Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-09-28
2004-05-11
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108400, C430S108500, C430S109100, C430S109400, C430S045320, C430S124300, C430S126200, C222SDIG001
Reexamination Certificate
active
06733939
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electrophotographic toner (“toner”), a developer and a container for the developer, a method of and an apparatus for forming image/s. More particularly, this invention relates to a toner used in a developer for developing images during electrophotography, electrostatic recording, electrostatic printing, and the like. Specific examples of such an apparatus for forming image are the copiers, laser printers or the plain-paper facsimiles, that involve a direct or indirect electrophotographic development system. Moreover, the apparatus for forming image may be a machine, like the full-color copiers, full-color laser printers or the full-color plain-paper facsimiles, that involve a direct or indirect electrophotographic multi-color image development system.
BACKGROUND OF THE INVENTION
A developer is used during electrophotography, electrostatic recording and electrostatic printing. In this process, first, the developer is deposited onto a substrate, such as a photosensitive body, on which an electrostatic image has been formed. Then, the developer is transferred from the photosensitive body onto a transfer medium such as a transfer paper. Then, the developer is fixed on a surface of a paper. Two types of developers are known. A two-component developer is the one that includes a carrier and a toner. A one-component developer is the one that does not have the carrier.
In case of the two-component developer, the carrier is used for charging and transporting the developer. After a mixture of the toner and carrier is agitated and mixed thoroughly in the development machine, the mixture is transported to the developer substrate and developed. In this system, charging and transport can be stably maintained even when the system is used for a relatively long period of time. For these reasons, the two-component developer can be efficiently used even in high-speed developing apparatuses.
However, in case of the two-component developer, the developer deteriorates as toner particles adhere on the surface of the carrier. Moreover, the concentration of the toner in the developer gradually decreases as only the toner is consumed. Moreover, since the ratio of the toner and the carrier in the developer has to be kept constant, there arises a problem, that size of the apparatus becomes large. The one-component developer is free from the problems listed in case of the two-component developer. Therefore, the size of the apparatus can be downsized. This advantage has made the one-component developer popular and widely used in present day developing systems.
The one-component developer can be further classified into two types. A magnetic one-component developer and a non-magnetic one-component developer. The magnetic one-component developer includes a magnetic material such as magnetite. This magnetic material is held on a substrate with a magnetic force. The substrate can be magnetized using a magnet. The magnetic toner on the substrate can be formed into a thin layer using a layer-thickness control member such as a blade or roller. This system has often been practically used recently for small-size printers.
As the name indicates, the non-magnetic one-component developer includes a non-magnetic toner. Therefore, the toner is supplied to a substrate by pressure welding a toner supply roller or the like onto the substrate. The toner is held firmly on the substrate with electrostatic force. The non-magnetic toner on the substrate can be formed into a thin layer in the same manner as the magnetic toner. The non-magnetic developer does not contain any colored substance. Therefore, the non-magnetic developer has an advantage over the magnetic developer in that the non-magnetic can be used for color image formation. Moreover, since the apparatus that uses the non-magnetic developer does not require any magnet the apparatus can be made light-weight and cheaper. These advantages have made the non-magnetic one-component developer popular and widely used in present day small-sized full-color printers.
However, the one-component developer still has many drawbacks. Since there is no stable charging and transport means as the carrier (as in case of the two-component developer), charging and transportation failures tend to occur frequently when the images are formed continuously for a considerably longer period of time or at higher speed.
As mentioned above, the one-component developer, after it is transported onto the developer substrate, is made into a thin layer by means of the layer-thickness control member and developed. At that time, contact between the toner and the developer, or contact between the toner and the layer-thickness control member is only for a very short period of time. Therefore, a time for which the toner is charged because of friction is very short. As a result, in contrast to the two-component development system using the carrier, more of the toner tends to have a low or opposite charge in the one-component development system. In the non-magnetic one-component system particularly, the toner (developer) is transported typically by means of at least one toner transport member. Apparently, it is known that the thickness of the toner layer on the toner transport member surface must be as thin as possible. Same is the case with the two-component developer having a carrier with a very small particle size. In particular, when a toner having a high electrical resistance is used as the one-component developer, the toner layer has to significantly thin since the toner has to be charged by the development apparatus. If the toner layer is thick, only a portion near the surface of the toner layer is charged and it becomes difficult to evenly charge the whole toner layer. Moreover, it is required that the toner is charged at speed that is fast, and an optimum level of charge is maintained.
The present day offices are flooded with office electric appliances such as personal computers, printers, copiers, scanners, and facsimile machines. Documents including text documents, graphs etc. are created using personal computers. Moreover, occasion where such documents are printed in color is increasing. Many of the images output by the printers are solid, line, or halftone images. Marketing needs for the image quality are changing accordingly and needs such as high reliability are increasing.
Conventionally, a charge control agent has been added to the toner to stabilize its charge. The charge control agent controls the frictional charge of the toner and maintains the charge level. Typical examples of negatively charging charge control agents are: monoazo dyes; metallic salts or metal complex salts of salicylic acid, naphthoic acid, and dicarboxylic acid; diazo compounds; and complex compounds of boron. Typical examples of positively charging charge control agents are, quaternary ammonium salt compounds, imidazole compounds, nigrosine dyes, and azine dyes. However, since these charge control agents are colored, there is a problem that the toner color phase is changed when they are used in color toners. Moreover, since these charge control agents have low dispersibility with a binder resin, the toner particles near the surface of the toner layer, i.e. the toner particles those contribute greatly to charging, tend to be detached easily, possibly causing problems such as variation in toner charging, staining of the development sleeve, “filming” on the photosensitive body, and the like.
This is why in the conventional charge control agents, images having a good quality are obtained at the initial stage, however, the image quality gradually changes, and the image starts to have background staining and unevenness. In particular, when the conventional charge control agents are used for a color copying machine, and the machine is used continuously while re-supplying the toner, there is a problem that the charge level of the toner gradually decreases and an image with a color tone significantly different from that of the image obtained at the initial stage is obtain
Fushimi Hiroyuki
Katoh Kohki
Nanya Toshiki
Uchinokura Osamu
Yagi Shinichiro
Oblon, Spiva, McClelland, Maier & Neustadt, P.C.
Ricoh & Company, Ltd.
Rodee Christopher
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