Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-04-28
2001-03-20
Martin, Roland (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S110100, C430S126200, C399S252000
Reexamination Certificate
active
06203955
ABSTRACT:
BACKGROUND OF THE INVENTION
In an electrophotographic apparatus or an electrostatic recording apparatus, a two-component developing system method using toner and a carrier and a monocomponent developing system method using toner which also functions as a carrier are extensively used to visualize an electrostatic latent image formed on an image carrier made of a photoreceptor or a dielectric material.
These developing methods include methods using nonmagnetic toner and magnetic toner.
As magnetic toner, Jpn. Pat. Appln. KOKAI Publication No. 1-40976 has disclosed one-component magnetic toner which contains, in toner particles, about 20 to 60 wt % of an iron oxide magnetic particle in which the FeO content, the number-average particle size, and the specific surface area are restricted to 16 to 25 wt %, 0.2 to 0.7 &mgr;m, and 2 to 10 m
2
/g, respectively. Jpn. Pat. Appln. KOKAI Publication No. 1-40976 describes that when image formation is performed using this magnetic toner, a high developing efficiency and a high transfer efficiency can be obtained.
A magnetic material used herein has a high degree of blackness as a black pigment and can hold an appropriate electrical resistance. Hence, the material stabilizes the toner charge amount and can thereby improve image density. Also, in respect of developing properties, the material improves the rank of fog on image. However, with recent increasing speed of copying machines, magnetic toner cannot well satisfy high resolution, high durability, and the like any longer. Especially in a low-temperature, low-humidity environment, the charge amount cannot be properly controlled. A lowering of image density and background contamination resulting from an appropriate increase in charge amount cannot be well controlled.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above situation, and has as its first object to provide a developing agent having appropriate flowability, showing stable charging property and image density throughout its life, and capable of forming high-quality images.
It is the second object of the present invention to provide an image forming apparatus showing stable charging property and image density throughout its life and capable of forming high-quality images.
It is the third object of the present invention to provide an image forming method showing stable charging property and image density throughout its life and capable of forming high-quality images.
According to the first aspect of the present invention, there is provided a developing agent containing a binder resin, a magnetic particle, rutile/anatase mixed crystal type titanium oxide treated to have hydrophobicity, and silica treated to have hydrophobicity.
According to the second aspect of the present invention, there is provided an image forming apparatus comprising
man image carrier,
a developing device provided opposite to the image carrier, and containing a developing agent which contains a binder resin, a magnetic particle, rutile/anatase mixed crystal type titanium oxide treated to have hydrophobicity, and silica treated to have hydrophobicity, the developing device forming a developing agent image by developing an electrostatic latent image formed on the image carrier by using the developing agent,
a transfer device for transferring the developing agent image onto a transfer medium, and
a fixing device for fixing the developing agent image transferred to the transfer medium.
According to the third aspect of the present invention, there is provided an image forming method comprising
an electrostatic latent image formation step of forming an electrostatic latent image on an image carrier,
a developing step of developing an electrostatic latent image formed on the image carrier by using a developing agent, containing a binder resin, a magnetic particle, rutile/anatase mixed crystal type titanium oxide treated to have hydrophobicity, and silica treated to have hydrophobicity, to obtain a developing agent image
a transfer step of transferring the obtained developing agent image onto a transfer medium, and
a fixing step of fixing the developing agent image, transferred to the transfer medium.
In the present invention, rutile/anatase mixed crystal type titanium oxide that is made hydrophobic is mixed in toner containing a magnetic particle. This gives appropriate flowability to a developing agent to thereby stabilize charging property. Consequently, a high-quality image having high image density can be obtained.
REFERENCES:
patent: 4946755 (1990-08-01), Inoue
patent: 5272040 (1993-12-01), Nakasawa et al.
patent: 5747211 (1998-05-01), Hagi et al.
patent: 5776646 (1998-07-01), Hagi et al.
patent: 5981132 (1999-11-01), Kurose et al.
patent: 6103441 (2000-08-01), Tomita et al.
patent: 6114077 (2000-09-01), Voets et al.
patent: 1-40976 (1989-09-01), None
Foley & Lardner
Martin Roland
Toshiba Tec Kabushiki Kaisha
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