Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-05-30
2002-09-10
Dote, Janis 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...
C430S101000, C430S110100, C430S110300, C430S110400, C430S111400, C430S122520, C430S126200
Reexamination Certificate
active
06447969
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a toner and an image forming method used in a recording method utilizing electrophotography, electrostatic recording, magnetic recording, toner jet recording, etc. More particularly, the present invention relates to a toner used in an image forming method for an image forming apparatus, such as a copying apparatus, wherein a toner image is once formed on an electrostatic image-bearing member and then transferred onto a transfer-receiving material to form an image thereon, and an image forming method using the toner.
Hitherto, a large number of electrophotographic processes have been known. Generally, in these processes, an electrostatic latent image is formed on an electrostatic image-bearing member (hereinafter represented by a “photosensitive member”) utilizing ordinarily a photoconductive material, the latent image is then developed with a toner to form a visible toner image, and the toner image, after being transferred as desired onto a transfer-receiving material such as paper, is fixed onto the transfer-receiving material by application of pressure, heat, etc., to provide a product copy or print. As a method for visualizing the electrostatic latent image, there have been known the cascade developing method, the magnetic brush developing method, the jumping developing method, the pressure developing method, etc.
U.S. Pat. No. 3,909,258 has proposed a developing method using a magnetic toner having an electroconductivity. More specifically, in the developing method, an electroconductive magnetic toner carried on a hollow cylindrical electroconductive sleeve with a magnet installed inside thereof is caused to contact an electrostatic image to develop the image. In this instance, at the developing region, an electroconductive path is formed of the toner particles between the electrostatic image-bearing member and the sleeve surface, and the toner particles are supplied with a charge via the electroconductive path, whereby the toner particles are attached to the electrostatic image based on a Coulomb force acting between the charge and the electrostatic image. The developing method using an electroconductive magnetic toner is an excellent method obviating problems accompanying the conventional two-component developing method, but as the toner is electroconductive, the method is accompanied with a difficulty in electrostatically transferring the developed toner image from the electrostatic image-bearing member to a transfer-receiving material (or recording material) such as plain paper.
As a developing method using a high-resistivity magnetic toner allowing electrostatic transfer, one utilizing dielectric polarization of toner particles is known. Such a developing method however essentially involves problems, such as slow developing speed and insufficient developed image density, so that the commercialization is difficult.
As another developing method using a high-resistivity insulating magnetic toner, there is known a method wherein toner particles are triboelectrically charged through friction between individual toner particles and between toner particles and a friction member such as a sleeve, and the thus-charged toner particles are caused to contact an electrostatic image-bearing member to effect a development. This method is however accompanied with a problem that the triboelectric charge is liable to be insufficient due to few opportunities of contact between the toner particles and the friction member and much magnetic material exposed to the surfaces of the magnetic toner particles, leading to inferior images due to the insufficient charge.
As another developing method, Japanese Laid-Open Patent Application (JP-A) 54-43027 and JP-A 55-18656, for example, disclose a so-called jumping developing method wherein a magnetic developer (toner) is applied in a thin layer on a developer-carrying member to be triboelectrically charged thereon, and the charged layer of the magnetic toner is moved under the action of a magnetic field to be opposed in close proximity to but free of contact with an electrostatic latent image to effect a development. According to this method,the magnetic developer is allowed to be sufficiently triboelectrically charged by application in a thin layer on the developer-carrying member, and the developer carried under a magnetic force is used for development in a state free from contact with the electrostatic latent image, so that a high definition image can be obtained with suppression of so-called “fog” caused by transfer of the developer onto non-image parts.
Such a mono-component developing method, does not require carrier particles, such as glass beads or iron powder, so that a developing device therefor can be small-sized and light in weight. Further, while the two-component developing scheme requires devices for detecting a toner concentration in the developer and for replenishing a necessary amount of toner based on the detected result in order to keep a constant toner concentration in the developer, the mono-component developing scheme does not require such devices, thus allowing a small-sized and light developing device also from these points.
However, the developing method using an insulating magnetic toner involves an unstable factor a ttributable to the use of the insulating magnetic toner. This arises from the feature that a substantial amount of fine powdery magnetic material is contained in dispersion within the insulating magnetic toner particles and a portion of the magnetic material is exposed to the toner particle surfaces to affect the flowability and the triboelectric chargeability of the magnetic toner, thereby causing a change or deterioration of properties required of the magnetic toner, such as developing performance and continuous image forming performance.
The above-mentioned problems accompanying the use of a conventional magnetic toner containing a magnetic material is considered to be principally caused by the exposure of a magnetic material to the magnetic toner particle surface. More specifically, as a result of exposure of fine particles of magnetic material having a lower resistivity than a toner biner principally constituting the toner to the toner article surfaces, various difficulties are caused, such as a lowering in toner chargeability, a lowering in toner flowability, and developer deteriorations during a long term of use, such as peeling-off of the magnetic particles due to friction between individual toner particles and toner particles and the regulating member resulting in image density lowering and occurrence of density irregularity called “sleeve ghost”.
Hitherto, various proposals have been made regarding magnetic iron oxide contained in magnetic toners, but room for improvement has yet been left.
For example, JP-A 62-279352 has proposed a magnetic toner containing silicon-containing magnetic iron oxide. The magnetic iron oxide is intentionally caused to contain silicon inside thereof, but the magnetic toner containing the magnetic iron oxide has left room for improvement regarding the flowability.
Japanese Patent Publication (JP-B) 3-9045 has proposed to provide magnetic iron oxide particles with a controlled spherical shape by adding a silicate salt thereto. The magnetic iron oxide particles obtained according to this proposal are caused to contain much silicon at an inner portion thereof and little silicon at the surface due to the use of a silicate salt for particle shape control and have a high surface smoothness. As a result, the resultant magnetic toner is provided with an improved flowability to some extent, but the adhesion between the toner binder resin and the magnetic iron oxide particles is liable to be insufficient.
JP-A 61-34070 has proposed a process for producing triiron tetroxide by adding a hydroxysilicate salt solution during oxidation to triiron tetroxide. The triiron tetroxide particles produced by the process contain Si in proximity to the surfaces thereof but are also caused to have a layer of Si in proximity to
Chiba Tatsuhiko
Hashimoto Akira
Ito Masanori
Komoto Keiji
Kukimoto Tsutomu
Canon Kabushiki Kaisha
Dote Janis L.
Fitzpatrick ,Cella, Harper & Scinto
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