Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-03-07
2001-11-20
Dote, Janis L. (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108240, C430S108300, C430S109400, C430S111400, C399S267000
Reexamination Certificate
active
06319647
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to toners, developers containing the toners, and a method of forming images with the developers utilizing a magnetic brush development system. More in particular, the invention relates to toners and developers having carefully controlled properties to provide superior print quality when used in developing electrostatic images with a magnetic brush development system.
2. Description of Related Art
U.S. Pat. No. 5,545,501 describes an electrostatographic developer composition comprising carrier particles and toner particles with a toner particle size distribution having a volume average particle size (T) such that 4 &mgr;m≦T≦12 &mgr;m and an average charge (absolute value) pro diameter in femtocoulomb/10 &mgr;m (C
T
) after triboelectric contact with said carrier particles such that 1 fC/10 &mgr;m≦C
T
≦10 fC/10 &mgr;m characterized in that (i) said carrier particles have a saturation magnetization value, M
sat
, expressed in Tesla (T) such that M
sat
≧0.30 T, (ii) said carrier particles have a volume average particle size (C
avg
) such that 30 &mgr;m≦C
avg
≦60 &mgr;m, (iii) said volume based particle size distribution of said carrier particles has at least 90% of the particles having a particle diameter C such that 0.5 C
avg
≦C≦2 C
avg
, (iv) said volume based particles size distribution of said carrier particles comprises less than b % particles smaller than 25 &mgr;m wherein b=0.35×(M
sat
)
2
×P with M
sat
: saturation magnetization value, M
sat
, expressed in T and P: the maximal field strength of the magnetic developing pole expressed in kA/m, and (v) said carrier particles comprise a core particle coated with a resin coating in an amount (RC) such that 0.2% w/w≦RC≦2% w/w. See the Abstract. This patent describes that such developer achieves images of offset-quality in systems in which a latent image is developed with a fine hair magnetic brush. See column 4, lines 7-17 in said patent.
XEIKON NV currently supplies the market with developers from AGFA for magnetic brush development systems. These developers are comprised of toner and carrier particles. The toner is believed to be comprised of pigments and two polyesters, a propoxylated bisphenol-A, hexanedioic acid, isophthalic acid polyester and an ethoxylated bisphenol-A ethylene glycol, isophthalic acid, terephthalic acid polyester, while the carrier is believed to be comprised of an iron-zinc-copper oxide core coated with a crosslinked siloxane. However, such developers suffer from lower triboelectric stability and image quality stability, and insufficient color gamut.
What is still desired is a set of developers comprised of toners and carriers that possess a combination of properties such that when used to develop a latent image on the surface of a photoreceptor with a magnetic brush, the color image produced in this xerographic manner exhibits a very high quality, improved in most properties over conventional magnetic brush toners and developers.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a set of color toners and developers each having a set of properties such that the developers containing such toners along with carrier particles can achieve images having high quality when formed with a magnetic brush system. It is a further object of the invention to obtain toners and developers having superior triboelectric and image quality stability.
It is a still further object of the invention to develop suitable carriers for use in combination with the toners in order to obtain two component developers possessing the desired properties.
It is a still further object of the invention to form images utilizing a magnetic brush with the developers of the invention, which images have superior quality compared to conventional magnetic brush developers.
These and other objects are achieved in the present invention by a toner comprising toner particles comprised of at least one binder, at least one colorant, and optionally one or more additives, wherein following triboelectric contact with carrier particles, the toner has a charge per particle diameter (Q/D) of from 0.6 to 0.9 fC/&mgr;m and a triboelectric charge of from 20 to 25 &mgr;C/g, wherein the toner melt viscosity at 100° C. ranges from 35,000 to 70,000 poise, and wherein the toner particles have an average particle diameter of from 7.8 to 8.3 microns. These objects are also achieved by a toner comprising toner particles comprised of at least one binder comprising a propoxylated bisphenol A fumarate resin containing gel for cyan, magenta and black toners but not containing gel for yellow toner, at least one colorant comprising pigment selected from the group consisting of cyan, yellow, magenta and black, and at least one external additive comprising one or more of silicon dioxide powder, untreated titanium dioxide powder or zinc stearate powder.
A developer comprising the toner particles in combination with carrier particles such that the developer has an A
T
of from 300×10
−2
&mgr;C/g to 500×10
−2
&mgr;C/g also achieves the objects of the invention. Finally, the invention also relates to an electrostatographic image forming apparatus comprising a photoreceptor, a magnetic brush development system, and a housing in association with the magnetic brush development system and containing the foregoing developer.
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R. J. Nash, and J. T. Bickmore, “Toner Impaction and Triboelectric Aging”, 4thInternational Congress on Advances in Non-Impact Printing Technology, R. J. Nash, ed., IS&T, Springfield, VA, pp. 113-126 (1988).
E.J. Gutman and G. C. Hartmann, Journal of Imaging Science and Technology, vol. 36, No. 4, Jul./Aug. 1992, pp. 335-349.
Ferguson Barbara M.
Gutman Edward J.
Dote Janis L.
Oliff & Berridg,e PLC
Palazzo Eugene O.
Xerox Corporation
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