Formation method, image formation system, and intermediate...

Details Formation method, image formation system, and intermediate... Formation method, image formation system, and intermediate...

1999-04-15

2001-04-03

Grimley, Arthur T. (Department: 2852)

Electrophotography

Image formation

Transfer

C399S066000

Reexamination Certificate

active

06212350

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to an image formation system using an electrophotographic technology, such as a copier, facsimile, or a printer, and more particularly to an image formation system using an intermediate transfer technique involving primary and secondary transfer steps with an intermediate transfer body, etc., intervening and an intermediate transfer body used with the image formation system.
A method of once primarily transferring a toner image (developed image) formed on an image support such as a photosensitive drum onto an intermediate transfer body other than transfer paper and then secondarily transferring the image onto transfer paper for providing a copy image is known as an image formation method (transfer method) in a color image formation system such as an electrophotographic copier.
It is known that this method can be used to suppress occurrence of a multiple transfer failure and a color registration shift caused by many factors of a transfer paper hold state, transfer paper thickness or firmness, a transfer paper surface property, etc.
FIG. 10
is a schematic representation of an image formation system in a related art using an intermediate transfer body incorporating the Invention.
In the figure, an image formation system F has a UI (user interface) and a transparent platen glass
2
on which an original (not shown) is placed.
The original placed on the platen glass
2
is illuminated by a light source
4
of an original light unit
3
. Original-reflected light is reflected on a first mirror
5
of the original light unit
3
and a second mirror
7
and a third mirror
8
of a mirror unit
6
, passes through an image formation lens
9
, and is read as analog signals of R, G, and B by a CCD (charge-coupled device).
The image signals read by the CCD are input to an IPS controlled by a controller C. Image read data output means
11
of the IPS converts the input read image signals from analog form into digital form. Image data output means
12
, which has an image memory
13
, converts the digital data provided by the image read data output means
11
into Y, M, C, X image data, performs data processing of density correction, scaling correction, etc., and outputs the resultant data as write image data (laser drive data).
A laser drive signal output unit
14
outputs a laser drive signal of an image responsive to the image data output from the IPS to an ROS (optical scanner, namely, a latent image formation unit) at a predetermined timing. The ROS outputs a laser beam L modulated by the laser drive signal.
An image support
16
which rotates in charged by a charger
17
, then an electrostatic latent image is written onto the image support
16
at a latent image write position Q
1
by the laser bean L and the electrostatic latent image is developed to a toner image by a rotary developing unit
18
having K (black), Y (yellow), M (magenta), and C (cyan) color developing devices
18
k
,
18
y
,
18
m
, and
18
c
rotating together with a rotation shaft
18
a
in a developing area Q
2
. The developed toner image is primarily transferred to an intermediate transfer belt B by means of a primary transfer roll (primary transfer device) in a primary transfer area Q
3
.
Residual toner on the surface of the image support
16
passing through the primary transfer area Q
3
is removed by an image support cleaner
20
.
The intermediate transfer belt B is supported by belt support rolls
26
-
29
of a drive roll
26
, a tension roll
27
, an idler roll
28
, and an inner secondary transfer roll (backup roll)
29
for rotation.
A secondary transfer device T
2
is made up of the inner secondary transfer roll
29
, an outer secondary transfer roll
30
placed between a distant position from the inner secondary transfer roll
29
and a near position at which the outer secondary transfer roll
30
is pressed against the inner secondary transfer roll
29
so that the outer secondary transfer roll
30
can be moved away from and toward the inner secondary transfer roll
29
, and an electrode roll
31
coming in contact with the inner secondary transfer roll
29
. The secondary transfer device T
2
is driven by a power supply circuit
32
controlled by the controller C.
The secondary transfer device T
2
secondarily transfers the toner images primarily transferred onto the intermediate transfer belt B in overlapped relation to a transfer material S passing through a secondary transfer area Q
4
formed in a nip (contact area) between the outer secondary transfer roll
30
and the intermediate transfer belt B.
Toner deposited on the surface of the outer secondary transfer roll
30
is removed by a secondary transfer roll cleaner
33
. A belt cleaner
34
in placed downstream from the secondary transfer area Q
4
along the surface of the intermediate transfer belt B.
A belt position sensor SN
1
is provided for detecting a position detection mark (not shown) to detect a rotation position of the intermediate transfer belt B. The latent image write timing onto the image support
16
is controlled by a position detection signal of the intermediate transfer belt B with very high accuracy output from the belt position sensor SN
1
.
The transfer material S stored in a paper feed tray
41
is taken out by a pickup roll
42
, is separated one sheet at a time by a handling roller
43
, is once stopped at a registration roll
44
, and is transported from a guide transport passage
45
to the secondary transfer area Q
4
at a predetermined timing. The transfer material S to which the toner image is secondarily transferred when the transfer material S passed through the secondary transfer area Q
4
is transported through a sheet guide
46
and on a sheet transfer belt
47
to a fixing area Q
6
. When the transfer material S passes through the fixing area Q
6
, the secondarily transferred toner image onto the transfer material S is fixed by a pair of fixing roll a of a fuser
48
and the transfer material S is diacharged to a paper discharge tray
49
.
The components
41
to
47
make up a transfer material transporter (
42
-
47
).
The image formation system incorporating the invention shown in
FIG. 10
uses the intermediate transfer belt B as an intermediate transfer body, but the invention can also be applied to an image formation system using an intermediate transfer drum in place of the intermediate transfer belt B.
In the image formation system using an intermediate transfer body as described above, hitherto a substance comprising a filler such as carbon or a metal compound dispersed in a polymeric material as a conductive agent has been used an the intermediate transfer body. (The Unexamined Japanese Patent Application Publication No. Hei 8-320622).
It is known that there is a close relation between the volume resistivity of the intermediate tranafer body and the toner image quality.
(When Volume Resistivity of Intermediate Transfer Body, &rgr;, is low)
When the volume resistivity of the intermediate transfer body, &rgr;, is too low (&rgr;≦10
6
&OHgr;cm), toner strikingly scatters at the transfer time and the image quality is degraded (The Unexamined Japanese Patent Application Publication No. Hei 8-248779). The possible reason is that when the volume resistivity of the intermediate transfer body is too low, a transfer electric field is easily applied to an area with no toner layer by the action of transfer current and transfer electric field produced by a primary transfer roll and thus a transfer area spreads and toner scatters and is transferred because of the effect.
(When Volume Resistivity of Intermediate Transfer Body is Intermediate)
The current intermediate transfer body of the image formation system in the actual use has an intermediate value of volume resistivity (10
6
&OHgr;cm≦&rgr;≦10
14
&OHgr;cm).
Such an image formation system has charges attenuated properly because of the semiconductivity of the intermediate transfer body. That is, an average value of the volume resistivity of the intermediate transfer body lies in the range in which the

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