U.S. patent application number 11/393664 was filed with the patent office on 2006-10-26 for electrophotographic belt, electrophotographic apparatus, process for producing the electrophotographic belt, and intermediate transfer belt.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Taku Kanai.
Application Number | 20060240248 11/393664 |
Document ID | / |
Family ID | 37187308 |
Filed Date | 2006-10-26 |
United States Patent
Application |
20060240248 |
Kind Code |
A1 |
Kanai; Taku |
October 26, 2006 |
Electrophotographic belt, electrophotographic apparatus, process
for producing the electrophotographic belt, and intermediate
transfer belt
Abstract
An electrophotographic belt is disclosed including a base layer
which contains a thermoplastic resin and has a mass loss percentage
of 0.30% or more after a Taber abrasion test (ASTM D-1175; at a
load of 4.9 N and 500 revolutions) and a cured resin film which has
been formed on the base layer by coating, contains conductive
particles and has a thickness of from 0.5 .mu.m or more to 3.0
.mu.m or less. The cured resin film has at its surface a mass loss
percentage of 0.050% or less after the Taber abrasion test. The
electrophotographic belt has volume resistivity .rho.v (.OMEGA.cm)
and surface resistivity .rho.s (.OMEGA./square) which satisfy the
following expressions (1), (2) and (3):
10.sup.6.ltoreq..rho.v.ltoreq.10.sup.10 (1),
10.sup.8.ltoreq..rho.s.ltoreq.10.sup.13 (2),
.rho.s/.rho.v.gtoreq.10.sup.2 (3).
Inventors: |
Kanai; Taku; (Yokohama-shi,
JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
TOKYO
JP
|
Family ID: |
37187308 |
Appl. No.: |
11/393664 |
Filed: |
March 31, 2006 |
Current U.S.
Class: |
428/336 ;
427/180; 427/372.2; 427/402; 428/411.1; 428/412; 428/421;
428/522 |
Current CPC
Class: |
G03G 15/75 20130101;
Y10T 428/31935 20150401; Y10T 428/265 20150115; G03G 5/105
20130101; Y10T 428/31504 20150401; G03G 5/14704 20130101; G03G
2215/00957 20130101; G03G 5/14743 20130101; G03G 5/14708 20130101;
G03G 5/14795 20130101; G03G 5/10 20130101; G03G 5/14734 20130101;
G03G 5/14786 20130101; Y10T 428/31507 20150401; Y10T 428/3154
20150401; G03G 5/14791 20130101 |
Class at
Publication: |
428/336 ;
428/411.1; 428/522; 428/421; 428/412; 427/402; 427/180;
427/372.2 |
International
Class: |
G11B 5/64 20060101
G11B005/64; B05D 3/02 20060101 B05D003/02; B05D 1/12 20060101
B05D001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2005 |
JP |
2005-127976 |
Claims
1. An electrophotographic belt which comprises a base layer
containing a thermoplastic resin and having a mass loss percentage
of 0.30% or more after a Taber abrasion test (ASTM D-1175; at a
load of 4.9 N and 500 revolutions) and a cured resin film formed on
the base layer by coating, containing conductive particles and
having a thickness of from 0.5 .mu.m or more to 3.0 .mu.m or less;
said cured resin film having at its surface a mass loss percentage
of 0.050% or less after the Taber abrasion test (ASTM D-1175; at a
load of 4.9 N and 500 revolutions); and said electrophotographic
belt having volume resistivity .mu.v (.OMEGA.cm) and, at the
surface of said cured resin film, surface resistivity .rho.s
(.OMEGA./square) which satisfy the following expressions (1), (2)
and (3): 10.sup.6.ltoreq..rho.v.ltoreq.10.sup.10 (1),
10.sup.8.ltoreq..rho.s.ltoreq.10.sup.13 (2),
.rho.s/.rho.v.gtoreq.10.sup.2 (3).
2. The electrophotographic belt according to claim 1, wherein said
cured resin film is a cured film formed by applying on said base
layer a coating fluid which contains dipentaerythritol hexaacrylate
and said conductive particles, followed by curing.
3. The electrophotographic belt according to claim 1, wherein the
thermoplastic resin contained in said base layer is polyvinylidene
fluoride or polycarbonate.
4. The electrophotographic belt according to claim 1, wherein said
cured resin film has a thickness of from 1.0 .mu.m or more to 3.0
.mu.m or less.
5. An electrophotographic apparatus which comprises the
electrophotographic belt according to claim 1.
6. A process for producing the electrophotographic belt according
to claim 1; the process comprising: a base layer forming step of
forming said base layer by using a thermoplastic resin; and a
surface layer forming step of applying on said base layer formed by
the base layer forming step a surface layer forming coating fluid
which contains a monomer and/or oligomer component as a raw
material for said cured resin film, conductive particles and a
solvent, followed by drying and curing to form said surface
layer.
7. The process according to claim 6, wherein said surface layer
forming coating fluid contains said monomer and/or oligomer
component in an amount of from 30 to 60% by mass, said conductive
particles in an amount of from 10 to 20% by mass, and said solvent
in an amount of from 30 to 60% by mass.
8. The process according to claim 6, wherein said surface layer
forming step is carried out in an environment of a temperature of
from 35 to 45.degree. C. and a humidity of from 5 to 20% RH.
9. The process according to claim 6, wherein said solvent contains
methyl ethyl ketone.
10. The process according to claim 6, wherein said monomer and/or
oligomer component is dipentaerythritol hexaacrylate.
11. An intermediate transfer belt which comprises a base layer
containing a thermoplastic resin and having a mass loss percentage
of 0.30% or more after a Taber abrasion test (ASTM D-1175; at a
load of 4.9 N and 500 revolutions) and a cured resin film formed on
the base layer by coating, containing conductive particles and
having a thickness of from 0.5 .mu.m or more to 3.0 .mu.m or less;
said cured resin film having at its surface a mass loss percentage
of 0.050% or less after the Taber abrasion test (ASTM D-1175; at a
load of 4.9 N and 500 revolutions); and said intermediate transfer
belt having volume resistivity .rho.v (.OMEGA.cm) and, at the
surface of said cured resin film, surface resistivity .rho.s
(.OMEGA./square) which satisfy the following expressions (1), (2)
and (3): 10.sup.6.ltoreq..rho.v.ltoreq.10.sup.10 (b 1),
10.sup.8.ltoreq..rho.s.ltoreq.10.sup.13 (2),
.rho.s/.rho.v.gtoreq.10.sup.2 (3).
12. The intermediate transfer belt according to claim 11, wherein
said cured resin film is a cured resin film formed by applying on
said base layer a coating fluid which contains dipentaerythritol
hexaacrylate and said conductive particles, followed by curing.
13. The intermediate transfer belt according to claim 11, wherein
the thermoplastic resin contained in said base layer is
polyvinylidene fluoride or polycarbonate.
14. The intermediate transfer belt according to claim 11, wherein
said cured resin film has a thickness of from 1.0 .mu.m or more to
3.0 .mu.m or less.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to an electrophotographic belt (belt
for electrophotography) such as a transfer material transport belt
or an intermediate transfer belt, used in image forming apparatus
which utilize electrophotographic systems, i.e., what are called
electrophotographic apparatus, and also relates to an
electrophotographic apparatus having the electrophotographic belt,
and a process for producing the electrophotographic belt.
Monochrome or color (inclusive of full-color) copying machines and
printers (such as LBPs) are available as electrophotographic
apparatus having electrophotographic belts.
[0003] 2. Related Background Art
[0004] In order to stably reproduce high-grade images by using an
electrophotographic apparatus having an electrophotographic belt,
it is important to balance the volume resistivity of the
electrophotographic belt and the surface resistivity of the surface
of the electrophotographic belt on which a toner image or a
transfer material is held.
[0005] Specifically, taking as an example the case of an
intermediate transfer belt, the intermediate transfer belt is
required to surely hold on its surface toner images primarily
transferred from an electrophotographic photosensitive member, and
is further required to allow the toner images held on its surface
to be secondarily transferred to a transfer material such as paper
in a good efficiency. In order to render such conflicting
performances compatible with each other at a high level, it is
effective to take into account the balance between volume
resistivity and surface resistivity of the intermediate transfer
belt.
[0006] For example, Japanese Patent Application Laid-open No.
H10-228188 discloses that where the surface resistivity and volume
resistivity of an intermediate transfer member (such as an
intermediate transfer belt) are represented respectively by
10.sup.x .OMEGA./square and 10.sup.y .OMEGA.cm, these are so set as
to be 10.ltoreq.x.ltoreq.14, y.ltoreq.13 and x.gtoreq.y. Then, it
discloses that by controlling the volume resistivity and surface
resistivity in this way, toner images primarily transferred onto
the intermediate transfer belt do not scatter and discharge
naturally occurs before subsequent toner images are primarily
transferred. It also discloses that the constitution of the
intermediate transfer belt may be either of a single-layer
structure and a multi-layer structure.
[0007] In addition, t is demanded for the electrophotographic belt
to have excellent flexing resistance in order to secure good
handling properties in the electrophotographic apparatus. It is
also demanded for the belt to have excellent wear resistance so
that as a result of wear, the surface of the electrophotographic
belt for holding toner images or a transfer material is not changed
in physical properties or in electrical properties required as the
electrophotographic belt. As a material that may satisfy the above
at a high level, for example, curable polyimide may be cited.
[0008] The curable polyimide, however, is commonly expensive.
Accordingly, in order to obtain a lower-cost electrophotographic
belt, the present inventors have made studies on an
electrophotographic belt comprising a base layer having a good
flexibility, containing a thermoplastic resin, and formed on the
base layer a surface layer having good wear resistance.
Specifically, they have studied how a cured resin film having a
uniform thickness and good adherence to the base layer can be used
as the surface layer.
[0009] As a result of the studies, the present inventors have
realized that the surface layer must be formed in a thickness of
3.0 .mu.m or less in order to prevent the surface layer from, e.g.,
becoming cracked when the electrophotographic belt is flexed. On
the basis of such realization, the present inventors have studied
how such preferable electrical properties as disclosed in the above
Japanese Patent Application Laid-open No. H10-228188 can be
imparted to an electrophotographic belt having on the base layer
containing a thermoplastic resin a surface layer composed of a thin
cured resin film. Therefore, the present inventors have attempted
to add conductive particles to the surface layer so as to balance
the volume resistivity and surface resistivity of the
electrophotographic belt.
[0010] However, the surface resistivity of the surface layer has
come to be too low (specifically, 10.sup.7 .OMEGA./square). Thus,
they have failed to impart to the electrophotographic belt the
preferable electrical properties disclosed in the above Japanese
Patent Application Laid-open No. H10-228188.
SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide an
electrophotographic belt having superior flexing resistance and
superior surface wear resistance and also having good electrical
properties, an electrophotographic apparatus having such an
electrophotographic belt, and a process for producing the
electrophotographic belt.
[0012] Another object of the present invention is to provide an
intermediate transfer belt having superior flexing resistance and
superior surface wear resistance and also having good electrical
properties.
[0013] More specifically, the present invention is an
electrophotographic belt which includes a base layer containing a
thermoplastic resin and having a mass loss (or "loss in mass")
percentage of 0.30% or more after a Taber abrasion test (ASTM
D-1175; at a load of 4.9 N and 500 revolutions) and a cured resin
film formed on the base layer by coating, containing conductive
particles and having a thickness of from 0.5 .mu.m or more to 3.0
.mu.m or less;
[0014] the cured resin film having at its surface a mass loss
percentage of 0.050% or less after a Taber abrasion test (ASTM
D-1175; at a load of 4.9 N and 500 revolutions); and
[0015] the electrophotographic belt having volume resistivity
.rho.v (.OMEGA.cm) and, at the surface of the cured resin film,
surface resistivity .rho.s (.OMEGA./square) which satisfy the
following expressions (1), (2) and (3):
10.sup.6.ltoreq..rho.v.ltoreq.10.sup.10 (1),
10.sup.8.ltoreq..rho.s.ltoreq.10.sup.13 (2),
.rho.s/.rho.v.gtoreq.10.sup.2 (3)
[0016] The present invention is also an electrophotographic
apparatus which comprises the above electrophotographic belt.
[0017] The present invention is still also a process for producing
the above electrophotographic belt; the process including:
[0018] a base layer forming step of forming the base layer by using
a thermoplastic resin; and
[0019] a surface layer forming step of applying on the base layer
formed by the base layer forming step a surface layer forming
coating fluid which contains a monomer and/or oligomer component as
a raw material for the cured resin film, conductive particles and a
solvent, followed by drying and curing to form the surface
layer.
[0020] The present invention is still also an intermediate transfer
belt which includes a base layer containing a thermoplastic resin
and having a mass loss percentage of 0.30% or more after a Taber
abrasion test (ASTM D-1175; at a load of 4.9 N and 500 revolutions)
and a cured resin film formed on the base layer by coating,
containing conductive particles and having a thickness of from 0.5
.mu.m or more to 3.0 .mu.m or less;
[0021] the cured resin film having at its surface a mass loss
percentage of 0.050% or less after a Taber abrasion test (ASTM
D-1175; at a load of 4.9 N and 500 revolutions); and
[0022] the electrophotographic belt having volume resistivity
.rho.v (.OMEGA.cm) and, at the surface of the cured resin film,
surface resistivity .rho.s (.OMEGA./square) which satisfy the
following expressions (1), (2) and (3):
10.sup.6.ltoreq..rho.v.ltoreq.10.sup.10 (1),
10.sup.8.ltoreq..rho.s.ltoreq.10.sup.13 (2),
.rho.s/.rho.v.gtoreq.10.sup.2 (3).
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a schematic sectional view of the
electrophotographic belt of the present invention.
[0024] FIG. 2 is a schematic sectional view of an
electrophotographic apparatus having an intermediate transfer
belt.
[0025] FIG. 3 is a schematic sectional view of another
electrophotographic apparatus having an intermediate transfer
belt.
[0026] FIG. 4 is a schematic sectional view of an
electrophotographic apparatus having a transfer material transport
belt.
[0027] FIG. 5 is a schematic sectional view of another
electrophotographic apparatus having a transfer material transport
belt.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] (Basic Constitution)
[0029] The electrophotographic belt of the present invention is
described below in detail with reference to the drawings.
[0030] FIG. 1 is a schematic sectional view of the
electrophotographic belt of the present invention. Reference
numeral 15 denotes a base layer containing a thermoplastic resin;
and 16, a cured resin film formed on the base layer by coating. In
this electrophotographic belt, where its volume resistivity surface
resistivity are represented by .rho.v (.OMEGA.cm) and .rho.s
(.OMEGA./square), respectively, the .rho.v and .rho.s satisfy all
the following expressions (1), (2) and (3):
10.sup.6.ltoreq..rho.v.ltoreq.10.sup.10 (1),
10.sup.8.ltoreq..rho.s.ltoreq.10.sup.13 (2),
.rho.s/.rho.v.gtoreq.10.sup.2 (3).
[0031] As stated previously, according to studies made by the
present inventors before arriving at the present invention, they
have failed to impart electrical properties that may satisfy all
the above expressions (1), (2) and (3), to the electrophotographic
belt having a base layer and, formed on the base layer by coating,
a surface layer composed of a thermoplastic resin and having a
thickness of 3.0 .mu.m or less.
[0032] As to the cause thereof, the present inventors made studies
in detail and, as a result of the studies, were able to have the
following findings. That is, the volume resistivity of the
electrophotographic belt was found to be very low because a greater
part of conductive particles migrated to the vicinity of the
surface of the surface layer as the solvent evaporated from a thin
wet coating formed of a surface layer forming coating fluid which
contained the conductive particles and was applied on the base
layer.
[0033] Accordingly, the present inventors controlled the rate of
evaporation of the solvent from the coating fluid applied on the
base layer, so as to prevent the conductive particles from
migrating to the surface of the surface layer. As a result, they
found that such control kept the volume resistivity from lowering
vastly and made obtainable the electrophotographic belt satisfying
all the above expressions (1), (2) and (3). Thus, they have
accomplished the present invention.
[0034] The constituents of the electrophotographic belt are
described below in order.
[0035] (Base Layer)
[0036] The base layer may preferably be one having good flexing
resistance, which may cause no cracking at its surface even when
flexed. Materials usable for such a base layer may include
thermoplastic resin materials as shown below, mixtures of any of
these, and thermoplastic elastomers formed by any of the mixtures:
Polycarbonate, polyvinylidene fluoride (PVDF), polyethylene,
polypropylene, polymethylpentene-1, polystyrene, polyamide,
polysulfone, polyarylate, polyethylene terephthalate, polybutylene
terephthalate, polyphenylene sulfide, polyether sulfone, polyether
nitrile, thermoplastic polyimide materials, polyether ether ketone,
thermotropic liquid-crystal polymers, and polyamic acid.
[0037] The base layers having good flexing resistance, formed from
the above materials may often have a surface having relatively low
wear resistance, which has a mass loss percentage of 0.30% or more
after a Taber abrasion test (ASTM D-1175; at a load of 4.9 N and
500 revolutions).
[0038] However, the formation of a surface layer described later
can improve surface wear resistance required as an
electrophotographic belt.
[0039] In the electrophotographic belt, in oder for all the above
expressions (1), (2) and (3) to be satisfied, the base layer may
preferably have a volume resistivity of from 1.0.times.10.sup.8
.OMEGA.cm or more to 1.0.times.10.sup.11 .OMEGA.cm or less, and
more preferably from 1.0.times.10.sup.9 .OMEGA.cm or more to
3.0.times.10.sup.10 .OMEGA.cm or less. Similarly, the base layer
may also preferably have a surface resistivity of from
1.0.times.10.sup.10 .OMEGA./square or more to 1.0.times.10.sup.13
.OMEGA./square or less, and more preferably from
5.0.times.10.sup.11 .OMEGA./square or more to 3.0.times.10.sup.12
.OMEGA./square or less.
[0040] The base layer having such volume resistivity and surface
resistivity may be obtained by, e.g., incorporating known
conductive particles or a known ionic conducting agent in the base
layer.
[0041] The base layer may also be incorporated with at least one
fine powder of an organic material or an inorganic material for the
purposes of effecting mechanical reinforcement, providing thermal
conductivity, and so forth. As the fine powder of an organic
material, for example, a condensation polyimide powder and an ionic
conductor are usable. As the fine powder of an inorganic material,
it is possible to use, for example, inorganic spherical fine
powders such as carbon black powder, magnesium oxide powder,
magnesium fluoride powder, silicon oxide powder, aluminum oxide
powder, boron nitride powder, aluminum nitride powder and titanium
nitride powder. As the fine powder of an inorganic material, it is
also possible to use fibrous powders such as carbon fibers and
glass fibers, and whiskery powders such as potassium titanate
powder, silicon carbide powder and silicon nitride powder. There
are no particular limitations on the particle shape, particle
diameter, content and so forth of such fine powders, and these may
preferably be so selected that the volume resistivity and surface
resistivity of the base layer may not deviate from the above
preferable range. However, taking into account the flexing
resistance, strength and thermal conductivity of the base layer,
the amount of any of these powders to be incorporated may
preferably be from 5% by mass or more to 70% by mass or less in
total, and more preferably from 5% by mass or more to 10% by mass
or less, based on the mass of the binder resin thermoplastic resin
material. The base layer may have a thickness of from 80 .mu.m or
more to 150 .mu.m or less, taking into account the strength
required for an electrophotographic belt.
[0042] (Surface Layer)
[0043] From the viewpoint of adherence to the base layer and
thickness uniformity, the surface layer is comprised of the cured
resin film formed on the base layer by coating. The surface layer
provides the surface of the electrophotographic belt with good wear
resistance such that the mass loss percentage after the Taber
abrasion test (ASTM D-1175; at a load of 4.9 N and 500 revolutions)
of the electrophotographic belt is 0.050% or less.
[0044] Such a cured resin film may be obtained by applying on the
base layer a coating fluid containing an acrylic monomer (such as
dipentaerythritol hexaacrylate) or a prepolymer of an acrylic
resin, followed by curing. In the present invention, the cured
resin film may have a thickness of from 0.5 .mu.m or more to 3.0
.mu.m or less, and preferably from 1.0 .mu.m or more to 3.0 .mu.m
or less, in order that the electrophotographic belt can be provided
with the given wear resistance and can fully follow the flexing of
the base layer.
[0045] (Conductive Particles)
[0046] In the present invention, conductive particles are added in
order that the surface layer comprised of the cured resin film can
be provided with the given resistivity. As the conductive
particles, any particles may be used as long as they are
resistance-controllable, and may include the following: Powders
such as carbon black, PAN-based carbon fibers and an
expanded-graphite pulverized product; powdery, fibrous or flaky
carbon-based conducting agents; powdery, fibrous or flaky
metal-based conducting agents of metals such as silver, nickel,
copper, zinc, aluminum, stainless steel and iron; and fine
particulate metal-oxide-based conducting agents such as
antimony-doped tin oxide, tin-doped indium oxide and aluminum-doped
zinc oxide.
[0047] Of these, in the present invention, fine particulate
metal-oxide-based conducting agents are preferred, which is
effective in a small quantity and can provide the surface layer
with surface smoothness. It is more preferable that the outermost
particle surfaces of the fine particulate metal-oxide-based
conducting agent are subjected to surface treatment with an
insulating inorganic compound such as SiO.sub.2 and Al.sub.2O.sub.3
to form thin shells thereon.
[0048] (Electrical Properties)
[0049] In the electrophotographic belt of the present invention,
where its volume resistivity and surface resistivity are
represented by .rho.v (.OMEGA.cm) and .rho.s (.OMEGA./square),
respectively, .rho.v and .rho.s satisfy the following expressions
(1), (2) and (3): 10.sup.6.ltoreq..rho.v.ltoreq.10.sup.10 (1),
10.sup.8.ltoreq..rho.s.ltoreq.10.sup.13 (2),
.rho.s/.rho.v.gtoreq.10.sup.2 (3).
[0050] In order to impart the electrical properties that may
satisfy all the above expressions (1), (2) and (3), to the
electrophotographic belt having the base layer and, formed on the
base layer by coating, the surface layer including a thermoplastic
resin and having a thickness of 3.0 .mu.m or less, it is necessary
to control, in conjunction with the addition of the conductive
particles to the surface layer, the rate of evaporation of the
solvent from the surface layer forming coating fluid coated on the
base layer, so as to keep the conductive particles from migrating
to the vicinity of the surface of the surface layer (hereinafter
also referred to simply as "surface migration") in the course of
drying when the surface layer is formed.
[0051] As a method for controlling the rate of evaporation of the
solvent, the following may be exemplified: In a high-temperature
and low-humidity environment, the surface layer forming coating
fluid is applied on the base layer and the wet coating formed is
dried, where the solvent can be evaporated very rapidly, thereby
effectively suppressing the surface migration of the conductive
particles. The high-temperature and low-humidity environment refers
specifically to an environment of 35 to 45.degree. C. and 5 to 20%
RH. Also, as the surface layer forming coating fluid, it may be
exemplified by a coating fluid containing, e.g., 50% by mass of an
acrylic monomer, 12% by mass of conductive particles and 38% by
mass of methyl isobutyl ketone.
[0052] Where methyl ethyl ketone is used as a chief solvent in the
surface layer forming coating fluid, methyl ethyl ketone evaporates
very rapidly even in a normal-temperature and normal-humidity
environment, and hence the surface migration of the conductive
particles can effectively be suppressed. The normal-temperature and
normal-humidity environment refers specifically to an environment
of 20 to 30.degree. C. and 30 to 50% RH.
[0053] Thus, a low-cost electrophotographic belt can be obtained
which has superior surface wear resistance and also superior
electrical properties. Of course, both the temperature and humidity
environment at the time of drying and the composition of the
surface layer forming coating fluid may be controlled so as to
suppress the surface migration of the conductive particles.
[0054] (Surface Layer Forming Coating Fluid)
[0055] The surface layer forming coating fluid used to form the
surface layer contains a raw material of the cured resin film, such
as an acrylic monomer or an acrylic oligomer, in order to improve
the wear resistance of the surface of the electrophotographic belt,
and also contains in its basic composition the conductive particles
for controlling the electrical properties of the surface layer and
a solvent. As described previously, in order to suppress the
surface migration of the conductive particles after the surface
layer forming coating fluid has been coated on the base layer, the
surface layer forming coating fluid may preferably be so composed
as to dry rapidly. As the solvent, it may include, e.g., isopropyl
alcohol, methyl ethyl ketone, ethanol and isobutanol. In
particular, in the case where the surface layer forming coating
fluid coated on the base layer is dried (and cured) in an
environment which is not the high-temperature and low-humidity
environment, for example, the normal-temperature and
normal-humidity environment, it is preferable to use methyl ethyl
ketone as a chief solvent as stated above.
[0056] As the composition of the surface layer forming coating
fluid, taking into account the coating properties on the base layer
and the stability of the coating fluid, it is preferable that the
content of the monomer and/or oligomer component, which is the raw
material of the cured resin film, is from 30 to 60% by mass based
on the total mass of the surface layer forming coating fluid, the
content of the conductive particles is from 10 to 20% by mass based
on the total mass of the surface layer forming coating fluid, and
the content of the solvent is from 30 to 60% by mass based on the
total mass of the surface layer forming coating fluid.
[0057] (Electrophotographic Apparatus)
[0058] Use embodiments of the electrophotographic belt of the
present invention are described below.
[0059] FIG. 2 is a schematic illustration of an electrophotographic
apparatus employing the electrophotographic belt of the present
invention as an intermediate transfer belt.
[0060] More specifically, in FIG. 2, reference numeral 1 denotes a
drum-shaped electrophotographic photosensitive member (hereinafter
also referred to as "photosensitive drum"), which is rotatively
driven at a given peripheral speed in the direction of an arrow.
The photosensitive drum 1 is, in the course of its rotation,
charged to a given polarity and potential by means of a primary
charging assembly 2, and then imagewise exposed to exposure light 3
emitted from an image exposure unit (not shown).
[0061] Letter symbol S1 denotes a power source of the primary
charging assembly. Thus, an electrostatic latent image is formed
which corresponds to a first color component image (e.g., a yellow
toner image) of the intended color image.
[0062] Next, the electrostatic latent image formed is developed by
means of a first developing assembly 41 (yellow Y developing
assembly) into the first-color component image (yellow toner
image). At this stage, second, third and fourth developing
assemblies, i.e., a magenta M developing assembly 42, a cyan C
developing assembly 43 and a black BK developing assembly 44, are
not operated and do not act on the photosensitive drum 1. Hence,
the first-color yellow component image is not affected by the
magenta developing assembly 42, cyan developing assembly 43 and
black developing assembly 44.
[0063] An intermediate transfer belt 7 is fitted over and around a
group of rollers 64, 65 and 66, and also is so disposed as to come
into contact with the photosensitive drum 1 and rotatively driven
at the same peripheral speed as the photosensitive drum 1. While
passing through the nip zone formed between the photosensitive drum
1 and the intermediate transfer belt 20, the first-color yellow
toner image formed on the photosensitive drum 1 is primarily
transferred to the surface of the intermediate transfer belt 7.
This primary transfer is performed by the aid of an electric field
generated by a primary transfer bias (with a polarity opposite to
that of the toner) applied from a bias power source S4 to a primary
transfer roller 62.
[0064] Yellow toner not primarily transferred and remaining on the
photosensitive drum 1 is removed by cleaning using a cleaning
assembly 13. Subsequently, the second-color magenta toner image,
the third-color magenta toner image and the fourth-color black
toner image are sequentially likewise transferred and superimposed
onto the intermediate transfer belt 7. Thus, synthesized color
toner images corresponding to the intended full-color image are
formed.
[0065] The synthesized color toner images transferred to the
intermediate transfer belt 7 are secondarily transferred to a
transfer material P. More specifically, the transfer material P is
fed from a cassette (not shown) through a transfer material feed
roller 10 and a transfer material guide 11 to the nip zone formed
between the intermediate transfer belt 7 and a secondary transfer
roller 63. A secondary transfer bias is simultaneously applied to
the secondary transfer roller 63 from a bias power source S5,
whereby the synthesized color toner images held on the intermediate
transfer belt 7 are secondarily transferred to the transfer
material P. The transfer material P to which the synthesized color
toner images have been transferred are guided into a fixing
assembly 14, where the synthesized color toner images are fixed to
the transfer material P.
[0066] Toners not transferred to the transfer material P and
remaining on the intermediate transfer belt 7 are charged by a
charging assembly 8, then they are transferred to the
photosensitive drum 1 at the nip zone formed between the
photosensitive drum 1 and the intermediate transfer belt 7, and
collected by the cleaning assembly 13.
[0067] FIG. 3 shows an image forming apparatus in which four of the
photosensitive drum 1 for forming respective-color toner images are
set and each of the photosensitive drums is so disposed as to come
into contact with an intermediate transfer belt 7. Members
corresponding to those in FIG. 2 are denoted by like reference
numerals.
[0068] FIGS. 4 and 5 are schematic sectional views of
electrophotographic apparatus each employing the
electrophotographic belt as a transfer material transport belt 12.
Members corresponding to those in FIG. 2 are denoted by the same
reference numerals.
[0069] In FIG. 4, a transfer material P is fed from a cassette (not
shown) through a transfer material feed roller 10 and a transfer
material guide 11 onto the transfer material transport belt 12.
Then, the transfer material P is carried on and transported by the
transfer material transport belt 12, and passes through the nip
zone formed between a photosensitive drum 1 and the transfer
material transport belt 12, when toner images formed on the
photosensitive drum 1 are transferred to the transfer material P.
Letter symbol S3 denotes a power source of a transfer bias applying
means. Four color toner images are transferred and superimposed,
and the transfer material P on which synthesized color toner images
corresponding to the intended full-color image have been formed is
guided into a fixing assembly 14, where the synthesized color toner
images are fixed to the transfer material P.
[0070] In FIG. 5, four of the photosensitive drum 1 for forming
respective-color toner images are set and each photosensitive drums
is so disposed as to form a nip with a transfer material transport
belt 12. A transfer material P is fed from a cassette (not shown)
passing a transfer material feed roller 10 and a transfer material
guide 11 onto the transfer material transport belt 12. Then, the
transfer material P is held on the transfer material transport belt
12, transported successively thereon, and passes through the nip
formed between each photosensitive drum 1 and the transfer material
transport belt 12, when respective-color toner images formed on the
photosensitive drum 1 are transferred and superimposed onto the
transfer material P. Reference numeral 6 denotes a transfer bias
applying means, and letter symbol S3 denotes a power source
thereof. Four color toner images are transferred and superimposed,
and the transfer material P on which synthesized color toner images
corresponding to the intended full-color image have been formed is
guided into a fixing assembly 14, where the synthesized color toner
images are fixed to the transfer material P.
EXAMPLES
[0071] The present invention is described below in greater detail
by giving Examples and Comparative Examples.
[0072] In Examples and Comparative Examples, the volume resistivity
.rho.v and the surface resistivity .rho.s were measured in the
following way.
[0073] That is, a measurement sample of 100 mm.times.100 mm in size
was cut out from the electrophotographic belt produced in each
Example and Comparative Example, and the measurement was made after
the measurement sample was beforehand left standing for 6 hours in
an environment of 23.degree. C./50% RH.
[0074] A high-resistance measuring instrument (trade name: HIRESTA
UP, MCP-HT450; manufactured by Mitsubishi Chemical Corporation) was
used as a measuring instrument. A ring-shaped probe (trade name:
URS; diameter of center electrode: 0.59 cm; inner diameter of
outside electrode: 1.1 cm; outer diameter of outside electrode:
1.78 cm; manufactured by Mitsubishi Chemical Corporation) was used
as a surface electrode.
[0075] In addition, as to the volume resistivity, the measurement
sample was placed on the polyamide surface side of REGI-TABLE UFL
(trade name; manufactured by Mitsubishi Chemical Corporation), and
a voltage of 10 V was applied across the center electrode of the
ring-shaped probe and the metal surface of REGI-TABLE UFL. A value
found after 10 seconds was regarded as a measured value.
[0076] As to the surface resistivity as well, the measurement
sample was placed on the polyamide surface side of REGI-TABLE UFL
(trade name; manufactured by Mitsubishi Chemical Corporation), and
a voltage of 100 V was applied across the center electrode of the
ring-shaped probe and the outside electrode. A value found after 10
seconds was regarded as a measured value.
[0077] In Examples and Comparative Examples, the Taber abrasion
test was conducted according to ASTM D-1175, corresponding to
Japanese Industrial Standards (JIS) K 7204 (1999) and using a Taber
abrasion tester (trade name: TABER ABRASION TESTER; manufactured by
Yasuda Seiki K. K.). CS10FA was used as an abrasion ring. The
measurement was carried out at a load of 4.9 N, 500 revolutions,
and 60 rpm.
Example 1
[0078] (i) Production of Base Layer:
[0079] A film composed of polyvinylidene fluoride resin containing
an ionic conducting agent, having a thickness of 50 .mu.m, a volume
resistivity .rho.v of 2.5.times.10.sup.9 .OMEGA.cm and a surface
resistivity .rho.s of 1.8.times.10.sup.11 .OMEGA./square, was
produced by extrusion. Using this film, a cylindrical endless belt
of 100 .mu.m in thickness was produced according to the method
described in Example 1 disclosed in Japanese Patent Application
Laid-open No. 2002-326287. This cylindrical endless belt was used
as the base layer of the electrophotographic belt. This cylindrical
endless belt had the same volume resistivity and surface
resistivity as those of the above film. Also, the mass loss
percentage of the belt surface (the surface to be coated with the
surface layer forming coating fluid described below) after the
Taber abrasion test (ASTM D-1175; at a load of 4.9 N and 500
revolutions) was 0.41%.
[0080] (ii) Preparation of Surface Layer Forming Coating Fluid:
[0081] In a container shielded from ultraviolet radiations, 12
parts by mass of an isopropyl alcohol sol of zinc antimonate as
conductive particles (trade name of the sol: CELNAX, available from
Nissan Chemical Industries, Ltd.) was mixed with 50 parts by mass
of an acrylic ultraviolet-curable hard coat material containing
dipentaerythritol hexaacrylate (trade name of the coat material:
DESOLITE; available from JSR Corporation). Thereafter, 38 parts by
mass of methyl isobutyl ketone (MIBK) was added to prepare an
ultraviolet-curable resin composition. The dispersion stability of
the conductive particles in the ultraviolet-curable resin
composition was good.
[0082] (iii) Production of Electrophotographic Belt:
[0083] In an environment of 40.degree. C./10% RH, the surface layer
forming coating fluid prepared in the above (ii) was applied by dip
coating on the surface of the base layer produced in the above (i)
to form a thin wet coating of the surface layer forming coating
fluid. This wet coating was dried for 30 seconds in the above
environment, and thereafter the coating dried was irradiated with
ultraviolet rays by using a UV irradiator (trade name: UE06/81-3;
manufactured by EYEGRAPHICS Co.; integral amount of light: 1,200
mJ/cm.sup.2) and cured to form a cured resin film of 1.0 .mu.m in
thickness. This cured resin film serves as the surface layer of the
electrophotographic belt.
[0084] Wearability of the surface of the surface layer of the
electrophotographic belt (i.e., the surface of the
electrophotographic belt) in this Example was evaluated by the
Taber abrasion test. As a result, the mass loss percentage of this
electrophotographic belt was 0%.
[0085] The volume resistivity .rho.v and surface resistivity .rho.s
of the electrophotographic belt were measured with a resistance
measuring instrument (trade name: HIRESTA; manufactured by
Mitsubishi Chemical Corporation) and found to be as shown below,
and the surface resistivity of the electrophotographic belt was
kept from vastly lowering due to the surface migration of the
conductive particles added. .rho.v=3.0.times.10.sup.9 .OMEGA.cm,
.rho.s=9.0.times.10.sup.11 .OMEGA./square,
.rho.s/.rho.v=3.0.times.10.sup.2.
[0086] Next, images were formed using the electrophotographic
apparatus shown in FIG. 5, in which the above electrophotographic
belt was used as the transfer material transport belt. Among the
rollers the electrophotographic belt was fitted over and around,
the smallest roller was 20 mm in diameter, and the severest (or
smallest) internal angle of the belt placed around the roller was
60 degrees.
[0087] Conditions for the image formation are shown below. [0088]
Electrophotographic photosensitive member: Organic photosensitive
member. [0089] Dark-area potential (non-image area potential): -700
V. [0090] Light-area potential (image area potential): -150 V.
[0091] Developer: Non-magnetic one-component developers (toners)
(for all four colors). [0092] Transfer voltage: 1.5 kV. [0093]
Process speed: 122 mm/s.
[0094] As a result, since the electrophotographic belt of Example 1
had a sufficiently low volume resistivity, charge-up did not occur.
Further, since the surface resistivity of the electrophotographic
belt had a great difference as compared with the volume
resistivity, the toner constituting toner images on the surface of
the transfer material carried on the transfer material transport
belt was not scattered, and high definition images were
obtained.
[0095] Moreover, in the electrophotographic apparatus of Example 1
in which the electrophotographic belt of Example 1 was set as the
transfer material transport belt, any cracking or the like was not
seen to occur on the transfer material carrying surface of the
electrophotographic belt even after 200,000 sheets of paper were
run (extensive operation).
Comparative Example 1
[0096] An electrophotographic belt was produced in the same manner
as in Example 1 except that the application of the surface layer
forming coating fluid on the base layer and the drying were carried
out in an environment of 25.degree. C./40% RH.
[0097] The volume resistivity .rho.v and surface resistivity .rho.s
of the electrophotographic belt thus produced were as shown below.
The surface resistivity of the electrophotographic belt lowered
greatly as compared with the electrophotographic belt of Example 1.
.rho.v=2.6.times.10.sup.9.OMEGA.cm, .rho.s=7.5.times.10.sup.8
.OMEGA./square, .rho.s/.rho.v=3.0.times.10.sup.-1.
[0098] The reason therefor is considered to be that the coating
environment was changed to the normal-temperature and
normal-humidity environment and hence, in the course of drying, the
solvent evaporated at a low rate from the thin wet film of the
surface layer forming coating fluid coated on the base layer, so
that the conductive particles migrated to surface migration.
[0099] Next, the electrophotographic belt of Comparative Example 1
was used as the transfer material transport belt of the same
electrophotographic apparatus as used in Example 1, and images were
formed under the same conditions as in Example 1.
[0100] As a result, the toner constituting toner images on the
surface of the transfer material carried on the transfer material
transport belt became scattered. As a result of visual comparison
with the images in Example 1, the image quality was clearly
inferior.
Example 2
[0101] An electrophotographic belt was produced in the same manner
as in Example 1 except that the surface layer (cured resin film)
was formed in a thickness of 3.0 .mu.m. Evaluation was made in the
same way as in Example 1.
[0102] The mass loss percentage of the electrophotographic belt of
Example 2 after the Taber abrasion test was 0%. The volume
resistivity .rho.v and surface resistivity .rho.s of the
electrophotographic belt of Example 2 were as shown below, and the
surface resistivity was kept from vastly lowering, as with the
electrophotographic belt of Example 1. .rho.v=6.5.times.10.sup.9
.OMEGA.cm, .rho.s=1.5.times.10.sup.12 .OMEGA./square,
.rho.s/.rho.v=2.3.times.10.sup.2.
[0103] Next, the electrophotographic belt of Example 2 was used as
the transfer material transport belt of the same
electrophotographic apparatus as used in Example 1, and images were
formed under the same conditions as in Example 1.
[0104] As a result, as with Example 1, the toner constituting toner
images on the surface of the transfer material carried on the
transfer material transport belt was not scattered, and high
definition images were obtained.
[0105] In the electrophotographic apparatus of Example 2, any
cracking or the like was not seen to occur on the transfer material
carrying surface of the electrophotographic belt even after 200,000
sheets of paper were run.
Example 3
[0106] An electrophotographic belt of Example 3 was produced in the
same manner as in Example 1 except that the surface layer forming
coating fluid, the application of the surface layer forming coating
fluid on the base layer and the conditions for drying were as shown
below.
[0107] (i) Preparation of surface Layer Forming Coating Fluid:
[0108] 12 parts by mass of an isopropyl alcohol sol of zinc
antimonate as conductive particles (trade name of the sol: CELLNAX,
available from Nissan Chemical Industries, Ltd.) was mixed with 50
parts by mass of an acrylic ultraviolet-curable hard coat material
containing dipentaerythritol hexaacrylate (trade name of the coat
material: DESOLITE; available from JSR Corporation). Thereafter, 38
parts by mass of methyl ethyl ketone (MEK) was added to obtain an
ultraviolet-curable resin composition.
[0109] (ii) Production of Electrophotographic Belt:
[0110] In an environment of 25.degree. C./40% RH, the surface layer
forming coating fluid prepared in the above (i) was applied on the
surface of the base layer produced in the same way as in the
procedure (i) in Example 1. The wet coating formed was dried, and
thereafter the coating dried was irradiated with ultraviolet rays
to form a surface layer (cured resin film), obtaining the
electrophotographic belt of Example 3.
[0111] Wearability of the surface of the electrophotographic belt
of Example 3 was evaluated by the Taber abrasion test. As a result,
the mass loss percentage of this electrophotographic belt was
0%.
[0112] The volume resistivity .rho.v and surface resistivity .rho.s
of the electrophotographic belt of Example 2 were as shown below.
.rho.v=3.8.times.10.sup.9 .OMEGA.cm, .rho.s=5.0.times.10.sup.11
.OMEGA./square, .rho.s/.rho.v=1.3.times.10.sup.2.
[0113] As shown above, in Example 3, in place of the methyl
isobutyl ketone used in Example 1, methyl ethyl ketone having a
lower boiling point was used as the chief solvent of the surface
layer forming coating fluid. In virtue of this solvent, the thin
wet film of the surface layer forming coating fluid applied on the
base layer dried rapidly even in the same environment of 25.degree.
C./40% RH as in the case of the application of the surface layer
forming coating fluid and the drying conditions in Comparative
Example 1. As a result, the surface migration of the conductive
particles was suppressed in the course of the drying of the wet
coating of the surface layer forming coating fluid, and the surface
resistivity of the electrophotographic belt was able to be
effectively kept from vastly lowering as seen in Comparative
Example 1.
[0114] Next, the electrophotographic belt of Example 3 was used as
the transfer material transport belt of the same
electrophotographic apparatus as used in Example 1, and images were
formed under the same conditions as in Example 1.
[0115] As a result, as with Example 1, the toner constituting toner
images on the surface of the transfer material carried on the
transfer material transport belt was not scattered, and high
definition images were obtained.
[0116] In the electrophotographic apparatus of Example 3, any
cracking or the like was not seen to occur on the transfer material
carrying surface of the electrophotographic belt even after 200,000
sheets of paper were run.
Comparative Example 2
[0117] An electrophotographic belt was produced in the same manner
as in Comparative Example 1 except that the surface layer (cured
resin film) of 1.0 .mu.m in thickness was formed in a thickness of
10.0 .mu.m.
[0118] Wearability of the surface of the electrophotographic belt
of Comparative Example 2 was evaluated by the Taber abrasion test.
As a result, the mass loss percentage of this electrophotographic
belt was 0%.
[0119] Since the thickness of the surface layer (cured resin film)
of the electrophotographic belt of Comparative Example 2 was as
large as 10 .mu.m, the conductive particles in the thin wet coating
of the surface layer forming coating fluid were not able to migrate
to the vicinity of the surface of the surface layer (cured resin
film) even in the environment of 25.degree. C./40% RH, so that as
far as the volume resistivity .rho.v and the surface resistivity
.rho.s were concerned, as shown below, the electrophotographic belt
produced was provided with all the electrical properties required
for the electrophotographic belt of the present invention.
.rho.v=8.0.times.10.sup.9 .OMEGA.cm, .rho.s=2.0.times.10.sup.12
.OMEGA./square, .rho.s/.rho.v=2.5.times.10.sup.2.
[0120] The electrophotographic belt of Comparative Example 2 was
used as the transfer material transport belt of the same
electrophotographic apparatus as used in Example 1, and images were
formed under the same conditions as in Example 1.
[0121] As a result, the transfer material carrying surface of the
transfer material transport belt was seen to become cracked after
500 sheets of paper were run. That is, it was ascertainable that
since the surface layer (cured resin film) was formed in a large
thickness, such a high-hardness surface layer (cured resin film)
lost performance following the flexing of the base layer, resulting
in a lowering of belt durability against extensive operation.
TABLE-US-00001 TABLE 1 Compara- Compara- Example tive Ex. Example
Example tive Ex. 1 1 2 3 2 Chief solvent: MIBK MIBK MIBK MEK MIBK
Coating environment: 40.degree. C./10% 25.degree. C./40% 40.degree.
C./10% 25.degree. C./40% 40.degree. C./10% Surface layer thickness
(pm): 1 1 3 1 10 .rho.v (.OMEGA.cm): 3.0 .times. 10.sup.9 2.6
.times. 10.sup.9 6.5 .times. 10.sup.9 3.8 .times. 10.sup.9 8.0
.times. 10.sup.9 .rho.s (.OMEGA.cm) 9.0 .times. 10.sup.11 7.5
.times. 10.sup.8 1.5 .times. 10.sup.12 5.0 .times. 10.sup.11 2.0
.times. 10.sup.12 .rho.s/.rho.v: 3.0 .times. 10.sup.2 3.0 .times.
10.sup.-1 2.3 .times. 10.sup.2 1.3 .times. 10.sup.2 2.5 .times.
10.sup.2
[0122] According to the present invention, an electrophotographic
belt can be provided having superior flexing resistance and
superior surface wear resistance in addition to good electrical
properties, an electrophotographic apparatus having such an
electrophotographic belt, and a process for producing the
electrophotographic belt.
[0123] According to the present invention, an intermediate transfer
belt also can be provided having superior flexing resistance and
superior surface wear resistance in conjunction with good
electrical properties.
[0124] This application claims priority from Japanese Patent
Application No. 2005-127976 filed on Apr. 26, 2005, which is hereby
incorporated by reference herein.
* * * * *