Electrophotography – Cleaning of imaging surface – Including lubricant
Reexamination Certificate
1999-12-28
2001-09-25
Brase, Sandra (Department: 2852)
Electrophotography
Cleaning of imaging surface
Including lubricant
C399S159000
Reexamination Certificate
active
06295437
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This document claims priority and contains subject matter related to Japanese Patent Applications Nos. JPAP10-373816, JPAP11-011380, and JPAP11-021102, filed on Dec. 28, 1998, Jan. 20, 1999, and Jan. 29, 1999, respectively, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image forming apparatuses, such as printers, facsimiles, copiers, and the like, and more particularly relates to an image forming apparatus and method for forming an image using a developing device adopting a contact developing system to develop an electrostatic latent image formed on a latent image bearing member,
2. Discussion of the Background
In an image forming apparatus using an electrophotography, a latent image bearing member is generally formed of a photoconductor and an optical writing operation to form an electrostatic latent image on a uniformly charged photoconductor using a laser light. The electrostatic latent image on the photoconductor is developed by developer. The developed visible image is transferred to a recording medium, such as a recording paper, and then a residual developer on the photoconductor is removed by a cleaning device to prepare the photoconductor for a next charging process, The visible image on the recording medium is fixed thereto by a fixing device. An example of the cleaning device is known, in which residual developer that adheres on a surface of the photoconductor is scraped off by a cleaning blade that is in contact with a surface of the photoconductor.
When a friction coefficient of the surface of the photoconductor is high, the cleaning blade may be dragged by a friction between the surface of the photoconductor and the cleaning blade and therefor the tip end of the cleaning blade contacting the surface of the photoconductor may be turned over in a moving direction of the surface of the photoconductor. Accordingly, a lubricant is applied to the surface of the photoconductor to decrease the friction coefficient of the photoconductor as described in, for example, Japanese Laid-Open Patent Publication No. 8-254993.
The objects to apply the lubricant to the surface of the photoconductor are, in addition to the aforementioned decrease of the friction between the surfaces of the photoconductor and the cleaning blade, as follows:
1. decreasing abrasion of the photoconductor and the cleaning blade; and
2. decreasing a background fouling (adhering of tone to a non-image part of an image area) on the surface of the photoconductor.
As a developing method to visualize the electrostatic latent image on the photoconductor, there is known a contact developing system using component developer including only magnetizable toner or a non-magnetizable toner. In this developing method, such one component-developer is thin layered on a developing roller as a developer bearing member, and the toner is transferred onto the electrostatic latent image on the photoconductor by causing the developing roller to contact a surface of the photoconductor.
When such a contact developing method and the above-described method to supply lubricant to the surface of the photoconductor are combined, advantages including a less toner scattering phenomenon and a good reproduction property of an image can be obtained.
However, when the image is visualized with the above described two methods combined, the following problems occur. First, even when the supplying amount of the lubricant is usually controlled, some of the lubricant may be transferred to the developing roller that contacts the photoconductor. Therefore, this disturbs toner to be uniformly thin layered on the developing roller. Namely, when the lubricant is transferred to the developing roller, the adhering amount of the toner to the developing roller varies over an entire surface of the developing roller depending upon the amount of the transferred lubricant. A toner layer having a predetermined uniform thickness cannot be formed, for example, due to partial lack of the adhering amount of toner on the surface of the developing roller, or the toner may not adhere to the surface of the developing roller at all.
When a thin layer of toner having a predetermined thickness cannot be formed on the developing roller, or when toner does not adhere to the developing roller at all, an abnormal image, such as for example, an image with insufficient density or that including a blank spot may be formed.
Japanese Laid-Open Patent Publication No. 9-73229 also describes a developing method using a one-component developer borne on a developing roller forming a toner layer thereon. The developing roller contacts the photoconductor and the surface of the developing caller moves faster than that of the photoconductor so as to decrease the background fouling. The linear speed of the surface of the developing roller may be 1.2 to 3.0 times faster than that of the photoconductor, and more specifically is desired to be from 1.5 to 2.5 times faster than that of the photoconductor.
Further, Japanese Laid-Open Patent Publication No. 9-274364 describes a developing device that uses developer including a non-magnetizable toner, in which an additive is added to increase the fluidity of the developer, and the developer is borne on a developer bearing member. The developing device conveys the developer to a developing area opposed to a latent image bearing member (a photoconductor). In this developing device, the friction-charge property of the additive relative to the non-magnetizable toner (namely, a property to charge toner by the friction caused between the additive and the toner) is set so as to be approximately equal to that of the developer bearing member, or the friction-charge property of the non-magnetizable toner relative to the additive is greater than that of the developer bearing member relative to the additive.
Japanese Laid-Open Patent Publication No. 6-332215 describes an image forming method, in which a toner image formed on the latent image bearing member is transferred onto a recording medium and a coagulation rate of the toner is 30% or greater. The coagulation rate represents a degree of a coagulation of the toner, which is defined and measured by a measuring method, described, for example, in Japanese Laid-Open patent application No. 7-160033. In addition, the latent image bearing member described in Japanese Laid-Open Patent Publication No. 6-332215 is provided with a transfer-property improving layer at a surface of the latent image hearing member so as to prevent the transfer property from lowering due to using a toner of the relatively high coagulation rate.
In all of the above-described background image forming apparatus, because a photoconductor and a developing roller contact each other via a toner layer, the toner layer accepts a relatively strong electrostatic force caused between the photoconductor and the developing roller. Further, the developer is generally provided with one to three kinds of external additives so that the fluidity of the developer is increased and a good charging stability is realized. Further, the toner that is once moved to the photoconductor from the developing roller in a developing operation is moved back to the developing roller side in the area where the friction coefficient of the surface of the photoconductor is relatively low, for example 0.1 to 0.2 (Such a force to move the toner once moved to the photoconductor back to the developing roller is hereinafter called a scavenging force). This is because the surface of the photoconductor having a relatively low friction coefficient easily releases the toner when the photoconductor and the developing roller contact with each other via the toner layer. A developing performance is therefore lowered, particularly at a low image density area of an image, and a low-density image may appear. In addition, when the developing performance is increased by increasing a developing potential between the photoconductor and the developing
Aoki Katsuhiro
Hodoshima Takashi
Matsumoto Jun-ichi
Brase Sandra
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
LandOfFree
Apparatus and method for forming an image using a developing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for forming an image using a developing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for forming an image using a developing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2545539