JP4033481B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic method such as a facsimile, a laser beam printer, and a copying machine capable of maintaining good image quality over a long period of time by constantly keeping the surface of a photoreceptor clean. . Specifically, a toner (contaminant) that deteriorates the image quality of the next copying cycle, such as toner, paper dust, and corona product remaining on or adhered to the photoreceptor after the toner image transfer. The present invention relates to an image forming apparatus using a cleaning device that can effectively remove and maintain the surface of a photoreceptor so as to obtain good image quality.

  In an image forming apparatus using an electrophotographic method such as a facsimile, a laser beam printer, a copying machine, etc., a device for charging, image exposure, development, transfer, separation, cleaning, static elimination, etc. is disposed around a photosensitive member. These devices sequentially act on the photoconductor to form an image. A direct current voltage or a DC voltage superimposed with an alternating voltage is applied to a charging device such as a corona charging device or a contact charging device, and the photosensitive member has a surface potential (for example, 400 to 1000 V in absolute value) necessary for image formation. Charged. During this charging, corona products such as ozone and nitrogen oxides are generated as discharge products in addition to electric charges. These corona products adhere to the surface of the photoreceptor without discharge and time, and cause deterioration in image quality such as resolution reduction and image flow.

  An electrostatic latent image corresponding to the image is formed on the photoconductor by image exposure using LD light after charging, and a developer (actor image) is formed by applying a developer. The toner composition includes pigments, resins, polarity control agents, silica and other lubricating substances, and a part of the composition adheres to the photoreceptor by the action of the cleaning blade and the corona product, and the toner filming layer. Form. When filming occurs, phenomena such as image unevenness, background dirt, resolution reduction, and image flow occur.

  The toner image is transferred to the transfer material that has entered by the transfer device. When copy paper is used as a transfer material, the copy paper is composed of cellulose, talc, silica, binder, etc., and this constituent material is released on the surface of the copy paper and a small amount adheres in the form of paper dust. . When the paper dust adheres to the photoconductor, filming occurs, which causes a reduction in resolution and an image flow phenomenon similar to the above-described phenomenon. If the cause substance (contaminant) causing the resolution reduction, the image flow, etc. is immediately after adhering, there is no actual harm and it can be removed relatively easily. Normally, contaminants adhering to the photoreceptor are removed to some extent by removing the photosensitive layer and contaminants by a developing device and a cleaning device, and a level of image quality that has almost no practical problem is provided. However, when the photoconductor has a high wear resistance, the copying speed is fast, the mass copying, etc., the wear of the edge of the cleaning blade advances, and the cleaning device or developing device keeps the surface of the photoconductor clean. Insufficient maintenance may sometimes cause the image quality degradation as described above.

  In order to maintain the image quality in a good state, it is necessary to provide protective means that suppresses the adhesion of contaminants to the extent that the image quality of the toner image does not deteriorate on the photoconductor or does not accept the influence of moisture in the atmosphere. It is necessary to take. Examples of methods for improving image flow (white spots) caused by corona products, photoconductor surface oxidation, toner filming, paper dust adhesion, and the like include the following disclosure examples.

1) A method in which a photoreceptor is heated to 40 to 60 ° C. to prevent a decrease in surface resistance and to suppress a decrease in resolution (for example, JP-A 63-40181, JP-A 62-296180, JP-A 51- 65941, JP-A-60-95467, etc.)
2) A method of wiping the surface of the photoreceptor with water and removing the corona product adhering to the surface to prevent deterioration of resolution (for example, JP-A-60-173570)
3) A method of removing the corona product by cleaning the photosensitive layer with activated carbon fiber (for example, US Pat. No. 5,264,903, JP-A-3-92882, etc.)
4) A method of removing the corona product by cleaning with a non-woven fabric of ultrafine fibers (for example, Japanese Patent Laid-Open Nos. 5-150693 and 5-134585, and Japanese Patent Laid-Open No. 8-248820)
5) To avoid white spots and white streaks on the image due to ozone and NOx, prevent deformation of the cleaning blade, and maintain a stable image over a long period of time, remove toner, carrier, etc. in order from the transfer device side. A residual developer removing member and a forced scraping member for removing sticking matters such as ozone and NOx are arranged (Japanese Patent Laid-Open No. 9-230767).
6) First blade cleaning means and first blade in order from the transfer device side in order to avoid abnormal images (background stains, white stripes, black stripes, etc. due to defective charging) that occur in the image forming apparatus using the charging roller. Is provided with a second blade cleaning means having a low electrical resistance and capable of applying a voltage.

  As described above, when contaminants such as corona products, toner components, and paper dust adhere to the surface of the photoconductor, the surface resistance of the photoconductor is lowered, causing a reduction in resolution and image flow. In addition, contaminants attached to the photoconductor damage the edge of the blade, resulting in poor cleaning, black streaks, reduced durability of the cleaning blade, deterioration of electrophotographic properties, scratches, uneven wear, etc. Causes durability to drop. Further, these foreign matters adhering to the photosensitive member are reattached to the charging roller, resulting in local charging failure, and black streaks and image unevenness. Therefore, in an image forming apparatus using electrophotography, a cleaning means for keeping the photosensitive member in a clean state is particularly important. As for the cleaning means or the means for improving the image flow, many solution means have been proposed as seen in the disclosed example, but there are differences in the effect depending on the system conditions, and the fundamental solution is reached. The current situation is not.

  In order to continue to provide good image quality over a long period of time, the present invention is the cause of the occurrence of these abnormal images from the viewpoint that there is no method other than keeping the surface of the photoreceptor always clean. In addition to maintaining the image quality in a good condition over a long period of time by reliably removing the contaminants adhering to the photoconductor every copying cycle and maintaining the surface state of the photoconductor always clean. By reducing the deterioration and damage of the cleaning blade, and reducing the durability of the photoconductor due to the adhesion of contaminants, damage to the cleaning blade, suppressing contamination of the charging member, rubbing noise, etc., image quality, photoconductor, An object of the present invention is to provide an image forming apparatus capable of improving the overall reliability of a blade, a charging member, and the like.

  In order to achieve the above object, the present invention charges a photosensitive member using a charging device, forms an electrostatic latent image by image exposure, develops the electrostatic latent image with a developer to form a toner image, and transfers it. In the image forming apparatus in which the toner image on the photosensitive member is transferred to a transfer material by the apparatus and the residual toner on the photosensitive member after the toner image is transferred is removed by the cleaning device, the cleaning device is in contact with the photosensitive member. The first cleaning blade abuts on the surface of the photoreceptor surface upstream of the second cleaning blade in the direction of movement of the photoreceptor surface, and the first cleaning blade has a second cleaning blade. The second cleaning blade comes into contact with the surface of the photosensitive member in a counter-facing posture. The cleaning device further downstream of the contact position of the first cleaning blade with respect to the photosensitive member and upstream of the contact position of the second cleaning blade with respect to the photosensitive member with respect to the moving direction of the surface of the photosensitive member. A cleaning brush that is in contact with the photosensitive surface portion on the side, wherein a contact pressure of the first cleaning blade with respect to the photoreceptor is set lower than a contact pressure of the second cleaning blade with respect to the photoreceptor. An image forming apparatus is proposed in which the cleaning blade is grounded or a DC voltage, an AC voltage, or a DC voltage weighting AC is applied.

  Furthermore, in the image forming apparatus according to claim 1, it is advantageous to use a photoreceptor having a coating layer having a thickness of 2 to 8 μm in which inorganic fine particles are dispersed on the photosensitive layer (claim 2).

  According to the invention of claim 1, by using at least two cleaning blades as means for releasing contaminants unnecessary for image formation such as toner, paper dust, corona product remaining on the photoreceptor, As compared with the prior art, finer cleaning can be achieved. In addition, by disposing a cleaning brush between the first cleaning blade and the second cleaning blade, minute contaminants such as corona products can be eliminated and the surface of the photoreceptor is further cleaned. However, it is possible to suppress degradation of image quality and provide good image quality over the entire environment. In addition, even if the surface of the photoconductor enters the first cleaning blade in a state where a large amount of toner or paper dust remains, it is possible to suppress problems that cause scratches or filming on the photoconductor. On the other hand, since most of the toner is removed by the first cleaning blade, even if the contact pressure of the second cleaning blade against the photosensitive member is slightly increased, scratches are unlikely to occur. Moreover, the rubbing force of the cleaning blade itself can be obtained by grounding the first cleaning blade or selecting and applying a DC voltage, an AC voltage, or a DC voltage superimposed with an AC voltage as the applied voltage. In combination, contaminants remaining on the photoreceptor can be efficiently removed.

  According to the second aspect of the present invention, it is possible to extend the durability of the photoconductor by providing an optically and electrically good wear-resistant coating layer on the photoconductor. If the coating layer is thinner than 2 μm, the durability cannot be maintained. If the coating layer is thicker than 8 μm, the durability increases. However, the increase in the residual potential causes a problem in image quality. By providing the coating layer of inorganic fine particles, there is also a merit that adhesion of foreign matters on the photoreceptor is reduced.

In the image forming apparatus of this example, two cleaning blades are arranged in order to reliably remove various contaminants adhering to the photoconductor that affects the image quality, or a cleaning brush is arranged between the two cleaning blades. The provided cleaning device is disposed between the transfer device and the charging device. The cleaning blade on the transfer device side is the first cleaning blade, and the cleaning blade on the charging device side is the second cleaning blade. The first cleaning blade is made of an elastic member capable of applying a voltage, for example, a rubber material. In order to configure the first cleaning blade so that a voltage can be applied, the first cleaning blade may be conductive or semiconductive. For example, the volume resistivity is 100 ^{0 to} 10 ¹¹ Ω · cm, preferably 100 ^{0 to} 10. ¹⁰ Omega · cm, particularly preferably set to 10 ⁰ to 10 ⁸ Ω · cm. Such a cleaning blade is a blade of an elastic member (preferably rubber-based) excellent in various properties such as heat resistance, ozone resistance, abrasion resistance, and pollution-free property having a hardness of 50 to 80 degrees and a thickness of about 1.5 to 4 mm. It is preferable that The conductivity of the cleaning blade can be achieved by adding materials such as carbon powder and carbon and alkali metal salts. The rubber material is optimally urethane rubber, but BSR, CR, silicone rubber, etc. can also be used.

  Making the first cleaning blade conductive or semi-conductive (medium resistor) can also be used by applying a voltage to the cleaning blade. This is to facilitate removal. When a voltage is applied, it is possible to select any one of a DC voltage, an AC voltage, and a DC voltage superimposed with an AC voltage according to the use conditions, and the cleaning blade can be grounded (0V) (see FIG. 1, see FIG.

  The reason for cleaning while grounding the cleaning blade or applying a voltage thereto is to electrostatically remove residues such as toner and paper dust on the photoreceptor. If toner or paper dust remains on the photoconductor due to poor cleaning, it will gradually adhere to the surface of the photoconductor due to heat or pressure generated during repeated use, and filming tends to occur. That is, since the toner and paper dust after passing through the transfer device are electrostatically and physically attached to the photoreceptor, they are used for a long time with one cleaning blade as in the conventional blade cleaning system. In cases such as this, or with photoconductors with significantly improved wear resistance, or models with fast copying speeds, when the blade edge is worn out, toner is lost and the contamination due to filming spreads rapidly, causing the image to spread. Affects quality. This poor cleaning can improve the cleaning efficiency by using two blade cleanings, but it is necessary to pay attention to the mounting position of the two cleaning blades, and the positions where these cleaning blades come into contact with the photoreceptor are close. If it is too much, the toner blocked by the second cleaning blade will not be removed, and there is a risk of adversely affecting the photoconductor, such as filming, black belts or poor cleaning. Therefore, it is preferable to set a position where the first and second cleaning blades abut on the photoreceptor so that such a problem does not occur.

  By applying a voltage to the cleaning blade, toner, paper dust and the like are electrostatically floated or sucked from the photoreceptor, and residues such as toner and paper dust on the photoreceptor are removed. However, the untransferred toner and paper dust do not hold a uniform polarity or charge, and may be positive, negative or almost 0V. Therefore, the voltage condition such as the polarity of the voltage applied to the first cleaning blade or its value (including 0 V) needs to be changed according to the system condition. A voltage having a polarity capable of electrostatically attracting toner on the photosensitive member is applied to the first cleaning blade, or the first cleaning blade is grounded.

  If the edge of the cleaning blade becomes worn, the cleaning performance of the photoconductor is reduced, and the photoconductor is easily contaminated. Therefore, the first cleaning blade removes the contaminants as much as possible, and residual contaminants and removal It is preferable to keep the photoconductor in a clean state by removing the corona product which is difficult to be removed with a second cleaning blade and further with a cleaning brush.

  The contact pressure of the first cleaning blade with respect to the photosensitive member is desirably set lower than the contact pressure of the second cleaning blade with respect to the photosensitive member. For example, if the contact pressure of the second cleaning blade is 60 to 80 mN / cm, the contact pressure of the first cleaning blade is set to 60 mN / cm or less. This is because if there is a lot of toner and paper dust, the photosensitive member is likely to be damaged, and the first cleaning blade comes into contact with the photosensitive member by grounding or applying a voltage to the first cleaning blade. The pressure can be set low. The toner that has escaped from the first cleaning blade can be supplemented by the second cleaning blade or a cleaning brush. However, even if a voltage is applied to the first cleaning blade, if the contact pressure of the first cleaning blade is reduced more than necessary, a cleaning failure occurs. Therefore, it is desirable that the voltage be higher than at least 40 mN / cm. By removing most of the residual toner with the first cleaning blade, the contact pressure of the second cleaning blade against the photosensitive member can be reduced, and this allows the durability of the photosensitive member as well as the cleaning blade to be reduced. Can be reduced. The voltage applied to the first cleaning blade may be set to, for example, an absolute value of about 200 to 800 VDC, an AC voltage of 200 to 1500 V, and a frequency of 100 to 2000 Hz as a sine wave.

  The contact method of the cleaning blade to the photosensitive member may be either the trailing method or the counter method, but considering the load on the photosensitive member and space saving, the first cleaning blade is the trailing method. In view of the cleaning performance, the second cleaning blade is preferably a counter type.

  Cleaning brushes are used to dig up and remove very fine corona products that are difficult to remove with a cleaning blade, and reaction products of oxides and resins on the photoconductors. It is an effective means. However, although the cleaning brush is sufficiently effective even with a copying speed of about 10 to 20 cpm, it is particularly effective with a copying speed of 40 cpm or more with high accumulation of contaminants and high consumption of cleaning members. Becomes higher. cpm indicates the number of copies per minute.

By using the cleaning device as described above, it is possible to eliminate almost all contaminants that reduce the image quality on the photoconductor, and to provide good image quality over a long period of time. This cleaning device is not limited to an organic photoconductor, but can be applied to an a-Si photoconductor, an Se photoconductor, and any overcoat photoconductor. However, depending on the physical characteristics and mechanical characteristics of the photoconductor, the effect may vary, and the present invention is highly effective when an organic photoconductor is used. Organic photoreceptors can be manufactured at a lower cost than photosensitive materials such as selenium and amorphous silicon, and have advantages such as easy production, no pollution, and high sensitivity. Most of the photoreceptors on the market are organic. It is a photoreceptor. However, since the organic photoreceptor is made of resin, the photosensitive layer is soft and the mechanical durability (abrasion resistance) is low, so when using a two-stage cleaning blade method, the abrasion resistance is disadvantageous depending on the setting conditions. As a result, the life of the photoconductor may be shortened. Therefore, when an organic photoreceptor is used, it is desirable to form a further wear-resistant coating layer on the photoreceptor. As a suitable method for the coating layer, the same binder resin as the photosensitive layer (for example, polycarbonate resin, polyester resin, etc.) is used on the photosensitive layer as a donor for improving the hole mobility, and if necessary, an antioxidant. Alternatively, a plasticizer is added, and a resin to which about 25 to 40% of inorganic fine particles of titanium oxide or alumina are added in order to further improve the wear resistance, and a dip coating method, a spray coating method, or the like is used. A coating layer of ˜8 μm is formed. Examples of the characteristics of the coating layer include an electrical resistance of 10 ¹² to 10 ¹⁴ Ω · cm, and a transmittance of 90% or more in the infrared region of 650 to 780 nm. As described above, when the inorganic fine particles are made of titanium oxide or alumina, good electrophotographic characteristics can be maintained both electrically and in image quality. Further, the foreign matter adhering to the photoconductor is easier to remove than the state without the coating layer. Therefore, the charging ability is high, the sensitivity is hardly decreased, and good image quality is provided. As described above, it is preferable to use a photoreceptor having a coating layer having a thickness of 2 to 8 μm in which inorganic fine particles are dispersed on the photosensitive layer. In this case, the inorganic fine particles constituting the coating layer of the photoreceptor are made of titanium oxide. Advantageously it is any of alumina.

  Even with the above configuration, the durability of the photoreceptor is greatly improved as compared with the conventional one, and sufficient characteristics can be maintained over a long period of time. If further improvement is desired, an appropriate amount of lubricant is applied to the surface of the photoreceptor, It is desirable to externally add lubricity. Although there is a method of internally adding a lubricant into the photosensitive layer, it is not practical because it is not durable and the amount of addition is limited. Since the lubricant relaxes the frictional resistance between the cleaning blade or developer and the photosensitive member, abrasion of the photosensitive layer is suppressed. As the island-like thin film of lubricant expands in the photosensitive layer, biting by the carrier gradually decreases and filming caused by toner, paper dust, and corona products is reduced.

  Lubricants that can be used include fluororesins (polytetrafluoroethylene, polyvinylidene fluoride, etc.), zinc stearate, etc. The lower the coefficient of friction after the addition of the lubricant, the less the wear of the photosensitive layer and the higher mechanical durability. Can be realized. However, if the friction coefficient decreases too much, the paper dust and corona product adhering to the photoconductor cannot be scraped off, which tends to cause image flow, and the coefficient of friction on the photoconductor surface is made lower than 0.1. That is not preferable. A preferable range of the friction coefficient is 0.1 or more and 0.5 or less, and particularly preferably 0.2 or more and 0.4 or less. However, since it depends on the surface condition (uniformity) of the photoreceptor, the friction coefficient alone is not enough, but if it is within the above range and the friction coefficient is low, the durability of the photoreceptor is It can be improved with certainty. Note that the coefficient of friction of the surface of the photosensitive member when no lubricant is externally added is about 0.6 to 0.63. By setting the friction coefficient to be in the above range, the durability of the photosensitive member can be 200,000 to 400,000 or more. The coefficient of friction is a numerical value when the Euler belt method is used, which will be described later. Another advantage of adding a lubricant is that the filming phenomenon caused by the sticking of the silica added to the toner as a fluidizing agent to the photoreceptor is moderately reduced, minimizing the deterioration of the appearance characteristics and image quality. It is recognized that it is difficult to stop.

Hereinafter, the image forming apparatus will be described more specifically.
1) Copying Process An outline of the image forming apparatus is shown in FIG. The image forming apparatus shown here uses a charging device 2 such as a charging roller as shown or a charging brush (not shown) or a corona discharge device as a photoconductor 1 that rotates in the clockwise direction. It is charged to a surface potential necessary for formation, for example, -400 to -1000V. Next, in a digital image forming apparatus, light from an LD or LED element having a wavelength of 630 to 820 nm or less is read from an electrical signal read or transmitted by a CCD (charge coupled device), a polygon mirror, a cylindrical lens, and a dot. The exposure apparatus 3 using a convex lens for reducing the diameter to 80 to 30 μm performs image exposure on the photoreceptor in the form of a dot pattern to form an electrostatic latent image. The electrostatic latent image thus obtained is visualized, that is, converted into a toner image using a developing device 4 using a one-component or two-component developer, and the toner image is a roller as shown in the figure. Alternatively, a transfer device 5 (transfer efficiency of 95 to 99%) is transferred to copy paper (plain paper) 9 as an example of a transfer material by a transfer device 5 such as a belt-shaped or corona discharge method (not shown), and a separation device The copy paper is separated from the photosensitive member. The copy sheet 9 is conveyed to the fixing device 8 where the transferred toner image is fixed to form a hard copy. Since the developer (almost toner) remains on the photoconductor after the transfer, it is cleaned by the cleaning device 6.

  As described above, the image forming apparatus shown in FIG. 1 uses a charging device to charge a photosensitive member, forms an electrostatic latent image by image exposure, and develops the electrostatic latent image with a developer to form a toner. After the image formation, the toner image on the photoconductor is transferred to a transfer material by a transfer device, and the residual toner on the photoconductor after the toner image transfer is removed by a cleaning device.

  Here, the cleaning device 6 has at least a first cleaning blade 10 and a second cleaning blade 11 that are in contact with the photoreceptor 1, and the first cleaning blade 10 is more photosensitive than the second cleaning blade 11. The first and second cleaning blades are disposed so as to abut on the surface of the photoreceptor on the upstream side in the surface movement direction, and the first cleaning blade 10 is made of an elastic member capable of applying a voltage as described above. Yes. Further, the cleaning device 6 is downstream of the contact position of the first cleaning blade 10 with respect to the photosensitive member in the moving direction of the surface of the photosensitive member, and the contact position of the second cleaning blade 11 with respect to the photosensitive member. In addition, the cleaning brush 12 is in contact with the photosensitive member surface portion on the upstream side. The cleaning brush 12 is provided as necessary, and the cleaning brush can be eliminated as in the cleaning device 6 shown in FIG. The image forming apparatus shown in FIG. 2 is the same as the image forming apparatus shown in FIG. 1 except that the cleaning device 6 does not have a cleaning brush.

  The first cleaning blade 10 closer to the transfer / separation apparatus is installed by a counter or a trailing method as shown in the figure, and the material is elastic and can be applied with a voltage. The second cleaning blade 11, which is a blade and is closer to the charging device, is composed of a cleaning blade made of an insulating material having elasticity that is installed in a counter manner. After the cleaning, the electrostatic latent image remaining in the photosensitive layer is erased by the static eliminating device 7 (which does not necessarily require neutralizing light) consisting of LED elements of long wavelength light, and the next copying cycle starts.

  As described above, a charging device, an image exposure device, a developing device, a transfer device, and two cleaning blades are arranged around the photoconductor in order along the moving direction of the surface. A cleaning device is arranged so that a voltage can be applied to the first cleaning blade. In this way, by providing a cleaning device incorporating two cleaning blades or further a cleaning brush in the image forming apparatus, there is no ozone odor and a good image quality is provided over a long period of time. On the other hand, since the photoconductor during image formation is released from contaminants, contamination of the photoconductor and the charging member is reduced, and durability of both members can be increased. The cleaning device can be used alone or incorporated into the process cartridge.

  Although FIG. 1 shows a copying process using a single color developer, it is basically applicable to a color type image forming apparatus using one photoconductor and a tandem type image forming apparatus using four photoconductors. Specifically, the copying process shown in FIG. 1 is used. In addition, a belt-shaped or drum-shaped intermediate transfer member is used as a transfer material, and the toner image on the photosensitive member is primarily transferred to the intermediate transfer member, and then the toner image is secondarily transferred to a final transfer material, for example, copy paper. The toner image can be fixed on the final transfer material. Furthermore, as the photosensitive member, a drum-shaped photosensitive member as shown in the drawing can be used, and an endless belt-shaped photosensitive member that is wound around and driven by a plurality of rollers can also be used.

2) Photoreceptor Basically, the photoconductor used in the above-described image forming apparatus can be any of an inorganic photoconductor such as a Se-based material or an a-Si-based material and an organic photoconductor. However, there are differences in how the phenomenon appears depending on the photoconductor, and it is also necessary to wear appropriately, so that it can be suitably used for an organic photoconductor. Hereinafter, the organic photoreceptor will be described in detail.

  In recent years, organic photoreceptors have been widely used as the mainstream of photoreceptors, and have advantages such as high charging ability, high sensitivity design, low cost, easy production by spraying and dipping methods, and non-pollution. . On the other hand, since it is made of resin, its hardness is low and it is brittle, so there is a problem that its durability is short. However, this durability can be improved by optimizing the copying system and the photoconductor configuration. A specific photoconductor structure is a photoconductor in which an undercoat layer 1b, a charge generation layer 1c, a charge transport layer 1d, and a coating layer 1f are sequentially laminated on a conductive support 1a as shown in an enlarged view in FIG. . In this example, the charging polarity is negative. FIG. 4 shows another example of a photoconductor in which a charge generation layer and a charge transport layer are integrated, and the operation polarity is mainly positively charged. Hereinafter, the structure of the photoreceptor in FIG. 3 will be described.

(1) Conductive support The material of the conductive support is generally aluminum that has undergone processing such as super-finishing and mirror finishing. However, it satisfies electrical, mechanical and chemical properties. In addition to metals such as stainless steel, copper and brass, conductive layers obtained by vapor deposition or sputtering of gold, aluminum, platinum, chromium, etc. on compressed paper, resin, or glass, and fine particles such as carbon, tin, etc. A dispersed conductive layer may be applied. The electrical resistance is a volume specific resistance, and there is no problem if it has a value of the order of 10 ⁶ Ω · cm or less. The shape is, for example, a drum shape, and the thickness depends on the diameter and material, but when aluminum is used, a thickness of about 0.5 to 3 mm is used. If the photosensitive member has a diameter of 24 to 80 mm, a conductive support having a thickness of about 0.8 to 1.5 mm is used.

(2) Undercoat layer The undercoat layer is used for maintaining charging characteristics by preventing charge injection from the conductive support, for preventing latent image disturbance due to irregular reflection in the photosensitive layer of the digitally converted image exposure, and for conducting. It is formed in order to improve the coatability and adhesiveness of both the support and the charge generation layer. The undercoat layer is an alumina deposition film, and in the case of a dispersion system, a metal oxide such as TiO ₂ or SnO ₂ is dispersed in alkyd resin, alkyd-melamine resin, polyvinyl alcohol, casein, etc. The film is applied to a thickness of 1 to 10 μm using an immersion method, a spray method, a ring coating method, or the like. Preferably, it is about 4 μm to 8 μm. If the undercoat layer is too thick, the residual potential tends to increase repeatedly, and if it is thin, the S / N ratio deteriorates, and noise (black spots, background stains, etc.) increases due to prolonged use. Normally, good electrophotographic characteristics can be maintained by uniformly forming an undercoat layer having a volume resistance of about 10 ⁹ to 10 ¹² Ω · cm with a thickness of 3 to 8 μm.

(3) Charge generation layer The charge generation layer is obtained by dispersing a charge generation material in a binder resin. In the case of organic photoreceptors, charge generating materials include metal phthalocyanine, metal-free phthalocyanine and other phthalocyanine series, azo pigments having skeletons such as carbazole, triphenylamine, fluorenone, oxadiazole, quinone such as perylene pigment and anthanthrone. Pigments, perylene pigments, benzoquinone and naphthoquinone pigments, polycyclic quinone pigments, quinoneimine pigments and the like can be used alone or in admixture of two or more. Moreover, you may add a low molecular transport material as needed. As the binder resin, polyamide resin, polyester resin, polycarbonate resin, polyurethane resin, acrylic resin, polyacrylamide resin, phenol resin and the like can be used. As the hole transport material, an oxazole derivative, an oxadiazole derivative, an imidazole derivative, a thiazole derivative, a triazole derivative, styrylanthracene, styrylpyrazoline, or the like is used alone or in combination. These charge generation materials and binder resins are dispersed in tetrahydrafuran, toluene, cyclohexanone, dichloroethane, etc. as a dispersion, uniformly in a ball mill, sand mill, vibration mill, etc., using a spray coating method, a dipping method, etc. It coats on the undercoat layer in a thickness of 0.05 to 5 μm, preferably 0.2 to 1 μm. If it is thicker than necessary, the space charge will increase and the light attenuation characteristics, residual potential, etc. will be affected.

(4) Charge transport layer The charge transport layer is obtained by dispersing a charge transport material in a binder resin. Low molecular transport materials include oxazole derivatives, oxadiazole derivatives (described in JP-A Nos. 52-139065 and 52-139066), imidazole derivatives, and triphenylamine derivatives (described in Japanese Patent Application No. 1-77839). , Α-phenyl stilbene derivatives (described in JP-A-57-73075), toniphenyl methane derivatives (described in JP-B 51-10983), anthracene derivatives (described in JP-A-51-94829), etc. Can be used. The binder resin used is polycarbonate resin (bisphenol A type, bisphenol C type, bisphenol Z type or a copolymer thereof), polyarylate resin, polyester resin, polystyrene resin, vinyl acetate resin, or a mixture of two or more. I can do it.

Moreover, in order to improve environmental resistance, antioxidant can be added in order to suppress a sensitivity fall and a residual potential rise. As an antioxidant, for example,
Monophenolic compounds such as 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol 2,2′-methylene-bis- (4 -Methyl-6-tert-butylphenol), bisphenyl compounds such as 2,2′-methylene-bis- (4-ethyl-6-tert-butylphenyl),
1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t- High molecular phenolic compounds such as butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane 2,5-di There are hydroquinones such as -t-octyl hydroquinone, 2,6-didodecyl hydroquinone, 2-dodecyl hydroquinone and 2- (2-octadecenyl) -5-methyl hydroquinone.

  The film thickness of the charge transport layer is desirably set in a homogeneous range of 5 to 30 μm. Setting the thickness to about 10 to 25 μm is advantageous for forming an electrostatic latent image having a high resolution of 600 to 1200 dpi or more. The resolution of the copy image is affected by the toner, carrier particle size, development method, original image dot system, transfer conditions, surface resistance of the charge transport layer, bulk resistance, etc. It is desirable to set the level as high as possible. The resolution of the electrostatic latent image on the photoreceptor tends to decrease with increasing film thickness because light and charge are diffused as the photosensitive layer becomes thicker. Therefore, a thinner charge transport layer is advantageous in terms of resolution.However, as the photosensitive layer is a dispersion layer, the non-uniformity in electrical resistance becomes more conspicuous as the thickness decreases. However, there are problems such as a decrease in SN ratio and electrical durability, and down without waiting for mechanical durability. Furthermore, by reducing the thickness of the charge transport layer, the contrast potential necessary for image formation cannot be obtained, and an image with low contrast and gradation is obtained.

(5) Coating layer The coating layer is formed on the photosensitive layer in order to ensure the mechanical and electrical durability of the photoreceptor, and is a high-hardness amorphous carbon film, amorphous silicon film, or high resistance. A thin film such as a tin oxide film of about 1 to 5 μm, a method of forming by a vacuum deposition method, a CVD method, a sputtering method, an ion plating method, etc., and a fine particle of about 0.05 to 5 μm are dispersed in a binder resin, and photosensitive There is a method of applying a thin film on the layer. By dispersing an appropriate amount of the inorganic fine particles in the binder resin, the durability of the photoreceptor can be improved. Examples of inorganic fine particles include titanium oxide, silica, alumina, zirconium oxide, indium oxide, and silicon nitride. Particularly, alumina and titanium oxide have good environmental stability in this order, and can be used as suitable inorganic fine particles. . These inorganic fine particles can be subjected to water repellent treatment using a silane coupling material or a fluorine-based silane coupling agent. Inorganic fine particles can be used as a binder resin dispersed in polycarbonate resin, polyethylene resin, polyurethane resin, acrylic resin, polyamide resin, etc., but preferably have no polarity dependency and have a good transparency of 10 ¹⁶ to 10 ¹⁷ Ω. -A polycarbonate resin having a high resistance of about cm is suitable.

  When dispersing inorganic fine particles in the binder resin, it is possible to improve water and water repellency and lubricity by improving dispersion of fluorine resin fine particles such as polytetrafluoroethylene and improve environmental and wear resistance. is there. The dispersion amount of the inorganic fine particles is preferably about 25 to 40% by weight based on the binder resin. When the addition amount increases, the wear resistance increases, but on the other hand, the light transmittance decreases and diffuses, and the mobility of charges. Decrease occurs, and it tends to cause resolution reduction, residual potential increase, sensitivity decrease, and the like. Further, contaminants that hinder image formation such as corona product adhering to the surface and filming due to toner components are less likely to be worn and may cause a reduction in resolution. On the other hand, when the amount of inorganic fine particles added is small, the coefficient of friction becomes high, the mechanical durability cannot be maintained, toner filming due to the developer, adhesion of silica or the like (piercing) easily occurs, and white Spots and unevenness may occur. Therefore, although the film thickness of the coating layer depends on the required durability, it is desirable to set it in the range of 2 to 8 μm, preferably about 3 to 6 μm.

  Since inorganic fine particles are dispersed in the coating layer, if there is an unevenness or poor dispersion of the particle size, the resolution, residual potential, mechanical durability, etc. are affected. Therefore, it is desirable that the inorganic fine particles in the coating layer are dispersed almost uniformly in the layer. The total film thickness of the photosensitive layer including the photosensitive layer (= charge generation layer + charge transport layer) and the coating layer is preferably set within a range of 15 to 30 μm.

3) Charging method and apparatus Charging prior to forming the electrostatic latent image on the photosensitive member and charging method for transferring the toner image onto the copy paper are contact using a charging member such as a corona discharge method, a charging roller, or a brush. Alternatively, it is performed by a non-contact charging method or the like. The corona discharge method is a method in which a high voltage of 4000 to 8000 V in absolute value is applied to a 40 to 80 μm tungsten wire or a sawtooth SUS plate placed in a metal case. Naturally, corona products such as ozone and nitrogen oxides are increased as compared with the contact charging method driven at a low voltage, which causes environmental problems. Since the corona discharge method (mainly scorotron charger) is non-contact, it does not damage the photoconductor, and it is operated at a distance of about 10 cm from the photoconductor so that it can be uniformly charged. The generated corona product flies toward the photoconductor. It is possible to reduce the chemical influence of the corona product exerted on the photoconductor by the contact charging method, for example, by providing a sucking step during the process. However, ozone and nitrogen oxides are generated in large quantities, and there are many environmental problems.

  On the other hand, in the contact charging method and the non-contact charging method in which charging is performed from a charging member installed at a distance of about 50 to 250 μm, a DC voltage or a sinusoidal AC voltage (absolute value 1000 V to 2000 V, 500 Hz to 2.5 KHz) is applied to the charging member. ) Is superimposed on a DC voltage and charged so that the surface potential is about 400 to 800 V in absolute value. However, since the applied voltage is low, corona products such as ozone and nitrogen oxide are one of the corona discharge methods. / 100 or less, and the exhaust treatment apparatus can be simple, so there is almost no environmental problem. However, even if the generation amount is very small, the influence of the corona product on the photoconductor is large and presents a serious problem in image quality such as resolution reduction, image flow, and uneven density of halftone image. The merit of the method of charging by slightly separating the charging member from the photosensitive member is advantageous in that damage to the photosensitive member is alleviated even if the charging member becomes dirty.

Since this corona product adheres very thinly on the photoconductor, it is not easy to remove it with a cleaning blade, and it cannot be removed as easily as a photoconductor with high wear resistance. Therefore, a cleaning method for cleaning the surface of the photoreceptor is extremely important. Although any of the above-described charging methods can be used in the present invention, a non-contact charging method in which charging is performed in close contact or in close proximity is preferable from the environmental characteristics. As described above, as a means for charging the photosensitive member, a contact charging device or a non-contact charging member that is arranged and separated from the photosensitive member by about 50 to 250 μm is used. The power and the power supply device can be reduced in size, ozone generation is minimal, and the environment is preferable. When a non-contact charging member is used, dust attached to the photoreceptor is difficult to adhere, so that the durability of the charging member can be further increased. An image is formed by applying a charge necessary for image formation to the photoconductor with a charging device comprising a conductive member in contact with or in close proximity to the photoconductor. For example, as shown in FIG. 1, a charging device 2 including a charging roller having an elastic layer having a volume resistivity of, for example, 10 ^{5 to} 10 ⁸ Ω · cm is used around a cored bar.

4) Cleaning device The cleaning device eliminates not only toner but also contaminants that cause problems in image formation, such as corona products, paper dust, and filming. The cleaning device 6 shown in FIG. 1 uses the first and second cleaning blades 10 and 11 and the cleaning brush 12, and the cleaning device 6 shown in FIG. 2 does not use the cleaning brush. The material of the first cleaning blade close to the transfer / separation device is preferably urethane rubber, but BSR, CR, silicone rubber or the like can also be used. These rubber materials are made by adding materials such as carbon powder, carbon and alkali metal salts, and having a volume resistivity of 10 ⁰ to 10 ⁸ Ω · cm and a hardness of 50 to 80 degrees. The blade can be used at a thickness of about 1.5 to 4 mm, and is usually about 2 mm. The first cleaning blade 10 may be installed on the photosensitive member 1 by either a counter or a trailing method, but is preferably installed by a trailing method so that the contact pressure is set lower than that of the second cleaning blade 11. For example, if the contact pressure of the second cleaning blade is 60 to 80 mN / cm, the contact pressure of the first cleaning blade is set to 60 mN / cm or less. This is because if the toner and paper dust are large, the photoconductor is easily damaged. By applying a voltage, it becomes possible to set the photoconductor to a low level. It can be supplemented with. When the cleaning performance of the cleaning device is improved, the charging roller is not contaminated, the charging property is stabilized, and the image quality can be maintained high. By applying a voltage to the first cleaning blade 10 or grounding the blade 10, paper dust, toner, and the like attached to the photoreceptor are easily removed. Depending on the use conditions, as shown in FIGS. 1 and 2, any one of grounding, a DC voltage, an AC voltage, and a DC voltage superimposed with an AC voltage can be selected. 1 and 2, reference numeral 14 indicates a DC power source, and reference numeral 13 indicates an AC power source. The voltage applied to the first cleaning blade 10 is a DC voltage of about 200 to 800 V, an AC voltage of 200 to 1000 V, and the frequency is a sine wave of about 50 to 2000 Hz.

  The second cleaning blade 11 attached to the charging device side sufficiently disposes toner paper powder and corona products that have escaped from the first cleaning blade 10 by placing urethane rubber on the counter. If the first cleaning blade 10 is working sufficiently, the contact pressure of the second cleaning blade 11 can be made lighter than that of a single cleaning device, so that the durability of the blade is increased. You can

The material of the cleaning brush installed between the first and second cleaning blades is, for example, a fiber having a fiber thickness of 15 to 20 denier such as polypropylene, polyethylene, nylon, etc. with a density of about 2000 to 3500 / inch ² on a resin roller. Planted and processed into brush-like rollers.

  The reason for installing the cleaning brush is particularly effective when a high-speed copying machine or a lot of corona products are generated. That is, high-speed photocopiers often use highly durable photoconductors, and contaminants such as paper dust and corona products increase with the copying speed and number of copies. Therefore, there are cases where two cleaning blades are insufficient. Since the cleaning brush cleans so as to scrape off contaminants adhering to the photosensitive member at the tip of the brush, the cleaning performance is surely improved as compared with the case of the blade alone. Needless to say, this method can be sufficiently used for an image forming apparatus having a copying speed of about 20 to 40 sheets. By using such a series of cleaning devices, it is possible to eliminate almost all contaminants that reduce the image quality on the photoconductor, and to provide good image quality over a long period of time.

5) Lubricant external addition method As described above, the reason for supplying the lubricant onto the photoreceptor is the influence of the appearance deterioration of the photoreceptor, for example, toner filming, the effect of the developer addition component such as silica or the like on the photoreceptor. However, by suppressing the above phenomenon, the lubricant easily acts on the photoconductor, which contributes to the reduction of the friction coefficient of the photoconductor. As a method for supplying the lubricant to the photoconductor, there is a method for supplying a powdery or block-like lubricant directly or indirectly to the photoconductor. For example, powdery zinc stearate, PTFE (polytetrafluoroethylene resin), polyfucavinylidene, or the like is added to the developer at a ratio of 0.01 to 0.5% with respect to the toner. If too much is added, the coefficient of friction of the photoconductor may be too low, or the physical characteristics (for example, Q / M) of the toner may be violated, the control may not be effective, and the toner may be excessively supplied. Usually, it is desirable to add between 0.01 and 0.3% of the toner. The amount of the lubricant added is sufficient to prevent filming and appearance defects caused by the toner. Incidentally, this amount of addition is only an amount that reduces the friction coefficient of 0.6 to about 0.45 to 0.55 when the lubricant is used alone (when the surface property adjusting member is not used in combination). . Therefore, there is almost no effect in suppressing wear of the photosensitive layer. As a method of supplying the solid lubricant, there is a method of using a member to be worn, for example, a dedicated brush or a cleaning brush (fur brush). In this method, a block-like lubricant is supplied to the photoreceptor while being worn with a brush. The supply amount is controlled by lightly contacting the lubricant with the brush. As another supply method, there is a method of supplying a film-like lubricant of about 50 to 200 μm in contact with the photoreceptor. In this method, the friction coefficient can be reduced by controlling the pressure of the lubricant contacting the photoconductor or by switching to another fluororesin.

6) Coefficient of friction The coefficient of friction is an important characteristic for improving the mechanical durability of the photosensitive layer. The coefficient of friction of the photoreceptor becomes about 0.3 to 0.5 (value measured by the Euler belt method described later) by adding a leveling agent (for example, silicone oil), and is 0 when no leveling agent is added. 6 or more. However, even when a leveling agent is added, if about 20 copies are made, the coefficient of friction immediately exceeds 0.6, and there is no sustainability. When such a photoreceptor without a coating layer is used, the wear of the photosensitive layer increases due to wear by the cleaning blade or developer, and durability cannot be maintained. In addition, the above-described silica may be attached or pierced, and filming or uneven wear may occur unevenly on the surface of the photoreceptor. The inorganic fine particles in the coating layer form irregularities on the surface layer of the photosensitive layer and reduce the frictional resistance with the cleaning blade. When about 30% of inorganic fine particles are added, the friction coefficient is about 0.4 to 0.6. Unlike the case where there is no coating layer, the friction coefficient is relatively persistent, so that wear is reduced in combination with fine particles of high hardness. By reducing the coefficient of friction, the pressure of the cleaning blade, developer, contact charging device, etc. in contact with the photoreceptor is reduced, so that the wear of the photosensitive layer is inevitably reduced. However, if the coefficient of friction is too low, the cleaning performance of the cleaning blade will be significantly reduced, making it difficult to remove contaminants such as corona products, paper dust, and filming, and reducing image quality such as reduced resolution and image flow. Produce. A preferable range of the friction coefficient is 0.1 or more and 0.5 or less, preferably 0.2 to 0.4. In the case of the vicinity of 0.6 or more, the wear of the photosensitive layer is promoted, but the wear may be influenced by the surface state of the photoreceptor. The method of externally adding a lubricant to a photoreceptor is to use a powdery, solid, or film-like fluororesin, a liquid lubricant such as zinc stearate, silicone oil, or fluorine oil, or a gaseous lubricant. In addition to the method of acting on the photoreceptor as an external addition method, there is a method of adding a small amount of lubricant to the developer.

  When using a film-like fluororesin to reduce the friction coefficient of the coating layer surface layer, the fluororesin (eg, PTFE = polytetrafluoroethylene) film with a thickness of about 100 to 400 μm is in soft contact with the photoreceptor. The coefficient of friction can be reduced by producing a lubricity-imparting member using an elastic member in combination and pressing the member uniformly against the surface of the coating layer. Depending on the pressing of the lubricity-imparting member to the photoconductor, the photoconductor may be rubbed and scratched. However, the inorganic fine particles are dispersed, and the friction coefficient is reduced to about 0.4. If they come into contact with each other, almost no scratches are given to the image. When a lubricant such as fluorine resin fat or zinc stearate is used, the lubricant can be once attached to an application member such as a brush and then supplied to the photoreceptor from the application member. Furthermore, when supplying powdery fluororesin (PTFE) to the photoreceptor, it can be attached to a feather or cotton-like material and supplied to the coating layer surface little by little. There is an intermittent method that supplies the coating layer surface continuously or at regular intervals. If the coefficient of friction is too low, the mechanical durability can be greatly increased, Too much increases the possibility of adverse effects such as image flow. Therefore, it is preferable to supply lightly or use an intermittent method that acts once on 50 to 100 copies. When a lubricant is added to the toner, for example, zinc stearate and powdered fluororesin are added to the toner in an amount of about 0.01 to 0.4%, preferably about 0.1 to 0.2%. If the amount of addition is large, the friction coefficient is significantly reduced while copying is in progress, leading to image flow.

The coefficient of friction is calculated by the following measurement method. As shown in FIGS. 5 and 6, the measurement photoreceptor 1 is fixed to a pedestal, and is a high-quality paper having a thickness of 85 μm cut to a width of 30 mm and a length of, for example, 297 mm [type 6200 paper manufactured by Ricoh Co., Ltd. The belt 24 is prepared as a belt 24. The belt 24 is wound around the circumferential surface of the photoreceptor 1 at an angle of 90.degree., And a weight 25 of 100 gr is passed through one end of the belt through a thread 20 with negligible weight. And a digital force gauge 23 for weight measurement is attached to the other end via a thread 21 whose weight is negligible. Slowly pull the digital force gauge 25 placed on the table in the direction of arrow A, read the weight when the belt 24 starts to slide on the photoconductor, and calculate the (static) friction coefficient using the following formula. .
μs = 2 / π × ln (F / W)
Where μs: static friction coefficient, F: reading load
W: Weight of weight π: Circumferential ratio This measurement method (Euler belt method) is also described in JP-A-9-166919.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Method for producing photoconductor for evaluation>
A photoreceptor was prepared in the following manner. An undercoating layer (UL) coating solution, charge generation layer (CGL) coating solution, and charge transport layer (CTL) coating solution on an aluminum drum having a diameter of 60 mm, a length of 340 mm, and a wall thickness of 1.2 mm. In this order, dip coating is performed, and a 3.5 μm undercoat layer, a 0.15 to 0.2 μm charge generation layer, and a 22 to 25 μm charge transport layer are applied by heat drying. Was made. Further, a binder resin, a donor, inorganic fine particles (metal oxide), and a solvent are placed on a glass pot on this photoconductor and dispersed with a ball mill for 24 hours, and an average particle size (measured with CAPA500 manufactured by Horiba Seisakusho) is about 0.45. A 0.55 μm coating solution is prepared, applied 1-3 times (about 1.5-2.0 μm / time) using a spray method, dried by heating to form a 1-10 μm coating layer, and electrophotographic photosensitive Completed the body. All parts described below represent parts by weight.

[Coating liquid for undercoat layer]
Alkyd resin (Beckosol 1307-60-EL, manufactured by Dainippon Ink and Chemicals) 6 parts Melamine resin (Super Becamine G-821-60, manufactured by Dainippon Ink and Chemicals) 4 parts Titanium oxide (CR-EL Ishihara Sangyo) 40 parts Methyl ethyl ketone 200 parts
[Coating liquid for charge generation layer]
Oxotitanium phthalocyanine pigment 2 parts Polyvinyl butyral (UCC: XYHL) 0.2 part Tetrahydrofuran 50 parts [Coating liquid for charge transport layer]
Bisphenol A type polycarbonate (manufactured by Teijin Kasei Co., Ltd .: Z Polyca) 10 parts Low molecular charge transport material with the following structure 12 parts

塩化メチレン １００部
メチルフェニルシリコーンオイル（５０ｃｓ） １部
〔無機微粒子層用塗工液〕
無機微粒子層用塗工液はバインダー樹脂と無機微粒子が重量比で２５％、電荷輸送物質とバインダー樹脂の比が７／１０に成るように混合し、シクロヘキサノンを溶媒としてスプレー法で１〜３回のスプレーを行い、４種の被覆層を形成した。
バインダー樹脂：ポリカーボネート樹脂（Ｚポリカ、帝人化成社製 Ｍｖ５万）
無機微粒子：アルミナ粉末（ＡＡ−４０ 住友化学工業社製）
低分子電荷輸送物質：下記構造

Methylene chloride 100 parts methylphenyl silicone oil (50cs) 1 part [coating liquid for inorganic fine particle layer]
The coating solution for the inorganic fine particle layer is mixed such that the binder resin and the inorganic fine particles are 25% by weight and the ratio of the charge transporting material and the binder resin is 7/10, and the spray method is performed 1 to 3 times using cyclohexanone as a solvent. The four types of coating layers were formed.
Binder resin: Polycarbonate resin (Z Polyca, Teijin Chemicals Mv50,000)
Inorganic fine particles: Alumina powder (AA-40, manufactured by Sumitomo Chemical Co., Ltd.)
Low molecular charge transport material:

溶媒：シクロヘキサノン

Solvent: cyclohexanone

<Charging member>
Image formation of a photoreceptor on a charging member having an electrical resistance of 2 to 6 × 10 ⁵ Ω · cm (when 100 VDC is applied) formed by coating epichlorohydrin rubber in which carbon is uniformly dispersed on an 8 mm brass rod and molding it to a thickness of 14 mmφ. A charging member processed so as to be 100 μm apart in the region was prepared. A single layer of PET (polyethylene terephthalate) having a thickness of 60 μm and a width of 10 mm was attached to both ends of the charging member and processed so as to have a void in the image forming area when brought into contact with the photoreceptor. In addition, the space | gap when arrange | positioning facing a photoreceptor was 85-100 micrometers. This charging member was set in a housing and used.

<Cleaning device>
(1) A cleaning device for one cleaning blade with a 2 mm-thick urethane rubber attached in a counter manner. (2) The first cleaning blade has a thickness of 2 mm, an electric resistance of 2 to 5 × 10 ⁶ Ω · cm, and a hardness of 60 degrees. 2 urethane rubber (made by Kinugawa Rubber) is attached by the trailing method as shown in FIG. 2, and 2 mm thick urethane rubber is used as the second cleaning blade as shown in FIG. A cleaning device attached, (3) a cleaning brush having a diameter of 30 mm, in which 17 denier polypropylene fibers are implanted at a density of 2500 fibers / inch ² (direct hair), as shown in FIG. 1, attached between two cleaning blades Three types of cleaning devices were prepared. The driving motor for the cleaning brush was externally attached, and was set to rotate in the forward direction with the rotation of the photosensitive member as shown in FIG. The rotation speed was 170 rpm.

<Evaluation method>
The image forming apparatus for evaluation includes (1) a cleaning apparatus having a single cleaning blade configuration, (2) a cleaning apparatus including a cleaning brush and two cleaning blades, and (3) a cleaning apparatus including two cleaning blades. An experimental electrophotographic copying machine having a copying speed of 28 (sheets / minute) modified so that the apparatus can be attached was prepared. The developer is cyan toner having a particle size of about 9.5 μm (SiO ₂ = 0.7%, TiO ₂ = 0.8%, lubricant (SZ2000) = 0.05% added as a flow agent), and a particle size of 80 μm. 5% concentration developer (Ricoh's prototype developer) dispersed in a magnetic carrier (FPC-300LC) was used. The charging member is a φ14 mm charging roller made of carbon-dispersed epichlorohydrin rubber having a gap of 85 to 100 μm with respect to the photosensitive member, and a DC voltage in which an alternating voltage is superimposed on the charging member with a high-voltage cable is applied from an external power source. . The voltage conditions were adjusted so that the alternating voltage was 1.5 KV / 1 KHz, and the DC voltage was adjusted so that the surface potential of the photoreceptor was −600 V. Note that Yokogawa's function generator FG-300 + Aichi Nagano HV-255 was used as the high-voltage application power source for the charging member, and the timing of voltage application to the photosensitive member was achieved with a trigger voltage.

  The evaluation items are the resolution after running paper in a normal humidity environment (22 ° C./55% RH), the appearance of the photoreceptor, and the coefficient of friction. Further, after humidity adjustment, that is, after running the paper, image formation is performed. This is the resolution and image quality when the image is formed after the apparatus is left at 30 ° C./90% RH for 3 hours. “After run” in the table means after running. Although not shown in the table, the amount of abrasion of the photosensitive layer was also evaluated. The amount of abrasion of the photosensitive layer was measured by using an eddy current film thickness meter (Fischerscope MMS) manufactured by Fischer, and measuring the film thickness at 26 points before and after running and determining the average value. The coefficient of friction was measured using a self-made device, using 30 mm x 297 mm high-quality paper (Ricoh type 6200 paper, vertical mesh), 100 g weight, digital force gauge (Simpo Industry FGC-2), The above-described Euler belt method was used. Image quality is determined by using a standard test chart with a JIS standard bamboo shoot chart attached as a document, and the resolution, sharpness, etc. are determined. A 5% line chart is used for a document for running paper. Evaluation of 100,000 sheets was performed at a rate of 99 sheets in one cycle.

Example 1
A first cleaning blade having a thickness of 2 mm, a hardness of 60 degrees, an electrical resistance of 2 to 5 × 10 ⁶ Ω · cm, and a contact pressure of 45, 55, 70, and 85 mN / cm, a thickness of 2 mm, and a contact pressure of 75 mN / cm A cleaning device composed of a second urethane rubber cleaning blade having a thickness of cm is mounted on an experimental electrophotographic copying machine, and the voltage applied to the first cleaning blade is grounded (0 V), −500 VDC, 1200 VAC / 1000 Hz, +300 VDC + 1200 VAC / Four conditions of 1000 Hz were used. A photoconductor having a charge transport layer (CTL) of 23 μm and a coating layer of 5.0 μm was prepared. As the developer, a toner (manufactured by Ricoh) in which 0.05% of zinc stearate was added to the toner was used. The results are shown in Tables 1 to 1. When the contact pressure of the first cleaning blade was set to 55 and 70 mN / cm, there was no problem with the image quality of the photoconductor. However, when the contact pressure was 45 and 85 mN, there was a slight problem, but the photoconductor was scratched or filled. However, it was not in a particularly problematic range. In the voltage condition applied to the first cleaning blade, a better result was obtained under the condition that the AC voltage is involved. However, in other conditions, the quality can be obtained without any problems by setting to a suitable condition. Can be set. The abrasion of the photoreceptor was 0.08 to 0.12 μm / 10,000 sheets, and durability equivalent to 300,000 to 400,000 sheets was confirmed.

(Comparative Example 1)
The cleaning device was changed to a device consisting of a single cleaning blade, the blade contact pressure was 75 mN / cm, and 0% and 0.05% zinc stearate was added to the developer. An organic photoreceptor having the same 5 μm coating layer as 1 was used. The evaluation results are shown in Table 2. In Comparative Examples 1-1 and 1-2, zinc stearate is 0%, and Comparative Examples 1-3 and 1-4 are 0.05%. The filming method is lighter when zinc stearate is added, and the degree of image flow remains locally. However, a cleaning device composed of one cleaning blade can remove contaminants on the photoconductor. However, there may be a problem in image quality after 100,000 sheets.

（実施例２）
第１と第２のクリーニングブレード間にクリーニングブラシを取り付けたクリーニング装置に交換し、第１のクリーニングブレードの当接圧を４５、５５、７０、及び８５ｍＮ／ｃｍ、第２のクリーニングブレードの当接圧を７５ｍＮ／ｃｍに設定した。また、現像剤をトナーに対し０．０５％のステアリン酸亜鉛とし、感光体にはアルミナ（ＡＡ−４０）をバインダー樹脂に対し３０％添加した５μｍの被覆層の実施例１に同等の有機感光体を使用した。評価結果を表３に示す。クリーニングブラシを追加した場合には、当接圧が８５ｍＮ／ｃｍを除いた以外、極めて良好な結果が得られた。摩擦係数は全体的に０．３前後であり、曇りも主に端部に筋状に生じた程度であったり、特に問題となるものではなかった。感光層の摩耗は実施例１より僅かに多い程度で、０．１〜０．１７μｍ／１万枚の摩耗が確認された。

(Example 2)
Replace the cleaning device with a cleaning brush attached between the first and second cleaning blades, the contact pressure of the first cleaning blade is 45, 55, 70, and 85 mN / cm, the contact of the second cleaning blade The pressure was set to 75 mN / cm. Further, an organic photosensitive equivalent to Example 1 of a 5 μm coating layer in which 0.05% zinc stearate with respect to the toner is added to the toner and alumina (AA-40) is added 30% with respect to the binder resin as the photoreceptor. Used the body. The evaluation results are shown in Table 3. When a cleaning brush was added, very good results were obtained except that the contact pressure was not 85 mN / cm. The coefficient of friction was about 0.3 as a whole, and cloudiness was mainly caused in the form of streaks at the ends, and there was no particular problem. The abrasion of the photosensitive layer was slightly higher than that in Example 1, and 0.1 to 0.17 μm / 10,000 sheets of wear were confirmed.

(Example 3)
Prepare a cleaning device with two cleaning blades, apply an AC voltage of 0V, 1100V / 1KHz to the first cleaning blade, set the contact pressure to 45, 55 and 70 mN / cm, The contact pressure of the cleaning blade was set to 65 mN / cm. The developer was evaluated by evaluating the characteristics by using 0.05% zinc stearate added to the toner as the developer, and using an organic photoreceptor having no coating layer as the photoreceptor. The results are shown in Table 4. Even if the photoreceptor has no coating layer, the generation of scratches can be reduced by reducing the contact pressure of the cleaning blade, and the image quality is also good. The abrasion of the photosensitive layer was 0.2 to 0.4 μm / 10,000 sheets because no coating layer was formed.

(Comparative Example 2)
A cleaning device having a single cleaning blade was prepared, and the contact pressure was set to 65 mN / cm. The developer was prepared by adding 0% and 0.05% zinc stearate to the toner, and an organic photoreceptor having no coating layer was used as the photoreceptor, and the characteristics were evaluated. In Comparative Example 2-1 and Comparative Example 2-2, zinc stearate is 0%, and Comparative Example 2-3 and Comparative Example 2-4 are 0.05%. The results are shown in Table 4. In a cleaning device composed of a single cleaning blade, filming caused by the adhering of contaminants such as toner, paper dust, corona products, etc., starting from silica or the like stuck in the surface of the photoreceptor appears, and the image quality is There were problems such as density unevenness and reduced resolution. Photosensitive layer wear tends to be mitigated when using toner with zinc stearate added, but in both cases, filming occurs to a greater or lesser extent, so apparent wear is small and increases depending on the location. Some parts were seen.

Example 4
Using a cleaning device having two cleaning blades, the contact pressure of the first cleaning blade was varied to 45, 55, and 70 mN / cm, and an AC voltage of 1400 V / 1 KHz was set as the applied voltage. The contact pressure of the second cleaning blade was set to 75 mN / cm. As the photoreceptor, three kinds of photoreceptors having a coating layer thickness of 2, 5, and 8 μm were used, and as the developer, 0.1% zinc stearate added to the toner was used. Evaluation was conducted based on these factors. The results are shown in Table 6. For the photoreceptor having a coating layer of 8 μm, the image density decreased due to a decrease in residual potential, but the appearance of the photoreceptor was good. For the 2 μm and 5 μm photoconductors, even if the contact pressure varies between 55 and 70 mN / cm, there is no clear abnormal phenomenon in the appearance and image quality of the photoconductor, and the contact pressure of the first cleaning blade is Even if it was as low as 45 mN / cm, there was no problem with respect to image quality and the photoreceptor. In the case of a photoreceptor having a coating layer of 2 μm, the photosensitive layer was scraped by 1.5 μm after 100,000 sheets, and thus it is considered that the durability is about 100,000 sheets, but an abnormal image could not be confirmed even with 100,000 sheets.

1 is a schematic diagram of an image forming apparatus. It is the schematic which shows the other example of an image forming apparatus. It is an expanded sectional block diagram of a photoreceptor. It is an expanded sectional block diagram of another photoconductor. It is a figure explaining an Euler belt system. FIG. 6 is a view of the photoreceptor and the belt in the direction of arrow VI in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 5 Transfer device 6 Cleaning device 9 Transfer material 10 First cleaning blade 11 Second cleaning blade 12 Cleaning brush

Claims (2)

The photosensitive member is charged using a charging device, an electrostatic latent image is formed by image exposure, the electrostatic latent image is developed by a developer to form a toner image, and the toner image on the photosensitive member is transferred to a transfer material by a transfer device. In an image forming apparatus that removes residual toner on a photoconductor after a toner image is transferred by a cleaning device,
The cleaning device includes a first cleaning blade and a second cleaning blade that are in contact with the photoconductor, and the first cleaning blade is a portion of the photoconductor surface upstream of the second cleaning blade in the photoconductor surface movement direction. The first cleaning blade contacts the surface of the photoconductor in a trailing orientation, the second cleaning blade contacts the photoconductor surface in a counter orientation, and the cleaning device includes: Further, with respect to the moving direction of the photosensitive member surface, the photosensitive member surface is downstream of the contact position of the first cleaning blade with the photosensitive member and upstream of the contact position of the second cleaning blade with the photosensitive member. A cleaning brush in contact with the portion, and the contact of the first cleaning blade against the photosensitive member The pressure is set lower than the contact pressure of the second cleaning blade against the photosensitive member, and the first cleaning blade is grounded or applied with a DC voltage, an AC voltage, or a DC voltage weighting AC. An image forming apparatus. The image forming apparatus according to claim 1, wherein a photosensitive member having a coating layer having a thickness of 2 to 8 μm in which inorganic fine particles are dispersed on the photosensitive layer is used.

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