Patent Application
20080219714
The exemplary embodiments are directed to an electrostatic image transfer apparatus, and a system and a method of transferring electrostatic images in an imaging device.
Electrostatic imaging and printing processes are comprised of several distinct stages. These stages may generally be described as (1) charging, (2) imaging, (3) exposing, (4) developing, (5) transferring, (6) fusing and (7) cleaning. In the charging stage, a uniform electrical charge is deposited on a charge retentive surface, such as, for example, a surface of a photorecentor, so as to electrostatically sensitize the surface.
Imaging converts an original, or digital image into a projected image on the surface of the photoreceptor and the image is then, exposed upon the sensitized photoreceptor surface. An electrostatic latent image is thus recorded on the photoreceptor surface corresponding to the original, or digital image.
Development of the electrostatic latent image occurs when charged toner particles are brought into contact with this electrostatic latent image, The charged toner particles will be attracted to either the charged or discharged regions of the photoreceptor surface that correspond to the electrostatic latent image, depending on whether a charged area development (CAD) or discharged area development (DAD, more common) is being employed.
In the case of a single step transfer process, the photoreceptor surface with the electrostatically attracted toner particles is then brought into contact with an image receiving surface, i.e., paper or other similar substrate. The toner particles are imparted to the image receiving surface by a transferring process wherein an electrostatic field attracts the toner particles towards the image receiving surface, causing the toner particles to adhere to the image receiving surface rather than to the photoreceptor. The toner particles then fuse into the image receiving surface by a process of melting and/or pressing. The process is completed when the remaining toner particles are removed or cleaned from the photoreceptor surface.
Hence, in the related art, electrostatic imaging and printing processes occur on the charge retentive surface, e.g., photoreceptor, as shown in
It would be advantageous to provide an imaging device that maintains, enhances or improves the quality of prints and the speed of printing, and extends the life expectancy of the photoconductive layer. To address or accomplish these advantages, advantages described below, and/or other advantages, the exemplary embodiments may include at least one module including a photoreceptor assembly, an intermediate transfer assembly adjoining the photoreceptor assembly, a developer assembly disposed adjacent to the intermediate transfer assembly, a cleaning assembly positioned adjacent to the intermediate transfer assembly, and a toner image transfer assembly located distally from the photoreceptor assembly, the toner image transfer assembly and the photoreceptor assembly being interposed by the intermediate transfer assembly. More specifically, the exemplary embodiments may include an electrostatic imaging device having a photoreceptor on which an electrostatic latent image is created, and may have a separate intermediate charge receptive device with developer station, transfuser station, cleaning station and/or other devices operated in conjunction with this separate intermediate charge receptive device such that these functions are removed from the photoreceptor surface.
Exemplary embodiments are described herein with respect to architectures for xerographic or electrophotographic print engines. However, it is envisioned that any imaging device that may incorporate the features of the electrostatic imaging apparatus described herein are encompassed by the scope and spirit of the exemplary embodiments.
The exemplary embodiments are intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the devices, methods and systems as defined herein.
For an understanding of the system, method and apparatus for electrostatic image transfer reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate similar or identical elements. The drawings depict various embodiments of illustrative electrophotographic printing machines incorporating the features of the exemplary embodiments therein. As shown, the drawings schematically depict the various components of electrophotographic printing machines that have the various features. In as much as the art of electrophotographic printing is well known, the various processing stations employed in the printing machines will be schematically shown herein and their operation described with reference thereto.
Referring now to
Photoreceptor assembly 106 includes a charge unit 108 and a photoreceptor 110. The photoreceptor 110 is illustrated in the shape of a roll. However, the photoreceptor 110 may alternatively be a belt, in any shape, or constitute any known or later developed device that may be electrostatically charged so that it may carry and transfer an electrostatic image, as discussed in more detail below. In the embodiment of
Similarly, the charge unit 108 is mounted rotatably on a carriage (not shown) that translates with the photoreceptor 110 so as to charge successive portions of a photoconductive layer 112 of the photoreceptor 110 to a relatively high, substantially uniform potential. While the charge unit 108 is depicted as a bias charging roll, alternatively this could be replaced by other charge devices such as a stationary charge corotron or scorotron device.
The photoreceptor 110 continues to rotate progressing the uniformly charged regions of the photoconductive layer 112 toward the region of the exposure system 107, which interacts with the photoconductive layer 112. The charged portion of the photoconductive layer 112 may be illuminated by a light image front an exposure system 107 thereby selectively discharging the charged portion of the photoconductive layer 112 so as to form an electrostatic latent image thereon. This latent image is carried on the surface of the photoreceptor 110 to the intermediate transfer assembly 140.
The intermediate transfer assembly 140 may include a transfer belt 142 and transfer rolls 148a-d that may be biased. The transfer belt 142 may be disposed so as to be supported by the biased transfer rolls 148a-d. As shown in
The transfer belt 142 and the photoconductive layer 112 of the photoreceptor 110 form an electrostatic image transfer nip 143. A myriad of configuration options for a region of the electrostatic image transfer nip 143 may be used. This may include conductive or semiconductive backed dielectric layers on the transfer belt 142 with pressure application or dielectric layers with biasing devices applied for field application to promote charge transfer. The transfer rolls 148a-b may be differentially biased so as to tailor the electrostatic field applied in this nip formed between the transfer belt 142 and the photoconductive layer 112, thereby achieving optimal conditions for electrostatic image transfer. Electrostatic image transfer is known to produce latent image resolution retention as high as 90 lines per millimeter and is thus capable of high image fidelity generation/retention. In an alternative embodiment, dimensions and torque loading of the photoreceptor roll can be minimized, and thus friction may drive the photoreceptor roll with the transfer belt 142, which may alleviate registration concerns in the nip region. The transfer belt 142 may have electrical properties that enable varied electrostatic fields about its circumferential working surface and may have a conductive layer or, in an alternative embodiment, a semiconductive layer. In yet another alternative embodiment, the transfer belt 142 may be constricted of a belt material selected to provide electrically relaxable properties whereby electrostatic fields are imparted by backing rolls, corresponding transfer or developer rolls or a cleaning device.
As the photoconductive layer 112 having a latent image retained thereon translates through nip region 143, the latent image may be transferred to the transfer belt 142 of the intermediate transfer assembly 140, which is disposed remotely from the photoreceptor 110. As the transfer belt 142 translates, the latent image carried thereby may be passed to an area of the development assembly 120.
Charged toner particles may be deposited by the development assembly 120 in a charged area of the image on the transfer belt 142 to define a visible toned image that corresponds to the latent image. The toned image may thus be defined on the transfer belt 142 in an area not in contact with the photoconductive layer 112 to reduce, minimize, and/or eliminate contact of the photoconductive layer 112 with the development assembly 120. Alternatively, toner charge polarity and biasing schemes may be employed to result in a toned region corresponding to the non-charged regions of the transfer belt 142.
The toner image may then be carried by the transfer belt 142 to an area of the toner image transfer assembly 160. The toner image transfer assembly 160 may include a toner image transfer belt 162 and at least one transfer roller 166. The toner image transfer belt 162 is constructed for the carriage of media, such as, for example, paper, or any other medium that can carry an image, not shown in
In an alternative embodiment, transfer roller 166 could be a heated fuser roll for thermally transferring the toner to the paper. Additionally, one of transfer rolls 148a-d located proximally to heated transfuse roll 166, such as transfer roll 148d shown in
Pressure and heat applied to the toner and media at the transfuse nip 115 by the transfer roll 148d and the transfer roller 166 may assist in transferring the image from the transfer belt 142 to the medium. In one embodiment, a post fusing step may be employed to increase or decrease gloss level, fix level or adjust other properties of the fused images. Following the transfer of toner particles from transfer belt 142 to the medium carried by toner image transfer belt 162, transfer belt 142 translates to pass a region of the cleaning assembly 130. Additionally, thermal control devices could be included to maintain transfer belt temperatures throughout the subsequent processes.
Cleaning assembly 130 may, for example, be a wiper blade or brush or other device that cleans any residual toner, paper fibers and/or debris, etc., from the transfer belt 142. In an alternative embodiment, a cleaning assembly and means for erasing charge, currently known or later developed, may be arranged around photoreceptor 110.
Referring now to
In yet another alternative embodiment, toner may be transferred directly to intermediate belt 162 in successive applications of toner that may have varying pigment. The multi-pigment image may then be transferred to media via the nip formed with the belt 162 and the roll 202. Such a configuration could also employ alternative transfer or transfuse configurations. For example, such configurations could accommodate electrostatic transfer from transfer belt 142 to toner image transfer belt 162 and subsequent electrostatic transfer to media from toner image transfer belt 162. Alternatively, the subsequent transfer from the toner image transfer belt 162 could be by heat and pressure transfer to media. Yet a further embodiment could employ heat and pressure transfer from the transfer belt 142 to the toner image transfer belt 162 and subsequent heat and pressure transfer from the toner image transfer belt 162 to media.
For example, as discussed above with respect to the embodiment of
The photoconductive layer 112 having the latent image thereon translates through the nip region 143 defined by the photoconductive layer 112 and the transfer belt 142 of the intermediate transfer assembly 140. Here, the latent image is transferred to the transfer belt 142. Once the latent image is carried by the transfer belt 142, the latent image may then be developed and then transfused to a medium that serves as output. According to the exemplary embodiments, the developing and the transfusing of the image is conducted on the surface of the transfer belt 142. Thus, the photoreceptor, with the photoconductive layer 112, is not subject to the developing and transfusing process. Similarly, the cleaning of excess toner, paper fibers, and/or other debris, occurs at the transfer belt 142, which further protects the photoconductive layer 112 of the photoreceptor from excessive use and damage.
According to the embodiment of
In yet another embodiment, the medium, such as paper, may be subject to duplex printing. That is, after the appropriate single color, or multicolor image is transferred to the medium, the medium may be flipped and transferred again to the toner image transfer assembly such that images are produced on both sides of the medium.
Referring to
The intermediate transfer assembly may include, for example, a transfer belt, a transfer drum, or other device constructed to accommodate receipt of the electrostatic latent image from the photoreceptor, as discussed above. The latent image may then be developed, away from the photoconductive layer as shown in development step S3, to produce a toned image. The development step may include application of a toner complex via electrostatic forces to the latent image. The toned image may then be transferred to media, as shown in transfuse step S4, by way of, for example, a transfuse process as discussed above, which is disposed a distance from the photoconductive layer. The transfuse step may include heat assisted mechanical transfer of the toned image to media carried by the toner image transfer belt.
The transfusion of the toned image from the transfer belt to the media is accomplished a distance away from the photoreceptor to guard or protect the photoconductive layer from the heat and pressure used to transfuse the image to the media. In an exemplary embodiment, the distance between the photoreceptor and the toner image transfer assembly is at least as long as the intermediate transfer assembly disposed between the photoreceptor and the toner image transfer assembly.
An alternative embodiment may include a transfer belt arranged about an electrostatic charge roll that would apply pressure in and electrical bias to the back side of the media, imparting an electrostatic field which would then attract the charged toner particles toward the media surface. The intermediate transfer assembly may then be cleaned, as shown in cleaning and erasing step S5.
The cleaning and erasing of the intermediate transfer assembly includes cleaning the transfer belt 142 with a brush, blade, or any other device that removes excess unused toner, paper fibers, debris and the like from the transfer belt 142. The cleaning of the transfer belt 142 occurs a distance from the photoconductive layer 112 and photoreceptor 110 to reduce and/or minimize wear and use of the photoconductive layer. For example, the transfer belt 142 may be cleaned following the transfuse step S4 near the toner image transfer assembly 160, or in any area between the toner image transfer assembly 160 and photoreceptor 110, preferably a distance from the photoreceptor 110.
After the cleaning and erasing step S5, the transfer belt may be used again and the process repeated.
Referring to
The intermediate transfer assembly may include, for example, a transfer belt constructed to accommodate receipt from the photoreceptor 110 of the electrostatic latent image, as discussed above. The latent image in may then be developed, away from the photoconductive layer, to produce a toned image. The development step may include application of a toner complex via electrostatic forces. The toned image may then be transferred to media by way of a transfuse process as discussed above, in which the transfuse step occurs a distance away from the photoconductive layer. The transfuse may include heat and/or pressure assisted mechanical transfer of the toned image to media carried by the toner image transfer belt 162.
The transfusion of the toned image from the transfer belt to the media is accomplished a distance away from the photoreceptor to guard or protect the photoconductive layer from the heat and pressure used to transfuse the image to the media. In an exemplary embodiment, the distance between the photoreceptor 110 and the toner image transfer assembly 160 is at least as long as the intermediate transfer assembly disposed between the photoreceptor 110 and the toner image transfer assembly 160.
An alternative embodiment may include a toner image transfer belt arranged about an electrostatic charge roll that would apply pressure and electrostatic fields via an applied bias to the back side of the media, which would then attract the charged toner particles toward the media surface. The intermediate transfer assembly may then be cleaned.
The cleaning and erasing of the intermediate transfer assembly includes cleaning the transfer belt 142 with a brush, blade, or any other device that removes residual toner, paper fibers, debris and the like from the transfer belt 142. The cleaning of the transfer belt 142 occurs a distance from the photoconductive layer 112 and photoreceptor 110 to reduce and/or minimize wear and use of the photoconductive layer. For example, the transfer belt 142 may be cleaned following the transfuse step S4 near the toner image transfer assembly 160, or in any area between the toner image transfer assembly 160 and photoreceptor, and a distance away from the photoreceptor. In an alternative embodiment, a cleaning assembly 130 and means for erasing charge could be arranged around photoreceptor 110.
After the cleaning and erasing step S5, the transfer belt may be used again and the process repeated.
Following application of a toner image to media by a first module, the media may then be carried to a second module. As shown in the toner transfer step of T3, a toner image produced by the method discussed above and having different pigment than that of the toner image in step T2 is applied to the media by the second module. The toner images on the media are applied in an aligned manner to produce a multicolor image. The method of
For purposes of explanation, in the above description, numerous specific details were set forth in order to provide a thorough understanding of the image transfer method, system and apparatus. It will be apparent, however, to one skilled in the art that image transfer as described above can be practiced without the specific details. In, other instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the image transfer method, system and apparatus described.
While image transfer has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, embodiments of the method, system and apparatus as set forth herein are intended to be illustrative, not limiting. There are changes that may be made without departing from the spirit and scope of the exemplary embodiments.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, and are also intended to be encompassed by the following claims.
