Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-03-28
2004-06-01
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S097000
Reexamination Certificate
active
06743560
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composition comprising release agent and particulate material, for application to one or both of the fuser member and the substrate in toner fusing systems and processes. The present invention further relates to combating toner marking, by means of applying the composition as indicated to one or both of the fuser member and the substrate in toner fusing systems and processes.
2. Description of Background and other Information
Generally in electrostatographic reproduction, the original to be copied is rendered in the form of a latent electrostatic image on a photosensitive member. This latent image is made visible by the application of electrically charged toner.
The toner thusly forming the image is transferred to a substrate—also referred to as a receiver—such as paper or transparent film, and fixed or fused to the substrate. Where heat softenable toners—for example, comprising thermoplastic polymeric binders—are employed, the usual method of fixing toner to the substrate involves applying heat to the toner, once it is on the substrate surface, to soften it, and then allowing or causing the toner to cool. This application of heat in the fusing process is preferably at a temperature of about 90° C.-220° C.; pressure may be employed in conjunction with the heat.
A system or assembly for providing the requisite heat and pressure customarily includes a fuser member and a support member. The heat energy employed in the fusing process generally is transmitted to toner on the substrate by the fuser member. Specifically, the fuser member is heated; to transfer heat energy to toner situated on a surface of the substrate, the fuser member contacts this toner, and correspondingly also can contact this surface of the substrate itself. The support member contacts an opposing surface of the substrate.
Accordingly, the substrate can be situated or positioned between the fuser and support members, so that these members can act together on the substrate to provide the requisite pressure in the fusing process. In cooperating, preferably the fuser and support members define a nip, or contact arc, in which the substrate is positioned or resides, and/or through which the substrate passes. Also as a matter of preference, the fuser and support members are in the form of fuser and pressure rollers, respectively. Yet additionally as a matter of preference, one or both of the fuser and support members have a soft layer that increases the nip, to effect better transfer of heat to fuse the toner.
During the fusing process toner can be offset from the substrate to the fuser member. Toner thusly transferred to the fuser member in turn may be passed on to other members in the electrostatographic apparatus, or to subsequent substrates subjected to fusing.
Toner on the fusing member therefore can interfere with the operation of the electrostatographic apparatus and with the quality of the ultimate product of the electrostatographic process. This offset toner is accordingly regarded as contamination of the fuser member, and preventing or at least minimizing this contamination is a desirable objective.
Release agents can be applied to fusing members during the fusing process, to combat toner offset. These agents usually are or include polyorganosiloxanes, particularly polyorganosiloxane oils.
U.S. Pat. No. 5,781,840 states that wicking agents may be applied to fuser members to prevent toner offset, and teaches a wicking agent comprising an organopolysiloxane, and at least about 1·10
−6
weight percent of a metal compound. The organopolysiloxane has Si—H functional groups, and the metal compound is effective for promoting reaction between the organopolysiloxane Si—H functional groups, and reactive sites on the fuser member surface.
The metal compound in the wicking agent may comprise a metal salt, and the salt may be complexed with an organic ligand. The fuser member may have a polymeric surface layer comprising inert particulate filler, such as metal oxides like aluminum and tin oxides.
Use of talcum powder as a release agent is also known. U.S. Pat. No. 4,000,957 discusses dispensing this powder either onto the toner and paper before it reaches the fuser roller, or onto the fuser roller itself. Application of talcum powder to the fuser roller is indicated to be either simultaneously with, or subsequent to, application of a liquid release material. Only separate application of talcum powder and liquid release material, each from its own dispenser, is disclosed.
As to the indicated application of powder to toner and paper, this patent teaches use of a dispensing mechanism suitable for dispensing approximately 0.25 milligrams of talcum powder per square centimeter of toner image. This rate of application for particulate material translates into over 4 kilograms of particulate material for every 10,000 copies.
Employment of particulate material at this high a rate is undesirable for high speed copier-printer applications. If particulate material applied at this rate were used in the form of dispersion in a liquid medium, such as a liquid release agent, viscosity would be unacceptably high.
This patent also teaches a preferred size of 0.1 to 10 microns for the talcum powder. Because of this particle size range and the distribution, the stability of the dispersion in carrier media would not be high; particulate accordingly would tend to accumulate in the dispensing mechanism, and affect flow rate.
Once the desired toner-formed image is fixed in its intended location on a substrate, it may be subjected to contact by other surfaces that will cause displacement from the intended location. This displacement may be in the form of smearing and/or transfer to the contacting surface, and can be referred to as toner marking.
For instance, in the case of the substrate being a single sheet, it may be subjected to folding, mailing, or reprinting (either the same side or the back side of the sheet). Where it is one of several or one of hundreds of sheets, the sheets may be processed further by operations including, for example, sorting, binding, insertion of other media, character recognition, and booklet making. Any of these or similar operations can cause the toner-formed image to contact other surfaces and leave an objectionable mark, caused by the relocation of toner from its original place of deposition and fixation. This marking can appear on a variety of locations—e.g., the backside of another sheet, another portion of the same sheet (when folded), or some other surface that would be visible to the intended recipient of the material.
It is known that toner marking can be combated by a number of methods. Among these are including wax additives in the toner, increasing the toughness of the toner, adding release lubricants to the toner surface, and reducing the force of contact causing the toner marking.
In this regard, U.S. Pat. Nos. 4,165,308 and 4,167,602 disclose electrographic recording materials, and coating compositions therefor, to improve toner adhesion and reduce toner smear. U.S. Pat. No. 4,859,550 discloses polymeric alcohols and aliphatic hydrocarbons as additives against toner offsetting and image smearing. U.S. application Ser. No. 09/387,586, filed Aug. 31, 1999, discloses a fuser member having a silicone rubber fusing surface that incorporates a controlled particle size filler; this fuser member maintains a low surface roughness, which reduces the roughness of the fused toner image, thus reducing toner marking. U.S. Pat. No. 5,209,464 discloses a sheet feed apparatus with a scuff feeder device that minimizes high pressure points contributing to toner ruboff.
In modern operations, images may be processed at a later time on unrelated equipment. Accordingly, sheets bearing these images should be able to minimize marking in a variety of paper handling equipment.
As indicated, application of release agents can be employed as a measure against toner offset. These materials, usually in the form of polydimethylsiloxane o
Pickering Jerry A.
Tyagi Dinesh
Wenzel Pauline K.
Goodrow John
Heidelberger Druckmaschinen AG
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