Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-05-11
2002-12-10
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108800
Reexamination Certificate
active
06492083
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to release agents, toner particulates and toner compositions. This invention also relates to methods of improving dry fuser release for the prevention of fuser jamming and fuser wrapping, and of methods of improving overhead projection transparencies.
BACKGROUND OF THE INVENTION
Numerous methods and apparatuses for electrophotography, electrostatic recording and electrostatic printing are known in the art. Typically, a charged photosensitive surface, for example a charged photosensitive drum, is irradiated with an optical image and an electrostatic latent image is formed on the photosensitive surface. In the development process, a developing agent, i.e., toner, is adhered to the electrostatic latent image.
Typically, toner is fed to a developer roller by a metering blade positioned against the surface of the developing roller. The developer roller, with the toner on its surface, is typically rotated in a direction opposite to that of the photosensitive drum (or in the same direction at a different speed), and toner adheres to the electrostatic latent image to develop the image. Various toner compositions have been developed in order to provide improved copying, recording and/or printing with such apparatus.
One method of fusing a toner image to a substrate is to bring the toner in contact with a hot surface such as a heated roller. However, there is a tendency for a fuser to collect small amounts of toner which in turn causes toner offset to build up on the fuser surface. This toner may be then transferred to a subsequent substrate, thereby causing a poor image.
The fuser roll surface may be wetted with a release agent such as a silicone oil in order to decrease the problem of toner offset. Unfortunately, the silicone oil release agent may leave oil residues on the paper, thereby interfering with the image quality. Additionally, the release agent material tends to migrate to other surfaces within the printer where it interferes with proper development of the latent image to diminish print quality, especially in the case of duplex printing. Therefore, a dry fuser, that is a fuser without any oil on its surface, is often desirable.
In order to solve the problem of toner offset with dry fusers, lubricants or waxes are often added to the toner. Unfortunately, at high concentrations effective for the purpose of dry fuser release many conventional lubricants tend to separate from the toner during the process of development, and stick to the doctor blade causing a filming problem which adversely affects print quality.
Toner release from dry fusers has been enhanced by modification of toner resin rheology. High molecular weight resins or resins having crosslinks may exhibit improved release. Unfortunately, use of such high molecular weight or crosslinked resins generally results in poor clarity of overhead projection transparencies or in inadequate fuse grade at higher speeds. Generally, high transparency or excellent high speed fuse grade requires lower melt temperature resins or higher fusing temperatures, but such resins or temperatures cause toners to adhere easily to dry fuser rollers. Thus, it is difficult to develop toners for transparencies or lower temperature fusing applications which exhibit good release, good fuse grade and the good transparency needed for reproduction of a large color gamut and for clarity. Generally, in order to maintain good clarity and high speed fuse grade, the lower melt temperature resins used in toners require that a separate release agent be used.
Tomita et al., U.S. Pat. No. 5,225,303, disclose a toner comprising binder resin, coloring agent, and a release agent, which contains as the main components a carnauba wax substantially free of aliphatic acids and/or a montan ester wax, and an oxidized rice wax with an acid value of 10 to 30. Tomita et al. teach that the acid value of the montan ester wax is preferably in the range of from 5 to 14, and that the carnauba wax preferably comprises 5 weight percent or less free aliphatic acids.
Inoue et al., U.S. Pat. No. 5,643,705, disclose a toner comprising a toner particulate containing a polyolefin wax and a modified polyolefin wax. Inoue et al. disclose the polyolefin wax is a low number-average molecular weight polyethylene or low number-average molecular weight polypropylene having a softening point of from 80° C. to 160° C., and that the modified polyolefin wax is mainly composed of low number-average molecular weight polyethylene, wherein the modifying component used to modify the polyolefin wax is an aromatic vinyl monomer, an acrylate monomer, an unsaturated dicarboxylic acid ester or a mixture thereof.
Taguchi et al., U.S. Pat. No. 5,466,555, disclose a releasing composition comprising 60 to 99.5% by weight of a low molecular weight polypropylene having a melt viscosity of 15 to 2,000 cps at 160° C., and 0.5 to 40% by weight of at least one modified polyolefin selected from the group consisting of low molecular weight polypropylene having a melt viscosity at 160° C. higher than that of the first polypropylene, modified with an ethylenically unsaturated carboxylic acid or an anhydride thereof, and a modified polyethylene comprising a low molecular weight polypropylene having a melt viscosity of 10 to about 8,000 cps at 1 40° C., modified with an ethylenically unsaturated carboxylic acid or an anhydride thereof.
Katada et al., U.S. Pat. No. 5,972,553, disclose a toner comprising polymer components, a colorant, a charge control agent, and a wax terminally modified with at least one of maleic acid, maleic acid half ester, or maleic anhydride. Katada et al. teach that the polymer components include a low molecular weight polymer component having an acid value A
vl
and a high molecular weight polymer component having an acid value A
vh
such that A
vl
is greater than Avh. Katada et al. further teach that the wax has an acid value A
vwax
satisfying A
vl
>A
vwax
, and A
vwax
>0 mg KOH/g, and that the wax may have an acid value of 1 to 15.
Unfortunately, many prior art toner compositions comprise large amounts of release agents such as waxes, and such large amounts tend to interfere with print quality. Other prior art toners comprising waxes have a poor fuse grade, that is, the print is not resistant to abrasion and may be abraded or scraped off. Some waxes, such as polyolefin waxes, tend to migrate to the photoreceptor causing poor print quality, or causing staining of the photoreceptors. Further, many color toners which contain release agents fail to exhibit both good release and the good transparency needed for reproduction of a large color gamut and for clarity.
In the pursuit of high quality, vibrantly colored overhead transparencies, it has been discovered that the achievement of this goal through electrophotography is dependent not only upon the inherent transparency of the binder resin, but upon the release/transparency (r/t) window of said binder resin. The r/t window of a toner is defined as that range of temperatures in which a toner is sufficiently fused to produce a bright, colorful image when projected and where it releases cleanly from the fuser hot roll. This window is the cross section of the independent release and transparency windows. Each resin system has its own characteristic cross section. “Release” refers to the tendency of a developed image to wrap the fuser roll upon nip exit at a given temperature. The release window is a range of temperatures bounded at the low end by cold offset and at the high end by fuser adhesion or hot offset. “Transparency” refers to the ability of a toner to transmit light without scatter. The transparency window can be measured by evaluating the percentage transmitted light through a sample that has been fused at a given temperature. It is a range of temperatures bounded by low fuse grade, characterized by muddy projected color, and hot offset, where the rough toner surface begins to scatter light. The overlap of the release range and the transparency range of a given toner at a specific mass per
Livengood Bryan P.
Morris Michelle K.
Olson John M.
Walsh Jodi P.
Zartman Franklin D.
Brady John A.
Lexmark International Inc.
Rodee Christopher
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