Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1999-08-31
2001-02-13
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S109500, C430S137170
Reexamination Certificate
active
06187495
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a yellow toner for developing electrostatic images in electrophotography or electrostatic printing or forming a toner image by toner jetting. The present invention also relates to a process for producing such a yellow toner and an image forming method using such a yellow toner.
Hitherto, a large number of electrophotographic image forming methods are known. Generally, in such methods, a photosensitive member comprising a photoconductive substrate is uniformly charged and then subjected to imagewise exposure to light to form an electrical latent image (electrostatic image) thereon, and the latent image is then developed with a toner to provide a visible toner image. The toner image is then transferred onto a transfer(-receiving) material, such as paper, as desired, and fixed onto the transfer material, for example, under application of heat, pressure, etc., to obtain a copy or a print.
Many developing methods are known to be incorporated in such an electrophotographic image forming method. Among these, the magnetic brush method and the cascade method using a two-component developer comprising principally a toner and a carrier have been extensively practiced commercially. These methods are both excellent methods capable of relatively stably providing good images but are accompanied with common difficulties arising from the use of a two-component developer, such as accumulation of spent toner on the carrier surface and the change in mixing ratio between the toner and the carrier.
Various proposals of using monocomponent developers consisting of only a toner have also been made including those comprising magnetic toner particles which exhibit excellent performances.
However, a magnetic monocomponent developer has a constraint of containing magnetic powder therein so that it is frequently used in providing black toner but is not used for providing toners used in full-color development in many cases. For this reason, nonmagnetic monocomponent developers are more frequently used in full-color development.
The use of a nonmagnetic monocomponent developer is accompanied with advantages, such as stabler control of developer concentration, simplification of components used in the apparatus and facilitation of accomplishing a compact apparatus body, but is liable to cause instability in charge-imparting performance and toner scattering in the apparatus compared with a conventional two-component developer including carrier particles. In recent years, however, not a few magnetic monocomponent developers capable of providing improved image qualities have been proposed accompanying a remarkable improvement in chargeability, whereby it is becoming possible to effect full-color image formation by using nonmagnetic monocomponent developers, which has been considered difficult heretofore.
In order to exhibit an improved chargeability, a toner has to be easily disintegrated to allow quick charge generation among toner particles. For accomplishing this, Japanese Laid-Open Patent Application (JP-A) 7-306584 has proposed an apparatus including a developing device equipped with means for disintegrating toner agglomerate and means for classifying and selectively supplying toner particles having sizes equal to those before the agglomeration to a developer-carrying member. By removing the toner agglomerate through the disintegration step for allowing selective supply of toner particles, it is actually possible to obviate toner scattering, but in this case, the toner utilization efficiency is lowered compared with the case of using a toner comprising toner particles which have been sufficiently disintegrated in advance. Further, as some portion of the toner particles is agglomerated, the uniform charging of the toner particles is liable to be difficult.
On the other hand, compared with a two-component developer requiring an appropriate rate of toner replenishing so as to keep a constant toner concentration, a toner constituting a nonmagnetic monocomponent developer is required to be instantaneously disintegrated to exhibit a high chargeability at the moment of being used for image formation while exhibiting a high packing rate in the developer container as the toner contained in the container is gradually consumed. JP-A 6-266219 has proposed to use toner particles having a shape factor of 50-85% so as to form a toner layer having a void percentage of 60-75% on the developer-carrying member for development. This is a proposal of defining the toner coating state in the developing region and does not take account of toner packing in a toner container.
JP-A 6-35320 has proposed to use toner stirring means, of which at least one of the shape, location, size and number of drive members of the toner stirring means is changed depending on the species of toner within a toner container. This is a proposal of absorbing the powder resistance of the toner per se within the toner container and does not contemplate the change of powder load resistance of the toner per se.
As means for absorbing powder load resistance of a toner contained in a toner vessel as represented by a developing vessel, a cartridge or a replenishing toner container, JP-A 5-46026 has proposed the detection of torque depending on a remaining toner amount, JP-A 5-107922 has proposed means for controlling toner stirring by detecting a toner powder pressure in proximity to the developing roller, JP-A 5-173417 has proposed to change not only the torque but conditions for stirring depending on a detected quantity, and JP-A 7-295360 has proposed means for load detection at the time of toner supply.
On the other hand, output or recording appliances, such as copying machines or laser beam printers using electrophotographic processes as described above, are required to provide higher quality images faithful to the original by using lots of image data accompanying the progress of digital technique and lower production cost. Particularly, in the case of photographic images, catalogue or technical brochures and maps, it is required to provide extremely fine and faithfully reproduced images without causing collapsion or interruption of even minute image portions.
Corresponding to such a technical trend, a developer subjected to process steps inclusive of developing, transfer and fixation is required to exhibit excellent performances including little toner scattering onto latent images, a high chargeability of the toner per se and a high transferability close to 100% of a developed toner image onto transfer paper.
Conventional methods of providing improved image qualities according to electrophotography have included a method of forming dense ears of a developer on a developer-carrying member and rubbing a latent image on a latent image-bearing member with the ears, and a method of applying a bias electric field between a developer-carrying member and a latent image-bearing member so as to facilitate the jumping of the toner. It has been also adopted to provide an improved toner stirring performance in the developer container, thereby consistently allowing the toner to exhibit a high chargeability. It has been also considered to provide an improved resolution by forming a smaller size of dots constituting a latent image.
Such method for improving the developing performances are very effective and play an important role in obtaining high image qualities, but it becomes necessary to improve the developer per se in order to provide further improved image quality.
Particularly, in the case of full-color image formation wherein monochromatic toners are used for developing and transferred plural cycles at a latent image portion to form multi-layer toner images for providing a full color image, the latent images are liable to lower the potential as they approach the surfacemost images, so that the toner developing performance is liable to change between toners for the uppermost layer and the lowermost layer.
Further, in the full-color image formation, a color mizability under heat-melting is also
Chiba Tatsuhiko
Fujita Ryoichi
Kawakami Hiroaki
Tomiyama Koichi
Yachi Shinya
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Goodrow John
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