Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2003-01-22
2004-12-14
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S109400
Reexamination Certificate
active
06830860
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is generally directed to toner compositions and processes thereof, and more specifically, to toner compositions comprised of a mixture of a crystalline resin, a branched amorphous resin, a colorant and optionally a wax. More specifically, in embodiments of the present invention, there is disclosed a toner composition with a low fixing temperature of from about 90° C. to about 110° C., and which toner is comprised of a colorant, such as a pigment, a crystalline resin such as an alkali sulfonated polyester, and a branched amorphous resin such as a branched alkali sulfonated polyester resin. Also, in embodiments, the present invention is directed to a process for generating low fixing toners, and which process is comprised of coalescing a mixture of colorant dispersion, a crystalline polyester emulsion and a branched amorphous polyester emulsion, and optionally a wax emulsion with a coagulant, such as zinc acetate or magnesium chloride, at a temperature of from about 60° C. to about 85° C.; a process for preparation of low fixing toners comprised of melt mixing a crystalline sulfonated polyester resin and a branched amorphous sulfonated polyester resin, followed by emulsification in water of the resulting melt mixed resin, and then by the addition of a colorant dispersion, optionally a wax emulsion and a coagulant, such as zinc acetate or magnesium chloride, and heating at a temperature of from about 60° C. to about 85° C.; a process for generating low fixing toners, and which process is comprised of melt mixing or kneading a crystalline resin, a branched amorphous resin, a colorant and optionally a wax, followed by grinding, pulverizing the mixture to provide toner particles, and classification.
Crystalline and branched resins are known; for example, crystalline refers to a polymer with a 3 dimensional order, and branched refers to a polymer with chains linked to form a crosslinked network.
Xerographic toners of a resin, a pigment, and a charge control agent are known. Toners useful for xerographic applications should exhibit certain performances related to storage stability, and particle size integrity, that is, it is desired to have the particles remain intact and not agglomerate until they are fused on paper. Since environmental conditions vary, the toners also should not substantially agglomerate up to a temperature of from about 50° C. to about 55° C. The toner composite of resins and colorant should also display acceptable triboelectrification properties which vary with the type of carrier or developer composition. A valuable toner attribute is the relative humidity sensitivity ratio, that is, the ability of a toner to exhibit similar charging behavior at different environmental conditions such as high humidity or low humidity. Typically, the relative humidity of toners is considered as the ratio between the toner charge at 80 percent humidity divided by the toner charge at 20 percent humidity. Acceptable values for relative humidity sensitivity of toner vary, and are dependant on the xerographic engine and the environment. Typically, the relative humidity sensitivity ratio of toners is expected to be at least 0.5 and preferably 1.
Another important property for xerographic toner compositions is its fusing properties on paper. Due to energy conservation measures, and more stringent energy characteristics placed on xerographic engines, such as on xerographic fusers, there has been exerted pressure to reduce the fixing temperatures of toners onto paper, such as achieving fixing temperatures of from about 90° C. to about 110° C., to permit less power consumption and allowing the fuser system to possess extended lifetimes. For noncontact fuser, that is a fuser that provides heat to the toner image on paper by radiant heat, the fuser usually is not in contact with the paper and the image. For contact fuser, that is a fuser which is in contact with the paper and the image, the toner should not substantially transfer or offset onto the fuser roller, referred to as hot or cold offset depending on whether the temperature is below the fixing temperature of the paper (cold offset), or whether the toner offsets onto a fuser roller at a temperature above the fixing temperature of the toner (hot offset). Another desirable characteristic is sufficient release of the paper image from the fuser roll; for oil containing fuser rolls, the toner composites may not contain a wax, however, for fusers without oil on the fuser (usually hard rolls), the toner composites will usually contain a lubricant like a wax to provide release and stripping properties. Thus, a toner characteristic for contact fusing applications is that the fusing latitude, that is the temperature difference between the fixing temperature and the temperature at which the toner offsets onto the fuser, should be from about 30° C. to about 90° C., and preferably from about 50° C. to about 90° C. Additionally, depending on the xerographic applications, other toner characteristics may be desired, such as providing high gloss images, such as from about 60 to about 80 Gardner gloss units, especially in pictorial color applications. Other toner characteristics relate to nondocument offset, that is, the ability of paper images not to transfer onto adjacent paper images when stacked up, at a temperature of about 55° C. to about 60° C.; nonvinyl offset properties; high image projection efficiency when fused on transparencies, such as from about 75 to 100 percent projection efficiency and preferably from about 85 to 100 percent projection efficiency. The projection efficiency of toners can be directly related to the transparency of the resin utilized, and clear resins are desired.
Additionally, small sized toner particles, such as from about 3 to about 12 microns, and preferably from about 5 to about 7 microns, are desired, especially in xerographic engines wherein high resolution is a characteristic. Toners with the aforementioned small sizes can be economically prepared by chemical processes, also known as direct or “In Situ” toner process, and which process involves the direct conversion of emulsion sized particles to toner composites by aggregation and coalescence, or by suspension, microsuspension or microencapsulation processes.
REFERENCES
Toner composites are known, such as those disclosed in U.S. Pat. No. 4,543,313, the disclosure of which is totally incorporated herein by reference, and wherein there are illustrated toner compositions comprised of a thermotropic liquid crystalline resin with narrow melting temperature intervals, and wherein there is a sharp decrease in the melt viscosity above the melting point of the toner resin particles, thereby enabling matte finishes. The aforementioned toners of the '313 patent possess sharp melting points and can be designed for non-contact fusers such as Xenon flash lamp fusers generating 1.1 microsecond light pulses. For contact fusing applications, sharp melting materials can offset onto the fuser rolls, and thus the toners of the '313 patent may possess undesirable fusing latitude properties.
In U.S. Pat. No. 4,891,293, there are disclosed toner compositions with thermotropic liquid crystalline copolymers, and wherein sharp melting toners are illustrated. Moreover, in U.S. Pat. No. 4,973,539 there are disclosed toner compositions with crosslinked thermotropic liquid crystalline polymers with improved melting characteristics as compared, for example, to the thermotropic liquid crystalline resins of the '313 or '293 patents.
Furthermore, it is known that liquid crystalline resins may be opaque and not clear, and hence such toners are believed to result in poor projection efficiencies. The toners of the present invention in contrast are comprised of a crystalline resin with sharp melting characteristics, and a branched resin with a broad molecular weight, and wherein there are permitted fusing characteristics, such as lower fixing temperatures of from about 90° C. to about 110° C. and a broad fusing latitude of from ab
Mahabadi Hadi K.
Mayer Fatima M.
McAneney T. Brian
Sacripante Guerino G.
Zwartz Edward G.
Chapman Mark A.
Xerox Corporation
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