Electrophotography – Image formation – Development
Reexamination Certificate
1999-11-29
2001-05-15
Grainger, Quana M. (Department: 2852)
Electrophotography
Image formation
Development
C399S249000
Reexamination Certificate
active
06233420
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to image reproducing systems, and more particularly relates to electrostatic latent image formation and development systems for enhancing latent image development.
Conventional electrostatographic copying and printing systems selectively charge and expose a photoreceptive member in an image-wise manner. This generates an input electrostatic latent image on the receiving member. The latent image is subsequently developed into a visible image by depositing charged development material on the surface of the receiving member. The developing material typically comprises carrier granules having marking or toner particles that electrically adhere to the latent image. The developed image is subsequently transferred, either directly or indirectly, from the receiving member to a copy substrate, such as paper or the like.
The above-described electrostatographic printing process is well known and has been implemented in various forms in the marketplace. Analogous processes also exist in other electrostatic printing applications, such as, for example, ionographic printing and reproduction where a charge is deposited in an image-wise configuration on a dielectric charge retentive surface, as well as in other electrostatic printing systems where a charge carrying medium is adapted to carry an electrostatic latent image.
In the foregoing electrostatographic printing processes, a development material, such as a toner cake, can be applied to the receiving member. The image quality in the printing process varies significantly due to numerous conditions affecting latent image formation on the toner cake as well as development of the image formed thereon. For example, the presence of excess fluid in the toner cake or the application of a relatively thick toner cake layer on the receiving member decreases image quality by exacerbating image “blooming” problems that are generally prevalent during copying. Moreover, the appropriate amount of fluid and the thickness of the toner cake necessary to promote relatively good image development is generally incompatible with the thickness and fluid content of the toner cake layer required for proper and adequate image separation and development.
An example of a prior ionographic image development system for creating a latent image in a toner layer on a support member is disclosed in U.S. Pat. No. 5,966,570, the contents of which are herein incorporated by reference. The system employs a charging device for directing a charge stream, which corresponds to the latent image, at the support member. The charge stream leads to image-wise charging of the toner layer, such that the toner layer becomes the latent image carrier. The toner layer is subsequently developed and transferred to a copy substrate.
An example of a prior image development system for creating a latent image in a toner layer on a support member is disclosed in U.S. Pat. No. 5,826,147, the contents of which are herein incorporated by reference. In this system, the support member is a photoreceptive member rather than a charge retentive member. Similar to the ionographic system, the present system can form a latent image in a layer of marking material on the photoreceptive member. A wide beam ion source is employed for directing free mobile ions at the support member. The latent image causes the free mobile ions to flow in an image-wise ion stream corresponding to the latent image. The ion stream leads to image-wise charging of the toner layer, such that the toner layer becomes the latent image carrier. The toner layer is subsequently developed and transferred to a copy substrate.
SUMMARY OF THE INVENTION
The present invention provides for an imaging system that employs structure, such as a fluid regulating device, to adjust the fluid content of a toner cake in order to reduce image blooming and enhance image quality and resolution. The fluid regulating device also adjusts the fluid content of the toner cake such that the fluid content of the toner cake is compatible with image separation and development, while concomitantly allowing the use of a thinner and more highly concentrated toner cake during the image formation process.
The imaging system of the present invention includes a toner cake applicator for applying toner cake onto a toner cake receiving member, a charging device disposed so as to form an electrostatic latent image in the toner cake, a separation subsystem positioned relative to the receiving member so as to selectively separate at least a portion of the imaged toner cake from the receiving member, and a fluid regulating device for regulating the amount of fluid in the toner cake.
According to one aspect, the fluid regulating device is adapted to adjust the amount of fluid present in the toner cake or in the separation subsystem so as to adjust the toner particle concentration in the toner cake. For example, the fluid regulating device is adapted to increase the concentration of toner particles in said toner cake by adjusting the amount of carrier fluid to promote or optimize the separation of the imaged toner cake from the receiving member.
According to another aspect, the toner cake applicator is adapted to apply a generally thin layer of toner cake to the receiving member. The toner cake has a selected concentration of toner particles for reducing image blooming. For example, the concentration of toner particles applied to the receiving member is higher than a concentration of toner particles employed to separate the imaged toner cake from the receiving member.
According to another aspect, the imaging system of the present invention further includes an imaging device positioned so as to apply an electrostatic latent image onto the receiving member prior to the application of the toner cake. The imaging device can include an image exposure station.
According to another aspect, the separation subsystem is adapted to receive at least a portion of the toner cake from the receiving member and for transferring at least a portion of the toner cake to a substrate. The separation subsystem includes an image bearing member for receiving a portion of the toner cake from the receiving member.
According to another aspect, the receiving member and the image bearing member are positioned relative to each other to form a nip therebetween for transferring at least a portion of the toner cake from the receiving member to the image bearing member. The fluid regulating device can be positioned to regulate the amount of fluid in the toner cake at the nip.
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Liu Chu-heng
Till Henry R.
Grainger Quana M.
Lahine & Cockfield, LLP
Xerox Corporation
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