Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2003-02-24
2004-05-04
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S111400, C399S252000
Reexamination Certificate
active
06730449
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a toner for developing an electrostatic latent image formed on a latent-image carrier and to an image forming apparatus for forming an image using this toner.
More particularly, the present invention relates to a non-magnetic mono-component toner to be used for developing an image according to a non-magnetic mono-component developing method using a conductive developing roller and to an image forming apparatus using the non-magnetic mono-component toner.
Further, the present invention relates to a toner in which additive particles are entrapped in mother particles and to an image forming apparatus using this toner.
Among conventional known image forming apparatuses, there is a multicolor image forming apparatus of intermediate transfer type as shown in FIG.
1
. In an image forming apparatus
1
of this type, an image is exposed to light as an electrostatic latent image onto a photoreceptor
2
as a latent image carrier. The electrostatic latent image on the photoreceptor
2
is developed by yellow, magenta, cyan, and black non-magnetic mono-component developing devices
3
,
4
,
5
,
6
in this order (the order of respective colors is arbitrary) so as to obtain visible developed images. The developed images on the photoreceptor are superposed and toned on an intermediate transfer belt
7
a
of an intermediate transfer member
7
, thus achieving primary transfer. After the primary transfer, the toned image is transferred to a recording media
9
such as a paper on a secondary transfer roller
8
a
of the transferring device
8
, thus achieving secondary transfer. After that, the image is heated and fixed to the recording media
9
by a fixing device
10
, thereby obtaining a desired image on the recording media
9
.
The respective non-magnetic mono-component developing devices
3
,
4
,
5
,
6
have substantially the same structure. That is, each of the developing devices
3
,
4
,
5
,
6
is of a contact developing type that a conductive developing roller
16
is arranged in contact with the photoreceptor
2
. As shown in FIG.
2
(
a
), non-magnetic mono-component toner particles T in a toner container
13
are carried by a toner carrying means
14
to a toner supply roller
15
as toner supply means and is further supplied to the developing roller
16
by the toner supply roller
15
. Accordingly, the non-magnetic mono-component toner particles T are held on the surface of the developing roller
16
. A bias voltage composed of an alternating current superimposed on a direct current is applied to the developing roller
16
and the, developing roller
16
is rotated at a high speed, whereby the non-magnetic mono-component toner particles T are regulated to be in a uniform thin layer by a toner regulating member
17
as toner regulating means, which is in press contact with the surface of the developing roller
16
, and are uniformly charged. After that, the non-magnetic mono-component toner particles T on the developing roller
16
are uniformly conveyed toward the photoreceptor
2
which is in contact with the developing roller
16
.
The non-magnetic mono-component toner particles T on the developing roller
16
is transferred to the photoreceptor
2
by developing voltage applied to the developing roller
16
, whereby an electrostatic latent image is developed with the non-magnetic mono-component toner particles T on the photoreceptor
2
.
The non-magnetic mono-component developing method employing conductive developing roller
16
also includes a non-contact developing method in which the developing roller
16
and a photoreceptor
2
are spaced apart from each other. In developing of the non-contact developing method, a developing voltage is applied to the developing roller
16
and non-magnetic mono-component toner particles T on the developing roller
16
is transferred by jumping to the photoreceptor
2
due to the developing voltage. That is, an electrostatic latent image on the photoreceptor
2
is developed with the non-magnetic mono-component toner particles T by jumping-developing.
By the way, in the non-magnetic mono-component developing method using such a conductive developing roller
16
, both cases of the non-contact development or contact development, an image force Fm acts between the non-magnetic mono-component toner particles T and the developing roller
16
as shown in FIG.
3
. To securely separate the non-magnetic mono-component toner particles T from the developing roller
16
and to transfer the toner particles T to the photoreceptor
2
, a coulomb force Fc capable of overcoming the image force Fm should be imparted to the non-mono-component toner particles T. Since the coulomb force Fc imparted to the non-magnetic mono-component toner particles T increases as the image force Fm increases, the developing voltage should be accordingly increased. However, too large developing voltage must cause discharge. Therefore, the developing voltage can not be increased so large. This means that the developing bias has an upper limitation. There is accordingly a problem of narrow margin for developing.
As the image force Fm is large, the effect of removing residual toner particles remaining on the developing roller
16
after developing by the toner supply roller
15
is reduced, thus facilitating producing undesirable developing hysteresis. That is, when the image force Fm is not so large, residual toner particles remaining on the developing roller
16
can be peeled off by the toner supply roller
15
as shown in FIG.
4
(
a
). Therefore, the residual toner particles do not pass through spaces between the developing roller
16
and the toner supply roller
15
and thus does not move to the toner regulating means
17
side. Therefore, toner particles on the developing roller
16
between the toner supply roller
15
and the toner regulating means
17
are new non-magnetic mono-component toner particles T supplied from the toner supply roller
15
only.
On the other hand, when the image force Fm is so large, the residual toner particles can not be completely peeled off by the toner supply roller
15
as shown in FIG.
4
(
b
). Therefore, some of the residual toner particles pass through spaces between the developing roller
16
and the toner supply roller
15
and thus move to the toner regulating means
17
side. Since no non-magnetic mono-component toner particle T is newly supplied from the toner supply roller
15
to portions, to which residual toner particles adhere, of the developing roller
16
, the residual toner particles are carried as developer and are further charged by passing through the toner regulating means
17
so as to have larger charge. Difference in charge leads to difference in image density between a portion developed with the residual toner particles and a portion developed with new non-magnetic mono-component toner particles. That is, undesirable developing hysteresis appears.
After a solid image is printed, the amount of residual toner particles is reduced and the influence of the image force Fm is thus reduced, so none of the residual toner particles passes through spaces between the developing roller
16
and the toner supply roller
15
. Therefore, non-charged new non-magnetic mono-component toner particles T, which are not charged yet, are supplied to the developing roller
16
from the toner supply roller
15
so that the non-magnetic mono-component toner particles T are suitably charged by the toner regulating means
17
. However, after a white solid image is printed, the amount of residual toner particles is increased because most of the non-magnetic mono-component toner particles T are not developed, so the influence of the image force Fm is thus increased. As the image force Fm is large, some of the residual toner particles pass through spaces between the developing roller
16
and the toner supply roller
15
. The residual toner particles are further charged by passing through the toner regulating means
17
so as to have larger charge. The charge of non-magnetic
Chapman Mark A.
Seiko Epson Corporation
Sughrue & Mion, PLLC
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