U.S. patent application number 12/665555 was filed with the patent office on 2010-11-11 for fluorocarbon resin composite, cookware, cooker, roller for office automation equipment, belt for office automation equipment, and method for producing them.
This patent application is currently assigned to SUMITOMO Electric Fine Polymer , Inc.. Invention is credited to Kazuaki IKEDA, Nobutaka MATSUSHITA, Yoshimasa SUZUKI.
Application Number | 20100285262 12/665555 |
Document ID | / |
Family ID | 40156173 |
Filed Date | 2010-11-11 |
United States Patent
Application |
20100285262 |
Kind Code |
A1 |
IKEDA; Kazuaki ; et
al. |
November 11, 2010 |
FLUOROCARBON RESIN COMPOSITE, COOKWARE, COOKER, ROLLER FOR OFFICE
AUTOMATION EQUIPMENT, BELT FOR OFFICE AUTOMATION EQUIPMENT, AND
METHOD FOR PRODUCING THEM
Abstract
[Object] There are provided a fluorocarbon resin composite
having improved abrasion resistance while nonadhesiveness, which is
a feature of a fluorocarbon resin, is maintained, cookware, and a
roller and a belt for use in office automation equipment. [Solving
Means] A fluorocarbon resin composite includes a fluorocarbon resin
layer on a base, in which a fluorocarbon resin constituting the
fluorocarbon resin layer is crosslinked by electron beam
irradiation, and the base has a desired shape obtained by
machining. The fluorocarbon resin is composed of a
tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer,
polytetrafluoroethylene, or a mixture of the
tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer and
polytetrafluoroethylene. A fluorocarbon resin composite, cookware,
and a roller and a belt for use in office automation equipment are
each produced by applying an uncrosslinked fluorocarbon resin on a
base, subjecting the fluorocarbon resin to electron beam
irradiation in a low-oxygen atmosphere to crosslink the
fluorocarbon resin while the temperature of the fluorocarbon resin
is maintained at a temperature equal to or higher than the melting
point of the fluorocarbon resin, and machining the base into a
desired shape. There is also provided methods for producing
them.
Inventors: |
IKEDA; Kazuaki; (Sennan-gun,
Osaka, JP) ; MATSUSHITA; Nobutaka; (Sennan-gun,Osaka,
JP) ; SUZUKI; Yoshimasa; (Sennan-gun ,Osaka,
JP) |
Correspondence
Address: |
DRINKER BIDDLE & REATH (DC)
1500 K STREET, N.W., SUITE 1100
WASHINGTON
DC
20005-1209
US
|
Assignee: |
SUMITOMO Electric Fine Polymer ,
Inc.
Sennan-gun ,Osaka
JP
|
Family ID: |
40156173 |
Appl. No.: |
12/665555 |
Filed: |
June 11, 2008 |
PCT Filed: |
June 11, 2008 |
PCT NO: |
PCT/JP2008/060660 |
371 Date: |
March 2, 2010 |
Current U.S.
Class: |
428/64.1 ;
264/485; 427/496; 428/336; 428/421; 524/545; 524/546 |
Current CPC
Class: |
A47J 36/025 20130101;
B05D 3/0486 20130101; B05D 3/068 20130101; B32B 15/18 20130101;
B32B 27/34 20130101; B32B 2307/306 20130101; Y10T 428/265 20150115;
G03G 15/0233 20130101; G03G 15/0808 20130101; B32B 27/30 20130101;
B32B 27/08 20130101; G03G 2215/2048 20130101; B32B 2439/00
20130101; C09D 129/10 20130101; B32B 27/281 20130101; B23P 13/00
20130101; B05D 2701/10 20130101; B32B 15/08 20130101; Y10T 428/3154
20150401; B32B 2307/554 20130101; B32B 15/20 20130101; B32B 27/304
20130101; C09D 127/18 20130101; B32B 2509/00 20130101; B32B 2413/00
20130101; G03G 2215/16 20130101; B32B 27/322 20130101; B29C 71/04
20130101; B05D 5/083 20130101; B32B 1/00 20130101; Y10T 428/21
20150115; B32B 2307/714 20130101; A47J 36/02 20130101 |
Class at
Publication: |
428/64.1 ;
524/545; 428/336; 428/421; 427/496; 524/546; 264/485 |
International
Class: |
B32B 15/085 20060101
B32B015/085; C08L 27/12 20060101 C08L027/12; B32B 3/02 20060101
B32B003/02; C08F 2/46 20060101 C08F002/46; C08L 27/18 20060101
C08L027/18; B29C 35/00 20060101 B29C035/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 20, 2007 |
JP |
2007-162671 |
Jul 3, 2007 |
JP |
2007-175346 |
Jul 3, 2007 |
JP |
2007-175348 |
Claims
1. A fluorocarbon resin composite comprising a fluorocarbon resin
layer on a base, wherein a fluorocarbon resin constituting the
fluorocarbon resin layer is crosslinked by electron beam
irradiation, and the base has a desired shape obtained by
machining.
2. The fluorocarbon resin composite according to claim 1, wherein
the fluorocarbon resin is composed of one selected from a
tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer,
polytetrafluoroethylene, and a fluorinated ethylene-propylene
copolymer, or a mixture of two or three compounds selected from the
tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer,
polytetrafluoroethylene, and the fluorinated ethylene-propylene
copolymer.
3. The fluorocarbon resin composite according to claim 1, wherein
an electron beam during the electron beam irradiation reaches the
base through the fluorocarbon resin layer.
4. The fluorocarbon resin composite according to claim 1, wherein
the fluorocarbon resin layer has a thickness of 70 .mu.m or
less.
5. The fluorocarbon resin composite according to claim 1, wherein
the amount of the electron beam irradiation is in the range of 1
kGy to 500 kGy.
6. The fluorocarbon resin composite according to claim 1, wherein
the base is composed of aluminum, an aluminum alloy, or stainless
steel.
7. The fluorocarbon resin composite according to claim 6, wherein
the fluorocarbon resin layer is formed on the non-surface-treated
base, and wherein in a cross-cut test (JIS-K-5400, 1998 edition),
the fluorocarbon resin layer is not detached after 100 repetitions
of a peeling operation using an adhesive tape.
8. Cookware comprising the fluorocarbon resin composite according
to claim 1.
9. A cooker comprising the cookware according to claim 8.
10. A method for producing a fluorocarbon resin composite
comprising the steps of applying an uncrosslinked fluorocarbon
resin onto a base; heating the fluorocarbon resin to a temperature
equal to or higher than the melting point of the fluorocarbon
resin; subjecting the fluorocarbon resin to electron beam
irradiation in a low-oxygen atmosphere to crosslink the
fluorocarbon resin; and machining the base in such a manner that
the base has a desired shape.
11. A roller or a belt for use in office automation equipment,
comprising a fluorocarbon resin layer on a circular base, wherein
the fluorocarbon resin layer is crosslinked by electron beam
irradiation.
12. The roller or the belt for use in office automation equipment
according to claim 11, wherein the fluorocarbon resin layer is
composed of one selected from a tetrafluoroethylene-perfluoro(alkyl
vinyl ether) copolymer, polytetrafluoroethylene, and a fluorinated
ethylene-propylene copolymer, or a mixture of two or three
compounds selected from the tetrafluoroethylene-perfluoro(alkyl
vinyl ether) copolymer, polytetrafluoroethylene, and the
fluorinated ethylene-propylene copolymer.
13. The roller or the belt for use in office automation equipment
according to claim 11, wherein an electron beam during the electron
beam irradiation reaches the circular base through the fluorocarbon
resin layer.
14. The roller or the belt for use in office automation equipment
according to claim 11, wherein the fluorocarbon resin layer has a
thickness of 20 .mu.m or less.
15. The roller or the belt for use in office automation equipment
according to claim 11, wherein the amount of the electron beam
irradiation is in the range of 1 kGy to 500 kGy.
16. The roller or the belt for use in office automation equipment
according to claim 11, wherein the circular base is composed of a
heat-resistant resin or a metal.
17. The roller or the belt for use in office automation equipment
according to claim 11, wherein the fluorocarbon resin layer is
formed on the non-surface-treated base, and wherein the
fluorocarbon resin layer has an adhesive strength of 0.5 Kg/1.5 cm
or more in a peeling test.
18. The roller or the belt for use in office automation equipment
according to claim 11, wherein an intermediate layer is formed
between the circular base and the fluorocarbon resin layer.
19. A method for producing a roller or a belt for use in office
automation equipment, comprising the steps of applying an
uncrosslinked fluorocarbon resin onto a circular base; heating the
fluorocarbon resin to a temperature equal to or higher than the
melting point of the fluorocarbon resin; and subjecting the
fluorocarbon resin to electron beam irradiation in a low-oxygen
atmosphere to crosslink the fluorocarbon resin.
20. A method for producing a roller or a belt for use in office
automation equipment, comprising the steps of placing a die
(outlet) of an extruder in a low-oxygen atmosphere; extruding an
uncrosslinked fluorocarbon resin from the die of the extruder onto
a circular base; and subjecting the fluorocarbon resin to electron
beam irradiation in the low-oxygen atmosphere to crosslink the
fluorocarbon resin before the temperature of the fluorocarbon resin
is decreased to a temperature equal to or lower than the melting
point of the fluorocarbon resin.
21. The method for producing a roller or a belt for use in office
automation equipment according to claim 19, further comprising
after the uncrosslinked fluorocarbon resin is heated to a
temperature equal to or higher than the melting point of the
fluorocarbon resin and then subjected to electron beam irradiation
in a low-oxygen atmosphere to crosslink the fluorocarbon resin,
performing rapid cooling before the temperature of a layer located
below the fluorocarbon resin reaches the decomposition temperature
of the layer.
22. The method for producing a roller or a belt for use in office
automation equipment according to claim 20, further comprising
after the uncrosslinked fluorocarbon resin is heated to a
temperature equal to or higher than the melting point of the
fluorocarbon resin and then subjected to electron beam irradiation
in a low-oxygen atmosphere to crosslink the fluorocarbon resin,
performing rapid cooling before the temperature of a layer located
below the fluorocarbon resin reaches the decomposition temperature
of the layer.
Description
TECHNICAL FIELD
[0001] The present invention relates to a fluorocarbon resin
composite, cookware and cookers including the fluorocarbon resin
composite, rollers including the fluorocarbon resin composite, for
example, fixing rollers, transfer rollers, pressing rollers,
charging rollers, and developing rollers, for use in office
automation equipment such as copiers, belts including the
fluorocarbon resin composite, for example, fixing belts, belts used
for fixing sections, transfer belts, and transfer fixing belts, for
use in office automation equipment, and methods for producing
them.
BACKGROUND ART
[0002] Fluorocarbon resins such as polytetrafluoroethylene (PTFE)
have excellent nonadhesiveness, heat resistance, and chemical
resistance and thus are often used as materials constituting
coatings of cookers such as rice cookers and cookware such as hot
plates and frying pans and topcoat layers of fixing rollers for use
in office automation equipment such as copiers. The reason
fluorocarbon resins such as PTFE have excellent heat resistance and
chemical resistance is that in a structural formula described
below, the bonding strength between C and F is the highest among
organic substances (116 kcal/mol) and that fluorine atoms (F)
entirely cover carbon chains to protect the C--C bonds. The reason
for the excellent nonadhesiveness is a very low polarization of
charges because of the symmetry of the atomic arrangement in a
molecule, a low cohesive force between molecules, and a
significantly low surface energy.
##STR00001##
[0003] Fluorocarbon resins have these excellent physical properties
but disadvantageously have poor abrasion resistance. The reason for
this is that molecules are readily detached because of a low
surface energy and a low cohesive force between fluorine atoms
(F--F).
[0004] To overcome this problem, currently commercially available
fluorocarbon resins compensate the weakness by forming very long
molecular chains having a degree of polymerization of about 10,000
to several hundred thousands, i.e., a molecular weight of about a
million to tens of millions, to increase the bonding strength
between fluorocarbon resins. However, it is difficult to achieve a
higher molecular weight because of problems with formability and so
forth (a reduction in flowability). Thus, sufficient properties are
not provided. Furthermore, the adhesion of fluorocarbon resins to
bases is a processing problem due to excellent nonadhesiveness. To
solve this problem, in the case of using a base composed of a metal
such as aluminum, it is necessary to conduct an additional step of
performing etching treatment to form irregularities or forming an
adhesive layer such as a primer.
[0005] In recent years, a technique in which a fluorocarbon resin,
which is a representative of polymers degraded by electron beams,
is crosslinked by electron beam irradiation at a temperature equal
to or higher than the melting point thereof in an oxygen-free
atmosphere has been developed (Patent Documents 1 and 2). It is
found that to solve the problem in which the molecules are readily
detached because of a low cohesive force between fluorine atoms
(F--F), crosslinking a fluorocarbon resin results in a
three-dimensional network structure of fluorine atoms as shown in a
structural formula below, so that the polymeric chains are strongly
bonded to each other, significantly improving the abrasion
resistance.
##STR00002##
[0006] [Patent Document 1] Japanese Patent No. 3587071
[0007] [Patent Document 2] Japanese Patent No. 3587072
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0008] However, in the technique described in each of Patent
Documents 1 and 2, crosslinking is performed by electron beam
irradiation of a fluorocarbon resin powder while the fluorocarbon
resin powder is floating, thus failing to provide a fluorocarbon
resin having a small particle size suitable for the formation of a
fluorocarbon resin dispersion (a dispersion of a fluorocarbon resin
having a particle size on the order of submicrons dispersed in
water). If pulverization is performed, it is usually difficult to
form a fluorocarbon resin having a particle size on the order of
submicrons. Thus, the resulting fluorocarbon resin is not suitably
used as a material for a dispersion commonly used for a thin film
of a fluorocarbon resin. Accordingly, it is difficult to form a
thin fluorocarbon resin layer (coating film) suitable for cookware
using a fluorocarbon resin dispersion containing a fluorocarbon
resin produced by this technique. Furthermore, it is difficult to
form a topcoat film of a fixing roller and surface layers of a
transfer belt and a transfer fixing belt.
[0009] For example, the fixing roller is used to fix toner
transferred to recording paper. The transfer belt is used to
transfer toner to recording paper. Thus, a fluorocarbon resin is
preferably used as a material constituting a topcoat film of the
fixing roller and a surface layer of the transfer belt because of
its excellent toner releasability.
[0010] Meanwhile, a fluorocarbon resin layer disadvantageously has
low abrasion resistance as described above. Thus, in the case where
toner-fixing treatment and toner-transfer treatment for hundreds of
thousands of recording sheets are performed using the fixing roller
and the transfer belt, the fluorocarbon resin layer is worn by
friction between the recording sheets and the fixing roller and
between the recording sheets and the transfer belt, thereby causing
problems such as a reduction in surface roughness (clogging of
toner and so forth reduces toner releasability). Alternatively, a
problem is caused in which the fluorocarbon resin layer is detached
at portions that come into contact with both edges of each of the
recording sheets. It is thus necessary to adequately ensure the
thickness of the fluorocarbon resin layer, leading to difficulty in
reducing the thickness of the topcoat film of the fixing roller or
the surface layer of the transfer belt.
[0011] Furthermore, in the case of the fixing roller and the
transfer fixing belt each having the function of fixing toner
transferred to a recording sheet, they are used while being heated
by a heater arranged inside thereof. In the case of a high-speed
copier, a large number of recording sheets takes heat from the
fixing roller and the transfer fixing belt; hence, the temperatures
of the fixing roller and the transfer fixing belt tend to be
reduced. Accordingly, in order not to reduce the temperatures of
the fixing roller and the transfer fixing belt, it is necessary to
reduce the thicknesses of the fixing roller and the transfer fixing
belt for efficient conduction of heat from the heater.
Alternatively, it is necessary to increase the heating temperature
of the heater.
[0012] To solve the above-described problems with the fixing
roller, the transfer belt, and the transfer fixing belt, it is
conceivable that the addition of a filler such as a fine glass
powder to a fluorocarbon resin will improve the abrasion
resistance, leading to a reduction in the thickness of the
fluorocarbon resin layer. However, this raises new problems in
which the nonadhesiveness and the surface roughness are
significantly reduced.
[0013] Meanwhile, an increase in the heating temperature of the
heater disadvantageously causes the deterioration of rubber
constituting an elastic layer and a further reduction in abrasion
resistance due to the thermal degradation of the fluorocarbon resin
layer. To impart elasticity to the belt, a soft intermediate layer
composed of silicone or the like is provided. However, an increase
in the thickness of the surface layer of the fluorocarbon resin
reduces the flexibility of the entire belt.
[0014] Accordingly, it is a first object of the present invention
to provide a fluorocarbon resin composite including a fluorocarbon
resin layer having improved abrasion resistance while
nonadhesiveness, which is a feature of a fluorocarbon resin, is
maintained, cookware, a cooker, and methods for producing them.
[0015] It is a second object to provide a roller or belt for use in
office automation equipment, the roller or belt including a
fluorocarbon resin layer having improved abrasion resistance and
heat resistance while nonadhesiveness, which is a feature of a
fluorocarbon resin, is maintained, and a method for producing the
roller or belt.
Means for Solving the Problems
[0016] The inventors have conducted intensive studies and have
found that the foregoing problems are easily solved by a devised
method for forming a fluorocarbon resin layer. This finding has led
to the completion of the present invention.
[0017] Furthermore, the inventors have conducted intensive studies
and have also found that after the application of a fluorocarbon
resin, an electron beam is allowed to reach a base or intermediate
layer (hereinafter, collectively referred to also as a "base and so
forth"), thereby significantly improving the adhesion of the
fluorocarbon resin to the base and so forth simultaneously with
improvement in abrasion resistance.
[0018] Inventions of claims 1 to 7 described below are defined as
an aspect common to a first aspect and a second aspect of the
present invention. Inventions of claims 8 to 10 are defined as the
first aspect of the present invention. Inventions of claims 11 to
21 are defined as the second aspect of the present invention. The
first aspect and the second aspect are aspects that achieve the
first object and the second object, respectively.
[0019] The inventions of the claims will be described below.
[0020] According to an invention described in claim 1,
[0021] a fluorocarbon resin composite includes a fluorocarbon resin
layer on a base, in which a fluorocarbon resin constituting the
fluorocarbon resin layer is crosslinked by electron beam
irradiation, and the base has a desired shape obtained by
machining.
[0022] In the invention of this claim, since the fluorocarbon resin
is crosslinked, it is possible to improve the abrasion resistance
of the fluorocarbon resin layer while maintaining the
nonadhesiveness of the fluorocarbon resin layer.
[0023] In a conventional technique for crosslinking a fluorocarbon
resin by electron beam irradiation, only a fluorocarbon resin
having a large particle size is obtained. It is thus difficult to
form a thin fluorocarbon resin layer suitable for cookware. That
is, the thin fluorocarbon resin layer is preferably formed as
follows: A dispersion of fluorine particles having a particle size
of 0.1 .mu.m to several micrometers dispersed in water is used. The
dispersion is applied to a target surface by, for example, a spin
coating method, a dipping method, or a spraying method, dried, and
baked (the particles are melted to form a fluorocarbon film).
However, a large particle size of the fluorocarbon resin causes the
precipitation of particles in the dispersion and the clogging of a
nozzle, leading to difficulty in performing coating. Even if
coating can be performed, it is difficult to obtain a smooth
surface because the surface state depends on the size of the
fluorocarbon particles.
[0024] In contrast, according to the invention of this claim, for
example, a fluorocarbon resin layer is formed on a substantially
flat base using a dispersion of usual uncrosslinked fluorocarbon
particles having a small particle size. Thus, it is possible to
easily form a thin fluorocarbon resin layer suitable for
cookware.
[0025] Conventionally, according to a common method for forming a
fluorocarbon resin layer in the production of cookware, it is
difficult to subject the entire fluorocarbon resin layer to
electron beam irradiation.
[0026] That is, as a method for forming a coating film for use in
cookware, a method is generally employed in which after a base is
pressed into a predetermined shape, the fluorocarbon resin is
applied by, for example, spraying and then baked (hereinafter, a
method in which a fluorocarbon resin is applied after machining is
referred to as an "after-coat method"). In the case where cookware
produced by the after-coat method is subjected to electron beam
irradiation to crosslink the fluorocarbon resin in order to improve
abrasion resistance, for example, it is difficult to simultaneously
subject a fluorocarbon resin layer arranged on a horizontal inner
wall of a bottom and a substantially vertical inner surface of a
side wall of a rice cooker or a frying pan to electron beam
irradiation.
[0027] That is, for the fluorocarbon resin layer located at a
surface perpendicular to the direction of electron beam
irradiation, the entire fluorocarbon resin can be subjected to
electron beam irradiation because the thickness direction
corresponds to the transmission direction of electron beams.
However, for the fluorocarbon resin layer located at a
substantially vertical surface obtained by machining, i.e., a
surface parallel to the direction of electron beam irradiation,
only part of the fluorocarbon resin (portion facing an electron
beam irradiation apparatus) is subjected to electron beam
irradiation because the thickness direction does not correspond to
the transmission direction of electron beams.
[0028] In contrast, according to the invention of this claim, after
the formation of the fluorocarbon resin layer on the base, electron
beam irradiation is performed before the base is machined (in this
way, a method of applying the fluorocarbon resin before machining
is referred to as a "precoat method").
[0029] As described above, since the base is substantially flat,
the entire surface of the fluorocarbon resin layer can be located
at a position perpendicular to the irradiation direction of
electron beams. That is, it is possible to subject the entire
fluorocarbon resin layer to electron beam irradiation because the
thickness direction of the entire fluorocarbon resin layer
corresponds to the transmission direction of electron beams,
thereby resulting in cookware including the fluorocarbon resin
layer having excellent abrasion resistance.
[0030] Furthermore, it is possible to efficiently produce cookware
because crosslinking is rapidly performed by electron beam
irradiation, which is a simple method. Note that a metal base is
mainly used as the base.
[0031] According to an invention described in claim 2,
[0032] in the fluorocarbon resin composite according to Claim 1,
the fluorocarbon resin is composed of one selected from a
tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer (PFA),
polytetrafluoroethylene (PTFE), and a fluorinated
ethylene-propylene copolymer (FEP), or a mixture of two or three
compounds selected from PFA, PTFE, and FEP.
[0033] In the invention of this claim, the fluorocarbon resin is
composed of one selected from the
tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer (PFA),
polytetrafluoroethylene (PTFE), and the fluorinated
ethylene-propylene copolymer (FEP), or a mixture of two or three
compounds selected from these compounds. Thus, a thin film of the
fluorocarbon resin having excellent heat resistance and resistance
to stress cracking is obtained.
[0034] According to an invention described in claim 3,
[0035] in the fluorocarbon resin composite according to Claim 1 or
2, an electron beam during the electron beam irradiation reaches
the base through the fluorocarbon resin layer.
[0036] Like the invention of this claim, the crosslinking of the
uncrosslinked fluorocarbon resin on the base by electron beam
irradiation in which an electron beam reaches the base through the
fluorocarbon resin layer significantly improves the adhesive
strength between the base and the fluorocarbon resin layer compared
with the case where an electron beam does not reach the base. The
reason for the improvement in the adhesion to the base is probably
as follows: Electron beam irradiation causes cleavage of a main
chain or a side chain. In particular, when the temperature of the
fluorocarbon resin is heated to a temperature equal to or higher
than its melting point, active radicals are generated. The
resulting radicals are bonded to the base because there is no
substance, such as oxygen, which is readily bonded to the radicals.
For example, the electron beam is allowed to reach the base by
adjusting an acceleration voltage during electron beam irradiation
in response to the thickness of the fluorocarbon resin layer.
[0037] According to an invention described in claim 4,
[0038] in the fluorocarbon resin composite according to any one of
Claims 1 to 3, the fluorocarbon resin layer has a thickness of 70
.mu.m or less.
[0039] For example, in a rice cooker, a frying pan, a pot, or the
like, generally, the fluorocarbon resin layer needs to have a
thickness of about 70 to 120 .mu.m. However, an increase in the
thickness of the fluorocarbon resin layer can form a crack on
baking the fluorocarbon resin layer. Frequently, multiple
applications of the fluorocarbon resin result in a multilayer
coating. This leads to increases in machining cost and the cost of
materials.
[0040] According to the invention of this claim, crosslinking by
electron beam irradiation improves the abrasion resistance of the
fluorocarbon resin layer, so that the thickness of the fluorocarbon
resin layer can be reduced to 70 .mu.m or less while the abrasion
resistance is maintained. As a result, the machining cost and the
cost of materials can be reduced by providing a single-layer
coating or a reduction in the number of layers of a multilayer
coating. From the viewpoint of thermal conductivity and
productivity, the fluorocarbon resin layer preferably has a
thickness of 30 .mu.m or less and more preferably 10 .mu.m or less.
In such a thin film, the abrasion resistance is ensured.
[0041] The distance in which an electron beam transmits the
fluorocarbon resin layer is determined by the acceleration voltage
of the electron beam and the specific gravity of the fluorocarbon
resin. The specific gravity is intrinsic to the fluorocarbon resin.
When the thickness of the fluorocarbon resin layer to be subjected
to crosslinking treatment is determined, an acceleration voltage
needed is determined. The distance in which an electron beam
transmits the fluorocarbon resin is increased with increasing
acceleration voltage. That is, an increase in the thickness of the
fluorocarbon resin layer increases the acceleration voltage
required to crosslink the entire fluorocarbon resin layer, so that
it is necessary to use a large-sized expensive electron beam
irradiation apparatus.
[0042] According to the invention of this claim, crosslinking by
electron beam irradiation improves the abrasion resistance of the
fluorocarbon resin layer. The thickness of the fluorocarbon resin
layer can be reduced to 70 .mu.m or less, preferably 30 .mu.m or
less, and more preferably 10 .mu.m or less while the abrasion
resistance is maintained. It is thus possible to perform
crosslinking with an ultrasmall, inexpensive general-purpose
electron beam irradiation apparatus with an acceleration voltage of
60 kV.
[0043] According to an invention described in claim 5,
[0044] in the fluorocarbon resin composite according to any one of
Claims 1 to 4, the amount of the electron beam irradiation is in
the range of 1 kGy to 500 kGy.
[0045] In the invention of this claim, the amount of the electron
beam irradiation is in the range of 1 kGy to 500 kGy, thereby
assuredly crosslinking the fluorocarbon resin and suppressing
cleavage of polymeric chains of the fluorocarbon resin due to
excessive irradiation.
[0046] An amount of the electron beam irradiation of 50 kGy or more
results in an increase in crosslink density, improving the abrasion
resistance. An amount of the electron beam irradiation of 300 kGy
or less provides the flexibility of the film, suppressing the
occurrence of cracking during processing such as pressing. An
amount of the electron beam irradiation exceeding 300 kGy causes
degradation of the polymer, reducing the abrasion resistance. Thus,
the amount of the electron beam irradiation is preferably in the
range of 50 kGy to 300 kGy.
[0047] According to an invention described in claim 6,
[0048] in the fluorocarbon resin composite according to any one of
Claims 1 to 5, the base is composed of aluminum, an aluminum alloy,
or stainless steel.
[0049] In the invention of this claim, the base is composed of
aluminum, an aluminum alloy, or stainless steel. In this case, the
base is easily subjected to machining such as pressing and spinning
and serves as a material for a lightweight cookware.
[0050] According to an invention described in claim 7,
[0051] in the fluorocarbon resin composite according to Claim 6,
the fluorocarbon resin layer is formed on the non-surface-treated
base, and in a cross-cut test (JIS-K-5400, 1998 edition), the
fluorocarbon resin layer is not detached after 100 repetitions of a
peeling operation using an adhesive tape.
[0052] In the invention of this claim, the fluorocarbon resin layer
having a strong adhesion to the base is obtained without performing
surface treatment of the base. It is thus possible to provide the
fluorocarbon resin composite that is easily produced.
[0053] Note that "not detached" described above indicates that the
fluorocarbon resin composite is classified into class 10 specified
by JIS-K-5400 (1998 edition).
[0054] According to an invention described in claim 8,
[0055] cookware includes the fluorocarbon resin composite according
to any one of Claims 1 to 7.
[0056] Fluorocarbon resins have excellent nonadhesiveness and the
advantage that food does not easily adhere to a rice cooker, a
frying pan, or the like. Disadvantageously, the adhesion strength
between the fluorocarbon resin and the base is low. To solve the
problem, a technique for etching a surface of a base (Japanese
Patent No. 1239856) and the use of a primer layer (adhesive layer)
are reported. However, they are not sufficient, causing an increase
in cost.
[0057] In contrast, the cookware according to the invention of this
claim is composed of the fluorocarbon resin composite. Unlike
conventional cookware, the cookware has excellent adhesive strength
between the base and the fluorocarbon resin layer and leads to low
cost.
[0058] According to an invention described in claim 9,
[0059] a cooker includes the cookware according to Claim 8.
[0060] In the invention of this claim, the cooker advantageously
has excellent properties described in claim 8.
[0061] According to an invention described in claim 10,
[0062] a method for producing a fluorocarbon resin composite
includes the steps of applying an uncrosslinked fluorocarbon resin
onto a base, heating the fluorocarbon resin to a temperature equal
to or higher than the melting point of the fluorocarbon resin,
subjecting the fluorocarbon resin to electron beam irradiation in a
low-oxygen atmosphere to crosslink the fluorocarbon resin, and
machining the base in such a manner that the base has a desired
shape.
[0063] In the invention of this claim, after the uncrosslinked
fluorocarbon resin is applied onto a base, the fluorocarbon resin
is heated to a temperature equal to or higher than the melting
point of the fluorocarbon resin, and then the fluorocarbon resin is
subjected to electron beam irradiation in a low-oxygen atmosphere
to crosslink the fluorocarbon resin. Thus, the thin crosslinked
fluorocarbon resin film on the base, which has been difficult to
form in the past, is easily formed. The uncrosslinked fluorocarbon
resin can be used as a powder having a small particle size. Thus,
the resin can be used as a raw material for a fluorocarbon resin
dispersion. Since a crosslinked fluorocarbon resin having a large
particle size is not used, a thin film can be formed.
[0064] For example, a fluorocarbon resin dispersion (a dispersion
of the uncrosslinked fluorocarbon resin dispersed in water) is
applied by spin coating to a surface of the plate-like base to form
a thin film of the fluorocarbon resin. Spin coating is a method as
described below. The fluorocarbon resin dispersion is dropped on
the middle portion of the base while the base is being rotated. The
dispersion is spread by a centrifugal force, so that the thin
fluorocarbon resin film having a uniform thickness is formed on the
surface of the base. Next, the fluorocarbon resin is baked by
heating. The resulting fluorocarbon resin is heated to a
temperature equal to or higher than its melting point. The
fluorocarbon resin is crosslinked by electron beam irradiation in a
low-oxygen atmosphere. After cooling the base and the fluorocarbon
resin, the base is machined into a desired shape. Machining
indicates that an inner pot of a rice cooker or a frying pan is
formed by pressing or spinning. In this way, it is possible to
easily produce cookware having improved abrasion resistance and
adhesive strength while nonadhesiveness, which is a feature of a
fluorocarbon resin, is maintained. To increase the crosslink
density, the oxygen concentration in the low-oxygen atmosphere is
preferably set 1000 ppm or less and more preferably 500 ppm or
less. Furthermore, an excessively small oxygen concentration is not
preferred. Specifically, a nitrogen gas atmosphere can be
preferably used.
[0065] According to an invention described in claim 11,
[0066] a roller or a belt for use in office automation equipment
includes a fluorocarbon resin layer on a circular base, in which
the fluorocarbon resin layer is crosslinked by electron beam
irradiation.
[0067] In the invention of this claim, the fluorocarbon resin is
crosslinked by electron beam irradiation. The abrasion resistance
of the fluorocarbon resin layer is improved while the
nonadhesiveness of the fluorocarbon resin is maintained, reducing
the thickness of the fluorocarbon resin layer. Thus, in the fixing
roller or a transfer fixing belt, heat from a heater arranged
inside thereof is efficiently conducted. In the case where the
fluorocarbon resin layer has a thickness of, for example, 10 .mu.m,
40% of heat from the heater arranged in the fixing roller or the
transfer fixing belt is lost. However, in the case where the
thickness is 5 .mu.m, only 20% of heat is lost. It is thus possible
to improve a print speed without increasing the heating temperature
of the heater.
[0068] An increase in the temperature of the heater causes thermal
degradation, reducing the abrasion resistance. However, in the
invention of this claim, the fluorocarbon resin is crosslinked by
electron beam irradiation, thus improving the abrasion resistance
of the fluorocarbon resin layer because the crosslinking of the
fluorocarbon resin eliminates the melting point, i.e., the
fluorocarbon resin is not melt. Furthermore, in the present
invention, the base is bonded to the fluorocarbon resin by electron
beam irradiation, thus eliminating an adhesive layer (primer);
hence, it is possible to significantly increase the thermal
conductivity of a roller or a belt for use in office automation
equipment.
[0069] The foregoing technique can be applied to another roller or
belt for use in office automation equipment. Examples of the roller
for use in office automation equipment include a fixing roller, a
transfer roller, a pressing roller, a charging roller, and
developing roller. Examples of the belt for use in office
automation equipment include a transfer belt, a transfer fixing
belt, and a belt used for a fixing section like the fixing
belt.
[0070] According to an invention described in claim 12,
[0071] in the roller or the belt for use in office automation
equipment according to Claim 11, the fluorocarbon resin layer is
composed of one selected from a tetrafluoroethylene-perfluoro(alkyl
vinyl ether) copolymer (PFA), polytetrafluoroethylene (PTFE), and a
fluorinated ethylene-propylene copolymer (FEP), or a mixture of two
or three compounds selected from PFA, PTFE, and FEP.
[0072] In the invention of this claim, the fluorocarbon resin is
composed of one selected from PFA, PTFE, and FEP, or a mixture of
two or three compounds selected from these compounds. Thus, a thin
film of the fluorocarbon resin having excellent heat resistance and
resistance to stress cracking is obtained.
[0073] According to an invention described in claim 13,
[0074] in the roller or the belt for use in office automation
equipment according to Claim 11 or 12, an electron beam during the
electron beam irradiation reaches the circular base through the
fluorocarbon resin layer.
[0075] As described above, the crosslinking of the uncrosslinked
fluorocarbon resin on the base by electron beam irradiation in
which an electron beam reaches the base through the fluorocarbon
resin layer significantly improves the adhesive strength between
the base and the fluorocarbon resin layer compared with the case
where an electron beam does not reach the base. According to the
invention of this claim, it is thus possible to provide the roller
or the belt, for use in office automation equipment, in which the
base and the fluorocarbon resin layer are strongly bonded to each
other.
[0076] According to an invention described in claim 14,
[0077] in the roller or the belt for use in office automation
equipment according to any one of Claims 11 to 13, the fluorocarbon
resin layer has a thickness of 20 .mu.m or less.
[0078] In the invention of this claim, the abrasion resistance of
the fluorocarbon resin layer is improved by crosslinking using
electron beam irradiation. Thus, the thickness of the fluorocarbon
resin layer can be reduced to 20 .mu.m or less, preferably 10 .mu.m
or less, more preferably 3 .mu.m or less for a roller, and 7 .mu.m
or less for a belt while the abrasion resistance is maintained.
Thus, it is possible to increase the thermal conductivity of the
roller or the transfer fixing belt. The temperature of the heater
need not be increased, thus suppressing the thermal degradation of
the fluorocarbon resin layer. Furthermore, it is possible to reduce
the machining cost and the cost of materials. Moreover, in the case
where the thickness is 20 .mu.m or less, it is possible to perform
crosslinking with an ultrasmall, inexpensive general-purpose
electron beam irradiation apparatus with an acceleration voltage of
60 kV.
[0079] According to an invention described in claim 15,
[0080] in the roller or the belt for use in office automation
equipment according to any one of Claims 11 to 14, the amount of
the electron beam irradiation is in the range of 1 kGy to 500
kGy.
[0081] In the invention of this claim, the amount of the electron
beam irradiation is in the range of 1 kGy to 500 kGy, thus
assuredly crosslinking the fluorocarbon resin.
[0082] According to an invention described in claim 16,
[0083] in the roller or the belt for use in office automation
equipment according to any one of Claims 11 to 15, the circular
base is composed of a heat-resistant resin or a metal.
[0084] In the invention of this claim, the circular base is
composed of a heat-resistant resin or a metal, thus providing the
roller or the belt, for use in office automation equipment, having
excellent heat resistance and mechanical strength. Examples of the
heat-resistant resin that can be used include polyimide resins and
polyamide-imide resins. Examples of the metal that can be used
include stainless steel and aluminum.
[0085] According to an invention described in claim 17,
[0086] in the roller or the belt for use in office automation
equipment according to any one of Claims 11 to 16, the fluorocarbon
resin layer is formed on the non-surface-treated base, and the
fluorocarbon resin layer has an adhesive strength of 0.5 Kg/1.5 cm
or more in a peeling test.
[0087] In the invention of this claim, it is possible to achieve
the adhesive strength of the fluorocarbon resin layer to 0.5 Kg/1.5
cm or more and preferably 0.8 Kg/1.5 cm or more by crosslinking
using electron beam irradiation. As a result, the fluorocarbon
resin layer having a strong adhesion to the base is provided
without performing adhesive treatment, e.g., the use of a primer on
a surface of the base.
[0088] According to an invention described in claim 18,
[0089] in the roller or the belt for use in office automation
equipment according to any one of Claims 11 to 17, an intermediate
layer is arranged between the circular base and the fluorocarbon
resin layer.
[0090] In the invention of this claim, the formation of the
intermediate layer between the base and the fluorocarbon resin
layer results in the roller or the belt, for use in office
automation equipment, capable of corresponding to requirement
specifications of various users in addition to the effects
described above. As the intermediate layer, for example, an elastic
material such as silicone rubber is used.
[0091] According to an invention described in claim 19,
[0092] a method for producing a roller or a belt for use in office
automation equipment includes the steps of applying an
uncrosslinked fluorocarbon resin onto a circular base, heating the
fluorocarbon resin to a temperature equal to or higher than the
melting point of the fluorocarbon resin, and subjecting the
fluorocarbon resin to electron beam irradiation in a low-oxygen
atmosphere to crosslink the fluorocarbon resin.
[0093] In the invention of this claim, after the application of the
uncrosslinked fluorocarbon resin onto the base, the fluorocarbon
resin is subjected to electron beam irradiation in a low-oxygen
atmosphere to crosslink the fluorocarbon resin while the
temperature of the fluorocarbon resin is maintained at a
temperature equal to or higher than its melting point. Thus, the
thin crosslinked fluorocarbon resin film on the base, which has
been difficult to form in the past, is easily formed.
[0094] The uncrosslinked fluorocarbon resin can be used as a powder
having a small particle size. Thus, a dispersion method or the like
can be employed. Since a crosslinked fluorocarbon resin having a
large particle size is not used, a thin film can be formed. As a
result, the thermal conductivity can be improved while the
nonadhesiveness, which is a feature of a fluorocarbon resin, is
maintained. Furthermore, it is possible to easily produce the
roller or the belt, for use in office automation equipment, having
improved abrasion resistance and heat resistance. As the low-oxygen
atmosphere, a nitrogen gas atmosphere or the like is preferred.
[0095] Moreover, after the formation of the uncrosslinked
fluorocarbon resin on the base, the resin is crosslinked by
electron beam irradiation, thus leading to a significantly strong
adhesion between the fluorocarbon resin and the base and
eliminating the need for an adhesive layer (primer). The reason for
the improvement in the adhesion to the base is probably as follows:
Electron beam irradiation causes cleavage of a main chain or a side
chain. Active radicals are generated because of a high temperature.
The resulting radicals are bonded to the base because there is no
substance, such as oxygen, which is readily bonded to the
radicals.
[0096] According to an invention described in claim 20,
[0097] a method for producing a roller or a belt for use in office
automation equipment includes the steps of placing a die (outlet)
of an extruder in a low-oxygen atmosphere, extruding an
uncrosslinked fluorocarbon resin from the die of the extruder onto
the circular base, and subjecting the fluorocarbon resin to
electron beam irradiation in the low-oxygen atmosphere to crosslink
the fluorocarbon resin before the temperature of the fluorocarbon
resin is decreased to a temperature equal to or lower than the
melting point of the fluorocarbon resin.
[0098] In the invention of this claim, the thin film of the
fluorocarbon resin is formed on the circular base by extrusion
suitable for mass production. Furthermore, electron beam
irradiation is performed before the temperature of the molten
fluorocarbon resin is decreased to a temperature equal to or lower
than the melting point of the fluorocarbon resin. Thus, the roller
or the belt for use in office automation equipment can be
efficiently produced at low cost.
[0099] According to an invention described in claim 21,
[0100] the method for producing a roller or a belt for use in
office automation equipment according to Claim 19 or 20 further
includes after the uncrosslinked fluorocarbon resin is heated to a
temperature equal to or higher than the melting point of the
fluorocarbon resin and then subjected to electron beam irradiation
in a low-oxygen atmosphere to crosslink the fluorocarbon resin,
performing rapid cooling before the temperature of a layer located
below the fluorocarbon resin reaches the decomposition temperature
of the layer.
[0101] As described above, the uncrosslinked fluorocarbon resin is
heated to a temperature equal to or higher than its melting point
and then subjected to electron beam irradiation in a low-oxygen
atmosphere, thereby easily and assuredly crosslinking the
fluorocarbon resin. The temperature of the layer located below the
fluorocarbon resin is increased by heat from the fluorocarbon resin
layer. However, rapid cooling is performed before the temperature
reaches the decomposition temperature of the layer, so that the
properties of the lower layer are not reduced. Furthermore, if the
fluorocarbon resin is rapidly cooled, the crystallization of the
fluorocarbon resin does not easily occur, thus improving the flex
resistance of the fluorocarbon resin layer.
[0102] That is, the uncrosslinked fluorocarbon resin is applied to
an inner peripheral surface of a ring-shaped die (cylinder) by a
thin-film formation method such as a dispersion method. For
example, silicone rubber is applied to the inner peripheral surface
of the circular fluorocarbon resin layer to form the intermediate
layer. Next, for example, a polyimide resin serving as a base is
applied to the inner peripheral surface of the intermediate layer
to form a circular base. Then the circular base, the intermediate
layer, and the fluorocarbon resin layer are pulled out from the
die. The uncrosslinked fluorocarbon resin surface layer is heated
to a temperature equal to or higher than its melting point,
subjected to electron beam irradiation in a low-oxygen atmosphere,
and rapidly cooled before the temperature of the intermediate layer
located below the fluorocarbon resin layer reaches the
decomposition temperature, thereby completing the belt for use in
office automation equipment.
[0103] When the electron beam irradiation is performed, spiral
irradiation is preferred. A small electron beam irradiation
apparatus is characterized in that the amount of electron beam
irradiation in the middle of an irradiation spot is large and the
amount of electron beam irradiation in the periphery is small. It
is thus difficult to uniformly irradiate a surface of the
fluorocarbon resin layer with electron beams by simple electron
beam, irradiation. Accordingly, the surface of the fluorocarbon
resin layer is uniformly subjected to electron beam irradiation
while the circular base provided with the fluorocarbon resin layer,
which is a target irradiated, on its outer peripheral surface is
being rotated and while the electron beam irradiation apparatus
arranged outside the base is being translated in the axial
direction of the circular base (that is, spiral irradiation).
Advantages
[0104] According to the first aspect of the present invention, the
fluorocarbon resin layer on the base is crosslinked by electron
beam irradiation and machined into a desired shape. Thus, it is
possible to provide the fluorocarbon resin composite, the cookware,
or the cooker including the thin film of the fluorocarbon resin
having excellent abrasion resistance while nonadhesiveness, which
is a feature of a fluorocarbon resin, is maintained.
[0105] According to the second aspect of the present invention, the
uncrosslinked fluorocarbon resin is formed on the base, and the
fluorocarbon resin is crosslinked by electron beam irradiation.
Thus, it is possible to provide the roller or the belt, for use in
office automation equipment, including the thin film of the
fluorocarbon resin having excellent abrasion resistance and heat
resistance while nonadhesiveness, which is a feature of a
fluorocarbon resin, is maintained.
BRIEF DESCRIPTION OF DRAWINGS
[0106] FIG. 1 is a graph showing the evaluation results of abrasion
properties of fluorocarbon resin layers used in the present
invention.
[0107] FIG. 2 is a graph showing the evaluation results of abrasion
properties of fluorocarbon resin layers used in the present
invention.
[0108] FIG. 3 is a conceptual cross-sectional view showing cookware
according to an embodiment of the present invention.
[0109] FIG. 4 is a flow chart illustrating a procedure of producing
cookware according to an embodiment of the present invention.
[0110] FIG. 5 is a conceptual cross-sectional view showing a step
according to an example of the present invention.
[0111] FIG. 6 is a conceptual drawing illustrating a method for
irradiating a fluorocarbon resin with electron beams.
[0112] FIG. 7 is a conceptual drawing illustrating a method for
irradiating a fluorocarbon resin layer with electron beams
according to an example of the present invention.
[0113] FIG. 8 is a graph showing the evaluation results of abrasion
properties of cookware according to an example of the present
invention.
[0114] FIG. 9 is a plan view of cuts in a fluorocarbon resin layer
of cookware according to an example of the present invention, the
cuts penetrating thorough the fluorocarbon resin layer.
[0115] FIG. 10 is a partially cutout conceptual drawing showing a
roller for use in office automation equipment according to an
embodiment of the present invention.
[0116] FIG. 11 is a flow chart illustrating a procedure for
producing a roller for use in office automation equipment according
to an embodiment of the present invention.
[0117] FIG. 12 is a flow chart illustrating another procedure for
producing a roller for use in office automation equipment according
to an embodiment of the present invention.
[0118] FIG. 13 is a conceptual partially cross-sectional view
illustrating a production process of a roller for use in office
automation equipment according to an embodiment of the present
invention.
[0119] FIG. 14 is a conceptual partially cross-sectional view
illustrating another production process of a roller for use in
office automation equipment according to an embodiment of the
present invention.
[0120] FIG. 15 is a partially cutout conceptual drawing of a belt
for use in office automation equipment according to an embodiment
of the present invention.
[0121] FIG. 16 is a flow chart illustrating a procedure for
producing a belt for use in office automation equipment according
to an embodiment of the present invention.
[0122] FIG. 17 is a flow chart illustrating another procedure for
producing a belt for use in office automation equipment according
to an embodiment of the present invention.
[0123] FIG. 18(A) is a conceptual front view and FIG. 18(B) is a
conceptual side view, both views illustrating a method of electron
beam irradiation in the production of a belt for use in office
automation equipment according to an embodiment of the present
invention.
REFERENCE NUMERALS
[0124] 1 base
[0125] 2 fluorocarbon resin layer
[0126] 3 stainless steel
[0127] 20, 38, 53 electron beam irradiation apparatus
[0128] 21 electron-beam tube
[0129] 31 fluorocarbon resin composite
[0130] 32 aluminum base
[0131] 33 chamber
[0132] 34 partition wall
[0133] 35 hot plate
[0134] 36 opening
[0135] 37 titanium foil
[0136] 38 cut penetrating to base
[0137] 41, 71 circular base
[0138] 51, 61 die (outlet) of extruder
[0139] 52, 62 opening
[0140] 63 hole
[0141] 72 intermediate layer
BEST MODE FOR CARRYING OUT THE INVENTION
[0142] The present invention will be described below on the basis
of the best mode for carrying out the invention. The present
invention is not limited to embodiments described below. Various
modifications can be made to the following embodiments within the
scope identical to the present invention and the scope of its
equivalence.
1. Evaluation Example
(Fluorocarbon Resin and Production and Evaluation of Fluorocarbon
Resin Composite Including Fluorocarbon Resin)
[0143] i. Basic Abrasion Properties
[0144] To check the effect of a crosslinked fluorocarbon resin, a
thin fluorocarbon resin film formed on a plate was crosslinked by
electron beam irradiation, and then adhesion and a change in
abrasion properties were evaluated.
[0145] A sample was produced as follows: A fluorocarbon resin
dispersion (PFA dispersion 950 HP, manufactured by Du Pont-Mitsui
Fluorochemicals) was applied by dipping on a 5-mm-thick aluminum
plate and baked at 380.degree. C. to form a film with a thickness
of 5 An irradiation unit equipped with a chamber and a hot plate
(min-EB, output: 30 kV, manufactured by Ushio Inc.) was prepared.
The aluminum plate coated with the fluorocarbon resin was placed on
the hot plate at a temperature of 400.degree. C. under a nitrogen
atmosphere and subjected to electron beam irradiation. Five
different amounts of irradiation were used: 30 kGy, 100 kGy, 300
kGy, 900 kGy, and only heating to 400.degree. C. (not
irradiated).
[0146] Abrasion properties were evaluated by the Taber's abrasion
resistance test. The Taber's abrasion resistance test is performed
by placing Scotch-Brite (registered trademark) (#3000) and a 2-kg
weight on the irradiated sample, rotating Scotch-Brite (registered
trademark) at 500 rpm, measuring a reduction in the thickness of
the PFA film due to friction applied by Scotch-Brite (registered
trademark) with respect to the number of revolutions.
[0147] FIG. 1 shows the evaluation results of the abrasion
properties. In FIG. 1, the horizontal axis of the graph indicates
the total number of revolutions of Scotch-Brite (registered
trademark). The vertical axis indicates the reduction in the
thickness of the sample. The results demonstrated as follows: The
amount of abrasion was reduced as the amount of irradiation was
increased from 30 kGy to 100 kGy compared with a nonirradiated
sample and that the abrasion resistance was significantly improved.
At 300 kGy, the reduction in thickness was increased. At 900 kGy,
the sample was immediately abraded. At 300 kGy and 900 kGy, the
fluorocarbon resin began to degrade, which revealed that the
abrasion resistance was reduced. Thus, in the case where this
fluorocarbon resin is used at the temperature, an amount of
irradiation of about 100 kGy is appropriate.
[0148] Next, comparisons were made between crosslinked PFA and
other materials. As other materials, three super engineering
plastics, which are hard and excellent in abrasiveness, were used.
Specifically, polyamide-imide (PAI) (Vylomax HR-16NN, manufactured
by Toyobo Co., Ltd.), polyimide (PI) (U-Varnish-S, manufactured by
Ube Industries, Ltd.), and polyetheretherketone (PEEK)
(PEEK-COATING, manufactured by Okitsumo Incorporated) were used.
FIG. 2 shows the evaluation results. The results demonstrated that
the crosslinked PFA had abrasion properties superior than those of
super engineering plastics, such as PAI, PI, and PEEK.
ii. Test of Adhesion Properties
[0149] Next, an experiment to improve the adhesion of a
fluorocarbon resin to a base by electron beam irradiation was
performed.
[0150] A sample was produced as follows: A fluorocarbon resin
dispersion (PFA dispersion 950 HP, manufactured by Du Pont-Mitsui
Fluorochemicals) was applied by dipping onto a 5-mm-thick aluminum
plate and polyimide (PI) (U-Varnish-S, manufactured by Ube
Industries, Ltd.) and baked at 380.degree. C., thereby forming
films each having a thickness of 5 .mu.m. The resulting films were
subjected to electron beam irradiation with an irradiation unit
equipped with a chamber and a hot plate (min-EB, output: 30 kV,
manufactured by Ushio Inc.) under a nitrogen atmosphere at a
hot-plate temperature of 400.degree. C. and an amount of electron
beam irradiation of 100 kGy.
[0151] The evaluation was made by a detachment test, what is called
a cross-cut test, according to JIS-K-5400 (1998 edition). The
cross-cut test is as follows: Cuts are made in a surface of the
sample so as to penetrate to the plate, thereby forming a grid of
100 squares each measuring about 1.times.1 mm. An operation in
which a tape is adhered to the grid and then removed is repeated.
This test is to determine how many repetitions of the operation are
necessary to detach the sample. The test results demonstrated that
all squares of nonirradiated PFA on the aluminum plate were
detached after several repetitions of the operation and that none
of the squares of each of the irradiated PFA films on the aluminum
plate and PI was detached even after 100 repetitions of the
operation. That is, according to the foregoing standard, the
evaluation of the detachment state is based on classes 0 to 10. The
samples were classified into class 10 (each cut is thin, the edges
of the cuts are smooth, none of the squares of the grid is
detached, and no flake is detached at the intersections of the
cuts). Thus, it was found that the irradiation of the fluorocarbon
resin with an electron beam at a high temperature under an
oxygen-free atmosphere significantly increases adhesion to the
base.
[0152] Next, the evaluation was made by a peeling test, in which a
sheet composed of a fluorinated ethylene-propylene copolymer (FEP)
is bonded to a fluorocarbon film on a base and a force necessary to
peel the film is measured. Table 1 shows the test results. In all
test pieces, although the evaluation was not completed because
detachment occurred at the interface between the FEP sheet and the
sample, it was found that each of the samples had an adhesive
strength as high as 1.7 kg/1.5 cm or more.
[0153] Note that in the case where a primer (adhesive) is not used
or etching treatment (surface treatment of the base) is not
performed, the adhesive strength determined by the peeling test is
an unmeasurable level (substantially zero).
TABLE-US-00001 TABLE I Amount of Adhesive strength irradiation
(kg/1.5 cm) Base (kGy) 1 2 Average Remarks Aluminum 30 2.24 1.63
1.93 Detachment at interface between fluorocarbon film and FEP
sheet Aluminum 100 1.98 1.53 1.76 Detachment at interface between
fluorocarbon film and FEP sheet Aluminum 300 1.76 1.7 1.73
Detachment at interface between fluorocarbon film and FEP sheet
Aluminum 900 2.3 2.51 2.41 Detachment at interface between
fluorocarbon film and FEP sheet Polyimide 100 1.5 0.61 1.05
Detachment at interface between polyimide and fluorocarbon film
2. First Embodiment
[0154] This embodiment is an embodiment according to the first
aspect and relates to cookware.
(Production of Cookware)
[0155] FIG. 3 is a conceptual drawing of an inner pot of a rice
cooker as an example of cookware. In FIG. 3, reference numeral 1
denotes a base, and reference numeral 2 denotes a thin film-like
fluorocarbon resin on the base 1.
[0156] The base 1 includes a bottom and a side. Examples of a
material for the base 1 that can be used include metals such as
stainless steel, aluminum, and aluminum alloys.
[0157] The fluorocarbon resin layer 2 is arranged on a horizontal
inner wall of the bottom and a substantially vertical inner wall of
the side, has a thickness of 15 .mu.m, and is crosslinked by
electron beam irradiation. The fluorocarbon resin layer 2 is
preferably formed of PFA (PFA dispersion 950 HP, manufactured by Du
Pont-Mitsui Fluorochemicals). The PFA is composed of a
thermoplastic fluorocarbon resin and has a solid content of 33% and
a particle size of approximately several tenths of a micrometer;
hence, the PFA is suitable for the formation of a thin film using,
for example, a fluorocarbon resin dispersion.
[0158] The inner pot having the structure described above is
produced in accordance with a flow chart of a production procedure
shown in FIG. 4.
[0159] First, a flat-shaped base is prepared. As shown in FIG. 5,
the flat-shaped base 1 composed of an aluminum alloy (Al--Mn-based,
ES 3003, 3004, or 3005) and having a thickness of about 0.6 to
about 3.0 mm is prepared. In an induction heating (IH) cooker, a
stainless steel sheet 3 is arranged on the back side of the base 1,
in some cases, as indicated by a chain double-dashed line in FIG.
5.
[0160] In step S2, a dispersion of a fine powder composed of an
uncrosslinked fluorocarbon resin (PFA) dispersed in water is
applied to the upper surface of the base 1 by spin coating to form
the thin fluorocarbon resin layer 2.
[0161] In step S3, the base 1 is placed in a temperature-controlled
oven and baked at 380.degree. C. to 420.degree. C. for 10 to 20
minutes. In step S4, electron beam irradiation is performed in a
nitrogen gas atmosphere to crosslink the resin while the
fluorocarbon resin layer 2 is melted at a temperature equal to or
higher than the melting point of the resin. That is, as shown in
FIG. 6, the base 1 that has the fluorocarbon resin layer 2 facing
down is transported above an electron beam irradiation apparatus 20
in the direction indicated by an arrow, so that the entire
fluorocarbon resin layer 2 is uniformly subjected to electron beam
irradiation. To sufficiently crosslink the fluorocarbon resin layer
2, the amount of electron beam irradiation is preferably about 100
kGy. The irradiation unit (min-EB, manufactured by Ushio Inc.)
including 10-electron-beam tubes 21 arranged in a staggered
configuration is used as the electron beam irradiation apparatus 20
because it is versatile, inexpensive, and compact.
[0162] According to the present invention, the fluorocarbon resin
layer has a small thickness. Thus, a single-layer coating can be
formed. Furthermore, electron beams reach the base with the
foregoing general-purpose electron beam irradiation apparatus,
providing a product having the strong adhesion of the fluorocarbon
resin layer to the base.
[0163] In step S5, the base 1 is subjected to pressing or spinning
so as to have a desired shape.
[0164] In this way, the inner pot provided with the crosslinked
thin fluorocarbon resin layer 2 formed on the base 1 is completed
by the production process suitable for mass production. The
abrasion resistance of the fluorocarbon resin layer 2 of the
resulting inner pot is evaluated by the Taber's abrasion resistance
test. Furthermore, the adhesive strength between the base and the
fluorocarbon resin layer is evaluated by the cross-cut test
(HS-K-5400, 1998 edition). In both cases, whether the results meet
predetermined criteria is checked.
[0165] A detailed description will be given below on the basis on
an example.
Example
[0166] In this example, a fluorocarbon resin composite including an
aluminum base was subjected to pressing with a press actually used
for producing an inner pot of a rice cooker in order to check
whether the fluorocarbon resin composite was able to withstand
pressing and whether the fluorocarbon resin composite did not cause
a problem.
(1) Production of Fluorocarbon Resin Composite
[0167] i. Coating of Fluorocarbon Resin on Base
[0168] Two different fluorocarbon resins, i.e., a PTFE dispersion
(D1-F, manufactured by Daikin Industries, Ltd.) and a PFA
dispersion (945 HP, manufactured by Du Pont-Mitsui
Fluorochemicals), were each applied by spin coating to a
disk-shaped aluminum (3004) base having a diameter of 360 mm and a
thickness of 1.2 mm, dried, and baked at 400.degree. C. to form two
different fluorocarbon resin composites each including a PTFE film
or a PFA film serving as fluorocarbon resin layer having a
thickness of 10 .mu.m on the aluminum base.
ii. Electron Beam Irradiation
[0169] FIG. 7 is a conceptual drawing showing an electron beam
irradiation method. In FIG. 7, the fluorocarbon resin composite 31
including the fluorocarbon resin layer 2 (PTFE or PFA film) facing
up and the aluminum base 32 facing down was placed on a hot plate
35 arranged in a chamber 33 for electron beam irradiation. An
opening 36 through which electron beams passed was arranged above
partition walls 34 of the chamber 33. To seal the chamber 33, the
opening 36 was covered with titanium foil 37 with a thickness of 30
.mu.m. The temperature of the hot plate 35 was set to 340.degree.
C. for the fluorocarbon resin composite including the PTFE film.
The temperature of the hot plate 35 was set to 310.degree. C. for
the fluorocarbon resin composite including the PFA layer. The gas
in the chamber 33 was replaced with nitrogen (an oxygen
concentration in the chamber after replacement of 5 ppm). The
layers were irradiated with electron beams at a dose of 60 kGy with
a conveyor-type electron beam irradiation system 38 (acceleration
voltage: 1.16 MeV, manufactured by NHV Corporation), thereby
crosslinking each of PTFE and PFA constituting the fluorocarbon
resin layers 2.
iii. Pressing
[0170] Each of the samples after electron beam irradiation was
cold-stamped into a bowl-shaped article with a die for an inner pot
of a rice cooker, thereby forming an inner pot having a depth of
120 mm and a diameter of 190 mm. Although the stamping of each
sample into the bowl-shaped article applied stresses, such as
pressure, friction, and tension, to the aluminum base 32 and the
fluorocarbon resin layer 2, the resulting PTFE and PFA films of the
inner pots were free from problems, such as detachment and flaws.
The results demonstrated that the PTFE film and the PFA film in
this example were able to withstand pressing without performing
surface treatment such as etching of the base.
(2) Performance Evaluation
[0171] i. Evaluation of Abrasion Resistance
[0172] The abrasion resistance of each of the resulting PTFE film
and the PFA film of the inner pots was evaluated by the Taber's
abrasion resistance test. FIG. 8 shows the evaluation results in
addition to results in the case where nonirradiated PTFE and PFA
films were provided. FIG. 8 demonstrated that the irradiation of
radiation resulted in a significant increase in the abrasion
resistance of the PTFE and PFA films. Furthermore, in the
irradiated PTFE film, surprisingly, the amount of abrasion was zero
even after 20,000 revolutions.
ii. Evaluation of Adhesive Strength
[0173] The adhesion strength of each of the resulting PTFE film and
the PEA film of the inner pots was evaluated by the detachment
test, what is called the cross-cut test. The evaluation was made
even if the films having flaws and pin holes were subjected to
pressing. Thus, 100 cuts were made in each of the PTFE film and the
PFA film so as to penetrate to a corresponding one of the bases,
thereby forming a grid of 100 squares. Furthermore, two different
projections, called Erichsen, having thicknesses of 5 mm and 10 mm
were formed in the middle of each sample. The evaluation of the
samples was made. A peeling operation was repeated 100 times. Table
II shows the test results.
TABLE-US-00002 TABLE II Material of fluorocarbon resin film PTFE
PFA Erichsen thickness (mm) 0 100/100 100/100 5 100/100 100/100 10
100/100 100/100 * In Table II, numerators are the numbers of
undetached squares, and denominators are the numbers of peeling
operations.
[0174] The results shown in Table II demonstrated that the PTFE
film and the PFA film formed in this example were not detached in
the test for evaluating the adhesive strength and thus had good
adhesive strength.
iii. Performance Evaluation as Cookware
[0175] An evaluation test in which actual cooking was simulated was
performed. Specifically, as shown in FIG. 9, cuts 39 each in the
form of an X were made in a PTFE film and a PFA film, each of the
cuts 39 having a length of 100 mm and a width of 50 mm and
penetrating to a corresponding one of the bases. "Oden No Moto
(Soup mix for ODEN)" (registered trademark) manufactured by S &
B Foods, Inc. was charged into a rice cooker and boiled for 1000
hours. Then whether the PTFE film and the PFA film were detached
from the bases or not was checked. If the adhesion between the
bases and the PTFE and PFA films is insufficient, a soup (Oden
soup) will penetrate to interfaces between them during boiling to
cause detachment of the PTFE film and the PFA film. In this
example, however, it was found that no detachment occurred and thus
the composites were able to be used as cookware without
problems.
3. Second Embodiment
[0176] This embodiment is an embodiment according to the second
aspect and relates to a roller for use in office automation
equipment.
(Production of Roller for Use in Office Automation Equipment)
[0177] FIG. 10 is a partially cutout conceptual drawing showing a
fixing roller for use in office automation equipment according to
the present invention. In FIG. 10, reference numeral 41 denotes a
circular base, and reference numeral 2 denotes a thin film-like
fluorocarbon resin layer on the circular base 41.
[0178] The circular base 41 has a cylindrical shape. A heater (not
shown) and so forth are accommodated in the cylinder. Examples of a
material constituting the circular base 41 include heat-resistant
resins such as polyimide resins and polyamide-imide resins and
metals such as stainless steel and aluminum. The fluorocarbon resin
layer 2 has a thickness of 15 .mu.m and is crosslinked by electron
beam irradiation.
[0179] The fixing roller having the structure described above is
produced in accordance with a flow chart of a production procedure
shown in FIG. 11.
[0180] First, in step S1, the circular base 41 is prepared. For
example, the circular base 41 composed of polyimide is produced by
a method described below. That is, polyimide varnish is applied to
the outside of a drum-shaped die having a predetermined outer
diameter and a predetermined length while the die is being rotated.
Then the die is heated to perform imidization, thereby forming the
circular base 41 around the die, the circular base 41 having a
thickness of about 80 .mu.m and being composed of polyimide.
[0181] In step S2, an uncrosslinked fluorocarbon resin 2 (PFA) is
applied onto the circular base 41 by a dispersion method or the
like to form a thin film. As a material of the fluorocarbon resin
2, PFA (950 HP, manufactured by Du Pont-Mitsui Fluorochemicals) is
preferably used. The PFA is composed of a thermoplastic
fluorocarbon resin and has a solid content of 33% and a particle
size of approximately several tenths of a micrometer; hence, the
PFA is suitable for the formation of a thin film by the dispersion
method or the like.
[0182] In the present invention, an elastic intermediate layer may
be formed on the outer surface of the circular base 41, and the
fluorocarbon resin 2 may be applied onto the outer surface of the
intermediate layer. For example, an intermediate layer composed of
synthetic rubber such as silicone rubber and having a thickness of
about 200 .mu.m is formed on a surface of the circular base 41 with
a dispenser. Then the fluorocarbon resin 2 is applied onto the
outside of the intermediate layer.
[0183] In step S3, the fluorocarbon resin 2 is heated to
380.degree. C. to melt dispersion particles, thereby forming a film
of the fluorocarbon resin 2. Simultaneously, the fluorocarbon resin
2 is subjected to electron beam irradiation in a nitrogen gas
atmosphere before the temperature of the fluorocarbon resin 2 is
decreased to a temperature equal to or lower than its melting
point, thereby crosslinking the fluorocarbon resin 2. Note that the
heating temperature is appropriately adjusted in response to a
material constituting the base. To sufficiently crosslink the
fluorocarbon resin 2, the amount of electron beam irradiation is
set to about 100 kGy. An irradiation unit (min-EB, manufactured by
Ushio Inc.) is used as an electron beam irradiation apparatus
because it is versatile, inexpensive, and compact. In the case
where electron beam irradiation is not performed, a primer layer is
needed to bond the circular base 41 to the fluorocarbon resin layer
2. In the method according to the present invention, strong bonding
can be achieved by electron beam irradiation without using the
primer layer.
[0184] In step S4, the fluorocarbon resin 2 is cooled, resulting in
the fixing roller. The abrasion resistance of the fluorocarbon
resin layer 2 of the resulting fixing roller is evaluated by the
Taber's abrasion resistance test. The adhesive strength between the
circular base 41 and the fluorocarbon resin layer 2 is evaluated by
the peeling test. In both cases, whether the results meet
predetermined criteria is checked. An example of another method for
evaluating abrasion resistance is a linear reciprocating wear test
(test temperature: 250.degree. C.).
4. Third Embodiment
[0185] This embodiment is an embodiment according to the second
aspect and relates to a roller for use in office automation
equipment.
(Production of Roller for Use in Office Automation Equipment)
[0186] FIG. 12 is a flow chart illustrating another procedure for
making a fixing roller.
[0187] In step S1, an uncrosslinked fluorocarbon resin (PFA) tube
is produced with an upright extruder shown in FIG. 13. In FIG. 13,
reference numeral 2 denotes a fluorocarbon resin (PFA) tube,
reference numeral 51 denotes a die (outlet) of the extruder, and
reference numeral 53 denotes an electron beam irradiation apparatus
53. The die 51 is surrounded by a nitrogen gas atmosphere.
[0188] A molten uncrosslinked fluorocarbon resin (PFA) obtained by
heating fluorocarbon resin pellets (PFA, 950 HP) to a temperature
equal to or higher than its melting point is fed into the die 51 of
the upright extruder. A ring-shaped opening 52 is arranged at the
lower end of the die 51. The molten uncrosslinked fluorocarbon
resin is extruded from the opening 52 in a downward direction to
form the uncrosslinked fluorocarbon resin tube 2.
[0189] In step S2, the downwardly extruded fluorocarbon resin tube
2 is subjected to electron beam irradiation in a nitrogen gas
atmosphere with the electron beam irradiation apparatus 53 arranged
in a circular pattern and below the extruder before the temperature
is decreased to a temperature equal to or lower than its melting
point, thereby crosslinking the resin. The foregoing irradiation
unit (min-EB, manufactured by Ushio Inc.) is used as the electron
beam irradiation apparatus 53. To sufficiently crosslink the
fluorocarbon resin tube 2, the amount of electron beam irradiation
is preferably about 100 kGy. The crosslinked fluorocarbon resin
tube 2 is cut into a predetermined length.
[0190] In step S3, the circular base 41 is produced. For example,
polyimide varnish is applied to the outside of a drum-shaped die
having a predetermined outer diameter and a predetermined length
while the die is being rotated. Then the die is heated to perform
imidization, thereby forming the circular base 41 having a
thickness of about 80 .mu.m and being composed of polyimide.
[0191] In step S4, the outer surface of the circular base 41 is
covered with the fluorocarbon resin tube 2 serving as the
fluorocarbon resin layer 2. An example of a covering method is a
method including applying a viscous adhesive to the outer
peripheral surface of the circular base 41 and then forcedly
sliding the fluorocarbon resin tube 2 over the circular base.
Another example thereof is a method using a heat-shrinkable
fluorocarbon resin tube as the fluorocarbon resin tube 2, the
method including inserting the circular base 41 into the
fluorocarbon resin tube 2 and then allowing the fluorocarbon resin
tube 2 to shrink by heating the fluorocarbon resin tube 2, thereby
bonding the outer peripheral surface of the circular base 41 to the
inner peripheral surface of the fluorocarbon resin tube 2.
[0192] In this way, the fixing roller including the thin
fluorocarbon resin layer 2 on the circular base 41 is completed by
extrusion suitable for mass production.
5. Fourth Embodiment
[0193] This embodiment is an embodiment according to the second
aspect and relates to a roller for use in office automation
equipment.
(Production of Roller for Use in Office Automation Equipment)
[0194] FIG. 14 is a conceptual partially cross-sectional view
illustrating a method for producing a fixing roller by another
extrusion. In FIG. 14, reference numeral 41 denotes the circular
base, reference numeral 61 denotes a die (outlet) of an extruder,
and reference numeral 53 denotes the electron beam irradiation
apparatus 53. The die 61 of the extruder has a hole 63 with a
diameter slightly larger than that of the circular base 41. As
described below, the circular base 41 passes through the hole 63.
An opening 62 of the die 61 arranged in a circular pattern is
located in the inner peripheral wall of the hole 63. The molten
uncrosslinked fluorocarbon resin (PFA) 2 that is heated to its
melting point or higher is fed into the die 61. The die 61 is
surrounded by a nitrogen gas atmosphere.
[0195] The electron beam irradiation apparatus 53 is arranged in a
circular pattern and behind the extruder. The foregoing irradiation
unit (min-EB, manufactured by Ushio Inc.) is used as the electron
beam irradiation apparatus 53.
[0196] When the circular base 41 transported from the direction
indicated by an arrow passes through the hole 63 of the extruder,
the molten uncrosslinked fluorocarbon resin (PFA) 2 heated to its
melting point or higher is extruded from the opening 62 of the die
61 so as to be uniformly applied to the outer peripheral surface of
the circular base 41.
[0197] The circular base 41 provided with the fluorocarbon resin 2
on its outer peripheral surface is further transported. The
fluorocarbon resin 2 is subjected to electron beam irradiation with
the electron beam irradiation apparatus 53 in a nitrogen gas
atmosphere at a position where the electron beam irradiation
apparatus 53 is arranged before the temperature of the fluorocarbon
resin 2 is decreased to a temperature equal to or lower than its
melting point, thereby crosslinking the fluorocarbon resin 2. To
sufficiently crosslink the fluorocarbon resin 2, the amount of
electron beam irradiation is preferably about 100 kGy.
[0198] Hereafter, the fluorocarbon resin 2 is cooled, resulting in
fixing roller. In this way, the thin fluorocarbon resin layer 2 is
formed on the circular base 41 by extrusion suitable for mass
production.
6. Fifth Embodiment
[0199] This embodiment is an embodiment according to the second
aspect and relates to a belt for use in office automation
equipment.
(Production of Belt for Use in Office Automation Equipment)
[0200] FIG. 15 is a partially cutout conceptual drawing showing a
transfer belt (or transfer fixing belt) for use in office
automation equipment according to the present invention. In FIG.
15, reference numeral 71 denotes a circular base 71, and reference
numeral 2 denotes a thin film-like fluorocarbon resin layer on the
circular base 71.
[0201] The circular base 71 has a strip-like shape. In the case of
using the circular base 71 as a belt, a heater and so forth are
accommodated in the inside. Examples of a material constituting the
circular base 71 include heat-resistant resins such as polyimide
resins and polyamide-imide resins and metals such as stainless
steel and aluminum.
[0202] The fluorocarbon resin layer 2 has a thickness of 10 .mu.m
and is crosslinked by electron beam irradiation. As a material of
the fluorocarbon resin layer 2, PFA (950 HP, manufactured by Du
Pont-Mitsui Fluorochemicals) is preferably used. The PFA is
composed of a thermoplastic fluorocarbon resin and has a solid
content of 33% and a particle size of about 0.2 .mu.m; hence, the
PFA is suitable for the formation of a thin film by the dispersion
method or the like.
7. Sixth Embodiment
[0203] This embodiment is an embodiment according to the second
aspect and relates to a belt for use in office automation
equipment.
(Production of Belt for Use in Office Automation Equipment)
[0204] The transfer belt (or transfer fixing belt) shown in FIG. 15
is produced by, for example, in accordance with a flow chart of a
production procedure shown in FIG. 16. In step S1, the circular
base 71 is produced. For example, the circular base 71 composed of
polyimide is produced by a method described below. That is,
polyimide varnish is applied, and then a die is heated to perform
imidization, thereby forming the circular base 71 around the die,
the circular base 71 having a thickness of about 80 .mu.m and being
composed of polyimide. In the present invention, an elastic
intermediate layer may be formed on the outer surface of the
circular base 71, and the fluorocarbon resin 2 may be applied onto
the outer surface of the intermediate layer. For example, an
intermediate layer composed of synthetic rubber such as silicone
rubber and having a thickness of about 200 .mu.m is formed on a
surface of the circular base 71 with a dispenser.
[0205] In step S2, an uncrosslinked fluorocarbon resin (PFA)
dispersion is applied to form a thin film composed of the
fluorocarbon resin on the circular base 71.
[0206] In step S3, the powdery fluorocarbon resin is melted by
heating (heating temperature: 380.degree. C.) to form a uniform
thin film. Simultaneously, the fluorocarbon resin is subjected to
electron beam irradiation in a nitrogen gas atmosphere before the
temperature of the fluorocarbon resin is decreased to a temperature
equal to or lower than its melting point, thereby crosslinking the
fluorocarbon resin. To sufficiently crosslink the fluorocarbon
resin, the amount of electron beam irradiation is set to about 100
kGy. An irradiation unit (min-EB, manufactured by Ushio Inc.) is
used as an electron beam irradiation apparatus because it is
versatile, inexpensive, and compact.
[0207] In step S4, the fluorocarbon resin is cooled. At this time,
if the fluorocarbon resin is rapidly cooled, the crystallization of
the fluorocarbon resin does not easily occur, thus improving the
flex resistance of the fluorocarbon resin layer 2. Furthermore, the
use of a side-chain-type fluorocarbon resin suppresses
crystallization and is thus preferred. Moreover, the use of a
fluorocarbon resin having a higher molecular weight improves flex
resistance and is thus preferred. Note that each of the circular
base, the silicone rubber, and the fluorocarbon resin is adjusted
by carbon conduction or ionic conduction so as to have a volume
resistivity of about 10.sup.11 .OMEGA.cm. Thereby, the transfer
fixing belt is completed. The abrasion resistance of the
fluorocarbon resin layer 2 of the resulting transfer belt is
evaluated by the Taber's abrasion resistance test. The adhesive
strength between the circular base 71 and the fluorocarbon resin
layer 2 is evaluated by the cross-cut test (JIS-K-5400, 1998
edition). In both cases, whether the results meet predetermined
criteria is checked. As another method for evaluating abrasion
resistance, the foregoing linear reciprocating wear test (test
temperature: 250.degree. C.) may be available.
8. Seventh Embodiment
[0208] This embodiment is an embodiment according to the second
aspect and relates to a belt for use in office automation
equipment.
[0209] The transfer belt shown in FIG. 15 is also produced in
accordance with a flow chart of a production procedure shown in
FIG. 17. In step S1, a dispersion of a fine powder composed of an
uncrosslinked fluorocarbon resin (PFA) dispersed in water is
applied to a ring-shaped stainless-steel die (cylinder) having a
mirror-polished inner peripheral surface by dipping and baked at
380.degree. C., thereby forming a thin film (with a thickness of
about 10 .mu.m) of the uncrosslinked fluorocarbon resin on the
inner peripheral surface of the ring-shaped die.
[0210] In step S2, an intermediate layer is formed. For example,
the ring-shaped die provided with the fluorocarbon resin layer on
its inner peripheral surface is placed in a plasma processing
chamber. A counter electrode is arranged inside the ring-shaped die
so as to face the ring-shaped die. The plasma processing chamber is
filled with a He atmosphere. A high-frequency power having
predetermined output, voltage, and frequency is applied to the
counter electrode and the ring-shaped die also functioning as an
electrode for plasma generation. This generates a plasma in a gap
between the ring-shaped die and the counter electrode, so that the
inner peripheral surface of the fluorocarbon resin layer is
subjected to plasma treatment.
[0211] After the treatment such as plasma treatment of the inner
peripheral surface of the fluorocarbon resin layer, primers 101A
and 101B (manufactured by Shin-Etsu Chemical Co.) are mixed in a
ratio of 1:1. The resulting mixture is applied to the inner
peripheral surface of the fluorocarbon resin and dried to form an
adhesive film having a thickness of about 5 .mu.m. Then silicone
rubbers KE-1370A and KE-1370B (manufactured by Shin-Etsu Chemical
Co.) are mixed in a ratio of 1:1. The viscosity of the mixture is
adjusted using a solvent. The mixture is applied to the adhesive
film and cured at 150.degree. C., thereby forming the intermediate
layer having a thickness of about 200 .mu.m.
[0212] In step S3, a circular base is formed. For example, the
inner peripheral surface of the intermediate layer is subjected to
plasma treatment in the same way as the plasma treatment of the
fluorocarbon resin layer. A thermoplastic polyimide (Rikacoat
PN-20, manufactured by New Japan Chemical Co., Ltd.) is applied and
dried at 220.degree. C., thereby forming the circular base 71
having a thickness of about 80 .mu.m. Then the circular base, the
intermediate layer, and the fluorocarbon resin layer are pulled out
from the die, thereby affording a circular belt including the
circular base 71, the intermediate layer 72, and the fluorocarbon
resin layer 2 (surface layer) shown in FIGS. 18(A) and 18(B). Note
that each of the surface layer (fluorocarbon resin layer), the
adhesive layer (primer layer), the elastic layer (silicone rubber
layer), and the base (polyimide layer) is adjusted by carbon
conduction or ionic conduction so as to have a volume resistivity
of about 10.sup.11 .OMEGA.cm.
[0213] In step S4, after a core is inserted into a hollow portion
of the circular belt, the circular belt is rotated as shown in FIG.
18. Nitrogen gas heated to 400.degree. C. is blown on the surface
layer of the circular belt, increasing the temperature of the
fluorocarbon resin layer 2 to a temperature equal to or higher than
its melting point. Then Electron beam irradiation is performed,
resulting in the crosslinked fluorocarbon resin layer 2. That is,
the entire fluorocarbon resin layer 2 is uniformly subjected to
electron beam irradiation while the circular belt provided with the
fluorocarbon resin layer 2, which is a target irradiated, on its
outer peripheral surface is being rotated and while the electron
beam irradiation apparatus 53 arranged outside the circular belt is
being translated in the x direction indicated by an arrow (that is,
spiral irradiation). To sufficiently crosslink the fluorocarbon
resin layer 2, the amount of electron beam irradiation is
preferably about 100 kGy. The foregoing irradiation unit (min-EB,
manufactured by Ushio Inc.) is used as the electron beam
irradiation apparatus 53. A cooling point is set at a position
located 180 degrees apart from a heating point. Rapid cooling is
performed so as not to degrade the intermediate layer 72 before the
temperature of the intermediate layer 72 located under the
fluorocarbon resin layer 2 reaches the decomposition temperature.
Rapid cooling also improves the flex resistance of the fluorocarbon
resin layer 2.
[0214] In this way, the transfer belt including the circular base
71, the intermediate layer 72, and the fluorocarbon resin layer 2
is completed by the production process suitable for mass
production.
* * * * *