U.S. patent application number 14/008263 was filed with the patent office on 2014-01-16 for process for producing roll of microporous plastic film.
The applicant listed for this patent is Takashi Ichinomiya, Tadashi Matsumoto. Invention is credited to Takashi Ichinomiya, Tadashi Matsumoto.
Application Number | 20140014762 14/008263 |
Document ID | / |
Family ID | 46930825 |
Filed Date | 2014-01-16 |
United States Patent
Application |
20140014762 |
Kind Code |
A1 |
Ichinomiya; Takashi ; et
al. |
January 16, 2014 |
PROCESS FOR PRODUCING ROLL OF MICROPOROUS PLASTIC FILM
Abstract
A microporous plastic film roll production method, comprising
the steps of: conveying microporous plastic film having
through-holes in its interior by using a plurality of conveyance
rollers at least one conveyance roller of which has a surface
roughness RzJIS (.mu.m) of 0.3.ltoreq.RzJIS.ltoreq.30 and has a
surface made of fluorine resin, silicone rubber, or a composite
material containing one of them; and winding it up in a roll.
Inventors: |
Ichinomiya; Takashi;
(Otsu-shi, JP) ; Matsumoto; Tadashi; (Otsu-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ichinomiya; Takashi
Matsumoto; Tadashi |
Otsu-shi
Otsu-shi |
|
JP
JP |
|
|
Family ID: |
46930825 |
Appl. No.: |
14/008263 |
Filed: |
March 22, 2012 |
PCT Filed: |
March 22, 2012 |
PCT NO: |
PCT/JP2012/057311 |
371 Date: |
September 27, 2013 |
Current U.S.
Class: |
242/520 |
Current CPC
Class: |
Y02E 60/13 20130101;
B65H 27/00 20130101; B65H 2701/1718 20130101; H01M 2/145 20130101;
H01M 2/162 20130101; B65H 2701/1752 20130101; B65H 2404/18
20130101; B65H 2401/111 20130101; B65H 18/08 20130101; Y02E 60/10
20130101; H01G 11/52 20130101; B65H 2404/531 20130101; B65H 18/10
20130101; B65H 2511/135 20130101 |
Class at
Publication: |
242/520 |
International
Class: |
B65H 18/08 20060101
B65H018/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2011 |
JP |
2011-074642 |
Claims
1. A microporous plastic film roll production method comprising the
steps of: conveying microporous plastic film having through-holes
in its interior by using a plurality of conveyance rollers at least
one conveyance roller of which has a surface roughness RzJIS
(.mu.m) of 0.3.ltoreq.RzJIS.ltoreq.30 and has a surface made of
fluorine resin, silicone rubber, or a composite material containing
one of them; and winding it up in a roll.
2. A microporous plastic film roll production method as described
in claim 1 wherein the surface of the conveyance roller is made of
polytetrafluoroethylene.
3. A microporous plastic film roll production method as described
in claim 1 wherein the microporous plastic film has a Gurley air
permeation resistance of 10 to 1,000 seconds per 100 ml.
4. A microporous plastic film roll production method as described
in claim 1 wherein the microporous plastic film has a porosity of
30% or more.
5. A microporous plastic film roll production method as described
in claim 1 wherein the microporous plastic film has an average
micropore size of 50 to 200 nm.
6. A microporous plastic film roll production method as described
in claim 1 wherein the microporous plastic film has a cushion rate
of 15% or more and less than 50%.
7. A microporous plastic film roll production method as described
in claim 1 wherein the microporous plastic film has a thickness of
50 .mu.m or less.
8. A plastic film roll production method as described in claim 1
wherein the microporous plastic film has a width of 100 mm or
more.
9. A microporous plastic film roll production method as described
in claim 1 to wherein the coefficient of static friction between
the microporous plastic film and the conveyance roller is 0.6 or
less.
10. A microporous plastic film roll production method as described
in claim 1 wherein the microporous plastic film is designed to
serve as a separator of secondary batteries or capacitors.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. National Phase application of
PCT/JP2012/057311, filed Mar. 22, 2012, and claims priority to
Japanese Patent Application No. 2011-074642, filed Mar. 30, 2011,
the disclosures of both applications being incorporated herein by
reference in their entireties for all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of manufacturing a
microporous plastic film roll.
BACKGROUND OF THE INVENTION
[0003] For conventional processes in which a microporous plastic
film for separators of secondary batteries and the like is conveyed
and wound up into a roll, it has been very difficult to prevent
wrinkle and breakage attributable to micropores.
[0004] Non-patent document 1 theoretically determines the critical
wrinkling values of general films and proposes a prevention method
under the title "Prevention of wrinkle". According to this
reference, the critical wrinkling value is represented in terms of
tension and alignment angle, and in particular, the critical
wrinkling value relating to tension depends on the thickness,
Young's modulus, width, and friction coefficient of the film. As a
prevention method, it proposes to adjust the tension of a film
while predicting the critical slip value that is in a trade-off
against wrinkle, in such a manner that it straddles the critical
wrinkling value determined by the aforementioned parameters.
According to knowledge of the present inventors, however, it is
difficult to freely adjust the tension of a film that is low in
resistance to breakage and liable to deformation in the thickness
direction, such as microporous plastic film. Accordingly, it has
been difficult for the aforementioned method alone to convey a film
without causing either wrinkle or breakage.
[0005] Compared to this, patent document 1 proposes to add
particles to the film surface and control its roughness and
friction coefficient in order to solve handling-related problems,
such as blobbing and wrinkle, with the polyester film used as high
density magnetic recording medium. According to knowledge of the
present inventors, however, the surface smoothness of microporous
plastic film is not a factor in the increase in the friction
coefficient, and therefore, it is difficult to prevent wrinkle by
adding particles by the method proposed in patent document 1.
Furthermore, particles cannot serve at all for solving the problem
of breakage.
[0006] Non-patent document 2 mentions the coefficient of static
friction and characteristics of substances. It is described that
the coefficient of static friction of a substance is proportional
to the ratio between its shear strength .tau. attributable to
intermolecular force and its hardness H, and the friction can be
reduced by using a material having a large H value and a small T
value (such as silver, fluorine resin, and lead). However, the
objective of this reference is to clarify the mechanism of friction
and also clarify the substantial friction phenomenon under air
lubrication, and it shows no specific methods to prevent both
wrinkle and breakage of microporous plastic films.
[0007] Non-patent document 3, furthermore, describes example cases
where the theory proposed in patent document 1 is applied to actual
production processes. Although some studies have insisted that the
reduction in friction coefficient is effective for the decrease of
wrinkles attributable to conveyance, but according to knowledge of
the present inventors, microporous plastic films require special
solution to problems with their unique friction generation
mechanism, and non-patent document 3 is not successful in showing a
specific method to prevent both wrinkle and breakage.
[0008] Patent document 2 proposes technique to form diamond like
carbon (hereinafter abbreviated as DLC) on the surface of the
conveyance roller to reduce the friction coefficient of the rubber
layer at the surface or a pressurizing rubber roller that is
pressed against a film roll so that the film can be wound up while
eliminating air. According to knowledge of the present inventors,
however, friction coefficient reduction effect of a DLC layer is
developed by preventing minute deformation and reducing the real
contact area of the surface by virtue of high hardness of the DLC
layer, and therefore, it cannot be highly effective for the
phenomenon in which the friction coefficient increases by virtue of
the flexibility of microporous plastic film itself.
[0009] Compared to this, patent document 3 proposes a method in
which scratches on a film is prevented by adopting a conveyance
roller that has a metal surface with a decreased surface roughness
and reducing its friction coefficient. According to knowledge of
the present inventors, however, although it can be expected in the
case of synthetic resin films with a smooth surface dealt with in
patent document 3 that the friction coefficient can be reduced by
decreasing protrusions on, that is, decreasing the roughness of,
the roller surface and by making use of a phenomenon that is
considered to be air lubrication, such air lubrication cannot be
expected in the case of a microporous plastic film, which will
undergo air release through micropores, and its contact with a
smooth metal surface will increase the friction coefficient
contrary to expectation, thus failing to prevent wrinkle and
breakage.
[0010] As stated above, no techniques have been available
conventionally to convey a microporous plastic film and wind it up
into a roll without wrinkle or breakage.
PATENT DOCUMENTS
[0011] Patent document 1: JP H11-314333 A [0012] Patent document 2:
JP 2004-251373 A [0013] Patent document 3: JP 2001-63884 A
NON-PATENT DOCUMENTS
[0013] [0014] Non-patent document 1: Hiromu Hashimoto,
"Uebuhandoringu no Kiso Riron to Oyo" (Basic Theory and Application
of Web Handling, in Japanese), 1st Ed., pub. by Converting
Technical Institute Co., Ltd., April 2008, p.p. 131-155 [0015]
Non-patent document 2: Hiromu Hashimoto, Convertech, July 2009
Issue, pub. by Converting Technical Institute Co., Ltd., July 2009,
p.p. 36-43 [0016] Non-patent document 3: Morikawa Akira,
Convertech, November 2010 Issue, pub. by Converting Technical
Institute Co., Ltd., November 2010, p.p. 58-63
SUMMARY OF THE INVENTION
[0017] The present invention provides a production method for
microporous plastic films, which have been conventionally difficult
to handle due to the existence of micropores that can cause wrinkle
and breakage.
[0018] The present invention provides a microporous plastic film
roll production method comprising the steps of: conveying
microporous plastic film having through-holes in its interior by
using a plurality of conveyance rollers at least one conveyance
roller of which has a surface roughness RzJIS (.mu.m) of
0.3.ltoreq.RzJIS.ltoreq.30 and has a surface made of fluorine
resin, silicone rubber, or a composite material containing one of
them; and winding it up into a roll.
[0019] A more preferred embodiment of the present invention
provides a microporous plastic film roll production method as
described above wherein the conveyance roller has a surface made of
polytetrafluoroethylene as its material.
[0020] Another preferred embodiment of the present invention
provides a microporous plastic film roll production method wherein
the microporous plastic film has a Gurley air permeation resistance
of 10 to 1,000 seconds per 100 ml.
[0021] Another preferred embodiment of the present invention
provides a microporous plastic film roll production method as
described above wherein the microporous plastic film has a porosity
of 30% or more.
[0022] Another preferred embodiment of the present invention
provides a microporous plastic film roll production method wherein
the microporous plastic film has an average micropore size of 50 to
200 nm.
[0023] Another preferred embodiment of the present invention
provides a microporous plastic film roll production method wherein
the microporous plastic film has a cushion rate of 15% or more and
less than 50%.
[0024] Another preferred embodiment of the present invention
provides a microporous plastic film roll production method wherein
the microporous plastic film has a thickness of 50 .mu.m or
less.
[0025] Another preferred embodiment of the present invention
provides a microporous plastic film roll production method wherein
the microporous plastic film has a width of 100 mm or more.
[0026] Another preferred embodiment of the present invention
provides a microporous plastic film roll production method wherein
the coefficient of static friction between the microporous plastic
film and the conveyance roller is 0.6 or less.
[0027] Also provided is a microporous plastic film roll production
method wherein the microporous plastic film is designed to be used
as the separator of either a secondary battery or a capacitor.
[0028] For the present invention, the "conveyance roller" includes
a means by which a microporous plastic film that is continuous in
the length direction is conveyed from the upstream side to the
downstream side in the production process and which is in the form
of a cylinder supported in a rotatable manner.
[0029] For the present invention, the term "RzJIS" refers to the
ten-point average roughness.
[0030] For the present invention, the term "fluorine resin" refers
collectively to synthetic resins partly containing the fluorine
element, such as ethylene based hydrocarbons.
[0031] For the present invention, the term "silicone rubber" refers
to silicone resin that exhibits rubber-like elasticity, and the
term "silicone resin" refers collectively to synthetic resins
having a siloxane bond that contains silicon and oxygen.
[0032] For the present invention, the term "composite material"
refers to a material produced by mixing a fluorine resin or a
silicone resin as described above to such an extent that their
properties can contribute effectively, such as one consisting of
layers of rubber material or metal-plated material and a fluorine
resin or silicone resin as described above added between them by
coating or filling.
[0033] For the present invention, the term "microporous plastic
film" refers to a thin polymer film having many minute holes in the
interior of the film, in which part or all of the micropores are
through-holes.
[0034] For the present invention, the term
"polytetrafluoroethylene", which may be abbreviated as PTFE, refers
to a kind of fluorine resin, otherwise known as
Tetrafluorideethylene. For the present invention, the term
"thickness" is calculated by dividing the volume of the microporous
plastic film constituting a roll by the width and length thereof,
and accordingly the thickness includes the air layers that form
part of the micropores.
[0035] For the present invention, the term "Gurley air permeation
resistance" refers to an index of air transmittance of a film or
sheet determined by the test method specified in Japanese
Industrial Standard (JIS) P8117 (2009).
[0036] As the air permeability increases, air passes through the
micropores in a shorter time and the Gurley air permeation
resistance decreases.
[0037] For the present invention, the term "porosity" refers to the
percentage portion of the cross section of a film accounted for by
the micropores.
[0038] For the present invention, the term "average micropore size"
refers to the average diameter of many micropores that differ in
diameter.
[0039] For the present invention, the term "cushion rate" refers to
the percentage change in the thickness of a sheet that takes place
when a pressure is applied in the thickness direction.
Cushion rate (%)=(1-T1/T2).times.100
[0040] T1: A gauge head with a diameter of 10 mm is fixed to a dial
gauge supplied by Mitutoyo Corporation and a load of 50 g is
applied to the gauge head to press a film specimen in the thickness
direction. The thickness T1 is measured after pressing the film
specimen for 30 seconds under above conditions as compared to the
thickness measurement made before attaching the film specimen,
which is assumed to be zero.
[0041] T2: A gauge head with a diameter of 10 mm is fixed to a dial
gauge supplied by Mitutoyo Corporation and a load of 500 g is
applied to the gauge head to press a film specimen in the thickness
direction. The thickness T2 is measured after pressing the film
specimen for 30 seconds under above conditions as compared to the
thickness measurement made before attaching the film specimen,
which is assumed to be zero.
[0042] For the present invention, the term "secondary battery"
refers to a rechargeable battery which is also referred to as a
storage battery.
[0043] For the present invention, the term "separator" refers to a
functional film designed to prevent short-circuiting between
electrodes. A film containing micropores and transmitting ion
electrolyte can be used as a separator.
[0044] For the present invention, the term "capacitor" refers to a
passive element that has an electrostatic capacity and can store
and discharge electric energy.
[0045] As described below, the present invention serves to provide
a microporous plastic film roll production method that can prevent
wrinkle and breakage to allow a high-quality microporous plastic
film to be produced with high productivity.
BRIEF DESCRIPTION OF THE FIGURES
[0046] FIG. 1 gives a schematic side view according to an
embodiment of the present invention.
[0047] FIG. 2 gives a schematic enlarged view of the surface of a
conveyance roller according to an embodiment of the present
invention.
[0048] FIG. 3 gives a separator of a secondary battery to which a
microporous plastic film produced according to an embodiment of the
present invention is applied.
[0049] FIG. 4 gives an enlarged plan view of a microporous plastic
film produced according to an embodiment of the present
invention.
[0050] FIG. 4 gives a schematic side view illustrating a method to
measure the coefficient of static friction between a film and the
portion of a conveyance roller that is in contact with the
film.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0051] An example of the invention is described below with
reference to drawings, taking as an example its application to a
process for the production of a microporous plastic film to be used
as a separator film of a secondary battery.
[0052] FIG. 1 gives a schematic side view showing the conveying and
winding-up steps in a microporous plastic film roll production
process according to an embodiment of the present invention.
[0053] The microporous plastic film 1 may be formed by any
appropriate method. As a preferable example, it can be produced by
kneading molten polyolefin resin with a highly volatile solvent in
an extruder, discharging it through an die onto a cooling drum to
form a gel sheet, and subjecting it to steps for stretching and
orientation as required, followed by washing off the solvent and
drying. In another example, it can be produced by kneading
polyolefin resin with a crystal nucleating agent, discharging it
through a die onto a cooling drum, and forming micropores by
controlling the crystal structure without using a solvent. In
another example, the microporous film 1 can be produced by
combining a heat resistant polymer such as polyamide or polyimide
with a solvent that differs in compatibility with it to form
micropores, followed by discharging or coating. In another example,
one side or both sides of a microporous polyolefin film is coated
with a heat resistant material that does not impair the gas
permeation function of the micropores. In still another example, a
microporous film, similar to paper and nonwoven fabrics, is formed
by stacking synthetic fibers.
[0054] A microporous plastic film 1 produced as described above is
preferably stretched uniaxially or biaxially as required to control
the pore structure and ensure high strength.
[0055] FIG. 4 gives an enlarged plan view showing an example of the
microporous plastic film 1. As illustrated in the figure, any
appropriate method may be used to form micropores in the plastic
film 1. In a stretched and oriented resin layer, the portions
around pores form fibrous columns as illustrated in the figure,
which may be referred to as fibrils 18. Part or all of these
micropores function as through-holes 17.
[0056] FIG. 3 gives an explanatory diagram showing a schematic
exploded view of part of a tubular lithium ion secondary battery. A
case 11 contains a positive electrode 14 and a negative electrode
15, with a separator 16 interposed between them to serve as an
insulator to prevent short circuiting between these electrodes. The
interior of the case is filled with a lithium ion electrolyte, and
the separator 16 is required to serve for both insulation and
transmission of ions in the electrolyte. This requirement is met
effectively by a microporous plastic film 1 partly or entirely
containing through-holes as produced by the production method
according to the present invention.
[0057] As shown in FIG. 1, the microporous plastic film 1 is
conveyed on a group of conveyance rollers 2 at a predetermined
speed and wound up on a core 6 under a predetermined tension to
form a film roll 12. In FIG. 1, the conveyance rollers 2 are driven
by a driving source 32, such as motor, via a driving force
transmission mechanism 4, such as belt or chain. The driving force
transmission mechanism 4 is given a necessary tension and supported
by a pulley 5. Here, it is not necessary for all conveyance rollers
2 to be driven by the driving source 32. If they are supported on
bearings in a rotatable manner, they can work as idlers to assist
the conveyance of the film 1. In this case, to avoid scratches and
abrasion powder on the film 1, they are preferably driven
indirectly via bearings, or some methods are preferably introduced
to minimize the inertia of the rollers and the friction loss of the
bearings.
[0058] A microporous plastic film 1 suitable for use as a battery
separator and the like is generally liable to suffer deformation of
micropores, leading to a hysteresis loss, increased real contact
area, and then increased coefficient of static friction to objects
in contact. In particular, if a plurality of conveyance rollers 2
are used to convey the film 1 as in the case shown in FIG. 1, the
coefficient of static friction may increase due to the
aforementioned factors in portions where rollers and the film come
in contact, and in addition, air lubrication, which is commonly
expected in the case of conveyance of a nonporous film, may not
take place due to air escape through these micropores, leading to a
large increase in the friction coefficient. As stated above, an
increase in the friction coefficient will cause problems such as
wrinkle and breakage on conveyance rollers or between conveyance
rollers. The present invention can avoid these problems and
successfully prevent the breakage of a microporous plastic film by
reducing the coefficient of static friction of the surface of at
least one conveyance roller of the plurality of conveyance rollers
2 to reduce the stress attributable to a difference in speed.
[0059] To reduce the coefficient of static friction of the
conveyance rollers 2, the ten-point average surface roughness of
the surfaces is in the range of 0.3.ltoreq.RzJIS (.mu.m).ltoreq.30.
If the RzJIS is 0.3 .mu.m or more, it will be possible to maintain
a small real contact area, which tends to increase if micropores
are deformed in the microporous plastic film 1, leading to a
reduced coefficient of static friction. In addition, moderately
rough surfaces of the conveyance rollers 2 can serve to reduce the
coefficient of static friction, although the microporous plastic
film 1 tends to suffer from an increase in the contact area as air
escapes through micropores due to gas permeation. If the conveyance
rollers 2 have too large a surface roughness, on the other hand,
processing the roller surfaces will be difficult and expensive and
low in accuracy if the RzJIS is more than 30 .mu.m. If the
roughness is too high as in this case, the coefficient of static
friction may increase contrary to expectation as a result of an
increase in the contact area between individual surface projections
and the film. The RzJIS is more preferably in the range of
2.ltoreq.RzJIS (.mu.m).ltoreq.10.
[0060] As a result of intensive studies carried out by the
inventors of the present invention, it has been found that
reduction in the coefficient of friction of the conveyance rollers
2 to a film of a microporous plastic material that is air permeable
and liable to suffer deformation of pores can be realized only by
controlling the intermolecular force in the surface material of the
conveyance rollers 2 instead of controlling the hardness of the
contact area by, for example, using diamond-like carbon (DLC) as
surface material to achieve a low friction. This is because the use
of rollers 2 having a surface of a hard material can not prevent
deformation of surface structures of the microporous plastic film
1, failing to decrease the real contact area.
[0061] For the present invention, therefore, a material with a
small intermolecular force, such as fluorine resin, silicone
rubber, or a composite material containing them, is used, instead
of commonly-used rubber, as the surface material of the conveyance
rollers 2 that will come in contact with the microporous plastic
film 1. From the viewpoint of maintaining a high durability and
ensuring uniform treatment, the thickness of a fluorine resin
surface is several tens of micrometers, preferably about 10 to 100
.mu.m. In general, fluorine resin is preferably calcined at 300 to
400.degree. C. If it is used to coat a resin or rubber surface, it
is preferable to perform molding at 100.degree. C. or less. In this
case, additional treatment by polishing will be effective to obtain
a roller with a high surface accuracy. Preferred methods for
forming a fluorine resin surface on the roller include coating,
spraying, and fitting. Others include, for instance, covering the
roller with a tape or a tube of fluorine resin. When covering the
roller with a tape or a tube of fluorine resin, its thickness is
preferably about several millimeters to ensure easy formation.
[0062] In the case of using silicone rubber, its thickness is
preferably several millimeters, specifically about 1 to 10 mm.
[0063] The base material 2A of the conveyance roller is preferably
steel, stainless steel, aluminum alloy, or CFRP.
[0064] Here, a composite material contains fluorine resin or
silicone rubber as mentioned above to such an extent that their
properties can contribute effectively to friction reduction. Such
materials include, for instance, one consisting of layers of rubber
material or metal-plated material and fluorine resin or silicone
rubber added between them by coating or filling. FIG. 2 shows an
example of such a composite material 9, in which a conveyance
roller is composed of a base material 2A, rigid chrome-plated layer
7, and fluorine resin 8 that impregnates the rough surface. Here,
in the portion in contact with the microporous plastic film 1, the
material of the metal-plated layer 7 and the fluorine resin 8 are
randomly distributed to allow both the advantage of friction
coefficient reduction by the fluorine resin and that of wear
resistance of the metal-plated layer to be realized
effectively.
[0065] When such fluorine resin is added to a plated layer to form
a composite material, a preferable processing method to obtain a
high-strength treated surface is calcination at a high temperature
as described above, and in that case, the base material 2A of the
conveyance roller may be steel that is heat-treated in advance to
prevent strain to take place at high temperatures.
[0066] To meet the aim of performing the aforementioned function,
it may be combined with materials other than metal-plated ones,
such as, for instance, ceramics, rubber, and other resins, to
provide a composite material. Another effective method is to coat
the roller surface with the aforementioned fluorine resin, silicone
rubber, or both of them.
[0067] Here again, these composite materials contain distributed
ceramics or other hard materials that work to control the wear
resistance and roughness of the surface in contact with fluorine
resin or silicone rubber.
[0068] The use of these materials serves to reduce the coefficient
of static friction of the surface to the microporous plastic film
1.
[0069] The selection of a material having appropriate roughness and
properties serves to reduce the coefficient of static friction of
the surface to the microporous plastic film 1 down to such a low
value that is required to prevent breakage and wrinkle. In other
words, the friction coefficient can be reduced effectively only
when using a material with a small intermolecular force and
controlling its properties in the aforementioned range so that the
contact area will be reduced effectively even if the surface
structure of the microporous plastic film is deformed.
[0070] When using a composite material, in particular, it is
necessary for the aforementioned roughness to be achieved not only
by using a plated layer 7 but by creating a surface of fluorine
resin or silicone rubber over the plated layer of the base and
carrying out polishing or other final finishing steps as required
so that the roughness will come in the aforementioned RzJIS
range.
[0071] The coefficient of static friction is preferably 0.6 or
less. A coefficient of static friction in a more preferable range
of 0.5 or less can be obtained by controlling the ten-point average
roughness at a high value in the aforementioned range, or by
combining it with good material properties.
[0072] For example, the material of the conveyance roller 2 is more
preferably polytetrafluoroethylene among other fluorine resin
compounds. Various fluorine resin compounds have different features
such as heat resistance and releasability depending on their
components, but the aforementioned resin compound was found to be
effective for reduction in friction coefficient in association with
its intermolecular force. A good combination of a roughness and
material properties can allow the coefficient of static friction to
come in a more preferably range of 0.3 or less.
[0073] As described above, the microporous plastic film 1 is
required, depending on uses, to have the ability to allow gas and
liquid to permeate through the aforementioned micropores. In the
case of separators for lithium ion secondary batteries as mentioned
above, in particular, the electrolyte permeability is generally
determined indirectly from the air permeability.
[0074] The gas permeability of a microporous plastic film can be
determined from the Gurley air permeation resistance defined in JIS
P8117 (2009), and a film can exhibit a suitable electrolyte
permeability for separators of batteries and capacitors in the
preferable range of 10 to 1,000 seconds per, 100 ml. If the Gurley
air permeation resistance is 10 seconds per 100 ml or more,
moderate insulating properties are maintained to permit the
production of a separator that can reduce the risk of
short-circuiting, and the film can have a high strength so that
film breakage during conveyance can be avoided when used in
combination with conveyance rollers designed for the present
invention. If the Gurley air permeation resistance is 1,000 seconds
per 100 ml or less, on the other hand, a large number of
through-holes can be maintained to permit smooth permeation of
required quantities of gas and liquid. When it is used as a
separator of a lithium ion secondary battery, in particular, a high
electrolyte permeability will be maintained to permit quick
recharging and discharging of the batteries. The use of the
aforementioned conveyance rollers 2 as part of the production
method for the microporous plastic film 1 serves to produce a
microporous plastic film 1 having a high functionality as separator
of a battery or the like and at the same time having a reduced
value of the coefficient of static friction to prevent wrinkle and
breakage.
[0075] The microporous plastic film 1 is pressed against a
conveyance roller under a tension T. The contact pressure in this
case is calculated as follows: tension.times.contact angle. This
contact pressure works to allow air to escape from the microporous
plastic film through micropores and the deformation of micropores
will cause a large friction with the conveyance roller. The
microporous plastic film 1, for which the conveyance roller
according to the present invention works effectively to prevent
wrinkle and breakage, undergo a high degree of deformation under
the contact pressure, and this degree is represented by the cushion
rate as a parameter. The cushion rate indicates the percentage
change in thickness of a film to which a load of 50 g or 500 g is
applied in the film thickness direction via the gauge head of a
dial gauge.
[0076] For cushion rate measurement, a load may be applied by any
appropriate method such as the use of a spring or weight, but it is
preferable to install a weight above the gauge head or the
indicator so as to minimize the moment applied to the gauge
head.
[0077] A microporous plastic film preferred for the present
invention has a cushion rate of 15% or more and less than 50%. If
the cushion rate is 15% or more, the micropores in the microporous
plastic film 1 maintains a certain degree of through-hole rate,
serving for smooth permeation of gas and liquid at required rates
while preventing an increase in the friction with the conveyance
roller. When it is used as a separator of a lithium ion secondary
battery, in particular, a high electrolyte permeability will be
maintained to permit quick recharging and discharging of the
batteries. If the cushion rate is less than 50%, on the other hand,
a moderate air permeation resistance is maintained to permit the
production of a separator that can prevent short-circuiting, and
film breakage during conveyance can be avoided. The use of the
aforementioned conveyance rollers 2 as part of the production
method for a microporous plastic film 1 having a cushion rate of
15% or more and less than 50% serves to produce a microporous
plastic film 1 having a high functionality as separator of a
battery or the like and at the same time having a reduced value of
the coefficient of static friction, which increases with the
cushion rate, to prevent wrinkle and breakage.
[0078] In addition, in order to prevent the friction coefficient
from increasing considerably with an increasing cushion rate, it is
preferable to control the porosity of the microporous plastic film
1 at 50% or less, particularly preferably 30% or less. If the
aforementioned plastic film is used as separator of a secondary
battery, the use of a microporous film with a high ion permeability
and a high porosity is preferable in order to achieve a high output
and shorten the recharging and discharging time. It is preferably
30% or more, more preferably about 50 to 80%. From the viewpoint of
breakage prevention, a porosity of 80% or less is essential.
[0079] Here, there are some measuring methods that seem to be
helpful for measuring the porosity of the microporous plastic film
1, but for the present invention, it is determined by sampling a
predetermined quantity of the film 1, calculating the volume Va of
the resin portion from the weight of the sample and the density of
the resin that constitutes the film, calculating the volume Vb from
measurements of the thickness, width, and length of the film, and
substituting them into formula 1. The thickness of the film is
preferably determined from continuous measurements made by applying
a light emitting/receiving type or reflection type laser sensor to
the conveyance roller. Other available methods include the use of a
radiation or infrared ray sensor, and the use of a dial gauge under
a low load to examine a specimen taken from the wound-up film
1.
[ formula 1 ] Porosity ( % ) = [ V b - V a V b ] .times. 100 (
formula 1 ) ##EQU00001##
[0080] The microporous plastic film 1 intended in an embodiment of
the present invention has an average pore size of 50 to 200 nm. If
a film with an average pore size is 50 nm or more is used as a
separator of a lithium ion secondary battery, a certain degree of
electrolyte permeability will be maintained to permit quick
recharging and discharging of the batteries. If the average pore
size is less than 200 nm, on the other hand, it will be possible to
produce a separator that can prevent short-circuiting, and film
breakage during conveyance can be avoided to some extent.
[0081] A film with a thickness of 50 .mu.m or less, which may serve
effectively as separator of a secondary battery or capacitor, will
be particularly liable to suffer wrinkle and breakage if the
friction coefficient is high as in the above case, and therefore,
the conveyance roller 2 can be used effectively.
[0082] If the microporous plastic film 1 has a width of more than
100 mm, wrinkle will take place severely. This is partly because an
alignment error occurs between conveyance rollers, leading to a
moment on the microporous plastic film 1. This moment that induces
wrinkle is proportional to the product of [.alpha..times.width of
film 1] where .alpha. represents the angle between the rotation
axes of two conveyance rollers. The angle .alpha., which represents
the alignment error, is zero when the conveyance rollers are
completely parallel to each other. When there exists an alignment
error as represented by .alpha., the wrinkle-inducing moment
decreases as the microporous plastic film 1 decreases in width. As
a result of intensive studies based on experiments, the inventors
of the present invention have found that the frequency of wrinkle
increases as the width decreases below 100 mm.
[0083] In addition, the microporous plastic film 1 receives strains
during film production and other various processing steps, and
consequently, its surface is not completely plain in most cases.
Thus, in addition to the aforementioned moment, which is a
geometrical factor associated with the parallelism of the rollers,
there exists another factor in wrinkle that is associated with the
planarity of the film. Therefore, there is a peak of wrinkle
frequency that is not associated with the alignment, and in
particular, wrinkle becomes more significant as the aforementioned
width exceeds 500 mm. In this way, the inventors of the present
invention found that although the microporous plastic film 1
becomes very difficult to handle as its width exceeds 100 mm,
particularly 500 mm, the reduction in the coefficient of static
friction to the conveyance rollers can serve to realize both the
prevention of wrinkle and the prevention of breakage even in the
case where conveyance rollers are low in parallelism or the
microporous plastic film 1 is low in planarity during its
conveyance.
[0084] More preferably, a method for removing wrinkles is carried
out additionally after reducing the coefficient of static friction
between the microporous plastic film 1 and the conveyance rollers 2
by the method described above, which will further serve to prevent
wrinkle of the microporous plastic film 1 during its
conveyance.
[0085] As stated previously with reference to FIG. 1, in the case
where at least one roller of the plurality of conveyance rollers 2
has a surface as described above, wrinkle and breakage can be
prevented effectively by reducing its coefficient of static
friction. Here, all of the conveyance rollers 2 may have a
coefficient of static friction as stated above, but it may be only
those rollers located, for example, where breakage or wrinkle can
easily take place, that have such a coefficient of static friction.
At positions where slippage between a conveyance roller 2 and the
film 1 should be avoided, it will be effective to use a wrinkle
removing device 19 instead of reducing the friction coefficient of
the conveyance roller 2. Specifically, it will be effective that
all or some of conveyance rollers 2 are rollers having a friction
coefficient of 0.7 or less, more preferably 0.5 or less, and
removing devices are provided at positions where a decrease in the
friction coefficient is not permitted, or cannot work to reduce
wrinkle, such as where achieving required parallelism is
difficult.
[0086] Here, the coefficient of static friction between a
conveyance roller 2 and the aforementioned plastic film 1 is
determined by a measuring method as described below. A method is
shown in FIG. 5 where a film 1 is brought into contact at an angle
of .theta.(rad) with a roller 2 that is fixed in a non-rotatable
manner. A weight of W (N) is hung and the tension T (N) at which
slippage starts is read on the spring balance scale 31, followed by
calculation using formula 2. An appropriate weight W is preferably
set based on the preferable tension conditions described later, and
there are no specific limitations on the width of the film 1. For
instance, when it is 0.1 m to ensure easy handling, the weight W is
preferably from 1 N/m.times.0.1 m to 30 N/m.times.0.1 m, namely,
0.1 N to 3 N. This is because the mode of pore deformation changes
leading to a variation in the values as the coefficient of static
friction deviates significantly from the aforementioned load
range.
[0087] In another method, the film 1 is attached to the contact
head of a portable tribometer (Muse, supplied by Shinto Scientific
Co., Ltd.) and the contact head is brought into contact with the
roller 2, followed by making measurements. To calculate the contact
pressure to the roller surface in the aforementioned tension range,
the contact pressure p [Pa], tension T [N/m], and roller diameter D
[m] have the following relationship: p=2T/D. For a roller diameter
D of 0.1 m, for example, the contact pressure p is preferably in
the range of 20 to 600 Pa when the tension is in the preferable
range described above. For Muse, the weight has a mass of 0.4 N and
a diameter of 0.03 m, the contact pressure p is 570 Pa, which is in
the aforementioned preferable range.
[ formula 2 ] .mu. s = 1 .theta. ln T W ( formula 2 )
##EQU00002##
[0088] In FIG. 1, the tension to the film 1 may be applied by the
torque of the motor 31 given in FIG. 1, or particularly when
conveying an easily breakable and deformable film such as
microporous plastic film, it may be effective to use a dancer
roller which can apply tension by a boost pressure and can control
a significantly small tension. In this case, the motor 31 and the
motor 32 are preferably of a speed- and rotation frequency
controllable type.
[0089] An appropriately selected tension may be used to realize the
effect of the invention, but from the viewpoint of breakage
prevention, it is preferable to use a smaller tension as compared
to cases with general resin films. For instance, it is preferably
in the range of 1 N/m to 30 N/m.
[0090] The tension is more preferably in the range of 5 N/m to 20
N/m to allow breakage and wrinkle to be prevented easily while
controlling the tension in the machine with appropriate
accuracy.
[0091] Here, breakage caused between conveyance rollers 2 is mainly
attributed to a slight difference in speed taking place between the
conveyance rollers. This is because there is a non-zero speed
control error when a plurality of motors are involved in driving
the rollers, and in the case of the example shown in FIG. 1, a
difference in speed can take place as a result of slippage between
a pulley and a drive controller 4 working to drive the conveyance
rollers 2 as well as an error in the outside diameters of pulleys.
In these cases, the difference in speed causes stress concentration
around micropores existing in the microporous plastic film, easily
leading to its breakage.
[0092] The mechanism of breakage caused by a difference in speed is
as follows. In the case where no slippage takes place, the strain
.di-elect cons. caused in the microporous plastic film 1 pulled by
the difference in speed in FIG. 1 is considered to be roughly
expressed by formula 3, where V2 is the circumferential rotation
speed of the conveyance roller 21 and V1 is the circumferential
rotation speed of the conveyance roller 23 assuming V2>V1.
According to Hooke's law, the stress .sigma.1 caused by this strain
is expressed by formula 4, where E represents Young's modulus of
the microporous plastic film 1 in the length direction.
[ formula 3 ] .apprxeq. V 2 - V 1 V 1 ( formula 3 ) [ formula 4 ]
.sigma. 1 = E .apprxeq. E V 2 - V 1 V 2 ( formula 4 )
##EQU00003##
[0093] On the other hand, the stress .sigma.2 caused by rotating
core torque is expressed by formula 5, where T represents the
tension applied during the process to a unit width of the
microporous plastic film 1 and t represents the thickness of the
microporous plastic film 1.
[formula 5]
.sigma..sub.2=Tt (formula 5)
[0094] Breakage occurs when the inequality of formula 6 is met,
where .sigma.b represents the rupture stress of the microporous
plastic film 1. Here, .sigma.b can be determined from rupture test
of the microporous plastic film 1 using a tensile tester or the
like. In the case of a micropore-containing film, however,
scratches tend to be caused by the blades of a continuous cutting
device installed in the production process to accelerate the stress
concentration in the cut portions. Consequently, breakage tends to
occur at a stress that is smaller than the rupture stress obtained
from the aforementioned tensile test. The inventors of the present
invention found that breakage can be prevented by minimizing the
value of .sigma.1. Thus, the strain .di-elect cons. is prevented
from being caused by a difference in speed and the stress is
maintained below .sigma.b by decreasing the coefficient of static
friction between the film and that portion of a conveyance roller 2
which comes in contact with the film. This successfully worked to
prevent breakage.
[formula 6]
.sigma..sub.b<.sigma..sub.1+.sigma..sub.2 (formula 6)
EXAMPLES
[0095] Given below are results of producing a microporous plastic
film roll for secondary battery separators by using the microporous
plastic film production method described above.
Example 1
[0096] A microporous plastic film 1 of polypropylene in which
through-holes as illustrated in FIG. 4 were formed by carrying out
a biaxial stretching step while controlling the crystal structure
of polypropylene was conveyed by a conveyance roller 2 as
illustrated in FIG. 1 and wound up continuously on a core 6 to
produce a microporous plastic film roll 12. The microporous
polypropylene film had a Gurley air permeation resistance of 500
seconds per 100 ml, porosity of 70%, average pore size of 100 nm,
and cushion rate of 17%. The film 1 had a width of 600 mm and
thickness of 60 .mu.m. The thickness was measured with an
emitting/receiving type laser sensor, and the porosity was
calculated by formula 6 from the measured thickness.
[0097] Here, the gas permeability is represented by the Gurley air
permeation resistance (seconds per 100 ml) as specified in MS P8117
(2001). The Gurley air permeation resistance is defined as the time
period required by 100 ml of air pressured under a constant
pressure to pass through a microporous film, and the Gurley air
permeation resistance, that is, the air passage time, decreases as
the gas permeability increases.
[0098] Here, the average pore size of the microporous plastic film
1 may be measured by any appropriate method, and can be determined
by using the following measuring device under the following
conditions.
Measuring device: Perm-Porometer, automatic micropore size
distribution measuring device supplied by Porous Materials, Inc.
Testing liquid: Fluorinert FC-40 supplied by 3M Testing
temperature: 25.degree. C.
Testing gas: air
[0099] Analyzing software: Capwin Measuring conditions: automatic
measurement under default conditions: Capillary Flow Porometry--Wet
up, Dry down Conversion equation: d=C.gamma./P.times.10 3 d: pore
diameter (nm), C: constant, .gamma.: Fluorinert surface tension (16
mN/m), P: pressure (Pa)
[0100] As illustrated in FIG. 1, the conveyance roller 21,
conveyance roller 23, and conveyance roller 24 driven by a motor 32
via a belt, and controlled at a constant speed immediately before
starting winding-up. Here, a load measuring device is provided on
the bearing of the conveyance roller 22 to measure the tension. The
conveyance roller 22 is driven by the film 1 instead of the motor
32, preventing the direction of the resultant tensional force from
being varied by the frictional force on the roller.
[0101] The core 6 is supported rotatably on the winding-up shaft
and driven by the motor 31 in such a manner that a constant tension
is maintained. For this example, a composite material of metal and
a tetrafluoroethylene--perfluoroalkylvinyl ether copolymer (PFA),
which is a fluorine resin, was formed on the surfaces of the
conveyance roller 21, conveyance roller 22, conveyance roller 23,
and conveyance roller 24 as illustrated in FIG. 2 so that the
portions of the four rollers, that is, conveyance rollers 21 to 24,
that come in contact with the film 1 have a coefficient of static
friction of 0.7 or less. To represent the surface roughness of the
roller surfaces, their ten-point average roughness RzJIS was
measured with a contact type surface roughness measuring device
supplied by Mitutoyo Corporation using a diamond stylus with a
stylus end radius of 2 .mu.m at a measuring force of 0.75 mN as
specified in Japanese Industrial Standards JIS B0601 (2001).
[0102] Consequently, the coefficient of static friction to the film
1 measured with Muse supplied by Shinto Scientific Co., Ltd. was
0.55. Here, the contact pressure p applied by the contact head was
about 570 Pa.
[0103] The production conditions for the microporous plastic film
roll 1 included a conveyance speed of 10 m/min and tension of 20
N/m, and a film roll was ejected by an automatic roll changer each
time the winding-up of a 1,000 m length is completed.
[0104] The combinations of these conditions are summarized in Table
1.
Example 2
[0105] A film 1 with a thickness of 20 .mu.m was wound up under the
same conditions as in Example 1 to provide a microporous plastic
film roll 12. The film had subsequently the same porosity as in the
example, but its Gurley air permeation resistance was 100 seconds
per 100 ml as a result of a smaller thickness.
Example 3
[0106] The same procedure as in Example 2 was carried out except
that a composite film of metal and polytetrafluoroethylene (PTFE)
was formed on the surfaces of the conveyance rollers 21 to 24 as
illustrated in FIG. 2 so that the portions of the four rollers
coming in contact with the film 1 had a coefficient of static
friction of 0.5 or less. To represent the surface roughness of the
roller surfaces, their ten-point average roughness was measured
under the same conditions as in Example 1.
Example 4
[0107] A microporous plastic film roll 12 was produced by the same
procedure as in Example 3 except that a film 1 with a Gurley air
permeation resistance of 400 seconds per 100 ml and porosity of 40%
was wound up.
Example 5
[0108] A microporous plastic film roll 12 was produced by the same
procedure as in Example 3 except that the four rollers used, that
is, the conveyance rollers 21 to 24, had surfaces with a small
roughness such that their portions that come in contact with the
film 1 had a coefficient of friction of 0.5 or less.
Example 6
[0109] A microporous plastic film roll 12 was produced by the same
procedure as in Example 3 except that a film 1 with a Gurley air
permeation resistance of 900 seconds per 100 ml and porosity of 30%
was wound up.
Comparative Example 1
[0110] A film 1 with a Gurley air permeation resistance of 100
seconds per 100 ml, porosity of 70%, and thickness of 20 .mu.m as
in Examples 2 and 3 was conveyed by four rollers, that is, the
conveyance rollers 21 to 24, in which the portions coming in
contact with the film 1 had surfaces plated with hard chromium
(Hcr) and having a surface roughness RzJIS of 0.1 .mu.m, and it was
wound up to produce a microporous plastic film 12.
Comparative Example 2
[0111] A film 1 with a Gurley air permeation resistance of 100
seconds per 100 ml, porosity of 70%, and thickness of 20 .mu.m as
in Examples 2 and 3 was conveyed by four rollers, that is, the
conveyance rollers 21 to 24, in which the portions coming in
contact with the film 1 had surfaces coated with diamond like
carbon (DLC) and having a surface roughness RzJIS of 3 .mu.m, and
it was wound up to produce a microporous plastic film 12.
Comparative Example 3
[0112] A film 1 with a porosity of 0% that contained no effective
through-holes required for the film to serve as a separator for
secondary batteries was conveyed by the same conveyance rollers as
used in Example 3 and wound up to produce a biaxially stretched
polypropylene film roll.
Comparative Example 4
[0113] A film 1 with a Gurley air permeation resistance of 100
seconds per 100 ml, porosity of 70%, and thickness of 20 .mu.m as
in Example 2 was conveyed by four rollers, that is, the conveyance
rollers 21 to 24, in which the portions coming in contact with the
film 1 had surfaces formed of a composite film of TFE and metal and
having a surface roughness RzJIS of 0.1 .mu.m, and it was wound up
to produce a microporous plastic film 12.
[0114] Table 1 shows results of the production of the microporous
plastic film rolls 1 for secondary separators conducted in Examples
and Comparative examples.
[0115] Here, the criteria for wrinkle were as follows: "C" for
cases where wrinkles formed during conveyance left in the film roll
1 and wrinkles were found in the wound-up roll, "B" for cases where
wrinkles were found in the film being conveyed, but not found in
the wound-up roll, and "A" for the other cases.
[0116] Here, the criteria for breakage were as follows: "C" for
cases where breakage took place before the completion of winding-up
of a length of 1,000 m, "B" for cases where breakage took place
once or more times before the completion of winding-up of a length
of 90,000 m, and "A" for the other cases.
[0117] The performance of a separator for secondary battery was
judged according to the Gurley air permeation resistance. A
preferred separator for secondary battery allows ions to pass
without resistance through minute through-holes that do not cause
dielectric breakdown. For its performance, a higher Gurley air
permeation resistance is more preferable. The criteria were as
follows: "C" for cases where the Gurley air permeation resistance
was 1,000 seconds per 100 ml or more, "B" for cases where it was
200 to 1,000 seconds per 100 ml, and "A" for cases where it was 10
to 200 seconds per 100 ml or less.
[0118] In Example 1, as seen from Table 1, the portion of a
conveyance roller 2 coming in contact with the microporous plastic
film 1 was formed a PFA composite material so that the coefficient
of friction to the film 1 was 0.6 or less, and consequently, a
microporous plastic film roll was able to be produced in a state
where wrinkle was completely prevented and the breakage frequency
was very low while realizing a porosity and Gurley air permeation
resistance required for a separator for secondary battery.
[0119] In Example 2, a decrease in thickness led to an improved gas
permeability and an increased risk of breakage and wrinkle, but
wrinkle and breakage frequency were minimized by using a PFA
composite film to ensure a coefficient of static friction of 0.6 or
less as in Example 1.
[0120] In Example 3, a film that was thin, low in porosity, and
difficult to handle as in Example 2 was used and the PTFE composite
film realized a coefficient of static friction of 0.6 or less,
serving to prevent wrinkle and breakage.
[0121] In Example 4, a decrease in porosity led to a slightly
inferior gas permeability, but the use of the same PTFE composite
film as in Example 3 served to realized a further decrease in the
friction coefficient, leading to good results in wrinkle and
breakage evaluations as in the other examples.
[0122] In Example 5, the composite film had a smaller roughness
than in Examples 1 to 4 and accordingly had a slightly higher
coefficient of static friction to cause wrinkle, but the use of
PTFE served to realize a coefficient of static friction of 0.6 or
less, leading to a good wound-up film free of wrinkles.
[0123] In Example 6, the film had a decreased gas permeability
(increased Gurley air permeation resistance) and also had a low
cushion rate, and accordingly, it had the lowest coefficient of
static friction, resulting in a conveyance performance as high as
that of common films when a composite film equivalent to that used
in Example 4 was adopted.
[0124] As compared to these, the conveyance roller prepared in
Comparative example 1 had a Hcr-plated surface with a small
roughness, and had a large contact area and large friction,
depending on the gas permeability and cushion rate of the
microporous plastic film, leading to a coefficient of static
friction largely exceeding 0.6. Consequently, the wound-up film
roll was found to contain wrinkled that would cause deterioration
in separator performance and breakage took place at a high
frequency, resulting in a low productivity.
[0125] In Comparative example 2, although the coefficient of
friction was improved from Comparative example 1 by coating the
surfaces of the conveyance rollers with DLC, the coefficient of
static friction was still more than 0.6 and failed to avoid
breakage by absorbing the difference in speed between the
conveyance rollers.
[0126] In Comparative example 3, the transparent polypropylene film
did not contain effective micropores required for a separator, and
although conveyance was performed without any problems attributable
to micropores, results showed that the film did not have gas
permeability required for a buttery separator.
[0127] In Comparative example 4, the surfaces of the conveyance
rollers, which were formed of a composite material of PTFE, was too
low in roughness to achieve a reduce in the friction coefficient
down to a required level, and failed to avoid breakage by absorbing
the difference in speed between the conveyance rollers.
[0128] In this way, the present invention serves to produce a
microporous plastic film roll with a preferred gas permeability for
a separator of a secondary battery, by conveying and winding up the
film without wrinkle and breakage.
TABLE-US-00001 TABLE 1 Gurley air Roughness Coefficient permeation
Average Evaluation results Surface RzJIS of static resistance
Porosity Cushion rate pore size Thickness air material (.mu.m)
friction (sec/100 ml) (%) (%) (nm) (.mu.m) wrinkle breakage
permeability Example 1 PFA 3 0.55 500 70 17 100 60 A B B Example 2
PFA 3 0.55 100 70 22 100 20 B B A Example 3 PTFE 3 0.35 100 70 22
100 20 A A A Example 4 PTFE 3 0.30 400 40 18 60 20 A A B Example 5
PTFE 0.7 0.45 100 70 22 100 20 B A A Example 6 PTFE 3 0.20 900 30
15 50 20 A A B Comparative Hcr 0.1 1.20 100 70 22 100 20 C C A
example 1 Comparative DLC 3 0.80 100 70 22 100 20 B C A example 2
Comparative PTFE 3 0.20 -- 0 0 -- 20 A A C example 3 Comparative
PTFE 0.1 0.80 100 70 22 100 20 B C A example 4
[0129] The present invention can be applied not only to separators
of secondary batteries but also to other various applications where
microporous plastic films can be adopted including, but not limited
to, separators of capacitors, separation films, membrane filters,
base material of optical reflection coatings, and printable
films.
EXPLANATION OF NUMERALS
[0130] 1 microporous plastic film [0131] 12 microporous plastic
film roll [0132] 2 conveyance rollers [0133] 21 conveyance roller A
[0134] 22 conveyance roller B [0135] 23 conveyance roller C [0136]
2A base of conveyance roller [0137] 3 driving source [0138] 4
driving force transmission mechanism [0139] 5 pulley [0140] 6 core
[0141] 7 metal-plated layer [0142] 8 fluorine resin layer [0143] 9
composite material [0144] 10 schematic exploded view of a lithium
ion secondary battery [0145] 11 case [0146] 13 electrode tab [0147]
14 positive electrode [0148] 15 negative electrode [0149] 16
separator made of microporous plastic film [0150] 17 through-hole
[0151] 18 fibrils [0152] 19 wrinkle remover [0153] 30 weight [0154]
31 spring scale [0155] A conveyance direction [0156] W mass of
weight
* * * * *