U.S. patent application number 10/484694 was filed with the patent office on 2005-03-24 for cylindrical developer carrier and production method thereof.
This patent application is currently assigned to Fuji Electric Imaging Device Co.. Invention is credited to Iguchi, Yasushi, Tsubota, Toshio.
Application Number | 20050065006 10/484694 |
Document ID | / |
Family ID | 19056299 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050065006 |
Kind Code |
A1 |
Tsubota, Toshio ; et
al. |
March 24, 2005 |
Cylindrical developer carrier and production method thereof
Abstract
A cylindrical developer carrier capable of fully charging a
toner compound on a developing sleeve via frictional force even
after being used repeatedly. The cylindrical developer carrier
includes an electrically conductive substrate having an evenly
roughened surface, and an alumite layer formed on the roughened
surface, wherein the alumite layer has a uniform distribution of
minute holes that reach the substrate surface. A method for
manufacturing the cylindrical developer carrier includes roughening
the electrically conductive substrate surface by blasting it with
spherical fine particles, forming the alumite layer on the
roughened surface by an anodizing method, and blasting the surface
of the alumite-layer with amorphous fine particles that a diameter
greater than that of the spherical fine particles.
Inventors: |
Tsubota, Toshio; (Nagano,
JP) ; Iguchi, Yasushi; (Nagano, JP) |
Correspondence
Address: |
RABIN & Berdo, PC
1101 14TH STREET, NW
SUITE 500
WASHINGTON
DC
20005
US
|
Assignee: |
Fuji Electric Imaging Device
Co.
4-18-1, Tsukama, Matsumoto-shi
Nagano 390-0821
JP
|
Family ID: |
19056299 |
Appl. No.: |
10/484694 |
Filed: |
November 24, 2004 |
PCT Filed: |
July 11, 2002 |
PCT NO: |
PCT/JP02/07056 |
Current U.S.
Class: |
492/37 ;
29/895.3 |
Current CPC
Class: |
Y10T 29/4956 20150115;
G03G 15/0818 20130101 |
Class at
Publication: |
492/037 ;
029/895.3 |
International
Class: |
B21B 027/02; B21D
053/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 24, 2001 |
JP |
2001-222884 |
Claims
1-12. (canceled)
13. A cylindrical developer carrier comprising an electrically
conductive substrate having an evenly roughened surface; and an
alumite layer formed on said surface, wherein said alumite layer
has a uniform distribution of minute holes respectively reaching
said substrate surface.
14. A cylindrical developer carrier according to claim 13, wherein
said electrically conductive substrate is formed primarily of an
aluminum-group metallic material.
15. A cylindrical developer carrier according to claim 13, wherein
said alumite layer comprises an alumite layer formed by an
anodizing method.
16. A cylindrical developer carrier according to claim 15, further
comprising nickel acetate sealing said alumite layer.
17. A cylindrical developer carrier according to claim 13, further
comprising nickel acetate sealing said alumite layer.
18. A cylindrical developer carrier according to claim 17, wherein
said alumite layer has a thickness in the range of 2 .mu.m to 5
.mu.m.
19. A cylindrical developer carrier according to claim 13, wherein
said alumite layer has a thickness in the range of 2 .mu.m to 5
.mu.m.
20. A cylindrical developer carrier according to claim 19, wherein
said minute holes, as a whole, account for 10% to 50% of the total
area of the alumite layer.
21. A cylindrical developer carrier according to claim 13, wherein
said minute holes, as a whole, account for 10% to 50% of the total
area of the alumite layer.
22. A method for manufacturing a cylindrical developer carrier
comprising the steps of: roughening an electrically conductive
substrate surface by blasting spherical fine particles onto the
substrate surface; forming an alumite layer on the roughened
surface by an anodizing method; and blasting the surface of the
alumite-layer with amorphous fine particles each having a diameter
greater than that of the spherical fine particles.
23. A method for manufacturing a cylindrical developer carrier
according to claim 22, wherein the blasting the spherical fine
particles includes blasting the electrically conductive substrate
surface with glass beads, and the blasting the surface of the
alumite layer with amorphous fine particles includes blasting the
alumite layer surface with amorphous fine particles formed
primarily of aluminum oxide, each of the amorphous fine particles
having a diameter greater than that of the spherical fine
particles.
24. A method for manufacturing a cylindrical developer carrier
according to claim 23, wherein the step of blasting said
electrically conductive substrate surface with spherical fine
particles includes a step of blasting the substrate surface with
spherical fine particles consisting solely of glass beads, so as to
form a number of projections and recesses each having a mean
surface roughness rated at Ra=0.8 .mu.m to 1.5 .mu.m, and the
blasting the surface of the alumite layer with amorphous fine
particles includes blasting the alumite layer surface with
amorphous fine particles formed primarily of aluminum oxide, each
of the amorphous fine particles having a diameter greater than that
of the spherical fine particles.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a cylindrical developer carrier
loaded on an electrophotographic apparatus such as an
electrophotographic printer, copying machine, or fax machine.
DESCRIPTION OF BACKGROUND ARTS
[0002] Conventionally, any electrophotographic apparatus, such as a
laser printer, LED printer, or copying machine using normal paper,
executes the formation of images through application of a so-called
Carlson process. The Carlson process is a method for forming an
image via the output of a toner image transcribed and fixed on copy
paper or the like every cycle of an electrophotographic process
executed via components for performing an electrification (i.e.,
charging), an exposure, a toner development, an image
transcription, and an electrical discharge. Such components
respectively are disposed on the circumferential surface of a
cylindrical photoconductor provided with a photosensitive
layer.
[0003] In the course of executing the above processes, when a
static latent image formed on the surface of the photoconductor via
the above electrifying and exposing steps is converted into a
positive image in the following toner developing step, toner
compound stored in a developer unit is held and carried to an area
close to the surface of the photoconductor through the application
of a static electrical force via a cylindrical developer carrier,
i.e., via a developing sleeve, before the static latent image
present on the surface of the photoconductor is eventually
developed into a positive image. In order to secure a satisfactory
image via the above developing method, it is extremely important
that the toner compound on the developing sleeve be held and
carried as a leveled layer free from the generation of
deflection.
[0004] Likewise, when an excessively thick or thin toner layer is
formed on the developing sleeve, in terms of developing density, a
satisfactory image cannot be obtained. To prevent this, aside from
the need to separately provide the system with a specific member
for regulating toner thickness on the developing sleeve, in
uniformly distributing toner compound over the entire developing
sleeve, surface conditions of the developing sleeve are also quite
important. A fully smoothed surface is not always the optimal
choice. It is, rather, conventionally considered to be more
advantageous to provide the surface of the developing sleeve with
projections and recesses each having appropriate magnitude so as to
enable optimum friction force to be generated between the
developing sleeve and the toner compound. On the other hand,
depending on the hardness of the developing sleeve, these
projections and recesses are subject to wear after repeated use.
This causes the quality of images to be gradually degraded, thus
leading to a problem. To cope with this problem, an improvement in
wear-resistance properties has been sought by those concerned. In
cases in which a developing sleeve is made of an aluminum alloy,
its Vickers hardness is rated to be as low as approximately 70 Hv.
Thus, it is known that wear-resistance properties can be improved
through the formation of an alumite surface layer generated by
anodization with a Vickers hardness as high as approximately 200 to
400 Hv after completing formation of projections and recesses on
its surface (refer to the Laid-Open Japanese Patent Publication No.
HEISEI 5-46008/1993).
[0005] On the other hand, in cases in which an alumite layer has
been formed on the surface of the developing sleeve, due to the
insulation characteristics of the alumite layer, its surface
resistance rises. However, in the case of a high surface resistance
value, the charge borne by the toner compound in the area
corresponding to the spot for forming an image applied during the
preceding developing process is apt to remain as it is without
fully shifting onto the surface of the photoconductor from the
developing sleeve. As a result, the amount of charge in a specific
area of the developing sleeve corresponding to the above-described
spot becomes greater than the amount of charge in those areas
without the formation of images. As a result, when another image is
formed in the ensuing developing step, in the above specific area
of the developing sleeve corresponding to the spot at which the
last image was formed, developing-agent is further drawn toward
another specific area of the developing sleeve containing a higher
charge. Thereby, the toner compound becomes more difficult to shift
onto the surface of the photoconductor. This in turn leads to
another problem in that a difference in depth is apt to be
generated on the developed image of the photoconductor through the
generation of a specific pattern corresponding to the image
generated during the last developing process. In other words, a
so-called "ghost image" is apt to be generated. In summary, the
above symptom of a defect may be defined as the difference in the
developing capability in correspondence with the toner development
history (hereinafter also referred to as "memory").
[0006] In consideration of the technical problems described thus
far, the invention aims at providing a novel cylindrical developer
carrier and a method for manufacturing it, wherein the cylindrical
developer carrier is capable of fully charging a toner compound on
a developing sleeve via friction force even after being used
repeatedly. The invention also aims to provide a cylindrical
developer carrier wherein toner compound in the form of a leveled
(even) layer can be properly held and carried, and the cylindrical
developer carrier does not generate even the slightest difference
in developing capability in correspondence with the toner
development history.
SUMMARY OF THE INVENTION
[0007] According to the invention, the above-specified object has
been achieved through the provision of a novel cylindrical
developer carrier incorporating an alumite layer coated on a
uniformly roughened surface of an electrically conductive
substrate. The alumite layer uniformly incorporates minute holes
reaching the above-described conductive substrate.
[0008] According to another aspect of the invention, the
cylindrical developer carrier is provided with an electrically
conductive substrate consisting primarily of an aluminum-group
metallic material. According to a further aspect of the invention,
the cylindrical developer carrier is composed of an alumite layer
formed through the application of an anodizing method. According to
still another aspect of the invention, the cylindrical developer
carrier is composed of an alumite layer having minute holes sealed
with nickel acetate. The alumite layer may have a thickness of 2
.mu.m to 5 .mu.m. According to a further aspect of the invention,
the minute holes account for 10% to 50% of the total area of the
formed alumite layer that constitutes the cylindrical developer
carrier.
[0009] According to an embodiment of the invention, a first method
for manufacturing the inventive cylindrical developer carrier
includes the following steps: Initially, the surface of an
electrically conductive substrate is roughened uniformly by
blasting spherical fine particles onto the surface. An alumite
layer is formed using anodization. The surface is blasted with
amorphous fine particles, each having a diameter greater than that
of said spherical fine particles.
[0010] According to another embodiment of the invention, a second
method for manufacturing the cylindrical developer carrier includes
the following steps: Initially, spherical fine particles, including
glass beads, are blasted onto the surface of an electrically
conductive substrate. An alumite layer is formed by anodization.
Then the surface is blasted with amorphous fine particles
consisting primarily of aluminum oxide, with each particle having a
diameter greater than that of the spherical fine particles.
[0011] According to a further embodiment of the invention, a third
method for manufacturing the cylindrical developer carrier includes
the following steps: Initially, spherical fine particles, including
glass beads, are blasted onto the surface of an electrically
conductive substrate. Projections and recesses are formed each
being provided with a mean surface roughness in a specific range
expressed in terms of Ra=0.8 .mu.m to 1.5 .mu.m. An alumite layer
is formed by anodization. Lastly, the surface is blasted with
amorphous fine particles consisting primarily of aluminum oxide,
and each particle has a diameter greater than that of said
spherical fine particles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] In the accompanying drawings:
[0013] FIG. 1 is a perspective view of the cylindrical developer
carrier according to an embodiment of the invention;
[0014] FIG. 2 is a partially enlarged cross-sectional view of a
cylindrical developer carrier according to an embodiment of the
invention; and
[0015] FIG. 3 is a schematic cross-sectional view of an image
forming apparatus loaded with a cylindrical developer carrier
according to an embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] With reference to the accompanying drawings, preferred
embodiments of the cylindrical developer carrier according to the
invention are described below. However, it should be understood
that the scope of the invention is by no means limited to the
embodiments described below.
[0017] FIG. 1 is a perspective view of a cylindrical developer
carrier, i.e., a developing sleeve 11, according to an embodiment
of the invention. FIG. 2 is a partially enlarged cross-sectional
view of the developing sleeve 11. FIG. 3 is a schematic
cross-sectional view of an image forming apparatus 100 loaded with
the developing sleeve 11 according to an embodiment of the
invention.
[0018] Referring to FIG. 3, the image forming apparatus 100
includes a variety of electrophotographic processing members,
including a toner developing unit (consisting of a roller
electrifying (charging) member 3, an image exposing means 4,
including an image exposing light source, a developing-agent
storage tank 5, and a developing sleeve 1, an image transcribing
unit 6, and a discharging member 7. These members respectively are
disposed on the external circumferential surface of a cylindrical
electrophotographic organic photoconductor 10.
[0019] The image forming apparatus 100, which is based on the
contact (roller) charging system shown in FIG. 3, serially executes
electrophotographic processes through application of the
above-described developing members, before eventually forming a
predetermined image. A method of forming an image is described
below. Initially, a predetermined voltage is added to the roller
charging member 3 disposed in contact with the surface of the
photoconductor 10. This electrifies the entire surface of the
photoconductor 10. Next, through the application of the image
exposing means 4, an image corresponding to a predetermined
document is exposed to the surface of the photoconductor 10, thus
forming a static latent image. Next, a toner compound, previously
stirred and electrified in the developing-agent storage tank 5, is
statically transferred and adhered to the circumferential surface
of the photoconductor 10 via the developing sleeve 11, before the
static latent image on the photoconductor 10 is converted to a
visible positive image. Next, the toner image formed on the surface
of the photoconductor 10 is transferred or transcribed onto an
image material such as paper fed via a paper-feeding roller and a
paper-feeding guide member. The transfer is performed through the
application of the transcribing unit 6. Finally, residual toner
compound remaining on the photoconductor 10 without having been
transcribed onto the sheet is collected by a cleaning member 12. In
the event that a residual charge still remains inside the
photoconductor 10, it is suggested that the residual charge be
eliminated through the application of an adequate voltage or light
beams to the photoconductor 10 via the discharging means 7. On the
other hand, the sheet material onto which a transcribed toner image
is formed is transferred to a fixing unit (not shown) via a
conveying unit, thus enabling the toner image to be fixed before
eventually being output as a visible positive image.
[0020] In the image forming apparatus 100, the light source for the
image exposing means 4 may consist of a halogen lamp, a fluorescent
lamp, laser beams, or the like. It is also permissible to add any
auxiliary processing step, as required. In addition to copying
machines, the image forming apparatus 100 may also be applied to a
wide variety of applicable electrophotographic devices, such as a
laser printer or an electronic photoengraving system, for
example.
[0021] As shown in the perspective view illustrated in FIG. 1, the
developing sleeve 11 consists of a 20 mm-diameter sleeve-shaped
electrically conductive substrate 1 fitted with a pair of shaft
holders on both sides, which is made entirely of aluminum alloy.
The actual diameter may be adjusted according to the type of
component loaded. Normally, the diameter will be in a range from 10
mm to 25 mm. In the above-cited example, the aluminum alloy is made
entirely of the composition corresponding to the JIS-A6063
standard. However, an aluminum alloy conforming to the JIS-A5056 or
JIS-A3003 standard may also be used. The aluminum sleeve substrate
1 is formed in accordance with the below-described series of steps.
Initially, the original pipe is manufactured by processing an
aluminum-alloy ingot using an extruding machine and a drawing
machine. Next, the surface of the formed original pipe is planed or
ground using a cutting tool or a grindstone until the pipe surface
is completely smoothed. Next, through the application of a number
of spherical glass beads, having a maximum mean particle size of 44
.mu.m (#600), the surface of the sleeve substrate 1 is treated
using a blasting process until recesses and projections created
thereby produce a mean surface roughness value Ra in a
predetermined range, from 0.8 .mu.m to 1.5 .mu.m. It should be
noted that, if the mean surface roughness value exceeds 1.5 .mu.m,
toner compound will remain in the recessed portions. Conversely, if
the mean surface roughness value is less than 0.8 .mu.m, the effect
of the frictional charge that can be borne by the toner compound
will become insufficient, resulting in a poor density of the toner
compound. This latter circumstance may lead to a failure to achieve
proper density in images. Further, inadequate mean surface
roughness leads to slippage of the toner compound. Therefore as a
result of which the toner layer will not be uniform due to uneven
propagation of the toner.
[0022] Next, through the application of an anode-oxidizing process
against the roughened surface of the sleeve substrate 1, an alumite
layer 2 is formed and then sealed. The sealing process preferably
is executed through the application of nickel acetate. However, the
invention also is realizable with the use of sealing methods. It is
preferred that the alumite layer 2 be provided with a thickness in
the range from 2 .mu.m to a maximum of 5 .mu.m. If the thickness
exceeds 5 .mu.m, it will become quite difficult uniformly to form a
plurality of minute holes 21 reaching the aluminum substrate 1
according to the invention, as described below. Conversely, if the
above thickness is less than 2 .mu.m, the alumite layer 2 will wear
quickly.
[0023] After the above alumite layer 2 has been formed, a plurality
of minute holes 21 are formed by blasting the layer surface with
fine particles of amorphous aluminum oxide (alumina), each having a
hardness value greater than that of alumite. Insofar as the
hardness value is greater than that of alumite, it is also possible
to use fine particles of another material. The particle size (such
as #320) of the usable alumina fine particles shall be greater than
the particle size (such as #600) of the above-described glass
beads.
[0024] The object of the blasting process following the formation
of the alumite layer 2, and the details of the process are
described below. Initially, among the projections and recesses
formed on the alumite layer 2, only the alumite layer 2 immediately
above the projections is removed. Then, a plurality of uniformly
distributed minute holes 21 reaching the aluminum substrate 1 are
provided so as to provide a plurality of uniformly distributed
leakage sites for allowing leakage from the charge borne by the
toner compound. Thereby, the surface resistance value of the
alumite layer 2 is minimized, which solves the above-described
technical problem arising from a difference in the developing
capability in correspondence with the surface's toner development
history.
EXAMPLE
[0025] In order to accurately determine the relationship of quality
of images to the ratio of the area of the minute holes formed
immediately above the projections on the alumite layer 2 to the
area shared by the formed alumite layer 2, the inventors conducted
experiments. Initially, actual samples of the developing sleeve 11
were prepared, and were individually provided with ratios 5%, 10%,
20%, 40%, 50%, 60%, 70%, and 100% of the total area of the minute
holes 21 to the actual area shared by the alumite layer 2
(hereinafter total ratios). The total area ratios were computed
based on the difference in the light reflection ratios as between
the alumite-layer formed portions and the minute holes 21. More
particularly, a light-reflection rating instrument was used, with
which the total area ratios of the minute holes 21 were computed
based on a calibration curve prepared from a previously known
sample. Alternatively, it is also allowable to compute area ratios
by referring to an enlarged photographic view of the sleeve
surface. The computed results are shown in TABLE 1.
[0026] Then, the actual quality of the formed images and actual
service life of the developing sleeves 11 were respectively
evaluated. Through the application of a Macbeth densiometer, the
density of images was evaluated, with ratings of 1.3 and above 1.3
designated by circular symbols (o), ratings of 1.2 to 1.3
designated by triangular symbols (.DELTA.), and ratings below 1.2
designated by a cross symbol (x), as shown in TABLE 1 below. It is
understood from the results of evaluation of the density of images
that the toner compound was fully subjected to friction, and the
subsequent charge was applied to the developing sleeve 11 before
being formed into a level layer of toner compound, which was then
properly held and carried without generating any deflection.
[0027] Following evaluation of an image memory (toner development
history) to check for a difference in the toner developing
capability, the results showing non-occurrence of a difference in
the developing capability were designated by circular symbols (o)
in TABLE 1 below. The results showing the occurrence of some
difference in the toner developing capability were designated by a
triangular symbol (.DELTA.). The results showing the actual
occurrence of a difference in the toner developing capability were
designated by cross symbols (x). It is thus understood from the
results of evaluation of the image memory shown in TABLE 1 that the
developing sleeve 11 retained a proper surface condition through
the preservation of appropriate leakage sites, without generating
any difference in the toner developing capability in correspondence
with the toner development history.
[0028] To evaluate the actual service life of the developing
sleeves 11, up to more than 20,000 copies were prepared with each
sleeve. Those sleeves found to be sufficiently durable after the
processing of more than 20,000 copies were designated by circular
symbols (o). Those sleeves found to be sufficiently durable for
processing only 10,000 to 20,000 copies were designated by
triangular symbols (.DELTA.), whereas those sleeves found to be
insufficiently durable to process even 10,000 copies were
designated by cross symbols (x) in TABLE 1 below. Thus, the results
of evaluation of the actual service life of the developing sleeves
corresponding to the former two groups enabled the inventors to
detect the presence or absence of variations in (or degradation of)
the physical characteristics of the developing sleeves as between
an initial state and after use to prepare a predetermined number of
copies.
[0029] To define the overall results of the evaluations of the
groups of sleeves with the respective minute hole area ratios,
results evaluated as (o) in all three categories were rated with a
designation (o). In the event that even a single characteristic was
rated with a cross symbol (x), the overall evaluation result for
the group of sleeves was designated by the cross symbol (x) as
well. Those sleeve groups for which at least one characteristic was
designated by the triangular symbol (.DELTA.), without the presence
of a designation with the cross symbol (x), were identified with
the triangular symbol (.DELTA.) in the designation of their overall
evaluation result.
1TABLE 1 Minute hole Image Image Sleeve Overall area ratio (%)
density memory life evaluation 5 .smallcircle. x .smallcircle. x 10
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 20
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 40
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 50
.smallcircle. .smallcircle. .smallcircle. .smallcircle. 60
.smallcircle. .smallcircle. .DELTA. .DELTA. 70 .DELTA.
.smallcircle. x x 100 x .smallcircle. x x
[0030] With reference to TABLE 1, the above three characteristics
(image density, image memory, and sleeve life) were evaluated as
(o) when the area ratio of minute holes to the area shared by the
alumite layer formed on the surface of the developing sleeve ranged
from 10% to 50%, and it is thus clear that the overall evaluation
result for these developing sleeves was favorably designated to be
(o) as well.
[0031] Thus, according to the invention, an alumite layer is
provided by coating over the entire surface of an electrically
conductive substrate that has been uniformly roughened, wherein the
alumite layer itself constitutes a cylindrical developer carrier
evenly incorporating minute holes respectively reaching the surface
of the above-described substrate. Due to this construction, even
after repeated use, toner compound can be subjected to and hold a
full, evenly propagated frictional charge on the developing sleeve,
thereby enabling the invention to provide a novel cylindrical
developer carrier without generating any difference in the toner
developing capability in correspondence with the toner development
history.
* * * * *