JP7556223B2 - Image forming apparatus and process cartridge - Google Patents

Description

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

Conventionally, in electrophotographic image formation, a latent image is formed by electrostatic charge on an image carrier whose outer periphery is made of a photoconductive material, and a visible image is formed by attaching charged toner particles to this electrostatic latent image. The visible image formed by the toner is finally transferred to a transfer medium such as paper, and then fixed to the transfer medium by heat, pressure, solvent gas, etc., to become an output image.

In these electrophotographic image forming devices, an image carrier (usually a photoconductor), which is generally in the shape of a drum or an endless belt, is uniformly charged while rotating. A latent image pattern is then formed on the image carrier using a laser beam or the like, which is then visualized by a developing device and then transferred onto a transfer medium.

After the toner image is transferred to the transfer medium, toner components that were not transferred remain on the image carrier. If the charging process is carried out while these remainders are still there, it may hinder the image carrier from being uniformly charged. Therefore, generally, after the transfer process, the toner components remaining on the image carrier are removed in a cleaning process to thoroughly clean the surface of the image carrier (hereinafter also simply referred to as the "image carrier surface") before charging.

In this way, the surface of the image carrier is subjected to various physical and electrical stresses during each process, such as charging, developing, transferring, and cleaning, and the surface condition changes over time. Of these stresses, the stress caused by friction during the cleaning process not only wears out the image carrier, but also shortens the lifespan of the cleaning member. There is great interest in the market for extending the lifespan of image forming devices and the members used therein, from the perspective of protecting the global environment by reducing running costs and waste. As a result of this trend, there has been a demand in recent years for extending the lifespan of not only image carriers but also peripheral members, and reducing stress during the cleaning process has become a major issue.

To solve this problem, a lubricant application device (also called a lubricant application means) has been proposed that supplies various lubricants to the image carrier and forms a film on it, with the aim of reducing the friction between the image carrier and the cleaning member, protecting both the image carrier and the cleaning member, and improving cleaning performance. The lubricant application device presses a solid lubricant against a roller member that contacts the photoreceptor, and supplies the lubricant to the photoreceptor surface by, for example, the roller member. A configuration is often used in which a blade is brought into contact with the photoreceptor downstream of the roller member in the rotation direction, and the lubricant applied to the photoreceptor surface is leveled. Known methods of blade contact include the trailing method and the counter method. This blade is called a lubricant leveling blade (Patent Document 1) or a thin layer blade (Patent Document 2) based on its function, but hereinafter it will be called a lubricant application blade or simply a coating blade.

Patent Document 1 discloses a trailing type lubricant application blade, in which the tip of the application blade is brought into contact with the photoconductor downstream in the rotation direction. The purpose is to prevent deterioration of the application performance of the lubricant due to wear of the application blade, and to prevent the occurrence of color streaks and images with uneven density. Moreover, the term "belt contact" means that a coating blade with a bent tip is used, and the surface in front of the tip edge of the coating blade is mainly in contact. In this way, the contact surface pressure can be reduced, and the amount of wear of the coating blade can be reduced.
Japanese Patent Application Laid-Open No. 2003-233693 discloses a counter type lubricant application blade, in which the edge of the application blade is opposed to and contacts the photosensitive drum in the rotational direction.

In conventional lubricant application devices, a method is often used in which a solid lubricant is ground with a roller member such as a brush or sponge, the ground lubricant powder is deposited on the image carrier, and then the lubricant is spread with a plate-shaped rubber blade.
However, due to the recent increase in process speed, there is a problem that the lubricant powder is not sufficiently spread by the blade and passes through the blade as powder. If the lubricant powder that has passed through enters the charging section, it electrostatically or physically adheres to the charging roller, wire, etc., causing contamination of the charging member. If the contamination of the charging member progresses, abnormalities such as black streaks appear on the image, which is undesirable.

Trailing-type lubricant application blades are more advantageous than counter-type ones in terms of space saving, and have the advantage of less stress on the image carrier due to the low torque at the contact point. However, their lubricant application performance and cleanability are inferior to those of counter-type blades, and the supplied lubricant powder cannot be spread sufficiently, so the powdered lubricant is likely to slip through the application blade, causing stains on the charging roller and abnormal images. On the other hand, when a counter-type lubricant application blade is installed, the amount of winding at the tip of the blade becomes larger, resulting in greater sliding resistance, and an increase in torque compared to the trailing type, which accelerates wear on the image carrier and causes problems such as abnormal noise at the sliding area between the image carrier and the blade.

In response to the above problems, Patent Document 3 proposes an image forming apparatus that suppresses the occurrence of chatter vibrations and abnormal noise, improves the lifespan of the image carrier and cleaning blade, maintains good cleaning performance over time, and produces good images. Patent Document 3 discloses that in addition to hardening the ridge at the tip of the cleaning blade, the coefficient of friction is set within a predetermined range, and a trailing or counter type lubricant leveling blade is used. Patent Document 4 discloses that the hardness, contact angle, and contact line pressure of the leveling blade are specified in order to apply the lubricant evenly.

However, in Patent Document 3, good lubricant application properties are still insufficient when using a lubricant application blade, and further improvements are required. There is a concern that poor lubricant application properties may cause filming or abnormal images. Furthermore, in Patent Document 4, there is a concern that if the hardness of the leveling blade is increased, the load on the image carrier increases, and wear and abnormal noise of the image carrier may occur due to increased torque. Thus, there is a demand for an image forming device that can solve the above problems.

The present invention aims to provide an image forming device that has good lubricant application properties, reduces wear on the image carrier, and suppresses the generation of abnormal noise.

In order to solve the above problem, the image forming apparatus of the present invention is an image forming apparatus including an image carrier and a lubricant application means for applying a lubricant to the image carrier, the lubricant application means including a roller member for grinding a solid lubricant into a powder and supplying the powdered lubricant to the image carrier, and a lubricant application blade arranged downstream of the roller member in the rotation direction of the image carrier, contacting the image carrier in a trailing manner, and leveling the powdered lubricant on the image carrier, the lubricant application blade including a blade member and a coating portion formed on at least a part of the surface of the blade member and contacting the image carrier, the average width of the surface contacting the image carrier in the rotation direction of the image carrier being 80 μm or more and 400 μm or less, and the friction coefficient of the coating portion being lower than the friction coefficient of the blade member.

The present invention provides an image forming device that achieves good lubricant application properties, reduces wear on the image carrier, and suppresses the generation of abnormal noise.

1 is a schematic cross-sectional view showing an example of an image forming apparatus according to the present invention. FIG. 4 is a schematic diagram for explaining a free length in an example of a lubricant application blade. 1A is a schematic diagram for explaining a contact point between an example of a lubricant application blade and an image carrier, and FIG. 1B is a diagram for explaining an example of measurement of the contact width. 1A and 1B are diagrams for explaining an example of measurement of a contact width in an example of a lubricant application blade. 1A and 1B are diagrams illustrating an example of a coated portion of a lubricant application blade, and FIG. 1C is a diagram after coating has been performed. FIG. 11 is a schematic diagram showing another example of an image forming apparatus according to the present invention. FIG. 2 is a schematic cross-sectional view showing an example of an image forming apparatus not included in the present invention.

The image forming apparatus and process cartridge according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiment shown below, and can be modified within the scope of what a person skilled in the art can imagine, including other embodiments, additions, modifications, deletions, etc., and any aspect is within the scope of the present invention as long as it achieves the functions and effects of the present invention.

The image forming apparatus of the present invention is an image forming apparatus including an image carrier and a lubricant application means for applying a lubricant to the image carrier, the lubricant application means including a roller member for grinding a solid lubricant into a powder and supplying the powdered lubricant to the image carrier, and a lubricant application blade arranged downstream of the roller member in the rotation direction of the image carrier, contacting the image carrier in a trailing manner, and leveling the powdered lubricant on the image carrier, the lubricant application blade including a blade member and a coating portion formed on at least a part of the surface of the blade member and contacting the image carrier, the average width of the surface contacting the image carrier in the rotation direction of the image carrier being 80 μm or more and 400 μm or less, and the friction coefficient of the coating portion being lower than the friction coefficient of the blade member.

The process cartridge of the present invention is a process cartridge that is detachable from the main body of an image forming apparatus and includes an image carrier, a cleaning means for cleaning the image carrier with a cleaning blade, and a lubricant application means that is disposed downstream of the cleaning means in the rotation direction of the image carrier and applies a lubricant to the image carrier, the lubricant application means including a lubricant supplying member that grinds a solid lubricant into powder and supplies the powdered lubricant to the image carrier, and a lubricant supplying member that grinds the solid lubricant into powder and supplies the powdered lubricant to the image carrier in the rotation direction of the image carrier. and a lubricant application blade that is disposed downstream of the lubricant supply member, contacts the image carrier in a trailing manner, and evens out the powdered lubricant on the image carrier. The lubricant application blade has a blade member and a coating portion that is formed on at least a portion of the surface of the blade member and contacts the image carrier, and is characterized in that the average width of the surface that contacts the image carrier in the rotation direction of the image carrier is 80 μm or more and 400 μm or less, and the friction coefficient of the coating portion is lower than the friction coefficient of the blade member.

The image forming apparatus of this embodiment is shown in FIG. 1. FIG. 1 is a schematic cross-sectional view of the main part of the image forming apparatus of this embodiment, illustrating one photosensitive unit (process cartridge).

The image forming apparatus of this embodiment is equipped with a photosensitive drum 8 as an image carrier (sometimes called a photosensitive body), a lubricant application means 2 that applies a lubricant to the photosensitive drum 8, and also includes a cleaning blade 27, a charging roller 9, etc. Although not shown in the figure, it also includes a developing means, a transfer means, and a fixing means.

The arrow in the figure indicates the direction of rotation of the photosensitive drum 8, and the cleaning blade 27 is disposed upstream of the lubricant application means 2. The cleaning blade 27 scrapes off and removes residual toner and other particles adhering to the photosensitive drum 8, and the powder transport coil 28 transports the residual toner and other particles removed from the photosensitive drum 8 by the cleaning blade 27.

The charging roller 9 is disposed downstream of the lubricant application means 2. The charging roller 9 contacts the photosensitive drum 8 via rollers outside the image area at both ends, and maintains a small gap between the charging roller 9 and the photosensitive drum 8. A charging bias is applied to the charging roller 9 to uniformly charge the surface of the photosensitive drum 8. The charging cleaner roller 26 is for cleaning the charging roller 9.

The lubricant application means 2, which is disposed opposite the photosensitive drum 8, which is an image carrier, is mainly composed of a lubricant 31, a lubricant supply member 30, a lubricant holding member 32, a pressing force applying mechanism 33, a lubricant application blade 34, etc.

The lubricant application blade 34 contacts the photoconductor drum 8 in a trailing manner when the rotation direction of the photoconductor drum 8 is used as a reference. The lubricant application blade 34 has a blade member and a coating portion (which may be called a coating film) that is formed on at least a portion of the surface of the blade member and that contacts the image carrier. The lubricant application blade is sometimes called an application blade.

The material used for the blade member of the lubricant application blade 34 is not particularly limited, and for example, elastic bodies such as urethane rubber, hydrin rubber, silicone rubber, and fluororubber, which are generally known as materials for cleaning blades, can be used alone or in blends. In addition, fillers such as other organic or inorganic fine particles may be dispersed as necessary to adjust the hardness of the elastic body.

The lubricant application blade 34 is fixed to the blade support 35 by any method such as adhesion or fusion so that the tip can be pressed against the image carrier surface. In the image forming apparatus of this embodiment, the lubricant application blade 34 contacts the photoconductor drum 8 in a trailing manner, which may also be referred to as contacting in the trailing direction.

On the other hand, an example of an image forming apparatus that employs a counter system, which is not included in the present invention, is shown in FIG. 7. As shown in FIG. 7, the lubricant application blade 34 abuts against the photosensitive drum 8 in the counter direction.

In the present invention, the lubricant application blade 34 has an average surface width (also called contact width) that contacts the photosensitive drum 8 in the direction of rotation of the photosensitive drum 8 of 80 μm or more and 400 μm or less.

According to the inventors' observations, the contact width between a conventional lubricant application blade and a photosensitive drum is set to approximately 60 μm or less, including over time, with most remaining within 40 μm, although there are slight differences depending on the model and whether it is a trailing or counter type. This is mainly based on the idea of narrowing the contact width and applying high surface pressure to block the lubricant powder. Conventional cleaning blades are also designed with this same idea in mind.

Compared to counter-type lubricant application blades, trailing-type lubricant application blades are advantageous in terms of space saving, and have the advantage of less stress on the photoconductor drum due to the low torque at the contact point with the photoconductor drum. However, the trailing-type lubricant application performance is inferior to that of the counter-type, and the supplied lubricant powder cannot be sufficiently spread, and the powdered lubricant is likely to slip through the application blade, causing stains on the charging roller and abnormal images. On the other hand, when a counter-type lubricant application blade is installed, the amount of winding at the tip of the blade becomes larger, resulting in greater sliding resistance, and the torque increases compared to the trailing-type, accelerating wear of the image carrier. Furthermore, when a counter-type lubricant application blade is installed, there are problems such as abnormal noise generated at the sliding area between the image carrier and the blade.

The inventors therefore conducted extensive research from the perspective of improving the applicability of the lubricant, and discovered that it would be better to adopt the trailing method and increase the contact width. With a trailing lubricant application blade, rather than narrowing the contact width to obtain locally high surface pressure, ensuring a wide contact width to increase the probability that the lubricant powder will be spread allows the lubricant to be spread sufficiently without the need for particularly high surface pressure.

After thorough investigation into the specific range of the contact width value, it was found that when the contact width is in the above-mentioned range of 80 μm or more and 400 μm or less, the lubricant application properties can be improved and filming on the image carrier can be suppressed. It was also found that by setting the contact width in the above range, the above effects can be obtained even when a small amount of lubricant is used.

On the other hand, if the contact width is less than 80 μm, the above effects are not obtained, and good lubricant application is not possible. In addition, since the above effects saturate at around 400 μm, if the contact width is made larger than 400 μm, there is a concern that side effects will increase and abnormal noise will occur over time.

Methods for setting the contact width within the above range include, for example, adjusting the length (free length) of the protruding portion of the lubricant application blade 34 or the amount of penetration into the photosensitive drum 8. Among these, changing the free length is simple and preferable. For example, by increasing the free length, it is possible to increase only the contact width with almost no change in the contact pressure on the photosensitive drum 8.

Figure 2 shows a diagram for explaining the free length. Here, the lubricant application blade 34 and the blade support 35 are shown. As shown in the figure, the length of the part of the lubricant application blade 34 that protrudes from the blade support 35 is the free length.

Methods for adjusting the amount of penetration of the lubricant application blade 34 into the photosensitive drum 8 include, for example, the following methods. To increase the amount of penetration, for example, a plate-shaped member is sandwiched between the unit and the blade holder when attaching the blade. To decrease the amount of penetration, for example, part of the unit or blade holder is scraped off.

An example of a method for measuring the contact width is described with reference to Figures 3 and 4. Note that the coated portion of the lubricant application blade 34 is not shown in Figure 3.

Figure 3(A) is a schematic diagram showing an example in which the lubricant application blade 34 is in contact with the photosensitive drum 8, and reference symbol 34c indicates the contact portion of the lubricant application blade 34 with the photosensitive drum 8. The contact width is also shown diagrammatically as indicated by the arrow. Figure 3(B) is a schematic diagram showing an example in which tape is applied to the lubricant application blade 34 removed from the unit in order to measure the contact width.

The method for measuring the contact width in this example will be described. As shown in Figure 3(A), paper is passed through the actual machine, and then the lubricant application blade 34 is gently removed from the unit. At this time, care is taken not to drop the lubricant adhering to the lubricant application blade 34. Next, as shown in Figure 3(B), tape 40 is attached to the lubricant application blade 34 removed from the unit, and the tape 40 is lightly pressed so that the lubricant adhering to the lubricant application blade 34 is transferred to the tape, and then the tape 40 is peeled off. Next, the tape 40 to which the lubricant has been transferred is observed with a SEM (scanning electron microscope) or the like to measure the contact width.

Figure 4 is a diagram for explaining an example of tape applied to the lubricant application blade 34. Figure 4(A) shows a side or cross section of the tape 40 when applied to the lubricant application blade 34, and Figure 4(B) shows a plan view of the tape 40 after it has been peeled off from the lubricant application blade 34. The reference numeral 40a corresponds to Figure 4(A) and Figure 4(B). The arrow in Figure 4(B) indicates the direction of rotation of the photosensitive drum 8.

As shown in FIG. 4B, the tape 40 peeled off from the lubricant application blade 34 has lubricant powder attached to the front and rear of the contact point (contact portion 43c) with the photosensitive drum 8, forming a powder puddle 51. On the other hand, there is almost no lubricant powder at the contact portion 43c. Therefore, the contact width between the lubricant application blade 34 and the photosensitive drum 8 can be measured by attaching the tape 40 to the lubricant application blade 34 removed from the unit, transferring the lubricant, peeling the tape 40 off, and measuring the width of the portion of the tape 40 where no lubricant is attached.

As shown in FIG. 4B, the contact width varies by about several μm in the longitudinal direction (the direction perpendicular to the direction of rotation of the photosensitive drum 8). For this reason, the average value in the longitudinal direction is calculated over the entire field of view. It is preferable to calculate the average value over, for example, about 20 measurement points.

As described above, by setting the average contact width to 80 μm or more and 400 μm or less, the lubricant application property is improved. However, as the inventors continued their research, they found that if the contact width is made larger than before and the contact area is increased, not only does the torque increase, but vibration occurs at the contact surface with the photosensitive drum, making it easier for abnormal noise to occur. This is because, even if the lubricant material is the same, a powder type has a greater lubricating effect than a film type, and it is presumed that by setting the contact width in the above range, the powder type lubricant, which was previously abundant, is stretched more into a film type. In addition, a new side effect was found in which the amount of wear on the photosensitive drum increased when a long-term running test was performed.

To solve this problem, the inventors conducted further research and discovered that applying a specific coating to the contact area of the lubricant application blade would be a good solution. That is, in a lubricant application blade having a blade member and a coating portion formed on at least a portion of the surface of the blade member and contacting the image carrier, the friction coefficient of the coating portion is made lower than the friction coefficient of the blade member. This prevents torque from increasing even when the contact width with the image carrier is large, and makes it possible to suppress the generation of abnormal noise due to vibration.

Therefore, according to the present invention, which has the requirements for the contact width and the coated area, good lubricant application properties can be obtained, abnormal images caused by filming do not occur over a long period of time, and side effects such as abnormal noise and wear on the image carrier can be suppressed.

The coated portion is formed by coating the surface of the blade member that comes into contact with the photosensitive drum with a material having a lower friction coefficient than the material of the surface of the blade member.
The material of the coating portion may be any material that, when coated on the surface of the blade member, reduces the coefficient of friction with respect to the image carrier compared to the original state (blade member). Examples of the material of the coating portion include well-known fluorine-based compounds, silicone-based compounds and their contents, inorganic lubricating substances, etc. Among them, diamond-like carbon (DLC) is preferable. DLC has a particularly low coefficient of friction and is particularly effective against wear of the image carrier. In addition to the advantage of being able to improve the durability of the coating portion, it also has the advantage of being easy to process using a vacuum thin film production method.

As for the DLC coating, any of the hydrogen-free DLCs Ta-C and a-C, and the hydrogen-containing DLCs Ta-C:H and a-C:H can be preferably used. DLC coatings impose too much strain on the image carrier in configurations where high surface pressure is applied over a narrow contact width, such as in counter-type cleaning blades, but are extremely advantageous in providing the lubricity required for trailing-type coating blades such as those of the present invention.

The method for coating these can be selected appropriately, and includes methods of coating the surface of the coating blade by known means. Among these, it is preferable to use a vacuum thin film production method. When using a vacuum thin film production method, the effect of the coating lasts for a longer period of time and torque is less likely to increase, so that a particularly excellent effect against wear of the image carrier can be obtained. It is also preferable to coat DLC using a vacuum thin film production method, which is particularly preferable in terms of the durability of the coated portion and the reduction of the friction coefficient.

Methods for producing vacuum thin films include known methods such as PVD (physical vapor deposition) methods such as vacuum deposition, ion plating, and sputtering, CVD (chemical vapor deposition) methods such as heat, light, and plasma, and the FCVA (Filtered Cathodic Vacuum Arc) method as shown in JP 2007-86329 A. Coating films formed by these methods are advantageous in terms of adhesion to the substrate, and all of them provide excellent durability.

To measure the coefficient of friction, an actual blade piece can be selected as the contact, and an image carrier or a flat plate simulating its surface can be selected as the sample. In the present invention, the coefficient of friction is defined as the dynamic friction coefficient, and the dynamic friction coefficient can be measured using, for example, a surface property measuring instrument TYPE: 14FW manufactured by Shinto Scientific Co., Ltd.

The area where the coating is formed, i.e., the area on the surface of the blade member where the coating is performed, can be selected as appropriate. The area where the coating is performed needs to include the contact surface (contact area) between the blade member and the photosensitive drum.

An example of the range to be coated is shown in Fig. 5. Fig. 5(A) shows a lubricant application blade 34 and a blade support 35, and for example, a range of 3 mm from the tip of the lubricant application blade 34 to both ends including the edge portion is coated. The coating range is indicated by reference numeral 36.
At this time, it is preferable to coat the entire width in the longitudinal direction. Fig. 5(B) is a view from the direction a in Fig. 5(A), in which the entire width in the longitudinal direction is coated. Fig. 5(C) is a schematic diagram of the lubricant application blade 34 after coating has been performed. As shown in the figure, a coating portion 34b is formed on the blade member 34a.

The thickness of the coating can be selected as appropriate, but is preferably 0.01 to 1 μm, for example.

The coefficient of friction of the coated portion is preferably, for example, 0.1 to 0.5.
The coefficient of friction of a blade member is usually about 1.0 to 2.0, and it is difficult to lower the coefficient of friction from the viewpoint of maintaining the strength and elasticity required for the blade member itself, for example, because improvements in terms of materials or the addition of lubricating substances would change the physical properties of the rubber. For this reason, by forming a coating portion with a low coefficient of friction only on the surface as described above, it is possible to maintain the physical properties required for the blade itself, without increasing the torque even when the contact width with the image carrier is large, and to suppress the generation of abnormal noise due to vibration.

Next, other components of the lubricant application means 2 will be described.
The lubricant 31 receives a pressing force from a pressing force applying mechanism 33 via a lubricant holding member 32 and comes into contact with a roller-shaped lubricant supplying member 30 .
The lubricant supplying member 30 grinds the solid lubricant 31 into powder and supplies the powdered lubricant 31 to the photosensitive drum 8. The lubricant supplying member 30 rotates with a linear speed difference with respect to the photosensitive drum 8 and rubs against the photosensitive drum 8, and at this time, supplies the lubricant held on the surface of the lubricant supplying member 30 to the surface of the photosensitive drum 8.

The lubricant supply member 30 may be a roller-shaped member as shown in the figure, or other known members such as a brush member made of flexible fibers or a sponge member made of urethane foam, etc., may be used.

The lubricant 31 may be made of known materials such as inorganic lubricants, fatty acid metal salts, waxes, oils, fluororesins, etc., and may be made of these materials molded into a bar shape. Among these, fatty acid metal salts are particularly preferred. When fatty acid metal salts are used, the lubricant has excellent extensibility, and the tolerance to filming in particular can be increased.

Examples of fatty acid metal salts include, but are not limited to, barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, cadmium stearate, magnesium stearate, zinc stearate, zinc oleate, magnesium oleate, iron oleate, cobalt oleate, copper oleate, lead oleate, manganese oleate, zinc palmitate, cobalt palmitate, lead palmitate, magnesium palmitate, aluminum palmitate, calcium palmitate, lead caprylate, lead caprate, zinc linoleate, cobalt linoleate, calcium linoleate, zinc ricinoleate, cadmium ricinoleate, barium laurate, lithium laurate, calcium laurate, and zinc laurate. Mixtures of these may also be used.

Among these, zinc stearate is particularly preferred. When zinc stearate is used, it is possible to improve the film-forming property and spreadability on the image carrier, which not only has a positive effect on filming but also increases the resistance to wear of the image carrier.

The content of the fatty acid metal salt can be selected as appropriate, but it is preferable to use it as the main component of the lubricant. In this case, the above-mentioned effects are more easily obtained. In this invention, the main component means that it accounts for more than 50% by weight of the entire lubricant.

FIG. 6 is a cross-sectional view showing an example of an image forming apparatus 100 according to the present invention.
In this example, a lubricant application device 2, a charging device 3, a latent image forming device 8, a developing device 5, a transfer device 6, and a cleaning device 4 are arranged around a drum-shaped image carrier 1. In this example, four removable photoconductor units (process cartridges) are provided corresponding to the image carriers 1K, 1C, 1M, and 1Y, respectively. The photoconductor units can be configured as shown in FIG. 1, for example. When the above image carriers are described without distinction, they will be referred to as image carrier 1.

A series of processes for forming an image will be explained using a negative-positive process.
An image carrier 1, typically a photoconductor (OPC) having an organic photoconductive layer, is neutralized by a neutralization lamp or the like, and is uniformly negatively charged by a charging device 3 having a charging member.

When the image carrier is charged by the charging device, a voltage of an appropriate magnitude, or a charging voltage with an AC voltage superimposed thereon, suitable for charging the image carrier 1 to the desired potential is applied to the charging member from the voltage application mechanism.

The charged image carrier 1 is irradiated with laser light by a latent image forming device 8 such as a laser optical system to form a latent image (the absolute value of the potential of the exposed area is lower than the absolute value of the potential of the non-exposed area). The laser light is emitted from a semiconductor laser and scans the surface of the image carrier 1 in the direction of the rotation axis of the image carrier 1 using a polygonal mirror (polygon) that rotates at high speed.

The latent image thus formed is developed by a developer consisting of toner particles or a mixture of toner particles and carrier particles supplied onto the developing sleeve, which is a developer carrier in the developing device 5, to form a visible toner image.

When the latent image is developed, a voltage application mechanism applies a development bias of an appropriate magnitude, or a development bias with an AC voltage superimposed thereon, to the developing sleeve between the exposed and non-exposed areas of the image carrier 1.

The toner images formed on the image carrier 1 corresponding to each color are transferred onto the intermediate transfer medium 60 by the transfer device 6, and the toner images are transferred onto a transfer medium such as paper fed from the paper feed mechanism 200. At this time, it is preferable that a potential of the opposite polarity to the toner charge polarity is applied to the transfer device 6 as a transfer bias. After that, the intermediate transfer medium 60 is separated from the image carrier 1, and a transfer image is obtained.

The toner particles remaining on the image carrier are collected by the cleaning member into the toner collection chamber in the cleaning device 4.

The image forming apparatus may be an apparatus in which a plurality of the above-mentioned developing devices are arranged, and a plurality of toner images of different colors, which are produced in sequence by the plurality of developing devices, are transferred in sequence onto a transfer material, which is then sent to a fixing mechanism, where the toner is fixed by heat or the like. Alternatively, a plurality of toner images produced in the same manner as above may be transferred in sequence onto an intermediate transfer medium, which is then transferred all at once to the transfer medium, which is then fixed in the same manner as above.

The charging device 3 may be of any known configuration, but it is more preferable that it is a charging device arranged in contact with or close to the image carrier surface. This makes it possible to significantly reduce the amount of ozone generated during charging, compared to corona dischargers that use a discharge wire, known as corotrons or scorotrons.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1
<Machining of lubricant application blade>
In a photoconductor unit of a black station of a Ricoh MPC5503 copier having a lubricant application means substantially equivalent to that shown in FIG. 1, the lubricant application blade (material: urethane rubber) was replaced with one processed as follows to prepare an evaluation unit.
A lubricant application blade with a free length 0.8 mm longer than the standard (free length: 5.5 mm) was prepared, and a hydrogen-free DLC Ta-C coat was formed by FCVA over a range of 3 mm on both sides of the lubricant application blade including the tip and edge, and over the entire longitudinal width (performed by Nanofilm Co., Ltd.) in the same manner as in the example shown in Fig. 5. The thickness of the coating film was 0.5 μm.
The lubricant application blade processed in this manner was returned to the original photoreceptor unit to prepare an evaluation unit. The contact width between the lubricant application blade and the photoreceptor of this unit was separately measured by the above-mentioned method and was found to be 245 μm.
The coefficient of friction of the lubricant application blade (blade member) before processing was 1.32, and the coefficient of friction after the Ta-C coating was 0.28. The dynamic friction coefficient of the lubricant application blade was measured as follows.

- Measurement of friction coefficient -
The measuring instrument used was a surface property measuring instrument TYPE: 14FW (manufactured by Shinto Scientific Co., Ltd.).
Another lubricant-coated blade manufactured under the same conditions as the one mounted on the actual device was peeled off from the support, cut into a piece 8 mm wide, and set in a blade holder attached to the surface property measuring device to form a contact.
A sample was prepared by dipping a glass plate with a material having the same formulation as the surface layer of the photoreceptor used in the RICOH MPC5503.
The average dynamic friction coefficient was measured when scanning in the trailing direction under a load of 100 g, a sample moving speed of 30 mm/min, and a sample moving distance of 5 mm.

The lubricant application means for the RICOH MPC5503 uses a lubricant containing 80% zinc stearate as its main component.

<Evaluation>
Using the image forming apparatus equipped with the photoreceptor unit obtained as described above, the actual device characteristics evaluation (evaluation of abnormal noise and wear amount) was carried out to confirm the lubricant application property and side effects as described below. Note that in each evaluation, the black station was used alone.

<<1. Evaluation of lubricant application properties>>
The better the lubricant applicability, the less filming occurs even under conditions where the amount of lubricant consumed is small. Therefore, the lubricant applicability was evaluated by the following method.
The pressure of the spring, which is the pressing force imparting mechanism (corresponding to pressing force imparting mechanism 33 in FIG. 1) included in the lubricant application means of RICOH MPC5503 manufactured by Ricoh Co., Ltd., was reduced to half to reduce the amount of lubricant consumed. Up to 30,000 sheets of A4 horizontal black vertical band chart were continuously fed in a high temperature and high humidity environment (30° C., 90%).
At this time, the photoconductor unit was taken out every 1000 sheets, and the photoconductor was visually checked for the presence or absence of filming. If filming occurred, a halftone image was output to check whether filming appeared as an NG level abnormal image. The number of sheets on which filming was visually confirmed and the number of sheets on which NG level abnormal images were confirmed were checked and used as the criterion for judging the lubricant applicability.
In the evaluation of filming, it is most preferable that filming does not occur. Even if filming occurs, it is judged as passing if no abnormal images due to filming are found in the evaluation of 30,000 sheets.

＜＜2. Evaluation of abnormal noise＞＞
In the evaluation of the lubricant application property, before removing the photoconductor every 1000 sheets, three blank charts were passed continuously in half-speed mode to check whether abnormal noises caused by the application blade were generated. When an abnormal noise that was clearly audible to the ear was generated, the number of sheets at that point was checked and used as the criterion for judging side effects.
The case where no abnormal noise was generated even at the time of 30,000 sheets was judged as pass, and the case where abnormal noise was generated at the evaluation of 30,000 sheets was judged as fail.

<<3. Checking the wear amount of the photoconductor>>
Since the higher the dynamic torque, the more the photoconductor wears, the thickness of the photoconductor was measured at the portion where no filming occurred among the photoconductors that had been run up to 30,000 sheets in the evaluation of the lubricant application property. The amount of wear from the initial stage was compared to determine the criterion for side effects.

Example 2
The evaluation was carried out in the same manner as in Example 1, except that the surface coating was carried out using a lubricant application blade whose free length was 1.1 mm longer than that of the standard product. The contact width between the lubricant application blade and the photoreceptor at this time was 396 μm.

Example 3
The evaluation was carried out in the same manner as in Example 1, except that the surface coating was carried out using a lubricant application blade whose free length was 0.5 mm longer than that of the standard product. In this case, the contact width between the lubricant application blade and the photoreceptor was 83 μm.

Example 4
The evaluation was performed in the same manner as in Example 1, except that the free length of the lubricant application blade was set to the standard, and the bite amount of the processed lubricant application blade into the photoreceptor was increased by 1.0 mm when returning the processed lubricant application blade to the photoreceptor unit. The contact width between the lubricant application blade and the photoreceptor at this time was 370 μm.

Example 5
In Example 4, the evaluation was performed in the same manner as in Example 1, except that the increase in the amount of penetration of the lubricant application blade into the photoreceptor was set to 0.5 mm. The contact width between the lubricant application blade and the photoreceptor in this case was 91 μm.

Example 6
The evaluation was carried out in the same manner as in Example 1, except that the surface of the lubricant application blade was coated in the following manner.
A lubricant application blade with a free length 0.8 mm longer than the standard product was prepared, and a PTFE coating was formed by spray coating over a range of 3 mm on both sides of the lubricant application blade, including the edge portion, and over the entire longitudinal width, in the same manner as in the example shown in Fig. 5 (performed by Fujikura Composites Co., Ltd.). The coating film had a thickness of 1.0 μm.
The lubricant application blade thus processed was returned to the original photoreceptor unit, and the contact width between the lubricant application blade and the photoreceptor was separately measured to be 260 μm. The friction coefficient after coating was 0.49.

(Example 7)
The evaluation was carried out in the same manner as in Example 1, except that the surface of the lubricant application blade was coated in the following manner.
A lubricant application blade with a free length 0.8 mm longer than the standard product was prepared, and a silicone resin coating was formed by dipping application over a range of 3 mm on both sides of the application blade, including the edge, and over the entire longitudinal width (performed by Fujikura Composites, Inc.), in the same manner as in the example shown in Fig. 5. The coating film had a thickness of 0.5 μm.
The lubricant application blade thus processed was returned to the original photoreceptor unit, and the contact width between the lubricant application blade and the photoreceptor was separately measured to be 243 μm. The friction coefficient after coating was 0.55.

(Example 8)
In Example 1, the lubricant used in the lubricant application device was a lubricant containing 80% zinc laurate instead of zinc stearate as the main component, with the other components being the same, and evaluation was performed in the same manner as in Example 1.

Example 9
In Example 1, the lubricant used in the lubricant application device was a lubricant containing 80% paraffin wax instead of zinc stearate as the main component, with the other components being the same, and the evaluation was performed in the same manner as in Example 1.

(Comparative Example 1)
In Example 1, a standard product was used as the lubricant application blade as it was, and evaluation was performed in the same manner as in Example 1, except that no coating was performed. In this case, the contact width between the lubricant application blade and the photoreceptor was 32 μm.

(Comparative Example 2)
The evaluation was carried out in the same manner as in Example 1, except that the surface was coated using a standard lubricant application blade. The contact width between the lubricant application blade and the photoreceptor was 30 μm.

(Comparative Example 3)
The evaluation was carried out in the same manner as in Example 1, except that the free length of the lubricant application blade was made 0.8 mm longer than the standard product and that no coating was performed. The contact width between the lubricant application blade and the photoreceptor in this case was 298 μm.

(Comparative Example 4)
The evaluation was carried out in the same manner as in Example 1, except that the surface coating was carried out using a lubricant application blade whose free length was 1.4 mm longer than that of the standard product. In this case, the contact width between the lubricant application blade and the photoreceptor was 480 μm.

The results of Examples 1 to 9 and Comparative Examples 1 to 4 are summarized in Table 1.

2 Lubricant application means 8 Photoconductor drum 31 Lubricant 30 Lubricant supply member 32 Lubricant holding member 33 Pressing force applying mechanism 34 Lubricant application blade 35 Blade support

JP 2011-191732 A JP 2013-148692 A JP 2009-300750 A JP 2007-140391 A

Claims (7)

An image forming apparatus including an image carrier and a lubricant application unit that applies a lubricant to the image carrier,
The lubricant application means includes:
a lubricant supplying member that grinds a solid lubricant into powder and supplies the powdered lubricant to the image carrier; and a lubricant application blade that is disposed downstream of the lubricant supplying member in the rotation direction of the image carrier, comes into contact with the image carrier in a trailing manner, and levels the powdered lubricant on the image carrier,
The lubricant application blade of the image forming apparatus has a blade member and a coating portion formed on at least a portion of the surface of the blade member and in contact with the image carrier, wherein the average width of the surface in contact with the image carrier in the direction of rotation of the image carrier is 80 μm or more and 400 μm or less, and the friction coefficient of the coating portion is lower than the friction coefficient of the blade member. The image forming apparatus according to claim 1, characterized in that the coating portion is made of diamond-like carbon. The image forming apparatus according to claim 1 or 2, characterized in that the lubricant contains 50% by mass or more of a fatty acid metal salt. 4. The image forming apparatus according to claim 3 , wherein the fatty acid metal salt is zinc stearate. a cleaning means having a cleaning blade for cleaning the image carrier;
5. The image forming apparatus according to claim 1, wherein the lubricant applying means is disposed downstream of the cleaning means in the rotation direction of the image carrier. The image forming device according to any one of claims 1 to 5, characterized in that the thickness of the coating portion is 0.01 μm or more and 1 μm or less. a process cartridge detachably attached to a main body of an image forming apparatus, the process cartridge comprising: an image carrier; a cleaning means for cleaning the image carrier with a cleaning blade; and a lubricant application means arranged downstream of the cleaning means in a rotation direction of the image carrier and for applying a lubricant to the image carrier, the process cartridge being
The lubricant application means includes:
a lubricant supplying member that grinds a solid lubricant into powder and supplies the powdered lubricant to the image carrier; and a lubricant application blade that is disposed downstream of the lubricant supplying member in the rotation direction of the image carrier, comes into contact with the image carrier in a trailing manner, and levels the powdered lubricant on the image carrier,
The lubricant application blade has a blade member and a coating portion formed on at least a portion of the surface of the blade member and in contact with the image carrier, the average width of the surface in contact with the image carrier in the direction of rotation of the image carrier being 80 μm or more and 400 μm or less, and the friction coefficient of the coating portion is lower than the friction coefficient of the blade member.

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