JP2005208177A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and a process cartridge capable of reliably suppressing faulty cleaning and filming and capable of forming an output image of high image quality even when a spherical toner of a small particle diameter is used. <P>SOLUTION: The image forming apparatus includes an image carrier 18 with a surface layer 18a formed thereon containing a release material which improves release property to toner T sticking to a surface thereof; a first cleaning blade 22 which is in contact with a top of the image carrier 18 and cleans the top of the image carrier 18; and a second cleaning blade 26 which is in contact with the top of the image carrier 18 and further cleans the top of the image carrier 18 cleaned by the first cleaning blade 22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or a multifunction machine thereof, and a process cartridge that is detachably installed therein.

  Conventionally, in color image forming apparatuses such as color copying machines, an abrasive is included on the surface of the photosensitive drum for the purpose of suppressing the occurrence of filming in which foreign matter adheres to the photosensitive drum (image carrier). A technique for bringing the cleaning blade into contact is known (see, for example, Patent Document 1).

Specifically, Japanese Patent Application Laid-Open No. H10-228561 discloses a technique for making the cleaning blade in contact with the surface of the photoconductor drum contain an abrasive and forming the surface of the photoconductor drum with high hardness.
As a result, untransferred toner adhering to the photosensitive drum is removed by the original function of the cleaning blade, and foreign matter adhering to the photosensitive drum is removed by the abrasive contained in the cleaning blade, thereby preventing filming. Can be expected to be maintained for a long time. Here, in order to reduce damage to the surface of the photosensitive drum due to the abrasive, the surface of the photosensitive drum is formed with high hardness. When filming occurs on the photosensitive drum, image quality deterioration such as image blurring occurs.

  On the other hand, in recent image forming apparatuses, a toner having a small particle size and a spherical shape (hereinafter referred to as “small particle size / spherical toner”) is often used for the purpose of achieving high image quality. ing. In addition, a technique for providing a surface layer containing a fluorine compound on the surface of the photosensitive drum is also known for the purpose of suppressing the occurrence of poor cleaning when a small particle size / spherical toner is used in the image forming process. (For example, refer to Patent Document 2).

  That is, the small particle size / spherical toner remaining on the photosensitive drum as untransferred toner enters the gap while rotating at the contact position with the cleaning blade. This is a phenomenon that passes between cleaning blades). In contrast, by providing a surface layer containing a fluorine compound on the surface of the photoconductive drum, the releasability of the surface of the photoconductive drum to the toner is enhanced, and cleaning is performed before the toner enters the contact portion of the cleaning blade. The effect of being removed from the surface of the photosensitive drum by the blade can be expected.

JP 2001-296781 A JP-A-11-344818

  In the conventional image forming apparatus described above, it is difficult to suppress both filming and poor cleaning in a balanced manner when a small particle size / spherical toner is used for the purpose of improving image quality.

  That is, in the technique of the above-mentioned patent document 1, etc., on the premise that the surface of the photosensitive drum is formed with high hardness, an abrasive is contained in the cleaning blade to suppress filming on the photosensitive drum. . When the hardness of the surface of the photoconductor drum cannot be increased, the surface of the photoconductor drum is damaged by the abrasive, and the scratch creates a gap between the cleaning blade and the photoconductor drum, resulting in poor cleaning.

  On the other hand, in the technique disclosed in Patent Document 2 and the like, since a surface layer (release layer) having high toner releasability is formed on the surface of the photosensitive drum, cleaning is performed even for a small particle size / spherical toner. While it is difficult for defects to occur, the hardness of the surface of the photosensitive drum cannot be increased so much. Therefore, in order to obtain the effect of this technique, it is necessary to use the photosensitive drum so as not to apply local stress to the surface of the photosensitive drum. When local stress is applied to the photoconductive drum, the surface of the photoconductive drum is damaged, and the scratch creates a gap between the cleaning blade and the photoconductive drum, resulting in poor cleaning.

  As a result of repeated research, the inventors of the present application have found that filming is particularly likely to occur when a small particle size / spherical toner is used. That is, the small particle size / spherical toner is externally or internally added with wax for enhancing releasability, inorganic fine particles for enhancing fluidity, and the like, as in a normal toner. Filming on the photosensitive drum is a phenomenon in which these additives are detached from the toner and adhered to the photosensitive drum without being cleaned. The additive content in the small particle size / spherical toner is larger than that in the normal toner, and the content rate tends to increase as the particle size is further reduced. Therefore, when a small-diameter / spherical toner is used, filming is likely to occur on the photosensitive drum as compared with a normal toner.

As described above, when the small particle size / spherical toner is used, the technique disclosed in Patent Document 2 or the like suppresses the cleaning failure, but cannot sufficiently suppress the occurrence of filming. On the other hand, when the small particle size / spherical toner is used, in the technique of Patent Document 1, the occurrence of filming is suppressed, but the cleaning failure cannot be sufficiently suppressed.
That is, in the conventional technique, when a small particle size / spherical toner is used, it is impossible to simultaneously prevent both a cleaning failure and filming.

  In particular, in recent image forming apparatuses, there is a strong demand for higher definition in output images, and in order to achieve higher resolution and gradation than conventional ones, toner particle diameters and spheroidization are increasingly promoted. The possibility is high. Therefore, the above-mentioned problems are increasingly not negligible.

  The present invention has been made to solve the above-described problems, and even when a small particle size / spherical toner is used, it is possible to reliably prevent defective cleaning and occurrence of filming. Another object of the present invention is to provide an image forming apparatus and a process cartridge on which a high-quality output image is formed.

  According to a first aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier on which a surface layer containing a release material that improves the releasability of toner adhering to the surface is formed; A first cleaning blade that contacts and cleans the image carrier, and a second cleaning blade that contacts the image carrier and cleans the image carrier cleaned by the first cleaning blade. And.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the release material is a fluorine compound, and the surface layer of the image carrier has a fluorine compound of 55. It is contained in a range of ˜70% by weight.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the second cleaning blade is formed of a rubber material having a rubber hardness in the range of 85 to 95 degrees. Provided with an elastic part.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the second cleaning blade is adapted to follow a moving direction of the surface of the image carrier. And abuts on the image carrier.

  According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the fourth aspect, wherein the second cleaning blade has the contact angle in a range of 5 to 25 degrees. It is in contact with the top.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, the second cleaning blade has a contact pressure of 9.8-78.4 N. / M is in contact with the image carrier so as to be in the range of / m.

  The image forming apparatus according to a seventh aspect of the present invention is the image forming apparatus according to any one of the first to sixth aspects, wherein the toner has a circular shape with a volume average particle diameter in the range of 3 to 8 μm. It is formed so that the degree is in the range of 0.93 to 0.98.

  An image forming apparatus according to an eighth aspect of the present invention is the image forming apparatus according to any one of the first to seventh aspects, wherein the toner is a polyester prepolymer having at least a functional group containing a nitrogen atom. The toner material liquid in which polyester, a colorant, and a release agent are dispersed in an organic solvent is formed by crosslinking and / or elongation reaction in an aqueous medium.

  The process cartridge according to claim 9 of the present invention is a process cartridge configured to be detachable from the main body of the image forming apparatus, and contains a release material that improves the releasability of the toner adhering to the surface. An image carrier having a surface layer formed thereon, a first cleaning blade that abuts on the image carrier and cleans the image carrier, abuts on the image carrier, and the first cleaning And a second cleaning blade for further cleaning the image carrier that has been cleaned by the blade.

  A process cartridge according to a tenth aspect of the present invention is the process cartridge according to the ninth aspect, wherein the developing means for developing the latent image formed on the image carrier and the charging means for charging the image carrier. And at least one of the means.

  The process cartridge according to an eleventh aspect of the present invention is the process cartridge according to the ninth or tenth aspect, wherein the release material is a fluorine compound, and the surface layer of the image carrier is The fluorine compound is contained in the range of 55 to 70% by weight.

  A process cartridge according to a twelfth aspect of the present invention is the process cartridge according to any of the ninth to eleventh aspects, wherein the second cleaning blade is a rubber material having a rubber hardness in the range of 85 to 95 degrees. It is provided with the elastic part formed by.

  A process cartridge according to a thirteenth aspect of the present invention is the process cartridge according to any one of the ninth to twelfth aspects, wherein the second cleaning blade is along a moving direction of the surface of the image carrier. It abuts on the image carrier.

  A process cartridge according to a fourteenth aspect of the present invention is the process cartridge according to the thirteenth aspect, wherein the second cleaning blade is placed on the image carrier so that the contact angle is in the range of 5 to 25 degrees. It abuts against.

  A process cartridge according to a fifteenth aspect of the present invention is the process cartridge according to any one of the ninth to fourteenth aspects, wherein the second cleaning blade has a contact pressure of 9.8 to 78.4 N / It abuts on the image carrier so as to be in the range of m.

  A process cartridge according to a sixteenth aspect of the present invention is the process cartridge according to any one of the ninth to fifteenth aspects, wherein the toner has a volume average particle size in the range of 3 to 8 μm and has a circularity. Is formed in a range of 0.93 to 0.98.

  The process cartridge according to claim 17 is the process cartridge according to any one of claims 9 to 16, wherein the toner includes at least a polyester prepolymer having a functional group containing a nitrogen atom, A toner material liquid in which polyester, a colorant, and a release agent are dispersed in an organic solvent is formed by crosslinking and / or elongation reaction in an aqueous medium.

  An image forming apparatus according to an eighteenth aspect of the present invention includes the process cartridge according to any one of the ninth to seventeenth aspects installed in the main body of the image forming apparatus.

In the present application, “process cartridge” means a charging unit (charging unit) for charging an image carrier, a developing unit (developing unit) for developing a latent image formed on the image carrier, and an image carrier. It is defined as a unit in which at least one of the cleaning means (cleaning unit) for cleaning the top and the image carrier are integrated and installed detachably with respect to the image forming apparatus main body.
The “contact angle” of the second cleaning blade refers to the tangent line on the image carrier at a virtual intersection where the second cleaning blade that does not bend in the absence of the image carrier and the image carrier, and the above-described deflection. This is defined as the angle formed by the second cleaning blade without any gap.

  The present invention provides a surface layer with high toner releasability on the image carrier to reliably clean small particle size / spherical toner with the first cleaning blade, and wax that has not been cleaned with the first cleaning blade, Foreign substances such as inorganic fine particles are removed by the second cleaning blade. Thus, even when a small particle size / spherical toner is used, an image forming apparatus and a process capable of reliably preventing defective cleaning and filming and forming a high-quality output image. A cartridge can be provided.

Embodiment.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of a copying machine as an image forming apparatus, 2 an original reading unit that optically reads image information of an original D, and 3 an exposure light L based on image information read by the original reading unit 2. 4 is a process cartridge as an image forming unit for forming a toner image on the photosensitive drum 18, and 7 is a toner image formed on the photosensitive drum 18. A transfer unit 10 for transferring the image to the document reading unit 2, a document conveying unit (ADF) for conveying the set document D to the document reading unit 2, 9 a fixing unit for fixing an unfixed image on the recording medium P, and 9a An installed fixing roller, 9b is a pressure roller installed in the fixing unit 9, and 12 to 14 are paper feeding units in which a recording medium P such as transfer paper is stored.

With reference to FIG. 1, an operation during normal image formation in the image forming apparatus will be described.
First, the document D is conveyed from the document table in the direction of the arrow in the drawing by the conveyance roller of the document conveyance unit 10 and passes over the document reading unit 2. At this time, the document reading unit 2 optically reads the image information of the document D passing above.
Then, the optical image information read by the document reading unit 2 is converted into an electric signal and then transmitted to the exposure unit 3 (writing unit). Then, exposure light L such as laser light based on the image information of the electrical signal is emitted from the exposure unit 3 toward the photosensitive drum 18 of the process cartridge 4.

On the other hand, in the process cartridge 4, the photosensitive drum 18 is rotated in the clockwise direction in the drawing, and image information is formed on the photosensitive drum 18 through a predetermined image forming process (charging process, exposure process, development process). A corresponding toner image is formed.
Thereafter, the toner image formed on the photosensitive drum 18 is transferred by the transfer unit 7 onto the recording medium P conveyed by the registration roller.

On the other hand, the recording medium P conveyed to the transfer unit 7 operates as follows.
First, one of the plurality of paper feeding units 12, 13, and 14 of the image forming apparatus main body 1 is automatically or manually selected (for example, the uppermost paper feeding unit 12 is selected). To do.)
Then, the uppermost sheet of the recording medium P stored in the paper feeding unit 12 is transported toward the position of the transport path K.

  Thereafter, the recording medium P passes through the conveyance path K and reaches the position of the registration roller. Then, the recording medium P that has reached the position of the registration roller is conveyed toward the transfer unit 7 at the same timing in order to align with the image formed on the photosensitive drum 18.

Then, the recording medium P after the transfer process passes through the position of the transfer unit 7 and then reaches the fixing unit 9 through the conveyance path. The recording medium P that has reached the fixing unit 9 is fed between the fixing roller 9a and the pressure roller 9b, and the toner image is fixed by the heat received from the fixing roller 9a and the pressure received from both the rollers 9a and 9b. Is done. The recording medium P on which the toner image has been fixed is delivered from between the fixing roller 9a and the pressure roller 9b and then discharged from the image forming apparatus main body 1 as an output image.
Thus, a series of image forming processes is completed.

Next, referring to FIG. 2, the configuration and operation of the image forming unit centering on the process cartridge 4 installed in the image forming apparatus main body 1 will be described in detail.
As shown in FIG. 2, the process cartridge 4 mainly includes a photosensitive drum 18 as an image carrier, a charging unit 19 (charging unit), a developing unit 20 (developing unit), and a cleaning unit 21 (cleaning unit). Are integrated with each other and are detachable from the image forming apparatus main body 1.

In the photosensitive drum 18, a charge generation layer, a charge transport layer, and the like are formed on a base tube made of aluminum, and a surface layer 18a (the uppermost layer) is formed on these layers.
The surface layer 18a of the photosensitive drum 18 contains a release material in order to improve the releasability with respect to the toner adhering to the drum surface. That is, the surface layer 18a functions as a release layer. As the release material contained in the surface layer 18a, fluorine compounds such as PFA (perfluorotetrafluoroalkyl vinyl ether resin) and PTFE (tetrafluoroethylene resin) can be used.

  Here, it is preferable to make the content rate of the fluorine compound in the surface layer 18a into the range of 55 to 70 weight%. As the content of the fluorine compound increases, the releasability to the toner increases. By setting the content of the fluorine compound to 55% by weight or more, good toner releasability can be maintained as long as no filming occurs on the photosensitive drum 18. On the other hand, if the content of the fluorine compound is too large, the surface layer 18a becomes turbid and sufficient exposure with the exposure light L cannot be performed. By setting the content of the fluorine compound to 70% by weight or less, a sufficient exposure process on the photosensitive drum 18 becomes possible.

  In the present embodiment, the surface layer 18a of the photosensitive drum 18 is composed of 55% by weight of powdered PFA, 42% by weight of Z-type polycarbonate “PCX5”, and 3 dispersers that increase the dispersibility of PFA in polycarbonate. It is formed so as to be weight%. The surface layer 18a is coated on the photosensitive drum 18 so that the layer thickness is 5 μm.

  Referring to FIG. 2, the cleaning unit 21 is in contact with the photosensitive drum 18 to mainly clean the untransferred toner, and the cleaning unit 21 is in contact with the photosensitive drum 18 and mainly a foreign matter that is a filming generation source. And a second cleaning blade 26 for cleaning the.

The first cleaning blade 22 is made of a rubber material that does not contain an abrasive, and is in contact with the surface of the photosensitive drum 18 in a counter manner. Specifically, the first cleaning blade 22 is in contact with the photosensitive drum 18 with a predetermined contact pressure by a spring 24 that biases the support plate 23 that holds the first cleaning blade 22. The first cleaning blade 22 is in contact with the photosensitive drum 18 so as to counter the rotational movement of the surface of the photosensitive drum 18 in the direction of the arrow (this contact method is referred to as a counter method).
Here, referring to FIG. 3, the counter system is in the quadrant S2 on the downstream side in the rotation direction R in the coordinates of the normal line V and the tangent line H with the contact point between the cleaning blade and the photosensitive drum 18 as the origin. The state where the cleaning blade is arranged.

  With the first cleaning blade 22 having such a configuration and the above-described highly releasable photosensitive drum 18, even if the toner T used in this image forming process is a small particle size / spherical toner, the photosensitive drum 18. Untransferred toner adhering to the top is reliably removed by the first cleaning blade 22.

On the other hand, the second cleaning blade 26 is an elastic body (elastic portion) made of a rubber material not containing an abrasive, and is in contact with the surface of the photosensitive drum 18 by a trailing method. Specifically, the second cleaning blade 26 is in contact with the photosensitive drum 18 with a predetermined contact pressure by a spring 28 that biases the support plate 27 that holds the second cleaning blade 26. The second cleaning blade 26 is in contact with the photosensitive drum 18 so as to follow the rotational movement of the surface of the photosensitive drum 18 in the direction of the arrow (this contact method is called a trailing method).
Here, in the trailing method, referring to FIG. 3, the quadrant on the upstream side in the rotation direction R in the coordinates of the normal line V and the tangent line H with the contact portion between the cleaning blade 26 and the photosensitive drum 18 as the origin. A state in which the cleaning blade 26 is disposed in S1 (the state of FIG. 3).

Here, the rubber hardness of the second cleaning blade 26 is preferably higher than the rubber hardness of the first cleaning blade 22 and is in the range of 85 to 95 degrees. The higher the rubber hardness, the higher the ability to remove deposits such as wax and inorganic fine particles adhering to the photosensitive drum 18. However, if the rubber hardness is too high, the curved surface shape of the photosensitive drum 18 is not achieved, and therefore a gap is generated in the blade 16 that contacts the photosensitive drum 18 unless the straightness of the blade 26 is high accuracy. By setting the rubber hardness of the second cleaning blade 26 in the range of 85 to 95 degrees, a gap with the photosensitive drum 18 is generated even if the toner T used in this image forming process is a small particle size and spherical toner. Without any problem, removal of the filming generation source is ensured.
The above rubber hardness is a value measured by “Asker C” (manufactured by Asker Polymer Instruments Co., Ltd.) based on the Japan Rubber Association Standard (SRIS).

  The contact angle α of the second cleaning blade 26 is preferably in the range of 5 to 25 degrees. As the contact angle α is smaller, the blade tip portion is not excessively stressed, so that the blade 26 is not turned over, chipped, or the like, but the ability to remove deposits decreases. The larger the contact angle α, the higher the ability to remove the deposits, but the blade 26 is more likely to be turned over or chipped. Further, when the contact angle α is large, the photoconductive drum 18 is turned, particularly when the photoconductive drum 18 is rotated in the reverse direction. Increase and uneven rotation speed will occur. By setting the contact angle of the second cleaning blade 26 in the range of 5 to 25 degrees, even if the toner T used in this image forming process is a small particle size / spherical toner, the above-described problems do not occur. Removal of the filming source is ensured.

  The contact angle α of the second cleaning blade 26 refers to the second cleaning blade (26A shown by a broken line in the figure) that does not bend in the absence of the photosensitive drum 18, with reference to FIG. ) Is an angle α formed by a tangent line H on the photosensitive drum 18 at a virtual intersection M where the photosensitive drum 18 intersects the second cleaning blade 26A without bending.

The contact pressure of the second cleaning blade 26 is preferably in the range of 9.8 to 78.4 N / m (10 to 80 gf / cm). As the contact pressure is smaller, the blade tip portion is not excessively stressed, so that the blade 26 is not turned over, chipped, or the like, but the ability to remove deposits decreases. The greater the contact pressure, the higher the ability to remove deposits, but the blade 26 is more likely to be turned over or chipped. By setting the contact pressure of the second cleaning blade 26 in the range of 9.8 to 78.4 N / m, even if the toner T used in this image forming process is a small particle size / spherical toner, the above-mentioned problem As a result, the filming generation source is surely removed.
The contact pressure of the second cleaning blade 26 refers to the length of the load applied to the contact portion of the second cleaning blade 26 in the longitudinal direction (perpendicular to the paper surface) of the contact portion of the second cleaning blade 26. It is the value (linear pressure) divided by this.

  In the present embodiment, the second cleaning blade 26 is made of a rubber material having a rubber hardness of 89 degrees and containing no abrasive. Further, the contact angle α of the second cleaning blade 26 was set to 11.3 degrees, and the contact pressure was set to 40.2 N / m (41 gf / cm).

  On the other hand, the developing unit 20 mainly includes a developing roller 20a facing the photosensitive drum 18, a first transporting screw 20b facing the developing roller 20a, and a second facing the first transporting screw 20b via a partition member 20e. The conveying screw 20c and a doctor blade 20d facing the developing roller 20a are configured. A two-component developer G composed of carrier C and toner T is accommodated in the developing unit 20.

  Here, the toner T used in the developing unit 20 is preferably a small particle size / spherical toner having a volume average particle diameter of 3 to 8 μm and a circularity of 0.93 to 0.98. As a result, the image quality of the toner image formed on the photosensitive drum 18 is improved without causing the cleaning failure by the first cleaning blade 22 described above, and the toner image on the photosensitive drum 18 is transferred to the recording medium P. It is possible to transfer well.

The circularity of the toner T (toner particles) is defined by the following equation.
Circularity = (perimeter of circle having the same area as the projected area of particle) / (perimeter of projected image of particle)
Therefore, when the circularity is 1.00, the toner particles have a true spherical shape. The circularity of the toner can be typically measured using a flow type particle image measuring device “FPIA” (manufactured by Hosokawa Micron).

  The volume average particle size of the toner T (toner particles) can be typically measured using a particle size distribution measuring device “Coulter Counter TA2 type” (manufactured by Coulter Electronics).

Such toner T is manufactured by the following manufacturing method.
First, a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent is dispersed in an organic solvent is formed. Then, the toner material liquid is cross-linked and / or elongated in an aqueous medium to form a toner T matrix. Finally, an external additive is added to the toner base. The toner T formed in this way has a relatively low melting point and can secure a desired fixing property even if the fixing temperature of the fixing roller 9a is set to be relatively low.

  Here, as polyester, what was formed by the polycondensation reaction of a polyhydric alcohol compound and a polyhydric carboxylic acid compound can be used, for example. As the colorant, for example, carbon black, nigrosine dye, iron black and the like can be used. As the release agent, for example, kaunaba wax, polyethylene wax, or the like can be used.

  In the present embodiment, the toner T used in the developing unit 20 forms a toner base having a volume average particle size of 4.9 μm and a circularity of 0.965 by the above-described manufacturing method. Further, 1.5 parts of silica fine particles “H2000” and 0.5 parts of titanium fine particles “MT-150AI” are added to the toner base as external additives.

Hereinafter, the image forming process performed on the photosensitive drum 18 of the process cartridge 4 will be described in detail with reference to FIG.
The photosensitive drum 18 is rotationally driven in the clockwise direction in FIG. The surface of the photosensitive drum 18 is charged to a desired charging potential at a position where the photosensitive drum 18 faces the charging unit 19 (charging process).

Thereafter, the surface of the charged photosensitive drum 18 reaches the irradiation position of the exposure light L. Then, a desired electrostatic latent image corresponding to the image information is formed on the photosensitive drum 18 while being exposed in the scanning direction of the exposure light L (the direction perpendicular to the paper surface).
Thereafter, the surface of the photosensitive drum 18 on which the latent image is formed reaches a position facing the developing unit 20. The developing unit 20 develops the latent image on the photosensitive drum 18 to form a desired toner image.

  Here, the developing roller 20a rotates in the direction of the arrow in FIG. The developer G in the developing unit 20 is longitudinally mixed while being agitated and mixed with the toner T replenished from the toner replenishing unit 32 through the replenishing port 20f by the rotation of the first conveying screw 20b and the second conveying screw 20c in the direction of the arrow. It circulates in the direction (circulation in the direction perpendicular to the paper surface). The toner T that is frictionally charged and adsorbed on the carrier C is carried together with the carrier C on the developing roller 20a. The developer G carried on the developing roller 20a is adjusted to an appropriate amount at the position of the doctor blade 20d, and then reaches a position facing the photosensitive drum 18. Then, the toner T in the developer G adheres to the latent image on the photosensitive drum 18.

  The toner supply unit 32 provided in the apparatus main body 1 includes a toner bottle 33 configured to be replaceable, a toner hopper unit 34 that holds and rotates the toner bottle 33 and supplies fresh toner T to the developing unit 20. , Is composed of. The toner bottle 33 contains toner T. In addition, a spiral protrusion is formed on the inner peripheral surface of the toner bottle 33. The toner T in the toner bottle 33 is appropriately supplied into the developing unit 20 from the supply port 20f as the toner T in the developing unit 20 is consumed. Consumption of the toner T in the developing unit 20 is indirectly detected by the photo sensor 30 facing the photoconductive drum 18.

  Thereafter, the surface of the photosensitive drum 18 on which the toner image is formed passes through the position of the photosensor 30 and then reaches a position facing the transfer unit 7. Then, the toner image on the photosensitive drum 18 is transferred onto the recording medium P conveyed to the position of the transfer unit 7. At this time, a small amount of untransferred toner T that has not been transferred to the recording medium P remains on the photosensitive drum 18.

  Thereafter, the surface of the photosensitive drum 18 to which the untransferred toner is attached reaches the position of the first cleaning blade 22. Then, the untransferred toner on the photosensitive drum 18 is removed from the drum surface by the first cleaning blade 22 in contact with the photosensitive drum 18. Untransferred toner removed from the surface of the photosensitive drum 18 is collected in a collection space of the cleaning unit 21. At this time, a part of the external additive and the release agent contained in the untransferred toner is slightly collected on the photosensitive drum 18 without being collected by the first cleaning blade 22.

  Thereafter, the surface of the photosensitive drum 18 to which an external additive or a release agent that causes filming is attached reaches the irradiation position of the static elimination light D emitted from the static elimination unit 31. Then, the surface potential on the photosensitive drum 18 is initialized while receiving the charge removal light D.

Thereafter, the surface of the photosensitive drum 18 whose surface potential is initialized reaches the position of the second cleaning blade 26. Then, the second cleaning blade 26 in contact with the photosensitive drum 18 completely removes deposits such as external additives and release agents attached on the photosensitive drum 18 from the drum surface.
Thus, a series of image forming processes performed on the photosensitive drum 18 is completed.

  In the image forming apparatus configured and operated as described above, image formation (copying) was performed 500,000 times. As a result, there was no defect such as defective cleaning in the output image, and filming on the photoconductive drum 18 was hardly generated. I couldn't see it.

Here, the degree of filming on the photosensitive drum 18 can be quantified by a measuring method (Euler belt method) shown in FIG. 4 in addition to visual observation.
In the Euler belt method, the coefficient of static friction on the photosensitive drum 18 is measured. When the measured static friction coefficient is high, the degree of occurrence of filming is high, and when the static friction coefficient is low, the degree of occurrence of filming is low.

Specifically, referring to FIG. 4, the photosensitive drum 18 is installed on the support block 50. Then, the medium-quality high-quality paper 53 is wound over a quarter of the peripheral surface of the photosensitive drum 18 so that the paper scribing direction is the longitudinal direction. Further, one end side of the quality paper 53 wound around the photosensitive drum 18 is connected to a force gauge 51 placed on the pedestal via a wire 52. Further, the other end of the fine paper 53 is connected to a weight W (for example, one having a weight of 100 g) via a wire 52.
Then, the force gauge 51 is pulled leftward in the figure, and the load value of the force gauge 51 at the moment when the fine paper 53 moves is read. Then, the read load value F is substituted into the following equation to calculate the static friction coefficient μs on the photosensitive drum 18.
μs = 2 / π × ln (F / 0.98)

  On the other hand, the initial coefficient of static friction μs on the photosensitive drum 18 is about 0.20, and it has been confirmed that image quality deterioration due to filming occurs when the coefficient of static friction is 0.3 or more. On the other hand, in the present embodiment, the static friction coefficient μs on the photosensitive drum 18 is 0.26 after the image formation of 500,000 times, and image quality deterioration was not confirmed. Further, no scratch on the photosensitive drum 18 was confirmed.

  As a first comparative experiment for the above experimental results, the second cleaning blade 26 of the present embodiment was made to contain an abrasive and images were continuously formed under the same conditions. As a result, it was confirmed that a large number of scratches were formed on the photosensitive drum 18 after image formation 1000 times, and the occurrence of defective cleaning due to the scratches was confirmed.

  Further, as a second comparative experiment with respect to the above experimental results, as the photosensitive drum 18, instead of the surface layer 18a (release layer) of the present embodiment, a drum surface coated with silicon oil is used. Images were continuously formed under the same conditions. As a result, the occurrence of defective cleaning was confirmed after 500 times of image formation. The static friction coefficient μs on the photosensitive drum 18 was about 0.20 in the initial stage, but increased to 0.51 after 500 times of image formation. It is considered that the silicone oil was removed by the cleaning unit 21 over time, and the toner releasability could not be maintained.

  Further, as a third comparative experiment for the above experimental results, the second cleaning blade 26 of the present embodiment was removed, and image formation was continuously performed under the same conditions. As a result, occurrence of defective cleaning was confirmed after 140,000 times of image formation. The static friction coefficient μs on the photosensitive drum 18 increased to 0.39 after 140,000 times of image formation. It is considered that the toner releasability on the drum is lowered due to adhesion of a release agent, an external additive or the like on the photosensitive drum 18. When the surface of the photosensitive drum 18 after 140,000 image formations was washed with alcohol, the static friction coefficient μs recovered to 0.26. Then, when image formation was performed again using the recovered photosensitive drum 18, no defective cleaning was observed.

  As described above, in the present embodiment, the surface layer 18a having a high toner releasability is provided on the photosensitive drum 18 so that the small particle size / spherical toner T is reliably cleaned by the first cleaning blade 22. ing. Further, deposits such as wax and inorganic fine particles that have not been cleaned by the first cleaning blade 22 are removed by the second cleaning blade 26 that is optimally set so as not to cause a problem even if the amount of toner input is small. As a result, even when the small particle size / spherical toner T is used, it is possible to reliably prevent cleaning failure and filming, and a high-quality output image can be stably formed.

  In the present embodiment, the neutralization process by the neutralization unit 31 is performed on the photosensitive drum 18 from the first cleaning blade 22 to the second cleaning blade 26. On the other hand, after the cleaning process by the first cleaning blade 22 and the second cleaning blade 26 is completed, the static elimination process by the static elimination unit 31 may be performed on the photosensitive drum 18. Also in this case, the same effect as this embodiment can be obtained.

  In this embodiment, the developer G stored in the developing unit 20 is a two-component developer composed of the carrier C and the toner T. The application of the present invention is not limited to this, and the developer G accommodated in the developing unit 20 may be a one-component developer composed only of the toner T (including a release agent, an external additive, etc.). The present invention can be applied. In this case, it is preferable that the toner T to be used is equivalently formed by the same manufacturing method as the toner T used in the present embodiment.

In the present embodiment, the photosensitive drum 18, the first cleaning blade 22, and the second cleaning blade 26 are integrated with the developing unit 20 and the charging unit 19 to configure the process cartridge 4. Thereby, the maintainability of the image forming unit is enhanced.
On the other hand, the present invention can also be applied to an image forming apparatus that does not have the configuration of the process cartridge 4. That is, the photosensitive drum 18, the first cleaning blade 22, and the second cleaning blade 26 described in the present embodiment can be separately installed in the image forming apparatus main body 1 without being integrated.

  Furthermore, the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be appropriately modified within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. Further, the number, position, shape, and the like of the above-described constituent members are not limited to the present embodiment, and the number, position, shape, and the like that are suitable for implementing the present invention can be used.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a process cartridge installed in the image forming apparatus of FIG. 1. FIG. 4 is a partially enlarged view showing a second cleaning blade installed in the image forming apparatus of FIG. 1. It is the schematic which shows the measuring method of the static friction coefficient of a photoconductor drum.

Explanation of symbols

1 image forming apparatus body (apparatus body),
2 Document reading section, 3 Exposure section, 4 Process cartridge,
7 Transfer section 9 Fixing section 10 Document transport section 12-14 Paper feed section
18 Photosensitive drum (image carrier), 18a Surface layer (release layer),
19 charging unit, 20 developing unit, 21 cleaning unit,
22 first cleaning blade, 23, 27 support plate,
24, 28 Spring, 26 Second cleaning blade,
31 Neutralizing unit, 32 Toner replenishing unit, α Contact angle.

Claims (18)

An image carrier on which a surface layer containing a release material that increases the releasability of toner attached to the surface is formed;
A first cleaning blade that abuts on the image carrier and cleans the image carrier;
An image forming apparatus comprising: a second cleaning blade that abuts on the image carrier and further cleans the image carrier cleaned by the first cleaning blade. The release material is a fluorine compound,
2. The image forming apparatus according to claim 1, wherein the surface layer of the image carrier contains a fluorine compound in an amount of 55 to 70% by weight. The image forming apparatus according to claim 1, wherein the second cleaning blade includes an elastic portion made of a rubber material having a rubber hardness in a range of 85 to 95 degrees. The image forming apparatus according to claim 1, wherein the second cleaning blade abuts on the image carrier so as to follow a moving direction of the surface of the image carrier. The image forming apparatus according to claim 4, wherein the second cleaning blade is in contact with the image carrier so that the contact angle is in a range of 5 to 25 degrees. 6. The second cleaning blade abuts on the image carrier so that a contact pressure is in a range of 9.8 to 78.4 N / m. The image forming apparatus described. 7. The toner according to claim 1, wherein the toner has a volume average particle diameter in the range of 3 to 8 [mu] m and a circularity in the range of 0.93 to 0.98. An image forming apparatus according to claim 1. In the toner, a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent is dispersed in an organic solvent is crosslinked and / or in an aqueous medium. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed by an extension reaction. A process cartridge configured to be detachable from the image forming apparatus main body,
An image carrier on which a surface layer containing a release material that increases the releasability of toner attached to the surface is formed;
A first cleaning blade that abuts on the image carrier and cleans the image carrier;
A second cleaning blade that abuts on the image carrier and further cleans the image carrier cleaned by the first cleaning blade;
A process cartridge comprising: 10. The apparatus according to claim 9, further comprising at least one of charging means for charging the image carrier and developing means for developing the latent image formed on the image carrier. Process cartridge according to. The release material is a fluorine compound,
The process cartridge according to claim 9 or 10, wherein the surface layer of the image carrier contains a fluorine compound in an amount of 55 to 70% by weight. The process cartridge according to any one of claims 9 to 11, wherein the second cleaning blade includes an elastic portion made of a rubber material having a rubber hardness in a range of 85 to 95 degrees. The process cartridge according to claim 9, wherein the second cleaning blade abuts on the image carrier so as to follow a moving direction of the surface of the image carrier. 14. The process cartridge according to claim 13, wherein the second cleaning blade contacts the image carrier so that the contact angle is in the range of 5 to 25 degrees. The said 2nd cleaning blade contact | abuts on the said image carrier so that a contact pressure may become the range of 9.8-78.4 N / m, The any one of Claims 9-14 characterized by the above-mentioned. The described process cartridge. 16. The toner according to claim 9, wherein the toner has a volume average particle size in the range of 3 to 8 [mu] m and a circularity in the range of 0.93 to 0.98. The process cartridge according to the above. In the toner, a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent is dispersed in an organic solvent is crosslinked and / or in an aqueous medium. The process cartridge according to claim 9, wherein the process cartridge is formed by an extension reaction. 18. An image forming apparatus comprising the process cartridge according to claim 9 installed in the main body of the image forming apparatus.

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