JP5793917B2 - Image forming apparatus and process cartridge - Google Patents

Description

  The present invention relates to an image forming apparatus and a process cartridge.

  In an electrophotographic image forming apparatus, a toner image is transferred from an electrostatic latent image holding member to a transfer target, and then a toner remaining on the peripheral surface of the electrostatic latent image holding member is removed. Is done. As the cleaning device, a method of scraping residual toner by bringing a cleaning blade made of an elastic body into contact with the peripheral surface of the electrostatic latent image holding body is often used.

  In recent years, the life of the image forming unit is required to be long, and the cleaning blade is also required to have high durability. A double-layered cleaning blade that has different characteristics for the cleaning layer and the back layer that are in contact with the electrostatic latent image holding body in order to increase the durability and to wear the electrostatic latent image holding body or to sag the cleaning blade. Has been proposed.

  For example, Patent Document 1 discloses that a cleaning layer that is in contact with a toner adhering body and a back surface layer provided on the back surface of the cleaning layer are composed of two layers, and the Young's modulus of the cleaning layer is 8 to 20 MPa and repulsion at 25 ° C. A cleaning blade having elasticity of 20 to 40%, defining the relationship between the Young's modulus of the clean layer and the back layer, and the thickness of the clean layer and the back layer, and the total Young's modulus of the clean layer and the back layer being 7 to 14 MPa A member is disclosed.

  Similarly, Patent Document 2 is composed of two layers, a clean layer and a back layer, and defines the material of the clean layer, and the relationship between the Young's modulus of the clean layer and the back layer, and the thickness of the clean layer and the back layer. And a cleaning blade member in which the Young's modulus of the entire cleaning layer and back layer is 5 to 14.0 MPa.

JP 2007-193306 A JP 2009-31773 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and a process cartridge using a cleaning blade that can suppress the occurrence of streaks in an image to be formed even if the electrostatic latent image holding member has a small diameter.

The said subject is achieved by this invention shown to the following <1>- <2> .
<1> An electrostatic latent image holding body capable of holding an electrostatic latent image formed on a peripheral surface thereof, which is cylindrical or columnar with an outer diameter of 27 mm or less, rotates around an axis, and
Charging means for charging the peripheral surface of the electrostatic latent image holding member;
An electrostatic latent image forming unit that forms an electrostatic latent image on the peripheral surface of the charged electrostatic latent image holding body;
Toner image forming means for supplying toner to the electrostatic latent image formed on the peripheral surface of the electrostatic latent image holding member to form a toner image;
Transfer means for transferring the toner image to a transfer object;
The front end is pressed against the peripheral surface at an angle with respect to the normal line from the peripheral surface of the electrostatic latent image holding body so that the rear end faces the rotation direction of the electrostatic latent image holding body, and the peripheral surface side The electrostatic latent image holding member peripheral surface remaining after transfer is not transferred by the cleaning blade having a two-layer structure of the cleaning layer positioned at the tip and the front surface contacting the peripheral surface and the back layer positioned on the back surface. Cleaning means for removing and cleaning the toner,
The ratio (w / r) of the dynamic hardness w of the clean layer and the dynamic hardness r of the back layer in the cleaning blade is 2.2 or more ,
Dynamic hardness w measured from the surface facing the peripheral surface of the electrostatic latent image holding member in the clean layer, and the electrostatic latent image holding member at the tip contacting the peripheral surface of the electrostatic latent image holding member. An image forming apparatus having a ratio (w / c) of 0.8 to 1.0 with respect to a dynamic hardness c measured from a surface opposed to the rotation direction .

<2> A process cartridge which is detachable from the image forming apparatus according to <1> and includes at least the electrostatic latent image holding member and the cleaning unit.

According to the invention according to <1>, the occurrence of streaks in an image to be formed can be further suppressed while the electrostatic latent image holding member has a small diameter, compared with a case where the present configuration is not provided.

According to the invention according to <2> , there is provided a process cartridge capable of suppressing the generation of streaks in an image to be formed while being a small-diameter electrostatic latent image holding member as compared with a case where this configuration is not provided. be able to.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment showing an exemplary aspect of the present invention. FIG. 2 is a schematic configuration diagram in which only an image forming engine is extracted and enlarged in the image forming apparatus of FIG. 1. FIG. 3 is an enlarged cross-sectional view in which a peripheral portion of a plate-like cleaning member in the image forming engine of FIG. 2 is extracted. It is a schematic explanatory drawing for demonstrating the measurement surface of the dynamic hardness in a plate-shaped cleaning member. 1 is a schematic cross-sectional view schematically showing a basic configuration of a preferred example of a process cartridge of the present invention. It is an expanded sectional view of a plate-shaped cleaning member periphery for explaining a mounting state of the plate-shaped cleaning member.

  The image forming apparatus and process cartridge of the present invention will be described in detail below.

[Image forming apparatus]
FIG. 1 is a schematic configuration diagram illustrating an exemplary aspect of an image forming apparatus of the present invention. In FIG. 1, illustrations of an incidental device configuration, a paper feeding device, a fixing device, and the like are omitted.

  The image forming apparatus according to the present embodiment is a so-called tandem type, and is connected to a control unit that controls the image forming unit and the like, for example, an image reading device and a personal computer (PC) in addition to the illustrated image forming unit. The image processing unit includes an image processing unit that performs image processing on the image data received from the image data.

  The image forming unit includes four image forming engines 30Y, 30M, 30C, and 30K arranged in parallel at regular intervals (hereinafter, each image forming engine may be simply referred to as “image forming engine 30”). .)

  FIG. 2 shows a schematic configuration diagram in which only the image forming engine 30 is extracted and enlarged. As shown in FIG. 2, the image forming engine 30 is an example of an electrostatic latent image holding body on which an electrostatic latent image is formed, and is a photosensitive drum 31 that rotates in the direction of arrow A, and the surface of the photosensitive drum 31. A charging roll 32 that is an example of a charging unit that uniformly charges, a developing device 33 that is an example of a toner image forming unit that develops an electrostatic latent image formed on the surface of the photosensitive drum 31, and the surface of the photosensitive drum 31 that is not yet A cleaning device 34, which is an example of a cleaning unit that removes transfer toner and the like, is provided. Also, an example of an electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the photosensitive drum 31 by scanning and exposing the respective photosensitive drums 31 of the image forming engines 30Y, 30M, 30C, and 30K with a laser beam 26. An exposure apparatus (not shown) is provided.

  Each image forming engine 30 is configured in substantially the same manner except that the color and type of toner (developer) stored in the developing device 33 are different. In each of the image forming engines 30Y, 30M, 30C, and 30K, yellow (Y), magenta (M), cyan (C), and black (K) toners are stored in the developing device 33. Each toner image is formed.

  The photosensitive drum 31 is an example of an electrostatic latent image holding member, and is formed in a drum shape as a whole, and has a photosensitive layer on the outer peripheral surface (drum surface). The photosensitive drum 31 is provided to be rotatable in the direction of arrow A in FIG.

  The photosensitive drum 31 has a function of forming at least a latent image (electrostatic charge image), and an electrophotographic photosensitive member is preferable. The photosensitive drum 31 has a cylindrical shape (in the present invention, it is not required to be cylindrical and may be a columnar shape that is not hollow inside) on the outer peripheral surface of a conductive substrate, an organic photosensitive layer or the like. A photosensitive layer containing is formed. In general, the photosensitive layer has an undercoat layer formed on the surface of the substrate as necessary, and further includes a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material in this order. It is. The order of stacking the charge generation layer and the charge transport layer may be reversed.

  These are laminated photoreceptors in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer), but both the charge generation material and the charge transport material are the same. A single layer type photoreceptor included in the layer may be used, and a laminated type photoreceptor is preferable. Further, an intermediate layer may be provided between the undercoat layer and the photosensitive layer. In addition to the organic photosensitive layer, other types of photosensitive layers such as an amorphous silicon photosensitive film may be used.

  The charging roll 32 is an example of a charging unit that uniformly charges the surface of the photosensitive drum 31. As the charging means, a charging roll 32 which is a conductive or semiconductive contact type charger as in this example may be used, but a non-contact type charger such as corotron may also be used. When the charging roll 32 is used, a direct current may be applied to the photosensitive drum 31 or an alternating current may be superimposed and applied. With such a charging roll 32, the surface of the photosensitive drum 31 can be charged by generating a discharge in a minute space near the contact portion with the photosensitive drum 31.

  The surface of the photosensitive drum 31 is normally charged to −300V to −1000V by the charging unit. The conductive or semiconductive charging roll may have a single layer structure or a multiple structure. Further, a mechanism for cleaning the surface of the charging roll may be provided.

  The exposure apparatus forms an electrostatic latent image by irradiating the photosensitive drum 31 uniformly charged by the charging roll 32 with an image-like laser beam 26. The exposure apparatus is not particularly limited, and examples thereof include an optical system device that exposes a light source such as semiconductor laser light, LED light, and liquid crystal shutter light on the peripheral surface of the electrostatic latent image holding body in a desired image manner. It is done.

  The developing device 33 has a function of developing a latent image formed on the peripheral surface of the electrostatic latent image holding member with a developer containing toner to form a toner image. The developing device 33 is not particularly limited as long as it has the above-described function, and may be appropriately selected according to the purpose. For example, a two-component developer containing a toner for developing an electrostatic image and a magnetic carrier And a developing device for adhering the toner to the photosensitive drum 31 with a magnetic brush formed of the magnetic carrier. At the time of development, a DC voltage is normally used for the photosensitive drum 31, but an AC voltage may be further superimposed and used.

  The primary transfer device 42 transfers the toner image formed on the surface of the photosensitive drum 31 to the outer peripheral surface of the endless intermediate transfer belt 41 (primary transfer) while holding the intermediate transfer belt 41 with the photosensitive drum 31. )

  As the primary transfer device 42, for example, a charge having a reverse polarity to the toner of the toner image is applied from the back side of the intermediate transfer belt 41, and the toner image is transferred to the surface of the intermediate transfer belt 41 by electrostatic force, or the intermediate transfer belt 41. What is necessary is just to use the transfer roll and transfer roll press apparatus using the electroconductive or semiconductive roll etc. which directly contact and transfer to the back surface of this.

  A direct current may be applied to the transfer roll as a transfer current applied to the photosensitive drum 31, or an alternating current may be applied in a superimposed manner. For the transfer roll, various conditions or specifications may be appropriately set according to the width of the image area to be charged, the shape of the transfer charger, the opening width, the peripheral speed, and the like. Further, a single layer foam roll or the like is suitably used as a transfer roll for cost reduction.

  The cleaning device 34 cleans (removes) the toner remaining on the surface of the photosensitive drum 31 after the transfer by the cleaning blade 35. The front end of the cleaning blade 35 is pressed against the peripheral surface at an angle with respect to the normal line from the peripheral surface of the photoconductive drum 31 so that the rear end thereof faces the rotation direction of the photoconductive drum 31 (arrow A direction). It is done.

  In each image forming engine 30, the surface of the photosensitive drum 31 is uniformly charged by the charging roll 32, and yellow (Y), magenta (M), cyan (C), black (K) based on image information by the exposure device. The latent image of each color component is formed, and an unfixed toner image is formed on each photoconductive drum 31 by the developing device 33 in which toner of each color is accommodated. Each color unfixed toner image formed on the surface of each photosensitive drum 31 is sequentially transferred to the surface of the intermediate transfer belt 41 by the primary transfer device 42.

  The intermediate transfer belt 41 includes a drive roll 43 that is rotationally driven by a rotational drive source (not shown), support rolls 44 and 45 that are driven to support the intermediate transfer belt 41, and a secondary transfer roll 40 in the secondary transfer device 46. Are arranged between the support roll 44 and the support roll 45 so as to pass through the primary transfer position of the photosensitive drum in each of the image forming engines 30. The intermediate transfer belt 41 is rotated in the direction of arrow C by the drive roll 43.

  The intermediate transfer belt 41 is not particularly limited and a conventionally known belt can be used without any problem. For example, a belt having a two-layer structure in which a surface layer is formed on the belt base material surface is used.

  Materials used for the intermediate transfer belt 41 include polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene phthalate, PC / polyalkylene terephthalate (PAT) blend material, ethylene tetrafluoroethylene copolymer (ETFE). / PC, ETFE / PAT, PC / PAT blend materials and the like are mentioned, but an intermediate transfer belt using a thermosetting polyimide resin is preferable from the viewpoint of mechanical strength.

  The main part of the secondary transfer device 46 is composed of a secondary transfer roll 40 and a backup roll 49 that are arranged to face each other with the intermediate transfer belt 41 interposed therebetween. An unfixed toner image on the surface of the intermediate transfer belt 41 is transferred to the surface of the paper P by inserting the paper P through a nip formed between the backup roll 49 and the intermediate transfer belt 41 and applying an electrostatic action. Is configured to do. There is no restriction | limiting in particular as the secondary transfer apparatus 46, A conventionally well-known structure can be employ | adopted without a problem. Specifically, the same configuration as that of the primary transfer device 42 described above can be applied.

  A fixing device (not shown) fixes the toner image transferred to the recording medium by heating, pressing, or heating and pressing. In addition to the two-roll method widely used, a belt-roll nip method in which the heating side or the pressure side is in the form of a belt and the other in the form of a roll, and a belt-like two-belt method in which both the heating side and the pressure side are in a belt form are exemplified. As for the belt, in addition to a system in which the belt is stretched by a plurality of rolls, a free belt system in which the belt is not stretched may be used. In the present invention, any type of fixing device may be used.

  Examples of the paper P on which the toner image is transferred to form a final recorded image include plain paper used for electrophotographic copying machines, printers, and OHP sheets. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording medium is as smooth as possible. For example, coated paper in which the surface of plain paper is coated with a resin, art paper for printing, etc. Preferably used.

  In the image forming apparatus of this embodiment, image data input from an image reading apparatus or a personal computer is appropriately subjected to image processing and supplied to a laser exposure apparatus (not shown). Then, after the surface of the photosensitive drum 31 is uniformly charged to a predetermined potential by the charging roll 32, the laser beam 26 modulated by the image data is scanned onto the photosensitive drum 31 by the laser exposure device. Exposed.

  As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 31. The formed electrostatic latent image is developed by the developing device 33. For example, in a magenta (M) image forming engine 30M, a magenta toner image is formed on the surface of the photosensitive drum 31. Similarly, yellow, cyan, and black toner images are formed in the image forming engines 30Y, 30C, and 30K.

  Each color toner image formed by each image forming engine 30 is electrostatically primary transferred sequentially by the primary transfer device 42 to the surface of the intermediate transfer belt 41 rotating in the direction of arrow C in FIG. A toner image superimposed on is formed.

  On the other hand, untransferred toner or the like remaining on the surface of the photosensitive drum 31 during the primary transfer is removed by a cleaning device 34 disposed on the downstream side of the primary transfer device 42. The cleaning device 34 includes a cleaning blade 35 disposed so that the tip thereof contacts the peripheral surface of the photosensitive drum 31.

  The superimposed toner image formed on the surface of the intermediate transfer belt 41 is directed to the secondary transfer portion where the secondary transfer roll 40 and the backup roll 49 are disposed as the intermediate transfer belt 41 is transported in the direction of arrow C. Are transported. On the other hand, the sheet P passes through a sheet supply unit (not shown) and a conveyance path, and is then supplied and conveyed to the position of the secondary transfer unit including the secondary transfer roll 40 and the backup roll 49.

  When the superimposed toner image is conveyed to the secondary transfer portion, the paper P is supplied in accordance with the timing, and the superimposed toner is generated by the action of the transfer electric field formed between the secondary transfer roll 40 and the backup roll 49. The image is electrostatically secondary-transferred collectively onto the surface of the paper P.

  Thereafter, the sheet P on which the superimposed toner image is electrostatically transferred is peeled from the intermediate transfer belt 41 and conveyed to a fixing device (not shown). The unfixed toner image on the sheet surface conveyed to the fixing device is fixed on the sheet by receiving a fixing process using heat and pressure. Then, the sheet on which the fixed image is formed is conveyed as it is in the direction of arrow B and discharged outside the apparatus.

  On the other hand, untransferred toner or the like remaining on the surface of the intermediate transfer belt 41 after the secondary transfer is removed by a belt cleaner 46 disposed in contact with the intermediate transfer belt 41 after the completion of the secondary transfer.

  FIG. 3 shows an enlarged cross-sectional view of the cleaning blade 35 in the present embodiment. As shown in FIG. 3, the cleaning blade 35 has a two-layer structure of a cleaning layer 351 whose tip is in contact with the peripheral surface of the photosensitive drum 31 and a back layer 352 provided on the back surface of the cleaning layer 351. It is what has. In the present embodiment, the thickness of the cleaning layer 351 is 0.5 mm and the thickness of the back layer is 1.4 mm. However, in the present invention, these thicknesses can be appropriately designed.

  At this time, it is desirable that the thickness of the cleaning layer is set so that the dynamic hardness of the cleaning layer hardly affects the spring constant of the entire plate-shaped cleaning member or is in a range where the influence is small. Specifically, the thickness of the clean layer is selected from the range of 0.2 to 0.7 mm, and the thickness of the back layer is selected from the range of 1.3 to 1.6 mm.

  There are no restrictions on the material of these two layers, and conventionally known materials include urethane rubber, neoprene rubber, and silicone rubber. Among them, it is particularly preferable to use a polyurethane elastic body because of its excellent wear resistance. It is preferable to have appropriate elasticity and strength as defined in Patent Document 1 and Patent Document 2, and polyurethane can be exemplified as a suitable material from this viewpoint.

  More specifically, for example, as the cleaning layer 351, a cast type polyurethane member formed by curing and molding a polyurethane composition containing a polyol, polyisocyanate, and a diamino compound having a melting point of 80 ° C. or less is suitable. It can be illustrated as. Such a clean layer 351 has low temperature dependence, relatively high hardness, high mechanical strength such as elongation at break and tensile strength, and excellent wear resistance.

  On the other hand, as the back layer 352, for example, a cast type polyurethane member formed by curing and molding a polyurethane composition containing a polyol, a polyisocyanate, a short-chain diol, and a short-chain triol can be exemplified as a suitable one. it can.

  The cleaning blade 35 made of the material as described above uses a polyurethane member having high hardness and excellent wear resistance as a cleaning layer 351, and a back layer on the back surface of the cleaning layer 351 in order to supplement the properties of the cleaning layer 351 such as sag resistance. By providing a two-layer structure by providing 352, even if the cleaning layer 351 in contact with the photosensitive drum 31 has a high hardness, the cleaning blade 35 is worn, the surface of the photosensitive drum 31 is worn more than expected, and the photosensitive layer is peeled off. Scratches and the like are suppressed. Therefore, according to the cleaning blade 35 having the structure, it can be expected that the photosensitive drum 31 is stably cleaned over a long period of time.

  On the other hand, in the present embodiment, the photosensitive drum 31 has a so-called organic photosensitive layer (generally referred to as an OPC layer) formed on the surface of a cylindrical tube, and the diameter thereof is 26 mmφ. In recent years, the electrostatic latent image holding member has been reduced in diameter due to demands for downsizing the apparatus, and the diameter thereof is 27 mmφ or less (preferably 26 mmφ or less, more preferably 25 mmφ or less) as in this embodiment. There is an increasing demand for a small-diameter electrostatic latent image carrier. When the diameter of the electrostatic latent image holding member is reduced, the external additive of the toner slips through the plate-like cleaning member and the charging device is contaminated. This is presumably because the smaller the diameter of the photosensitive drum, the greater the influence of blurring at the contact point with the plate-like cleaning member, and higher design accuracy is required. For this reason, it is desired to prevent the external additive from slipping through the plate-like cleaning member and prevent contamination of the charging device even when the diameter of the electrostatic latent image carrier to be cleaned is reduced.

  In the present embodiment, the ratio (w / r) between the dynamic hardness w of the cleaning layer 351 and the dynamic hardness r of the back layer 352 in the cleaning blade 35 used in the cleaning device 34 is set high. By giving a certain hardness difference between the two layers, the back surface layer 352 is easily deformed and the deformation in the clean layer 351 is small. Therefore, when the curvature of the surface to be cleaned is large like the small-diameter photosensitive drum 31. Even in this case, a stable nip state can be maintained near the tip of the cleaning blade 35, and slipping of the external additive can be stably suppressed.

  FIG. 4 is a schematic explanatory diagram for explaining the measurement surface of the dynamic hardness in the cleaning blade 35. The dynamic hardness w of the clean layer 351 is measured from the direction indicated by the arrow w in the figure, and the dynamic hardness r of the back layer 352 is measured from the direction indicated by the arrow r in the figure. At this time, all measure the vicinity of the center of each surface.

  In the present invention, the ratio (w / r) between the dynamic hardness w of the clean layer and the dynamic hardness r of the back layer (hereinafter sometimes simply referred to as “dynamic hardness ratio (w / r)”). It is calculated | required that it is 2.2 or more, Preferably it is 2.4 or more.

  On the other hand, the upper limit of the dynamic hardness ratio (w / r) is preferably 3.6 or less. If the dynamic hardness w of the clean layer becomes too large compared with the dynamic hardness r of the back layer, the effect of suppressing damage to the peripheral surface of the electrostatic latent image holding member due to wear or rubbing due to dynamic hardness improvement of the dynamic hardness w of the clean layer is Although it can be expected, the cleaning performance of the transfer residual toner and the external additive is lowered, the charging member is contaminated, and appears in an image formed as density unevenness, lines, and streaks. This is considered due to the fact that the tip of the plate-like cleaning member has poor adhesion to the peripheral surface of the electrostatic latent image holding member or is easily chipped. Therefore, as described above, the upper limit of the dynamic hardness ratio (w / r) is preferably 3.6 or less.

  Dynamic hardness is also called “dynamic micro hardness” and is a hardness index based on the depth (elastic deformation + plastic deformation) in the indentation process. Has been. Specifically, it can be obtained by the following formula (1) from the measurement result by a dedicated measuring instrument.

Dynamic hardness = 3.8854 × P / D ² Formula (1)
(In the above formula (1), P represents the test load (mN) and D represents the indentation depth (μm).)

  In this embodiment, a dynamic microhardness meter DUH-W201 manufactured by Shimadzu Corporation is used, test load P = 1 mN, triangular pyramid indenter (ridge angle = 115 °, diamond / tip R = 0.1 μm or less), 24-25 The measurement was performed under the conditions of a measurement environment of ° C / 50-60% RH. The measurement was performed at five locations, and the average value was adopted.

  The range of the dynamic hardness r of the back layer is naturally determined from the spring constant required as its function, and is specifically selected from the range of about 0.05 to 0.07. As described above, the dynamic hardness w of the clean layer is appropriately selected in relation to the dynamic hardness r of the back layer.

  Adjustment of the dynamic hardness of the back layer and the clean layer may be controlled by conventionally known knowledge in accordance with the production of the material depending on the material used. For example, when these layers are formed of polyurethane, the polyol, polyisocyanate base material and blending ratio, crosslinker material and blending, reaction time and temperature, aging time and temperature after molding, etc. should be controlled. The dynamic hardness can be controlled with. For example, if the time during the curing reaction is lengthened, curing proceeds and the hardness increases, and if it is shortened, the hardness decreases. Moreover, if the reaction temperature is raised, the reaction is more likely to proceed. The items to be actually controlled are not limited to the above-mentioned items, but may be selected and combined based on conventionally known knowledge, so that the desired dynamic hardness can be controlled.

  The dynamic hardness w of the clean layer and the dynamic hardness r of the back layer were measured from the exposed surfaces (up to a maximum depth of 10 μm).

  Also in the clean layer 351 alone, the dynamic hardness w measured from the surface facing the circumferential surface of the photosensitive drum 31 (arrow w in FIG. 4; hereinafter, sometimes referred to as “tip surface”), and the photosensitive drum The ratio with the dynamic hardness c measured from the surface (arrow c in FIG. 4; hereinafter sometimes referred to as “flat plate surface”) facing the rotation direction of the photosensitive drum 31 at the tip portion in contact with the circumferential surface of 31. (W / c) is preferably 0.8 or more.

  As a result of the study by the present inventors, it is found that in the clean layer 351, the flat surface (arrow c) tends to have a lower hardness than when measured from the tip surface (arrow w). However, the hardness of the flat plate surface with respect to the tip surface is increased to a certain level, specifically, the ratio of the dynamic hardness of the flat plate surface (arrow c) to the dynamic hardness of the tip surface (arrow w) in the clean layer 351 (w / c) (hereinafter, sometimes simply referred to as “dynamic hardness ratio (w / c)”) of 0.8 or more can further prevent slipping of the external additive. It is possible to further suppress the occurrence of streaks in the formed image due to the above. At this time, in each case, the vicinity of the center of each surface (for the front end surface, the vicinity of the center in the thickness direction of the end surface of the cleaning layer 351 front end) is measured.

  The “clean layer dynamic hardness w” in the “ratio of the dynamic hardness w of the clean layer and the dynamic hardness r of the back layer (w / r)” and the “surrounding surface of the electrostatic latent image holding member” described above. Between the dynamic hardness w measured from the surface facing the surface and the dynamic hardness c measured from the surface facing the rotation direction of the electrostatic latent image holding member at the tip portion in contact with the peripheral surface of the electrostatic latent image holding member (w / C) "is a dynamic hardness w measured from the surface facing the circumferential surface of the electrostatic latent image holding member, which is measured at substantially the same location although the expression is different.

  The adjustment of the dynamic hardness of the front end surface and the flat plate surface in the clean layer may be controlled by conventionally known knowledge in accordance with the manufacture of the material depending on the material used. For example, when these layers are formed of polyurethane, the polyol, polyisocyanate base material and blending ratio, crosslinker material and blending, reaction time and temperature, aging time and temperature after molding, etc. should be controlled. The dynamic hardness can be controlled with. For example, if the time during the curing reaction is lengthened, curing proceeds and the hardness increases, and if it is shortened, the hardness decreases. Moreover, if the reaction temperature is raised, the reaction is more likely to proceed. The items to be actually controlled are not limited to the above-mentioned items, but may be selected and combined based on conventionally known knowledge, so that the desired dynamic hardness can be controlled. That is, the respective conditions may be adjusted appropriately so that the tip surface and the flat plate surface have a desired dynamic hardness.

  While the image forming apparatus of the present invention has been described in detail with reference to the preferred embodiment, the present invention is not limited to the above embodiment. For example, in the above embodiment, each color image forming unit having an electrostatic latent image holding member, a charging unit, a toner image forming unit, a cleaning unit, etc. for the number of colors is arranged in parallel so as to face the intermediate transfer member, respectively. An example of an image forming apparatus generally referred to as a tandem system is illustrated in which toner images of respective colors formed by these units are primarily transferred to an intermediate transfer medium, sequentially stacked, and then collectively transferred to a recording medium. Alternatively, the present invention may be applied to an apparatus having a structure in which a latent image of each color is formed on one electrostatic latent image holding member and transferred to an intermediate transfer member each time by a rotary developing device having a developing device for the number of colors. Also in the case of the tandem method, when the color image forming units are arranged in parallel, they may not be physically linear.

  The image forming apparatus of the present invention can be added with various conventionally known or non-known various components in addition to the components described in the above embodiment, and the image forming apparatus of the present invention is still added by the addition. Of course, it is included in the category of the present invention. For example, a charge removal means can be provided as a subsequent process of the cleaning means. The static elimination means will be outlined in the process cartridge section.

  In addition, those skilled in the art can appropriately modify the image forming apparatus of the present invention in accordance with conventionally known knowledge. Of course, such modifications are included in the scope of the present invention as long as the configuration of the image forming apparatus of the present invention is provided.

[Process cartridge]
In the present invention, the “process cartridge” is integrally provided with two or more of the components in the image forming apparatus, and is removable from the image forming apparatus main body for the purpose of maintenance, repair, periodic replacement of consumables, and the like. Means a collection of components. In the present invention, among the components in the image forming apparatus, at least the electrostatic latent image holding member and the cleaning unit are included, and other components are optional.

  FIG. 5 is a schematic cross-sectional view schematically showing a basic configuration of a preferred example of the process cartridge of the present invention. In the process cartridge 100 shown in FIG. 5, together with the electrostatic latent image holder 131 rotating in the direction of arrow E, a charger (charging means) 132, a developing device (toner image forming means) 133, and a cleaning device (cleaning means). 134, and an opening 118 for exposure and an opening 117 for static elimination exposure are provided on the exterior, and a mounting rail 116 is further attached, and these are integrated. The electrostatic latent image holding member 131 and the cleaning device 134 have the above-described features of the present invention.

  The process cartridge 100 is detachable from an image forming apparatus main body including a primary transfer device 142, an intermediate transfer belt 141, and other components not shown, and the image forming apparatus is mounted together with the image forming apparatus main body. Configure.

  The electrostatic latent image holding member 131, the charger (charging unit) 132, the cleaning device (cleaning unit) 134, and the intermediate transfer belt 141 have already been described in the section of the embodiment of the image forming apparatus. Although omitted, the same thing can be used in the process cartridge 100.

  As for the primary transfer device 142 that transfers the toner image developed on the surface of the electrostatic latent image holding member 131 to the intermediate transfer belt 141, both the primary transfer unit and the secondary transfer unit are described in the section of the embodiment of the image forming apparatus. Since the contents collectively described as “transfer means” also apply to the process cartridge 100 as they are, a detailed description thereof will be omitted.

  Examples of the static eliminator (light static eliminator) (not shown) include tungsten lamps and LEDs. Examples of the light quality used in the photostatic process include white light such as tungsten lamps and red light such as LED light. Is mentioned. The intensity of irradiation light in the light neutralization process is usually set to output several times to about 30 times the amount of light indicating the half exposure sensitivity of the electrostatic latent image carrier.

  In the process cartridge 100 of this example, the light from such a charge removal device is taken in through the opening 117, and the surface of the electrostatic latent image holding member 131 is discharged.

  On the other hand, image-like exposure light from an exposure apparatus (exposure means) (not shown) is taken from the opening 118 in the process cartridge 100 of this example, and is irradiated onto the surface of the electrostatic latent image holder 131 to cause electrostatic latent image. An image is formed.

  The process cartridge 100 shown in FIG. 5 includes a charger 132, a cleaning device 134, an opening 118 for exposure, and an opening 117 for discharge exposure, in addition to the electrostatic latent image holding member 131 and the developing device 133. However, in the present invention, these devices and the like can be selectively combined. In the process cartridge of the present invention, cleaning means such as an electrostatic latent image holding member and a cleaning device 134 are essential components, and other configurations are optional elements.

  Such a process cartridge of the present invention is mounted on the above-described image forming apparatus of the present invention. When mounted on the image forming apparatus of the embodiment shown in FIG. 1 described above, the process cartridge constitutes each image forming engine 30 or a part thereof. According to the process cartridge of the present invention, there are excellent actions and effects based on the present invention.

[Verification test]
With respect to the image forming apparatus shown in FIG. 1 and FIG. 2, a verification test on the operation or effect of the present invention was performed by varying the diameter of the photosensitive drum 31 and the hardness of the cleaning blade 35. Unless otherwise specified, all “parts” and “%” are based on mass.

  The toner used in this verification test was a black (K) toner prepared by an emulsion polymerization method, and had a volume average particle size of 5.8 μm as measured with a Coulter counter (manufactured by Coulter Co.). The toner particle diameter is not necessarily limited to this, and may be 3 to 7 μm. Further, the shape of the toner used in this verification test was obtained by performing an image analysis with an image analyzer Luzex3 (manufactured by NIRECO) on an enlarged photograph obtained with an optical microscope (Microphoto FXA; manufactured by Nikon Corporation) according to the following formula (2). The calculated shape factor SF1 is 130 to 140.

SF1 = (ML ² / A) × (π / 4) × 100 (2)
In the above formula (2), ML represents the absolute maximum length of the toner, and A represents the projected area of the toner.

  The toner shape factor SF1 is an index of circularity (sphericity) expressed by the ratio of the projected area of the toner and the area of a circle circumscribing the toner, and is 100 for a true sphere, and increases as the shape collapses. . The shape factor SF1 is calculated for a plurality of toner particles, and the average value is used as a representative value.

  In the toner, inorganic fine particles of silica having an average particle diameter of 40 nm, silica of 140 nm and titanium oxide of 40 nm are used as external additives, and the amounts are 2.15% by mass, 1.73% by mass and 0.88% by mass, respectively, based on the toner. Added. Further, in order to improve the lubricity between the cleaning blade 35 and the surface of the photosensitive drum 31, 0.2 mass% of polytetrafluoroethylene (PTFE) having an average particle diameter of 300 nm was externally added to the toner. This was mixed with a carrier made of ferrite beads having a volume average particle size of 35 μm, and this was used as a developer and charged into the developing device 33 in the black (K) image forming engine 30K in the image forming device. In the following description, for the reference numerals indicating the respective members, the part of the alphabet K indicating the color (for example, the part of “K” in the “image forming engine 30K”) may be omitted.

  In addition, as the photosensitive drum 31, organic photosensitive members having six types of outer diameters of 22 mmφ, 24 mmφ, 26 mmφ, 28 mmφ, 30 mmφ, and 40 mmφ were prepared.

  On the other hand, while preparing the polyurethane resin A used for the clean layer 351 and the polyurethane resin B used for the back layer 352 so as to obtain desired physical properties, each layer was formed according to molding conditions for obtaining desired physical properties of each layer. .

  A polyurethane resin A having a thickness of 0.5 mm and a polyurethane resin B having a thickness of 1.4 mm were integrally molded by centrifugal molding to produce a cleaning blade having a size of 330 mm × 12.5 mm. Note that the back layer 352 is on the mold side during molding, and the surface of the clean layer 351 is on the air side.

  In the obtained cleaning blade (corresponding to “cleaning blade” in Table 1 below), the cleaning layer 351 has a JIS-A hardness of 78 ° and a rebound resilience (according to the method described in JIS K6255) of 43%. The back layer 352 had a JIS-A hardness of 63 °, a rebound resilience (same as above) of 33%, and a permanent elongation (according to the method described in (tensile permanent strain) JIS K6262) of 0.5%.

  In addition, by changing the composition and molding conditions of the polyurethane resin B of the cleaning layer 351 as appropriate, the dynamic hardness of the front end surface c and the flat plate surface w (see FIG. 4) of the cleaning layer is changed. Cleaning blades 1 to 10 having dynamic hardness ratios (w / r) and dynamic hardness ratios (w / c) shown in Table 1 were produced.

(Test A)
The manufactured cleaning blades 1 to 4 were attached as the cleaning blade 35 (see FIGS. 1 and 2) in the image forming engine 30K. FIG. 6 shows an enlarged cross-sectional view around the cleaning blade 35 for explaining the attachment state at this time. As shown in FIG. 6, the cleaning blade 35 has its tip at an angle with respect to the normal L from the circumferential surface of the photosensitive drum 31 so that the rear end thereof faces in the rotation direction (arrow A direction) of the photosensitive drum 31. Was attached so as to be pressed against the peripheral surface.

  At this time, as indicated by a solid line in FIG. 6, the cleaning blade 35 is bent due to a load pressed against the circumferential surface of the photosensitive drum 31. If the circumferential surface of the photosensitive drum 31 does not exist, a state in which the cleaning blade 35 is not bent is depicted by a dotted line in FIG. 6. The distance (Nip) from the front end position retracted by the peripheral surface of the body drum 31 is the amount of biting, the tangent of the contact point of the front end of the cleaning blade 35 on the peripheral surface of the photosensitive drum 31 and the surface of the cleaning blade 35 that is not bent. The angle (BSA) formed by is called a set angle.

  A photosensitive unit corresponding to the outer diameter of the photosensitive drum, to which the charging roll 32, the cleaning blade 35, and the photosensitive drum 31 in the image forming apparatus shown in FIGS. An off-line device to which the photosensitive unit, the developing device 33, and the transfer device can be attached and bias can be applied was used. An LED bar was used for the exposure apparatus, and the surface potential of the photoreceptor and the toner image creation width were adjusted according to the amount of light and the lighting time.

  The process speed of the apparatus was 225 mm / sec, the charging potential on the surface of the photosensitive drum 31 was −710 V, and the exposure portion potential by the exposure unit was −300 V. A toner image is formed by applying a developing bias voltage in which a rectangular wave with an amplitude (peak to peak voltage) of 1.0 kV, a frequency of 6 kHz, and a duty of 60% is superimposed on a developing roller of the developing device 33 to a DC component of −560V. did. This toner image was transferred to the intermediate transfer belt 41, further transferred to the paper P, and fixed by a fixing device (not shown).

  In this verification test, the biting amount Nip = 1.2 mm for the center aim (assuming normal use) in the actual use range and the set angle BSA = 26 °, and the lower limit aim in the actual use range (external toner additives are easy to slip through). (Consumption assumption) The verification test was performed under two conditions of Nip = 1.0 mm and set angle BSA = 24 °. Further, a verification test was performed on all the prepared photosensitive drums having an outer diameter. Under these conditions, the four types of cleaning blades described above were tested brute force.

  In the verification test, continuous driving equivalent to 3 prints of A4 size paper (longitudinal direction) at one time and continuous printing equivalent to 50 sheets of A4 size paper (longitudinal direction) are alternately performed at a temperature of 28 ° C. A deterioration test was conducted so that the driving time was equivalent to 7000 sheets of A4 size in each of an environment with a humidity of 85% and a temperature of 10 ° C. and a humidity of 15%.

  The test image was a black (K) single color, and was formed by line and patch images with a size corresponding to 1% in terms of image area ratio. After the deterioration test, the charging roll 32 was attached to a photosensitive unit that can be mounted on the image forming apparatus, halftone images with an image density of 30% and 50% were printed, and the toner external additive slipped through the cleaning blade. In addition to confirming the state of occurrence of streaks presumed to be caused by the above, evaluation was performed by visually observing the surface of the charging roll. The results are summarized in Table 2 below. The evaluation criteria are as follows.

○: No streaking occurs.
Δ: Minor streaks occurred.
X: A streak clearly recognized by visual observation was generated.

(Test B)
The manufactured cleaning blades 5 to 10 were attached as the cleaning blade 35 (see FIGS. 1 and 2) in the image forming engine 30K in the same manner as in (Test A). Note that the mounting condition was only one condition of the biting amount Nip = 1.0 mm and the set angle BSA = 24 ° aimed at the lower limit in the actual use range (assuming the condition that the external additive of the toner is easy to slip through).

  Further, only a photosensitive drum having an outer diameter of 22 mmφ was used. In all other conditions, a verification test was performed in the same manner as in (Test A), and the evaluation was performed by the same method or evaluation standard. The results are summarized in Table 3 below.

  26: Laser light, 30Y, 30M, 30C, 30K: Image forming engine, 30: Image forming engine, 31: Photosensitive drum, 32: Charging roll, 33: Developing device, 34: Cleaning device, 35: Cleaning blade, 40 : Secondary transfer roll, 41: intermediate transfer belt, 42: primary transfer apparatus, 43: drive roll, 44, 45: support roll, 46: belt cleaner, 46: secondary transfer apparatus, 49: backup roll, 100: process Cartridge: 116: mounting rail, 117, 118: opening, 131: electrostatic latent image holder, 132: charger, 133: developing device, 134: cleaning device, 141: intermediate transfer belt, 142: primary transfer device, 351: Clean layer, 352: Back layer

Claims (2)

An electrostatic latent image holding body capable of holding an electrostatic latent image formed on a circumferential surface of a cylindrical or columnar shape having an outer diameter of 27 mm or less and rotating around an axis;
Charging means for charging the peripheral surface of the electrostatic latent image holding member;
An electrostatic latent image forming unit that forms an electrostatic latent image on the peripheral surface of the charged electrostatic latent image holding body;
Toner image forming means for supplying toner to the electrostatic latent image formed on the peripheral surface of the electrostatic latent image holding member to form a toner image;
Transfer means for transferring the toner image to a transfer object;
The front end is pressed against the peripheral surface at an angle with respect to the normal line from the peripheral surface of the electrostatic latent image holding body so that the rear end faces the rotation direction of the electrostatic latent image holding body, and the peripheral surface side The electrostatic latent image holding member peripheral surface remaining after transfer is not transferred by the cleaning blade having a two-layer structure of the cleaning layer positioned at the tip and the front surface contacting the peripheral surface and the back layer positioned on the back surface. Cleaning means for removing and cleaning the toner,
The ratio (w / r) of the dynamic hardness w of the clean layer and the dynamic hardness r of the back layer in the cleaning blade is 2.2 or more ,
Dynamic hardness w measured from the surface facing the peripheral surface of the electrostatic latent image holding member in the clean layer, and the electrostatic latent image holding member at the tip contacting the peripheral surface of the electrostatic latent image holding member. An image forming apparatus having a ratio (w / c) of 0.8 to 1.0 with respect to a dynamic hardness c measured from a surface opposed to the rotation direction .   A process cartridge which is detachable from the image forming apparatus according to claim 1 and includes at least the electrostatic latent image holding member and the cleaning means.

Images