Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-09-11
2004-10-12
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...
C430S137200
Reexamination Certificate
active
06803164
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a magnetic black toner used in image-forming processes such as electrophotography, electrostatic recording, electrostatic printing and toner jet recording.
2. Related Background Art
As the electrophotography, recorded images are commonly obtained by forming an electrostatic latent image on a photosensitive member by various means utilizing a photoconductive material, subsequently developing the latent image by the use of a toner to form a toner image, and transferring the toner image to a transfer material such as paper as occasion calls, followed using fixing by the action of heat, pressure, heat-and-pressure or solvent vapor.
In recent years, as copying machines and printers have been made to have multiple function, to record images in a higher image quality and to have a higher process speed, toners have also become required to have much severer performances. Accordingly, toners are made smaller in particle diameter (made into fine particles) and are required to have particle size distribution which is sharp enough to contain no coarse particles and less ultrafine powder.
Making toners into fine particles can improve the resolution and sharpness of images, but brings about various problems.
Making a toner have a small particle diameter results in a large specific surface area of the toner to achieve a larger charge quantity itself of the toner, but at the same time results in a broad distribution of its charge quantity to tend to cause fog where the toner is developed in non-image areas. Also, when the toner is transferred from the surface of the photosensitive member to the transfer material and where a toner having been charged in excess is present there, a phenomenon called black spots around line images may occur, in which the toner scatters around characters or line images. Where the toner is not sufficiently charged in order to control such black spots around line images, a toner charged insufficiently is present there to lower developing performance or cause fog.
Moreover, the chargeability of toners more tends to be affected by environment. In order to make this fog less occur, it is also attempted to make toners have a sharp particle size distribution. This, however, may be the cause of a cost increase due to, e.g., a low yield in the production of toners.
Furthermore, as toners are made into fine particles, the dispersibility of internal additives in binder resins more tends to influence the performance of toners. In particular, in the case of a toner having iron oxide particles as a magnetic powder, problems such as a decrease in image density, a lowering of running stability and a lowering of image quality may be caused depending on the state of dispersion of the iron oxide particles.
Where the iron oxide particles stand non-uniform in toner particles, the amount of any iron oxide particles depositing on the surfaces of the toner particles differs between individual particles. Hence, when the toner is triboelectrically charged with a charge-providing member (developing sleeve) and where the iron oxide particles are not present at all on the toner particle surfaces, or present in a very small quantity, the toner particle surfaces are high charged. Conversely, where the iron oxide particles are present in excess on the toner particle surfaces, the iron oxide particles act as leak sites and the toner particle surfaces are low charged. Thus, the breadth of charge distribution may more increase to cause the above various problems.
Japanese Patent Applications Laid-Open No. 3-101743 and No. 3-101744 disclose that, in order to disperse the magnetic powder uniformly in toner particles, the magnetic powder is made to have a small particle diameter and a narrow particle size distribution. It is true that such measures make it easy for the magnetic powder to be uniformly dispersed in toner particles, but a problem may occur which is due to making the magnetic powder to have a small particle diameter.
Conventionally, the degree of blackness of the iron oxide particles, in particular, iron oxide particles containing FeO (or Fe(II)), such as magnetite is influenced by the content of FeO. However, this FeO content in iron oxide particles decreases with progress of the deterioration with time caused by oxidation after production. As the result, this is accompanied with a phenomenon that the degree of blackness deteriorates. Needless to say, this deterioration with time is greatly influenced by the environment where the iron oxide particles are placed, but the deterioration of the degree of blackness is accelerated as the iron oxide particles are made into fine particles.
In order to obtain iron oxide particles having a high degree of blackness and superior environmental properties, techniques have ever been disclosed in which various elements are added to iron oxide particles. Such iron oxide particles may include, e.g., iron oxide particles having composite iron oxide coatings containing Co as disclosed in Japanese Patent Applications Laid-Open No. 6-100317 and No. 8-133744, iron oxide particles having composite iron oxide coatings containing Zn as disclosed in Japanese Patent Application Laid-Open No. 8-133745, and iron oxide particles containing a composite iron oxide containing Mn, Zn, Cu, Ni, Co or Mg as disclosed in Japanese Patent Application Laid-Open No. 4-162050.
The role of these additive elements is to keep the degree of blackness from deteriorating, by covering particles with an additive-element oxide so that the FeO does not come into direct contact with the outside atmosphere, or by replacing the FeO with an additive-element oxide that may not cause a decrease in the degree of blackness.
The iron oxide particles obtained by such methods can prevent the degree of blackness from decreasing or can keep it from deteriorating with time. However, their uniform dispersion in toner particles is insufficient, and some additive elements may affect magnetic properties of the iron oxide particles themselves to cause defects concerned with development other than a tint.
In the image-forming process described above, transfer residual toner is present on the photosensitive member after the toner image has been transferred from the surface of the photosensitive member to the transfer medium.
In order to perform continuous copying quickly, this residual toner on the photosensitive member must be removed by cleaning. The residual toner thus removed and collected is further put into a container or collection box provided inside the main body, and thereafter discarded or recycled through a suitable step.
To grapple with environmental problems, a construction designed to provide a recycle system inside the main body is required as a waste-tonerless system. However, in order to make copying machines and printers have multiple function, record images in a higher image quality and have a much higher process speed, a fairly large recycle system is required in the main body, resulting in large copying machines and printers in themselves. This is not feasible for making machines small-size from the viewpoint of space saving. Making machines small-size is similarly not feasible also in a system in which the waste toner is held in a container or collection box provided inside the main body and a system in which the photosensitive member and the part where the waste toner is collected are set in one unit.
To deal with these adequately, it is necessary to improve the transfer efficiency required when the toner image is transferred from the surface of the photosensitive member to the transfer medium.
Japanese Patent Application Laid-Open No. 9-26672 discloses a method in which in a toner produced by pulverization a transfer efficiency improver having an average particle diameter of 0.1 to 3 &mgr;m and a hydrophobic fine silica powder having a BET specific surface area of 50 to 300 m
2
/g are incorporated so that the toner can have a low volume resistance and the transfer efficiency improver can form a thin-film lay
Dojo Tadashi
Hasegawa Yusuke
Mizoo Yuichi
Shibayama Nene
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Goodrow John L
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