Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – To produce color reproduction
Reexamination Certificate
1999-09-14
2001-02-27
RoDee, Christopher D. (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
To produce color reproduction
C430S043100, C430S044100, C430S030000, C399S049000, C399S066000
Reexamination Certificate
active
06194109
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to methodology associated with toner transfer in electrophotographic image forming devices, such as laser printers and copiers. In particular aspects, the invention pertains to methods of detecting and correcting inaccuracies in toner transfer from a photosensitive drum to an intermediate transfer belt.
BACKGROUND OF THE INVENTION
In electrophotographic image transfer, a pattern of electrostatic charges corresponding to an image is developed on an optical photoreceptor (OPR), such as a photosensitive drum. Toner is applied to the OPR, and that toner which is retained as a result of not being repelled by electrostatic charges forms a pattern which is transferred to an intermediate transfer belt, and then to a substrate (such as, for example, paper or plastic media). In color image forming devices, there typically will be four colors of toner (black, magenta, cyan and yellow) applied to the photosensitive drum and subsequently transferred from the drum to the intermediate transfer belt (although in some systems only three colors are used, and in other systems more than four colors can be used, with an exemplary seven-color system using black, magenta, yellow, cyan, red, green, and blue). The colors are generally transferred in the order of black, magenta, cyan, and finally yellow, with the transfer of any color not occurring until the transfer of all colors preceding that color in the listed order are finished. Accordingly, the formation of a pattern on the photosensitive drum, and subsequent transfer of the pattern to the intermediate transfer belt, occurs four times (once for each of the colors black, magenta, cyan and yellow), with the overlapping patterns on the intermediate transfer belt forming an image that is to be transferred to the substrate. It is noted that single-color patterns are typically transferred from the OPR to the intermediate transfer belt before an entirety of the single-color of toner that is ultimately to be formed on the intermediate transfer belt has been transferred to the OPR. For instance, black toner will typically begin to transfer from the OPR to the intermediate transfer belt while additional black toner is still being applied to the OPR. The toner is not, however, typically transferred from the intermediate transfer belt to the substrate until an entire image (i.e., an image containing all four of the colors of magenta, cyan, yellow and black) is formed on the intermediate transfer belt. The image formed on the intermediate transfer belt can correspond to, for example, an entirety of an image formed on a single sheet of paper. The intermediate transfer belt can be, for example, long enough to contain a complete legal document image wrapped around its circumference, plus a few extra inches. The extra space on the intermediate transfer belt between the top and bottom of the image formed on the intermediate transfer belt is called the inter-document zone.
Specific steps utilized in forming an image with a prior art image transfer device are described with reference to
FIGS. 1-3
. Referring to
FIG. 1
, a prior art image forming device
10
comprises a rotating photosensitive drum
12
(with the rotation indicated by an arrow
23
) and an intermediate transfer belt
14
moving past drum
1
2
in a direction indicated by arrow
25
. Photosensitive drum
1
2
carries a pattern of positive charges
1
6
on its surface, and such positive charges retain negatively charged toner particles
1
8
.
A support structure
20
and a primary transfer roller
22
are provided to support intermediate transfer belt
14
. Primary transfer roller
22
is in electrical connection with a DC power source
24
, and is utilized to provide a positive charge to intermediate transfer belt
14
. Such positive charge attracts the negatively charged toner from photosensitive drum
12
onto intermediate transfer belt
14
. The
FIG. 1
process of transferring toner from photosensitive drum
12
to intermediate transfer belt
14
is repeated four times in a color image transfer process (one time each for the black, magenta, cyan and yellow toners). The positive bias applied to transfer roller
22
is generally increased after each toner pass to compensate for increasing layers of toner.
FIG. 2
illustrates intermediate transfer belt
14
after an entire image has been formed on intermediate transfer belt
14
. Specifically, four layers of toner
18
(only some of toner
18
is labeled in
FIG. 2
) are shown applied over transfer belt
14
, with the layers corresponding to black, magenta, cyan and yellow toners. In the view of
FIG. 2
, transfer belt
14
is moved in a direction indicated by arrow
30
.
FIG. 2
further shows a substrate
34
being fed through feed support structures
33
of apparatus
10
and across a secondary transfer roller
36
, in a direction indicated by arrow
31
. Secondary transfer roller
36
is in electrical connection with a DC power source
38
. Power source
38
creates a positive charge which pulls toner
18
from intermediate transfer belt
14
onto substrate
34
. After the toner is transferred to substrate
34
, the toner is fused to substrate
34
. Subsequently, substrate
34
exits device
10
.
A difficulty in the processing of
FIGS. 1 and 2
can be in maintaining consistent toner density during repeated printing operations. For instance, it is found that toner density can vary due to environmental conditions, deteriorated toner, or a deteriorated photosensitive drum. A method of monitoring and maintaining toner density is described with reference to FIG.
3
.
FIG. 3
illustrates the photosensitive drum
12
of apparatus
10
, and further shows a pattern of toner patches
40
(only some of the toner patches
40
are labeled) which has been provided over a surface of photosensitive drum
12
. Toner patches
40
preferably vary in density relative to one another, with the densities being determined by a controller
42
. Controller
42
is in data communication with a density sensor
45
which comprises a light emitting diode (LED)
44
, and a pair of photodiodes
46
and
48
. Density sensor
45
is utilized to read densities of toner patches
40
. Specifically light is emitted from LED
44
and received directly by photodiode
48
, as well as reflected from toner patches
40
to be received by photodiode
46
. The signals received by photodiodes
46
and
48
are compared utilizing processing circuitry within controller
42
. Controller
42
can then adjust parameters associated with toner transfer to correct for errors encountered in the densities of toner patches
40
.
In spite of the above-described methodologies for correcting errors in toner density, inaccuracies in toner application (such as, for example, errors in spatial alignment) can still be found in images formed by image transfer devices of the type described with reference to
FIGS. 1-3
. A method of detecting such errors is to print test patterns on substrate passed through apparatus
10
.
However, while such test patterns can be useful for identifying errors, it is generally time-consuming to run and utilize such test patterns. Further, it is generally desirable to utilize methodologies which can be incorporated into image forming apparatuses to automatically detect and correct toner transfer errors without human intervention. The printing of test patterns on substrates passed through an image forming device is generally difficult to incorporate into such automatic detection and correction mechanisms. Accordingly, it would be desirable to develop alternative methodologies for detecting toner transfer inaccuracies and to incorporate such methodologies into processes which can automatically detect inaccuracies in toner transfer and correct such inaccuracies.
SUMMARY OF THE INVENTION
In one aspect, the invention encompasses a method of using an image forming device. A first pattern of toner is provided on a photosensitive drum of the image forming device. The toner is transferred from the photosensitive drum to an intermediate transf
Hewlett--Packard Company
Rodee Christopher D.
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