Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-01-09
2002-07-16
Chapman, Mark (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108100, C430S108300, C399S117000, C399S252000
Reexamination Certificate
active
06420079
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an electrophotographic toner and an electrophotographic apparatus, and in particular relates to an electrophotographic toner which has fine particles externally added so as to provide an abrading effect and refresh the photoreceptor surface well as relating to an elect:rophotographic apparatus having an efficiently functional developing system.
(2) Description of the Prior Art
Conventionally, the electrophotographic technique, the application of the Carlson process, has been widely used for image forming using the toner. An apparatus using the Carlson process typically uses a photoreceptor drum having a photosensitive layer on the surface thereof and has a charger, an exposing device, a developing device, a transfer device, a fixing device, a cleaner and an erasing device, all arranged around the photoreceptor drum in the mentioning order. Now, the Carlson process will be explained. In this process, first in the dark place, the photoreceptor drum surface is uniformly charged by the charger. Then, the exposing device illuminates the photoreceptor drum surf ace with a light image of a document so as to release charge at the areas which have been illuminated with light, thus forming an electrostatic latent image on the photoreceptor drum surface.
Next, the toner which has been charged with a polarity that is opposite to the electric field of charge on the photoreceptor drum adheres to this static latent image so as to develop the static latent image into a visual image. Thereafter, a recording material such as paper is laid over the visual image while charge with a polarity opposite to the toner is given to the rear side of the recording material by corona discharge from the transfer device, whereby the toner image is transferred to the recording material. After the transfer step, the toner image is fixed to the recording material by the heat and pressure from the fixing device, forming a permanent image.
The leftover toner that has not transferred to the recording material and remains on the photoreceptor drum is removed by the cleaner. The static latent image on the photoreceptor drum is charge erased by the erasing device. Thereafter, the above process, starting with charging of the photoreceptor drum, is repeated so as to effect continual image forming. The toner to be used for the electrophotocraphic technology using the above-mentioned Carlson process is a coloring powder forming visual images and also has the charge function and the fixing function to recording materials. Further, the toner is given with various functions, depending upon the properties of the apparatus to which the toner is used.
As one of the functions of the toner, the toner performs the function of abrading the photoreceptor and refreshing the photoreceptor surface when the toner remaining on the photoreceptor surface after the transfer stage is removed. This function is mainly attributed to inorganic particles externally deposited over the toner surface. In order to make the function of refreshing the photoreceptor surface more efficient, Japanese Patent Application Laid-Open Hei 8 No.137124 discloses a technique for uniformly dispersing the abrasive over the toner surface by preliminary mixing of the abrasive and a fluidizer and then blending them with the toner particles by a large-scale mixer.
However, if fine particles having abrading effect are externally added to the toner by this method, the particles themselves may firmly Stick to the photoreceptor surface and produce image deficiencies.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the above drawbacks and it is therefore an object of the present invention to provide an electrophotographic toner which provides the function of refreshing the photoreceptor surface without causing any damage to the images and also provide an electrophotographic apparatus having a developing system providing the optimized effective function.
The inventors hereof have made various investigations in order to solve the above drawbacks and have found out the new fact that a toner can produce the function of refreshing the photoreceptor surface without causing any deficiency by limiting the volume mean diameter, specific surface area and the mixing ratio of the fine inorganic particles eternally added and adhering to the toner to associated specified ranges and thus have completed the invention.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the first aspect of the present invention, an electrophotographic toner constituting a dual component developer in combination with a powdered magnetic carrier, comprises:
toner base particles made up of a binder resin containing a coloring agent and the like with a fluidizer and other particles adhering to the surface thereof; and
fine inorganic particles having a volume mean diameter of 250 to 600 nm (i.e., 0.25 to 0.6 &mgr;m) with a specific surface area of 0.25 to 0.5 m
2
/g for serving as an abrasive, and is characterized in that 1.5 to 2 parts by weight of the abrasive is externally added to 100 parts by weight of the toner base particles and made to be deposited over the toner base particle surface.
In accordance with the second aspect of the present invention, the electrophotographic toner having the above first feature is characterized in that the fine inorganic particles are made to be externally deposited over the toner base particle surface by blending the two components in a mixer for 30 to 90 seconds with the mean linear speed of the mixer's agitator blade set at 600 m/min to 900 m/min.
In accordance with the third aspect of the present invention, an electrophotographic apparatus for performing an electrophotographic process using a dual-component developer made up of a toner and a powered magnetic carrier, comprises: a photoreceptor cleaning device is located above the level that passes through the center of the photoreceptor drum, and is characterized in that the electrophotographic toner constituting a dual component developer in combination with a powdered magnetic carrier, comprises: toner base particles made up of a binder resin containing a coloring agent and the like with a fluidizer and other particles adhering to the surface thereof; and fine inorganic particles having a volume mean diameter of 250 to 600 nm (i.e., 0.25 to 0.6 &mgr;m) with a specific surface area of 0.25 to 0.5 m
2
/g for serving as an abrasive, and that 1.5 to 2 parts by weight of the abrasive is externally added to 100 parts by weight of the toner base particles and made to be deposited over the toner base particle surface.
In accordance with the fourth aspect of the present invention, the electrophotographic apparatus using an electrophotographic toner, having the above third feature, is characterized in that the fine inorganic particles are made to be externally deposited over the toner base particle surface by blending the two components in a mixer for 30 to 90 seconds with the mean linear speed of the mixer's agitator blade set at 600 m/min to 900 m/min.
In accordance with the fifth aspect of the present invention, an electrophotographic apparatus for performing an electrophotographic process using a dual-component developer made up of a toner and a powered magnetic carrier, comprises:
a photoreceptor drum having a diameter of 30 to 40 mm and rotating at a linear speed of 80 mm/s or higher, and is characterized in that the electrophotographic toner constituting a dual component developer in combination with a powdered magnetic carrier, comprises: toner base particles made up of a binder resin containing a coloring agent and the like with a fluidizer and other particles adhering to the surface thereof; and fine inorganic particles having a volume mean diameter of 250 to 600 nm (i.e., 0.25 to 0.6 &mgr;m) with a specific surface area of 0.25 to 0.5 m
2
/g for serving as an abrasive, and that 1.5 to 2 parts by weight of the abrasive is externally added to 10
Akazawa Yoshiaki
Imafuku Tatsuo
Morinishi Yasuharu
Saito Junichi
Takesue Yuichiro
Chapman Mark
Sharp Kabushiki Kaisha
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