Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-09-27
2004-11-30
Goodrow, John L (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, C430S111410, C430S045320
Reexamination Certificate
active
06824942
ABSTRACT:
BACKGROUND
This invention relates to toners, developers containing toners, processes thereof, and methods for generating developed images with, for example, offset-like print quality. More specifically, in embodiments thereof the present invention relates to toners and developers with, for example, controlled properties that provide offset-like print quality when used in developing electrostatic images with, for example, a device containing a hybrid scavengeless development system, and wherein calcium stearate is selected as a toner additive.
The toners and developers of the present invention can be selected for a number of electrophotographic marking processes including color processes. One type of color electrophotographic marking process, referred to as image-on-image (IOI) processing, superimposes toner powder images of different color toners onto the photoreceptor prior to the transfer of the composite toner powder image onto the substrate. While the IOI process provides a number of benefits, such as a compact architecture, there can be several challenges to its successful, implementation. For instance, the viability of printing system concepts, such as IOI processing, can require development systems that do not interact substantially with a previously toned image. Since several known development systems, such as conventional magnetic brush development and jumping single-component development, interact with the image on the receiver, a previously toned image will be scavenged by subsequent development if interacting development systems are used. Thus, for the IOI process, there is a need for scavengeless or noninteractive development systems, and which need is achievable with the toners and developers of the present invention.
Hybrid scavengeless development (HSD) technology develops toner via a conventional magnetic brush onto the surface of a donor roll. A plurality of electrode wires is closely spaced from the toned donor roll in the development zone. An AC voltage is applied to the wires to generate a toner cloud in the development zone. This donor roll generally comprises a conductive core covered with a thin, for example about 50 to about 200 &mgr;m, partially conductive layer. The magnetic brush roll is held at an electrical potential difference relative to the donor core to produce the field necessary for toner development. The toner layer on the donor roll is then disturbed by electric fields from a wire or set of wires to produce and sustain an agitated cloud of toner particles. Typical AC voltages of the wires relative to the donor are about 700 to about 900 V
pp
at frequencies of about 5 to about 15 kHz. These AC signals are often square waves, rather than pure sinusoidal waves. Toner from the cloud is then developed onto the nearby photoreceptor by fields created by a latent image. In the present invention in embodiments, while any suitable electrostatic image development device may be used, it is preferred to use a device employing the hybrid scavengeless development system, such as the system illustrated herein, and, for example, U.S. Pat. No. 5,978,633, the disclosure of which is totally incorporated herein by reference.
The achievement of stringent offset-like print quality requirements in a xerographic engine has been enabled in the present invention by IOI xerography of which hybrid scavengeless development is an excellent subsystem component. Both the image quality and the unique subsystem requirements result in highly constrained toner designs of which the toners of the present invention are useful. In addition to achieving offset-like print quality, a digital imaging processes enables customnization of each print (such as an address, or special information for regional distribution), which is not as practical with offset lithography.
REFERENCES
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 the carrier particles such that 1 fC/10 &mgr;m≦C
T
≦10 fC/10 &mgr;m, and wherein (i) the carrier particles have a saturation magnetization value, M
sat
, expressed in Tesla (T) such that M
sat
≧0.30 T; (ii) the carrier particles have a volume average particle size (C
avg
) such that 30 &mgr;m≦C
avg
≦60 &mgr;m; (iii) the volume based particle size distribution of the carrier particles has at least 90 percent of the particles having a particle diameter C such that 0.5 C
avg
≦C≦2 C
avg
; (iv) the volume based particles size distribution of the carrier particles comprises less than b percent particles smaller than 25 &mgr;m wherein b=0.35 X (M
sat
)
2
X 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) the carrier particles comprise a core particle coated with a resin coating in an amount (RC) such that 0.2 percent w/w≦RC≦2 percent w/w, see the Abstract. This patent indicates that the developers thereof can achieve images when a latent image is developed with a fine hair magnetic brush, see for example, column 4, lines 7 to 17.
Nevertheless, there continues to be a need for 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, preferably in an image-on-image device, and more specifically, in such a device also utilizing a hybrid scavengeless development system, the color image produced exhibits a quality analogous to that achieved in offset lithography. Further, there is a need for toners and developers wherein a toner additive does not substantially interact with fuser oils, fuser rolls, and the like to thereby, for example, increase the useable life, for example from about 200,000 prints to about 1,000,000 prints, of fuser devices, such as fuser rolls, and wherein the toners and developers thereof possess excellent triboelectrical, conductivity, and developability characteristics.
SUMMARY
It is a feature 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 can achieve xerographically produced images having offset like print quality.
It is a further feature of the invention to provide a set of color toners and developers capable of producing excellent images when used in a development apparatus utilizing a hybrid scavengeless development system.
It is a still further feature of the invention to provide processes for the preparation of the toners and developers with certain consistent, and predictable properties.
Additionally, it is a still further feature of the invention to provide suitable carriers for use in combination with toners to obtain two component developers possessing excellent properties.
Moreover, in another feature of the present invention there are provided toners and developers wherein the lifetime of certain components, such as fuser rolls, fuser oils, and the like, are extended; for example, the life of a fuser roll can be extended from less than about 350,000 impressions to about 1 million or more impressions with the toners of the present invention in embodiments thereof, and wherein there can be achieved developed images with lithographic image quality.
Furthermore, another feature of the present invention relates to the selection of calcium stearate as a lubricant component for toners and developers thereof to thereby permit the toner to adequately move on the surface of the carrier and to provide high developer conductivity, reduced sensitivity of the developer conductivity to the toner concentration, and decreased toner impactation on the carrier particles.
Embodiments
Aspects of the present invention include a toner comprising at least one binder in an amount, for
Angra Padam K.
Bayley Denise R.
Ciccarelli Roger N.
Hollenbaugh, Jr. William H.
Kaplan Samuel
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