for rubbing the surface of the image carrier is provided, the member is a magnetic brush, and Sm> D, where D (μm) is a carrier particle size used for the magnetic brush. The image forming apparatus according to 1.   5. The charging process according to claim 1, wherein the charging step is performed by a contact roller member, and the rotation shaft of the contact roller member and the rotation shaft of the image carrier are arranged to intersect each other. The image forming apparatus described in 1. The cleaning step is performed by a cleaning blade that contacts the image carrier. The cleaning blade has a hardness of 60 to 85 (Shore hardness HS), a 100% modulus of 20 to 80 (kgf / cm ² ), and a resilience of 5 6. The image forming apparatus according to claim 1, wherein the image forming apparatus is in a range of ˜50%.   The image forming apparatus according to claim 6, wherein a coefficient of dynamic friction μ between the surface of the image carrier and the cleaning blade is 0.1 ≦ μ ≦ 3.

Images