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AssigneeEastman Kodak Company
InventorsThomas A. Jadwin, John F. Crichton, Robert D. Fields, Eric C. Stelter
Estimating the term…
Development systems and methods for developing using magnetic toner are disclosed. The present invention further discloses developers used in development systems as well as the toner used in developer for magnetic ink character recognition printing. With respect to the development system, a development system is disclosed which includes a supply of dry developer mixture which contains magnetic toner particles and hard magnetic carrier particles. The development system further includes a non-magnetic, cylindrical shell for transporting the developer between the supply and the development zone, wherein the shell can be rotatable or stationary. A rotating magnetic core of a pre-selected magnetic field strength and means for rotating at least the magnetic core to provide for the transport of the toner particles from the shell to an electrostatic image also provided as part of the development system. A method for developing electrostatic image with magnetic toner is further disclosed, for example, involving the above-described development system. Magnetic toner particles having a low magnetic loading such as on the order of 28% by weight or less, based on the weight of the toner are further described wherein these magnetic toners can include a spacing agent on the surface of the magnetic toner particles. A developer is further disclosed which contains the magnetic toner particles of the present invention with hard magnetic carrier particles. Other developer compositions are also described.
A development system for magnetic toner comprising:
A method for developing an electrostatic image with a magnetic toner comprising developing an electrostatic image member bearing an electrostatic image pattern by moving the image member through a development zone and transporting developer through the development zone in developing relation with the charge pattern of the moving imaging member by rotating an alternating-pole magnetic core of a pre-selected magnetic field strength within an outer non-magnetic shell, which is rotating or stationary, and controlling the directions and speeds of the core and optionally the shell rotations so that developer flows through the development zone in a direction co-current with the image member movement, wherein said developer comprises charged magnetic toner particles and oppositely charged hard magnetic carrier particles.
A developer comprising carrier particles and toner, wherein the toner is present in an amount of from about 8 wt % to about 45 wt %, based on the total weight of the developer.
A MICR developer comprising magnetic toner particles having a magnetic loading of less than 28% by weight, based on the weight of the toner and hard magnetic carrier particles.
A MICR developer comprising hard magnetic carrier particles and magnetic toner particles comprising at least one magnetic additive, at least one resin, at least one charge agent, and optionally, at least one colorant, wherein said magnetic toner particles have a spacing agent located on the surface of said magnetic toner particles.
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
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With toner particles: magnetic toner particles
Nanotechnology for interacting, sensing or actuating
With toner particles: plasticisers; Charge controlling agents
Plasticisers; Charge controlling agents: inorganic compounds
Term end not estimated
The present invention relates to magnetic toners and development systems for magnetic toners.
Magnetic ink character recognition (MICR) printing has been used for many years for checks and negotiable documents as well as for other documents in need of high speed reading and sorting. Various electrophotographic printers which are capable of printing magnetic inks or toners have been available from such sources as IBM and Kodak. Typically, the toner or ink used for MICR applications contains a heavy loading of iron oxide or other magnetic material in order to obtain the required adequate magnetic signal strength for speed reading and sorting and the like. However, MICR toner having such heavy iron oxide loadings can be quite difficult to manufacture since an adequate dispersion of the iron oxide particles in the toner resin, for instance, is hard to achieve and maintain. Furthermore, the resulting image quality from the MICR toner can be degraded relative to images made with normal toner due to decreased toning and fusing efficiencies resulting from the magnetic loadings that are required in the toner.
Accordingly, there is a significant trade off that currently occurs in the MICR technology; namely, a significant amount of magnetic loadings are required in order to achieve the necessary magnetic signal strength and yet this same magnetic loading leads to degraded images or images that have low quality. In order to obtain a higher image quality, the magnetic loading would need to be reduced which would then jeopardize the necessary magnetic signal strength that is required. Accordingly, the industry has simply accepted the lower quality of image in view of the need for the adequate magnetic signal strength that must be present in the MICR toner. Currently, MICR toners in the industry range in iron oxide loadings of up to and even above 50% by weight of the toner. With a loading of over 28% by weight Fe3O4 in a conventional MICR developer for an IBM 3828 MICR printer (2 component developer using a soft magnetic carrier), the signal strength for the release toner is between 120% and 140% average signal strength of the “on-us” characters as measured on a DOCU-MATE Check Reader. This 120% signal strength is sufficient and required to compensate for character voids and otherwise low density individual image. However, as indicated above, using such a toner, no matter what currently available printer or development system is used, typically leads to image quality which is at best mediocre.
FIG. 1 is a graph plotting the performance of various MICR toners of the present invention printed in a Digisource 9110-like printer.
FIGS. 2a, 2b, 3a, and 3b are SEM photographs showing several embodiments of toners of the present invention.
FIG. 4 shows two magnified photographs of images printed with MICR toner with surface treatment and without surface treatment.
The present invention may be more fully understood with reference to the accompanying figures. The figures are intended to illustrate exemplary embodiments of the present invention without limiting the scope of the invention. The accompanying figures, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the present invention and together with the description, serve to explain the principles of the present invention.
A feature of the present invention is to provide a development system for magnetic toner which provides a printed image having sharp image quality.
Another feature of the present invention is to provide magnetic toner having a reduced magnetic loading and yet achieves the desired magnetic signal strength.