Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-12-28
2004-02-03
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...
C430S108700, C430S110100
Reexamination Certificate
active
06686110
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a toner, composed of a plurality of mother particles and a plurality of external additive particles such as particles of silica, for developing an electrostatic latent image formed on a latent image carrier, and to an image forming apparatus for forming an image using the toner.
More particularly, the present invention relates to a toner, in which at least a plurality of particles of silica are used as an external additive and which has a function of preventing filming of toner to toner-contact members such as a latent image carrier, a toner carrier, and a toner regulating member, with which the toner may come in contact, thereby improving the durability of toner-contact members and also allowing the low-temperature fixing to be conducted well.
Further, the present invention relates to a toner in which at least a plurality of particles of titanium oxide or particles of alumina are used as an external additive and which is capable of stabilizing the charging property of toner, and to an image forming apparatus using this toner.
In an image forming apparatus using a toner, an image is obtained by developing an electrostatic latent image on a latent image carrier by a toner, transferring the developed image from the latent image carrier to a recording media such as paper to form a transferred image of the electrostatic latent image exposed on the latent image carrier, and finally fixing the transferred image to the recording media.
Among conventional 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
2
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
.
Then, residual toner particles T′ remaining on the photoreceptor
2
after the developed images are transferred to the intermediate transfer belt
7
a
are removed by a cleaning blade
11
and are collected in a residual toner box
12
. Similarly, residual toner particles remaining on the intermediate transfer belt
7
a
after the primary transferred image is transferred to the recording media
9
are removed by a cleaning blade and are collected in a residual toner box.
The respective non-magnetic mono-component developing devices
3
,
4
,
5
, 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
), 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 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 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 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 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 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 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 toner particles T by jumping-developing.
In the conventional non-magnetic mono-component developing device, some toner particles T may be fused to toner-contact members, with which the toner may come in contact, such as the developing roller
16
, the toner regulating blade
17
, and/or the photoreceptor
2
or, alternatively, liberated external additive particles may be separated from the toner particles, thus leading to the occurrence of filming. Due to the filming, the insufficiency of toner carrying function of the developing roller
16
, the insufficiency of regulating function of the toner regulating blade
17
, and/or the insufficiency of developing function of the photoreceptor
2
may be occurred, thus further leading to degradation of image quality.
When the toner particles T are not uniformly charged, the insufficiency of toner carrying function of the developing roller
16
, and/or the insufficiency of developing function of the photoreceptor
2
may be similarly occurred, thus further leading to similar problems.
To solve these problems, conventionally, resin mother particles
18
of the toner T are coated with external additive particles
19
as shown in FIG.
2
(
b
). The size of the external additive particles
19
is set to be significantly smaller than the size of the mother particles
18
.
Since use of a fixing device
10
for heat fixing enables the low-temperature fixing, conventionally, the mother particles
18
of the toner T have a low softening point so that the mother particles
18
are soft even at ordinary temperature.
On the other hand, in the conventional non-magnetic mono-component developing device, at least silica (SiO
2
)
19
is added as the external additive
19
in order to prevent the occurrence of the filming.
Further, in the non-magnetic mono-component developing device, titanium oxide (TiO
2
)
19
is added as the external additive
19
serving as a charge controlling agent as shown in FIG.
2
(
b
) in order to stabilize the charge of the toner T.
Furthermore, in the non-magnetic mono-component developing device, alumina (Al
2
O
3
)
19
is added as the external additive
19
serving as a charge controlling agent and a cleaner as shown in FIG.
2
(
b
) in order to stabilize the charge of the toner T and to clean the photoreceptor
2
.
Particularly, most of conventional color toners employ a combination of silica and titanium oxide.
By the way, as for the aforementioned toner T, the external additive particles
19
adhere to the mother particles
18
by agitating the mother particles
18
and the external additive particles
19
. As shown in FIG.
2
(
b
), actually there are mother particles
18
and external additive particles
19
which adhere to each other (it should be noted that the numeral
18
is used for designating mother particles themselves as described above and also designating mother particles to which external additive particles
19
adhere and that
Chapman Mark A.
Seiko Epson Corporation
Sughrue & Mion, PLLC
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