Technical Field
[0001] The present invention relates to a metal foil machining roller. More specifically,
the present invention mainly relates to an improvement in a metal material that constitutes
a metal foil machining roller in which a plurality of recessed portions are formed
in a surface thereof.
Background Art
[0002] Conventionally, a plating method, an etching method and the like are generally utilized
to form protrusion portions on the surface of a metal foil with a thickness of several
tens of microns. However, in the case of forming several tens to several hundreds
of micron-sized protrusion portions per 1cm
2 of a metal foil surface by such a method, precision machining that involves a large
number of steps is performed, which requires complicated operations and a long time,
yet a sufficiently low defect rate cannot be achieved. Treatment of wastewater generated
through the use of a plating solution, an etching solution and the like is also a
problem. In addition, protrusion portions that are formed by such a method do not
have sufficient bonding strength with a metal foil, so they often separate from the
metal foil when external stress is applied. Accordingly, it cannot be said that the
plating method, the etching method and the like are industrially advantageous in manufacturing
a metal foil that has protrusion portions on the surface thereof.
[0003] Atechnique of pressure-molding a plate-shaped metal material by allowing the plate-shaped
metal material to pass through a press-contact nip portion that is formed by a pair
of rollers that are pressed into contact with each other is widely used. A typical
example of a pressure-molding technique could be the cold-drawing of a steel material,
for example.
A dull roller in which, for example, a crater-like recessed portion and a raised portion
that is raised along the periphery of the crater-like recessed portion are formed
on the surface of the dull roller has been proposed (see, for example, Patent Document
1). Dull rollers are used to form what are called dull marks on the surface of a cold-drawn
steel plate between a cold-drawing step and an annealing step. By doing so, seizure
of the steel plate is prevented in the case of the annealing step being batch annealing.
In the case of the annealing step being continuous annealing, a steel plate is prevented
from meandering when the steel plate is delivered into an annealing furnace.
[0004] Patent Document 1 also describes that the raised portion formed on the dull roller
surface is firmly pressed against the steel plate surface, causing a plastic flow
of the steel plate material locally on the steel plate surface, as a result of which
the steel plate material flows into the recessed portion of the dull roller, roughening
the steel plate. Patent Document 1 further describes that a dull roller is manufactured
by directing a laser pulse onto a roller with a smooth surface while rotating the
roller so as to melt the roller surface at a regular interval to form crater-like
recessed portions at a regular interval.
[0005] However, Patent Document 1 merely discloses a technique of making the surface of
a several hundreds of µm to several mm thick cold-drawn steel plate more rough, and
it contains no disclosure of the formation of protrusion portions on the surface of
a metal foil with a thickness of only several tens of µm. Moreover, Patent Document
1 does not describe a specific material for the dull roller, so the dull roller is
considered to be made of a commonly used material. Such a commonly used material can
be, for example, a steel material that is harder than a steel plate to be cold drawn.
With a dull roller made of such a material, crater-like recessed portions formed on
the surface are easily worn out or the like and disappear. Accordingly, it cannot
be utilized for industrial scale formation of protrusion portions. In addition, when
a dull roller is manufactured by subjecting a roller made of such a material to laser
machining, recessed portions that have a desired opening shape cannot be formed. For
example, when an attempt is made to form recessed portions with a rhombic opening
shape, the opening periphery of the recessed portions melt due to the residual heat
of the laser, resulting in an elliptic shape.
[0006] Also, a drawing roller in which recesses and protrusions are formed on the surface
of the roller, the recessed portions have a depth of 5 to 100 µm, and the ratio of
the total tip surface area of protrusion portions with respect to the total surface
area is 10 to 80% has been proposed (see, for example, Patent Document 2). However,
the technique of Patent Document 2 is also a technique of forming dull marks on the
surface of a several hundreds of µm to several mm thick cold-draw steel plate, and
is not a technique of forming projecting protrusion portions on the surface of a several
tens of µm thick metal foil. Patent Document 2 also does not describe a specific material
for the drawing roller, so, as is the case with the dull roller of Patent Document
1, the drawing roller of Patent Document 2 cannot be utilized for industrial scale
formation of protrusion portions, and it is not possible to form recessed portions
of a desired opening shape with the drawing roller.
[0007] Also, a drawing apparatus that indudes a first work roller in which a plurality
of annular recessed portions (annular grooves for forming protrusions) that extend
along a circumferential direction are formed and a second work roller with a smooth
circumferential surface has been proposed (see, for example, Patent Document 3). In
the drawing apparatus of Patent Document 3, the first work roller and the second work
roller are pressed into contact such that their axes are parallel to each other, so
as to form a press-contact nip portion. When a long plate-shaped metal material is
allowed to pass through the press-contact nip portion, a plurality of projections
are formed on one surface of the plate-shaped material in a thickness direction, and
a metal plate for manufacturing a flat tube is obtained. By bending the metal plate
for manufacturing a flat tube, a flat tube is obtained. Such a flat tube is used as
a coolant flow tube for a capacitor.
[0008] Patent Document 3 proposes a cemented carbide as a material for the first work roller,
and also discloses cemented carbides such as JIS V10 to V60. However, the technique
of Patent Document 3 is not intended to machine a metal foil with a thickness of several
tens of µm. Patent Document 3 discloses only engraving as a specific example of a
method of forming annular recessed portions, and it contains no disclosure of laser
machining. It is very difficult to form a plurality of micron-sized recessed portions
at an interval of about 10 to 50 µm by engraving. Even when a plurality of miaon-sized
recessed portions are formed in a cemented carbide by laser machining, recessed portions
with openings of a uniform shape and diameter are not necessarily obtained. In Patent
Document 3, a cemented carbide is used only for the purpose of preventing the bottom
faces of annular recessed portions from wearing out
[0009] Meanwhile, conventionally a technique of boring a hole in an electronic component
such as a ceramic green sheet, circuit board or the like by laser machining is well
known (see, for example, Patent Document 4). That is, laser machining is often utilized
to form recessed portions in the surface of a ceramic layer, resin layer or the like.
However, there has been no proposal or report of a technical conception in which a
large number of micron-sized recessed portions, namely, several hundreds to several
tens of millions of recessed portions are formed on a metal surface by laser machining.
Moreover, when a large number of such recessed portions are formed on the surface
of a commonly used metal such as stainless steel, the opening shape and opening diameter
of the recessed portions formed on the metal surface will be non-uniform. Also, a
problem arises in that the formed recessed portions will have reduced mechanical strength,
wear resistance and the like, as a result of which wear, deformation, breakage and
the like will likely occur.
[0010] Furthermore, a technique is commonly performed in which a resin sheet is pressure-molded
by using a ceramic roller in which a plurality of recessed portions are formed on
the circumferential surface so as to emboss the surface of the resin sheet. However,
when a metal foil is pressure-molded by using a ceramic roller in which recessed portions
are formed on the circumferential surface, a large number of cracks, chips, fractures
and the like occur in the circumferential surface of the ceramic roller, so it is
not possible to continuously pressure-mold such a metal foil.
[Patent Document 1] Japanese Laid-Open Patent Publication No.
S63-10013
[Patent Document 2] Japanese Laid-Open Patent Publication No.
H10-166010
[Patent Document 3] Japanese Laid-Open Patent Publication No.
2005-997
[Patent Document 4] Japanese Laid-Open Patent Publication No.
2005-111524
Disclosure of the Invention
Problem to be Solved by the Invention
[0011] It is an object of the present invention to provide a metal foil machining roller
in which a plurality of recessed portions are formed on a circumferential surface,
wherein the recessed portions are unlikely to wear out, deform or the like, and it
is possible to efficiently manufacture a metal foil that has protrusion portions even
when metal foil machining is performed on an industrial scale.
Means for Solving the Problem
[0012] The present inventors conducted in-depth studies to solve the above problems, and
found during the course of the studies that two properties, namely, Rockwell hardness
and transverse rupture strength, among the various properties of metal materials significantly
affect the opening shape and opening diameter of recessed portions during laser machining.
The present inventors conducted further studies based on this finding. As a result,
they found that by forming micron-sized recessed portions in the surface of a roller
made of a metal material that has a specific Rockwell hardness and transverse rupture
strength, even though the number of recessed portions is large (several hundreds to
several tens of millions of recessed portions), it is possible to form approximately
uniform recessed portions in which non-uniformity in the opening shape and opening
diameter is very small. They also found that the recessed portions have a high level
of durability against external stress, such as a fictional force, and are unlikely
to undergo wear, deformation, breakage and the like. With this background, the present
invention has been accomplished.
[0013] That is, the present invention relates to a metal foil machining roller in which
a plurality of recessed portions are formed on a circumferential surface by laser
machining, wherein at least a surface layer portion in which the recessed portions
are formed indudes a metal material that has a Rockwell hardness in A scale of HRA
81.2 to 90.0 and a transverse rupture strength of 3 GPa to 6 GPa.
[0014] It is preferable that a aoss-sectional shape of the recessed portions in a direction
vertical to the circumferential surface of the metal foil machining roller is a taper
shape in which a cross-sectional width becomes gradually or continuously smaller from
the circumferential surface of the metal foil machining roller toward a bottom face
of the recessed portions.
It is preferable that an opening shape of the recessed portions in the circumferential
surface of the metal foil machining roller is an approximately circular shape, an
approximately elliptic shape, an approximately rhombic shape or an approximately regular
polygonal shape.
It is preferable that an opening diameter of the recessed portions in the circumferential
surface of the metal foil machining roller is 1 µm to 35 µm.
It is preferable that a pitch of the recessed portions in a direction of an axis of
the metal foil machining roller in the circumferential surface of the metal foil machining
roller is 4 µm or more.
[0015] It is preferable that the metal material has a Rockwell hardness in A scale of HRA
83.9 to 89.
It is preferable that the metal material has a transverse rupture strength of 3.3
GPa to 5.5 Gpa.
It is preferable that the metal material contains at least one high melting point
metal material selected from the group consisting of a cemented carbide, a cermet,
a high speed steel, a die steel and a forged steel.
It is preferable that the metal foil machining roller is used such that the bottom
face of the recessed portions and a surface of a metal foil do not come into contact.
Effect of the Invention
[0016] In a metal foil machining roller according to the present invention, a plurality
of recessed portions are formed on the circumferential surface thereof by laser machining.
In the metal foil machining roller of the present invention, a metal material that
has a Rockwell hardness and a transverse rupture strength within the above ranges
is contained in at least a surface layer portion in which recessed portions are formed,
whereby it is possible to form openings of approximately uniform opening shape and
opening diameter in the circumferential surface of the roller. It is also possible
to adjust the opening shape and opening diameter to an arbitrary shape and diameter.
For example, recessed portions with an opening diameter of several microns to several
tens of microns can be formed. Also, recessed portions with an opening shape such
as an approximately perfect circle, an approximately rhombic shape or an approximately
regular polygonal shape can be formed. It is also possible to form such recessed portions
at a pitch of about 10 to 50 µm.
The recessed portions have a very high level of durability against external stress,
and superior releasability with protrusion portions of a metal foil that are formed
in the inner spaces of the recessed portions. Accordingly, even when a metal foil
is continuously machined on an industrial scale, it is possible to stably and efficiently
form protrusion portions of approximately the same shape that are unlikely to wear
out, deform or the like.
Brief Description of the several views of the Drawing
[0017]
Fig. 1 is a side view schematically showing a configuration of a metal foil machining
apparatus.
Fig. 2 is an enlarged perspective view showing a configuration of a relevant part
of the metal foil machining apparatus shown in Fig.1.
Fig. 3 is a perspective view showing an external appearance of a metal foil machining
roller.
Fig. 4 is an enlarged perspective view of a surface region of the metal foil machining
roller shown in Fig. 3.
Best Mode for Carrying Out the invention
[0018] A metal foil machining roller of the present invention is used to, for example, pressure-mold
a metal foil so as to obtain a metal foil that has protrusion portions on either or
both surfaces in a thickness direction (hereinafter referred to as a metal foil with
protrusion portions). Specifically, a mold-machining apparatus that indudes a metal
foil machining roller of the present invention and a metal roller with a smooth surface
is used. The metal foil machining roller and the metal roller are pressed into contact
with each other such that their axes are parallel to each other, whereby a press-contact
nip portion is formed. By feeding a metal foil and allowing the metal foil to pass
through the press-contact nip portion such that a surface on which protrusion portions
are to be formed comes into contact with the circumferential surface of the metal
foil machining roller, a metal foil that has protrusion portions on one surface thereof
can be obtained. Alternatively, by allowing two metal foil machining rollers to be
pressed into contact with each other for use, a metal foil that has protrusion portions
on both surfaces thereof can be obtained.
[0019] Examples of metal foils that can be pressure-molded by the metal foil machining roller
of the present invention include, but are not particularly limited to, a copper foil,
a copper alloy foil, a tin foil, a stainless steel foil, an aluminum foil, an aluminum
alloy foil, a lead foil, a nickel foil, a zinc foil, and so on. It is preferable that
the metal foils that can be pressure-molded by the metal foil machining roller of
the present invention have properties such as an easily deformable grain boundary
and a low annealing temperature. The thickness of the metal foil is preferably, but
not particularly limited to, 10 to 100 µm, and more preferably 10 to 50 µm.
[0020] A metal foil with protrusion portions formed of a copper foil, a copper alloy foil
or the like through the use of the metal foil machining roller of the present invention
can be preferably used as, for example, a negative electrode current collector for
a lithium secondary battery. In the surfaces of the individual protrusion portions
of the metal foil with protrusion portions formed of a copper foil, a copper alloy
foil or the like, columns that contain a negative electrode active material and function
as a negative electrode active material layer are formed by vacuum deposition. As
the negative electrode active material, for example, silicon, silicon oxide, a silicon-containing
alloy, a silicon compound, tin, tin oxide, a tin-containing alloy, a tin compound
or the like can be used.
By forming a negative electrode active material layer consisting of such columns on
the protrusion portion surface, stress that is generated by expansion and contraction
of the negative electrode active material when absorbing and desorbing lithium ions
is absorbed, as a result of which not only deformation of the negative electrode current
collector, but also deformation of the negative electrode, as well as separation of
the negative electrode active material layer from the negative electrode current collector,
and the like are prevented. As a consequence, it is possible to obtain a lithium ion
secondary battery that has superior charge/discharge cycle properties, long-term safety
and the like and that is capable of providing high power output
The metal foil with protrusion portions obtained by the present invention can also
be preferably used as, for example, a metal foil or metal layer for use in a flexible
printed circuit board, a metal substrate for a lead frame or the like.
[0021] The metal foil machining roller of the present invention has two features. The first
feature is that a plurality of recessed portions are formed on the circumferential
surface of the metal foil machining roller. The second feature is that at least a
surface layer portion in which recessed portions are formed contains a metal material
that has specific properties.
The recessed portions are spatial regions that have an opening in the circumferential
surface (hereinafter referred to simply as "roller circumferential surface") of the
metal foil machining roller of the present invention and that are recessed or dented
inwardly from the roller circumferential surface. The bottom face of the recessed
portions may be approximately a flat plane, or may have a dome-like shape, or the
like.
[0022] Normally, individual recessed portions are formed independently of each other such
that adjacent recessed portions are not connected to each other. However, the present
invention is not limited to this configuration, and the recessed portions may be partially
connected into a single piece, or entirely connected into a single piece. Preferably,
individual recessed portions are formed independently of each other so as not to be
connected to each other.
The opening shape of the recessed portions in the roller circumferential surface can
be, but is not particularly limited to, an approximately circular shape, an approximately
elliptic shape, an approximately rhombic shape, an approximately regular polygonal
shape or the like. Preferred regular polygonal shapes are a triangle, a quadrangle,
a pentagon, a hexagon, a heptagon, and an octagon, and a quadrangle and a hexagon
are more preferable. As used herein, "approximately circular shape" encompasses a
circular shape and a shape dose to the circular shape. The same applies to other shapes.
[0023] The opening diameter of the recessed portions in the roller circumferential surface
is preferably, but is not particularly limited to, 1 µm to 35 µm, and more preferably
2 to 30 µm. When the opening diameter is less than 1 µm, it is difficult to obtain
recessed portions with an approximately uniform opening diameter. An opening diameter
exceeding 35 µm is inappropriate for surface machining of a metal foil with a thickness
of about several tens of µm. In addition, the recessed portions may be worn out, deformed
or the like by the stress applied when pressure-molding a metal foil. When the opening
shape is an approximately circular shape, an approximately elliptic shape or an approximately
regular polygonal shape, the opening diameter is the length of the diameter of the
smallest perfect circle that encloses the circular shape, the elliptic shape or the
regular polygonal shape. When the opening shape is an approximately rhombic shape,
the opening diameter is the length of a longer diagonal line of the diagonal lines
of the rhombic shape.
[0024] There is no particular limitation on the depth of the recessed portions. The depth
can be selected as appropriate according to, for example, the height of protrusion
portions to be formed on a metal foil surface, or the like, but it is preferable that
the depth is 0.2 to 1.5 times the opening diameter, and more preferably, 0.3 to 1.2
times the opening diameter. With recessed portions with a depth of less than 0.2 times
the opening diameter, protrusion portions of a uniform size and shape may not be formed
on a metal foil surface. On the other hand, it is extremely difficult to form recessed
portions with a depth exceeding 1.5 times the opening diameter by a laser machining
method. With a cutting method, it takes a considerable amount of time to form recessed
portions, or it is substantially impossible to form recessed portions. As used herein,
the depth of recessed portions refers to the length of a vertical line that extends
from the deepest point of the bottom face of the recessed portions to an imaginary
roller circumferential surface assumed to exist on the opening of the recessed portions.
[0025] In the roller circumferential surface, the pitch at which recessed portions are formed
is not particularly limited both in a direction (longitudinal direction) of the axis
of the roller and in a direction of the circumference. The pitch of recessed portions
in the axial direction can be selected as appropriate according to the opening diameter
and opening shape of recessed portions, the roller length, the design values of a
metal foil with protrusion portions to be obtained, and so on. The pitch is preferably
4 µm or more, more preferably 8 to 30 µm, and particularly preferably 15 to 30 µm.
When the pitch of recessed portions in the axial direction is less than 4 µm, recessed
portions are likely connected to each other when formed by a laser machining method.
Accordingly, the area between adjacent recessed portions in the roller surface will
be extremely small. As a result, the dividing portion between adjacent recessed portions
may be deformed by the stress applied when pressure-molding a metal foil. The upper
limit value for the pitch in the axial direction can be selected as appropriate according
to the roller length or the like.
[0026] Likewise, the pitch of recessed portions in the circumferential direction can be
selected as appropriate according to the opening diameter and opening shape of recessed
portions, the length of the circumference of the roller, the design values of a metal
foil with protrusion portions to be obtained, and so on. The pitch is preferably 4
µm or more, and more preferably 5 to 20 µm. When the pitch of recessed portions in
the circumferential direction is less than 4 µm, recessed portions are likely to be
connected to each other when formed by a laser machining method. Accordingly, the
area that divides adjacent recessed portions in the roller surface will be extremely
small, as a result of which the partition between adjacent recessed portions may be
deformed by the stress applied when pressure-molding a metal foil. The upper limit
value for the pitch in the circumferential direction can be selected as appropriate
according to the length of the circumference of the roller or the like.
[0027] In this specification, the pitch in the axial direction (longitudinal direction)
is the distance (length) between two parallel lines that pass through the centers
of two adjacent recessed portions in the axial direction and extend in the circumferential
direction. The pitch in the circumferential direction is the distance (length) between
two parallel lines that pass through the centers of two adjacent recessed portions
in the circumferential direction and extend in the axial direction. The center of
a recessed portion means the center of the opening of the recessed portion. The center
of the opening means, when the opening shape of the recessed portion is an approximately
circular shape, an approximately elliptic shape or an approximately regular polygonal
shape, the center of the smallest perfect drde that encloses the circular shape, the
elliptic shape or the regular polygonal shape. When the opening shape of the recessed
portion is an approximately rhombic shape, the center of the opening means the point
at which two diagonal lines intersect.
[0028] It is preferable that the cross-sectional shape of recessed portions in a direction
vertical to the circumferential surface of the roller is a taper shape in which the
cross-sectional width becomes gradually or continuously smaller from the roller circumferential
surface toward the bottom face of the recessed portions. With such recessed portions
with a taper-shaped cross section, when forming protrusion portions on a surface of
a metal foil by pressure-molding the metal foil, the releasability between the recessed
portions in the roller circumferential surface and the protrusion portions of the
metal foil is improved significantly, as a result of which it is very unlikely that
defects, such as the deformation of protrusion portions, occur.
Recess portions are formed by laser machining, and the laser machining will be described
later in detail.
[0029] In the metal foil machining roller of the present invention, at least a surface layer
portion in which recessed portions are formed contains a specific metal material.
The metal material has a Rockwell hardness in A scale of HRA 812 to 90.0, preferably
HRA 83.9 to 89.0, and a transverse rupture strength of 3 GPa to 6 GPa, preferably
3.3 GPa to 5.5 GPa.
[0030] When the Rockwell hardness in A scale is less than HRA 81.2, the roller can be flattened
or bent in the axial direction when pressure-molding a metal foil, failing to apply
enough pressure to the metal foil, and resulting in insufficient formation of protrusion
portions or resulting in protrusion portions with a reduced height, or it may not
be possible to form uniform protrusion portions with a size and shape approximately
dose to the design values. Accordingly, it may not be possible to obtain a desired
metal foil with protrusion portions. In addition, due to wearing out of the surface
of the metal foil machining roller, the recessed portions are easily worn out, deformed
or the like. On the other hand, when the Rockwell hardness in A scale exceeds HRA
90.0, fractures, chips, cracks and the like are likely to occur in the recessed portions
of the metal foil machining roller, which may result in insufficient pressure-molding
of a metal foil, such as deformed protrusion portions being formed, or protrusion
portions being formed at an unwanted position.
[0031] In this specification, Rockwell hardness (HRA) is specifically a value calculated
from the following equation based on JIS Z-2245:

where h represents a difference h in penetration depth of a diamond penetrator.
The difference h in penetration depth of a diamond penetrator is determined as follows.
With the use of a diamond penetrator that has a tip with a radius of curvature of
0.2 mm and a conical angle of 120°, an initial load of 98.07 N is applied to the surface
of a sample. Then, a test load of 588.4 N is applied, and the initial load is again
applied. The depth to which the diamond penetrator has penetrated is measured twice,
that is, at the time of the first application of the initial load and the second application
of the initial load. The difference between these measured values is defined as the
difference h in penetration depth of a diamond penetrator.
[0032] When the transverse rupture strength is less than 3 GPa, fractures, chips, cracks
and the like are likely to occur in the recessed portions of the metal foil machining
roller, which may result in insufficient pressure-molding of a metal foil, such as
deformed protrusion portions being formed, or protrusion portions being formed at
an unwanted position. Accordingly, there is a possibility that the metal foil machining
roller may not withstand long-term use and insufficient formation of protrusion portions
may occur even during the initial period of use and the defect rate increases. On
the other hand, when the transverse rupture strength exceeds 6 GPa, the roller can
be flattened or bent in the axial direction when pressure-molding a metal foil, failing
to apply enough pressure to the metal foil, and resulting in insufficient formation
of protrusion portions or resulting in protrusion portions with a reduced height,
or it may not be possible to form uniform protrusion portions with a size and shape
approximately dose to the design values. In addition, the wear resistance of the surface
of the metal foil machining roller is reduced, as a result of which wear, deformation
and the like are likely to occur in the recessed portions. Furthermore, the releasability
between the metal foil machining roller and a mold-machined metal foil is reduced,
which may cause defects, such as the metal foil being caught in the metal foil machining
roller.
[0033] In this specification, the transverse rupture strength is specifically a value measured
in the following manner based on JIS Z-2248. As a test piece, a round bar with a diameter
D of 13 mm and a length of 300 mm is used. Transverse rupture strength measurement
testing is carried out as a three-point bending test by using a universal testing
machine and a bend testing apparatus attached to the universal testing machine and
by setting a distance between supporting points L to 200 mm. Where a load when the
test piece ruptures is set to a maximum load W
max, transverse rupture strength σ
b can be calculated from the following equation:

[0034] In the present invention, it is preferable to use, as a metal material that has a
Rockwell hardness and a transverse rupture strength within the prescribed value ranges
given above, at least one high melting point metal material selected from the group
consisting of a cemented carbide, a cermet, a high speed steel, a die steel and a
forged steel. Among them, it is more preferable to use a cemented carbide, a high
speed steel, a forged steel or the like, and a forged steel is particularly preferable.
Metal materials that belong to such high melting point metal materials and that have
a prescribed Rockwell hardness and transverse rupture strength are capable of undergoing
laser machining, and have very superior shape- and size-reproducibility. In addition,
even when metal foil mold-machining with which recessed portions are formed in such
a metal material by laser machining is repeatedly carried out, it is very unlikely
that the recessed portions undergo wear, deformation, breakage or the like, so the
level of long-term endurance is high. The metal foil machining roller may contain
one or more metal materials.
[0035] As the cemented carbide, any known cemented carbide can be used and, specifically,
for example, cemented carbides obtained by sintering particles of carbide of a metal
that belongs to Group IVA, Group VA and Group VIA in the periodic table with a metal
binder such as Fe, Co or Ni can be used. Specific examples of such cemented carbides
include tungsten carbide-based cemented carbides such as a WC-Co-based alloy, a WC-Cr
3C
2-Co-based alloy, a WC-TaC-Co-based alloy, a WC-TiC-Co-based alloy, a WGNbC-Co-based
alloy, a WC-TaC-NbC-Co-based alloy, a WC-TiC-TaC-NbC-Co-based alloy, a WC-TiC-TaC-Co-based
alloy a WC-ZrC-Co-based alloy, a WC-TiC-ZrC-Co-based alloy, a WC-TaC-VC-Co-based alloy,
a WC-TiC-Cr
3C
2-Co-based alloy, a WC-TiC-TaC-based alloy, a WC-Ni-based alloy, a WC-Co-Ni-based alloy,
a WC-Cr
3C
2-Mo
2G-Ni-based alloy, a WC-Ti (C,N)-TaC-based alloy, a WC-Ti(C,N)-based alloy; a Cr
3C
2-Ni-based alloy; and so on.
[0036] As the cermet, any known cermet can be used and, specific examples include a TiC-Ni-based
material, a TiC-Mo-Ni-based material, a TiC-Co-based material, a TiC-Mo
2C-Ni-based material, a TiC-Mo
2C-ZrC-Ni-based material, a TiC-Mo
2C-Co-based material, a Mo
2C-Ni-based material, a Ti(C,N)-Mo
2C-Ni-based material, a TiC-TiN-Mo
2C-Ni-based material, a TiC-TiN-Mo
2C-Co-based material, a TiC-TiN-Mo
2C-TaC-Ni-based material, a TiC-TiN-Mo
2C-WC-TaC-Ni-based material, a TiC-WC-Ni-based material, a Ti(C,N)-WC-Ni-based material,
a TiC-Mo-based material, a Ti(C,N)-Mo-based material, boride-based materials (a MoB-Ni-based
material, a B
4C/(W,Mo)B
2-based material, etc.), and so on. Among them, titanium carbonitride-based cermits,
such as a Ti(C,N)-Mo
2C-Ni-based material, a TiC-TiN-Mo
2GNi-based material, a TiC-TiN-Mo
2C-Co-based material, a TiC-TiN-Mo
2C-TaC-Ni-based material, a TiC-TiN-Mo
2C-WC-TaC-Ni-based material, a Ti(C,N)-WC-Ni-based material and a Ti(C,N)-Mo-based
material, are preferable.
[0037] High speed steel is a material with increased hardness achieved by adding a metal
such as molybdenum, tungsten or vanadium to iron, and subjecting it to a heat treatment.
As the high speed steel, any known high speed steel can be used. Examples include:
a high speed steel composed primarily of iron, and containing carbon, tungsten, vanadium,
molybdenum and chromium; a high speed steel composed primarily of iron, and containing
carbon, tungsten, vanadium, molybdenum, cobalt and chromium; a high speed steel composed
primarily of iron, and containing carbon, vanadium, molybdenum and chromium; a high
speed steel composed primarily of iron, and containing silicon, manganese, chromium,
molybdenum and vanadium; a high speed steel composed primarily of iron, and containing
carbon, silicon, manganese, chromium, molybdenum and vanadium; a high speed steel
composed primarily of iron, and containing carbon, silicon, manganese, chromium, molybdenum,
tungsten, cobalt and vanadium; and so on.
[0038] As a die steel, any known die steel can be used, such as, for example, a die steel
containing iron, carbon, tungsten, vanadium, molybdenum and chromium; a die steel
containing iron, carbon, vanadium, molybdenum and chromium; a die steel containing
iron, carbon, silicon, manganese, sulfur, chromium, molybdenum and/ortungsten, vanadium,
nickel, copper and aluminum; and so on.
[0039] Forged steel is a material manufactured by heating a steel ingot formed by casting
molten steel into a mold, or a steel billet manufactured from such a steel ingot,
forging it by means of a press and a hammer or drawing and forting it by means of
a press and a hammer, and subjecting it to a heat treatment. As the forged steel,
any known forged steel can be used. Examples include: a forged steel composed primarily
of iron, and containing carbon, chromium and nickel: a forged steel composed primarily
of iron, and containing silicon, chromium and nickel; a forged steel containing nickel,
chromium and molybdenum; a forged steel composed primarily of iron, and containing
carbon, silicon, manganese, nickel, chromium, molybdenum and vanadium; a forged steel
composed primarily of iron, and containing carbon, silicon, manganese, nickel, chromium
and molybdenum; and so on.
A metal material that exhibits a prescribed Rockwell hardness and transverse rupture
strength can be obtained by selecting a component composition as appropriate from
among the high melting point metal materials listed above. As for the high melting
point metal materials subjected to a heat treatment during the production step thereof,
such as forged steel, by selecting a heat treatment temperature as appropriate, a
material with a desired Rockwell hardness and transverse rupture strength can be obtained.
[0040] In the metal foil machining roller of the present invention, the thickness of a surface
layer portion that contains a metal material with a prescribed Rockwell hardness and
transverse rupture strength is preferably, but not particularly limited to, about
5 to 50 mm.
A metal foil machining roller that has such a surface layer portion can be produced
by, in the case of the metal material being a high melting point metal material, for
example, thermal fitting or cool fitting a cylinder made of the high melting point
metal material to a core roller. As used herein, "thermal fitting" means that a high
melting point metal material cylinder produced to have an inner diameter slightly
smaller than the outer diameter of a core roller is fitted to the core roller by heating
the high melting point metal material cylinder to expand it. "Cool fitting" means
that a core roller contracted by cooling is fitted to a high melting point metal material
cylinder produced to have an inner diameter slightly smaller than the outer diameter
of the core roller. The core roller can be, for example, a roller made of stainless
steel, iron or the like.
In the metal foil machining roller of the present invention, not only the surface
layer portion, but also the entire roller may be made of a metal material with a prescribed
Rockwell hardness and transverse rupture strength.
[0041] The recessed portions in the circumferential surface of the metal foil machining
roller of the present invention are formed by laser machining. That is, a conventional
boring method that employs a laser can be used to form recessed portions. In laser
machining, a laser machining apparatus that indudes a roller rotating apparatus, a
laser oscillator, a machining head, a light guide path, a mask unit and an actuator
can be used.
The roller rotating apparatus includes, for example, a roller support and a drive
device. The roller support supports a roller in which at least a surface layer portion
contains a metal material with a prescribed Rockwell hardness and transverse rupture
strength and recessed portions are not formed in the circumferential surface so as
to be capable of rotation around its axis. The drive device drives the roller (hereinafter
referred to as a "roller in which recessed portions are to be formed") supported by
the roller support to thereby rotate the roller around the axis.
[0042] The laser oscillator is an apparatus that outputs laser light. As the laser oscillator,
any known laser oscillator can be used, such as a solid-state laser oscillator (Nd:YAG
laser, Nd:YVO
4 laser) that employs a laser medium obtained by mixing neodymium ions with a YAG crystal
(yttrium, aluminum, garnet) or YVO
4 crystal. Other examples include a carbon dioxide laser, an excimer laser and so on.
The output power of the laser oscillator is, for example, 50 mW to 200 W. The laser
light frequency is preferably 100 Hz to 100 kHz. The laser light irradiation time
is preferably, but not particularly limited to, 10 ps to 200 ns per instance. When
the irradiation time is less than 10 ps, heat conduction due to laser light irradiation
does not occur, so only a monoatomic layer can be removed, which may result in insufficient
formation of recessed portions. On the other hand, when the irradiation time exceeds
200 ns, laser light may sweep the surface of the roller in which recessed portions
are to be formed due to rotation of the roller.
[0043] The machining head is a member that is provided on a downstream side from the light
guide path in a direction in which the laser oscillator outputs laser light The machining
head collects laser light output from the laser oscillator and transmitted through
the light guide path, and irradiates the outer circumferential surface of the roller
in which recessed portions are to be formed. The machining head includes, for example,
a condenser lens. The condenser lens is provided perpendicular to the traveling path
of laser light, and collects laser light transmitted through the light guide path
and irradiates the outer circumferential surface of the roller in which recessed portions
are to be formed. The focal length of the condenser lens is preferably selected from,
but not particularly limited to, a range ranging from 5 mm to 200 mm. An assist gas
is introduced into the machining head. As the assist gas, for example, oxygen, nitrogen,
helium, argon, a mixed gas containing two or more of these, or the like can be used.
The pressure of the assist gas may be selected from, for example, a range ranging
from 0.1 MPa to 1 MPa.
[0044] The light guide path is a member that is provided on a downstream side from the laser
oscillator in a direction in which the laser oscillator outputs laser light, and that
guides laser light output from the laser oscillator to the machining head. The light
guide path includes, for example, a plurality of reflecting mirrors. By disposing
a plurality of reflecting mirrors at appropriate positions, laser light is reflected
by the reflecting mirrors and guided to the machining head. One mirror of the plurality
of reflecting mirrors that is closest to the machining head and that directly guides
laser light to the machining head is provided so as to be capable of reciprocation
in conjunction with the reciprocation of the machining head.
[0045] The mask unit is a member that is provided somewhere midway in the light guide path,
and that shapes the outline of laser light into a desired shape. In the mask unit,
laser-passing apertures, that is, through apertures with the same shape as the opening
shape of recessed portions to be formed, are formed. The laser light that has passed
through the laser-passing apertures is formed in outline to conform to the opening
shape of the laser-passing apertures, and is imaged by the condenser lens of the machining
head to form an image with the same shape as the opening shape of the laser-passing
apertures on the outer circumferential surface of the roller in which recessed portions
are to be formed. That is, the opening shape of laser-passing apertures is the opening
shape of recessed portions.
[0046] The actuator is provided vertically below the laser oscillator, the machining head,
the light guide path and the mask unit, and collectively supports these apparatuses
and members so as to be capable of reciprocation. The actuator reciprocates these
apparatuses and members parallel to the longitudinal direction of the roller in which
recessed portions are to be formed.
Such a laser machining apparatus is widely, commercially available. Even with a laser
machining apparatus without a roller rotating apparatus, by mounting a roller rotating
apparatus at a prescribed position, laser machining for forming recessed portions
can be carried out.
[0047] Recess portions are formed by applying laser light to the circumferential surface
of the roller in which recessed portions are to be formed continuously or intermittently,
preferably intermittently, by the laser machining apparatus. After the formation of
recessed portions, the roller in which recessed portions are to be formed is rotated,
or the machining head or the like is moved in the longitudinal direction of the roller
in which recessed portions are to be formed by the actuator, and new recessed portions
are formed. Through the repetition of this operation, recessed portions are formed
in a desired region of the roller in which recessed portions are to be formed, and
the metal foil machining roller of the present invention is obtained.
A situation may arise in which when recessed portions are formed by laser machining,
a bulge is formed along the perimeter of the opening of the recessed portions in the
roller circumferential surface. Such a bulge is preferably removed by, for example,
polishing or the like. Polishing can be earned out according to any known method.
For example, it is possible to perform polishing by using diamond particles as an
abrasive and a polishing apparatus including a polishing pad while supplying a medium
such as water.
[0048] The manufacture of a metal foil with protrusion portions by using the metal foil
machining roller of the present invention will be described next in detail. Fig. 1
is a side view schematically showing a configuration of a metal foil machining apparatus
10. Fig. 2 is an enlarged perspective view showing a configuration of a relevant part
(machining means 4) of the metal foil machining apparatus 10 shown in Fig.1. Fig.
3 is a perspective view showing an external appearance of a metal foil machining roller
1. Fig. 4 is an enlarged perspective view of a surface region 1 x of the metal foil
machining roller 1 shown in Fig. 3.
[0049] A metal foil 2 with protrusion portions is a metal foil in which protrusion portions
9 are formed in the surface, and can be manufactured by for example, the metal foil
machining apparatus 10 shown in Fig.1. The metal foil machining apparatus 10 includes
a metal foil feeding means 3, a machining means 4 and a metal foil winding means 5.
The metal foil feeding means 3 is, specifically, a metal foil feeding roller. The
metal foil feeding roller is axially supported by a supporting means (not shown) so
as to be capable of rotation around the axis. A metal foil 8 is wound around the circumferential
surface of the metal foil feeding roller. The metal foil 8 is fed to a press-contact
nip portion 6 of the machining means 4.
[0050] The machining means 4 includes, as shown in Figs.1 and 2, two metal foil machining
rollers 1. The two metal foil machining rollers 1 are pressed into contact such that
their axes are parallel to each other, whereby the press-contact nip portion 6 is
formed. Athin sheet-like material such as the metal foil 8 can be passed through the
press-contact nip portion 6. The metal foil machining rollers 1 are each axially supported
by supporting means (not shown) so as to be capable of rotation, and provided so as
to be capable of being rotated around the axis by a drive means (not shown). The two
metal foil machining rollers 1 both may function as drive rollers, or it is also possible
to employ a configuration in which one of the metal foil machining rollers 1 function
as a drive roller and the other functions as a driven roller that is rotated in conjunction
with the rotation of the drive roller.
In order to prevent the metal machining rollers 1 from being bent or deformed, a back
roller (not shown) is pressed into contact with each of the metal machining rollers
1. The axis of the metal machining rollers 1 and the axis of the back-up rollers are
parallel to each other The metal foil 8 is guided from an inlet of the press-contact
nip portion 6 to an outlet of the same by the two metal foil machining rollers 1 being
rotated, and the metal foil 8 is pressure-molded, whereby a metal foil 2 with protrusion
portions in which protrusion portions 9 are formed on the surface of the metal foil
8 is obtained.
[0051] The metal foil machining rollers 1 are rollers according to the present invention
in which a plurality of recessed portions 1a are formed on the circumferential surface.
In this embodiment, the arrangement pattern of recessed portions 1a in the circumferential
surface of a metal foil machining roller 1 of the present is as follows. As shown
in Fig. 4, a procession of a plurality of recessed portions 1 a at a pitch P
1 in the longitudinal direction of the metal foil machining roller 1 is defined as
a unit line 7. A plurality of unit lines 7 are arranged at a pitch P
2 in the circumferential direction of the metal foil machining roller 1. The pitch
P
1 and the pitch P
2 can be set freely. It should be noted that, in the circumferential direction of the
metal foil machining roller 1, adjacent unit lines 7 are arranged such that the recessed
portions 1 a are offset to each other in the longitudinal direction of the metal foil
machining roller 1.
In this embodiment, the recessed portions 1 a are offset at 0.5P
1 in the longitudinal direction, but the value is not limited thereto, and can be set
freely. In addition, in this embodiment, the recessed portions 1a in the circumferential
surface of the metal foil machining roller 1 have an approximately circular opening
shape, but the opening shape is not limited thereto, and can be, for example, an approximately
elliptic shape, an approximately rhombic shape, an approximately equilateral triangular
shape, an approximately square shape, an approximately regular hexagonal shape, an
approximately regular octangle shape or the like.
[0052] The cross section of recessed portions 1a in a direction vertical to the circumferential
surface of the metal foil machining roller 1 has a taper shape in which a width of
the cross section in a direction parallel to the circumferential surface of the metal
foil machining roller 1 becomes gradually smaller from the circumferential surface
of the metal foil machining roller 1 toward the bottom portion of the recessed portions
1 a, whereby the releasability of a pressure-molded metal foil 2 with protrusion portions
from the metal foil machining roller 1 is improved.
The diameter of the metal foil machining roller 1 is preferably, but not particularly
limited to, about 30 mm to 200 mm. The press-contact pressure (linear pressure) of
two metal foil machining rollers 1 is preferably, but not particularly limited to,
about 5 kN · cm to 20 kN · cm.
[0053] In this embodiment, the metal foil machining rollers 1 of the present invention are
used as two rollers forming a press-contact nip portion 6, but the configuration is
not limited thereto. For example, it is possible to employ a configuration in which
the metal foil machining roller 1 of the present invention is used as one of two rollers,
and a roller with a smooth surface without recessed portions on the surface is used
as the other roller. In this case, a metal foil in which protrusion portions are formed
on one surface in a thickness direction is obtained.
As described above, a metal foil 8 is passed through the press-contact nip portion
6 and the metal foil 8 is compressed, at which point a hermetically sealed space surrounded
by a recessed portion 1a and the surface of the metal foil 8 is formed. Air remains
in the hermetically sealed space. When the pressure force (press-contact pressure)
of the metal foil machining roller 1 against the metal foil 8 is within the above-mentioned
appropriate range, the hermetically sealed space is maintained while the metal foil
8 is machined, so a non-contact state is maintained between the bottom face of the
recessed portion 1a and the surface of the metal foil 8 with the remaining air interposed
therebetween.
[0054] The metal foil winding means 5 is, specifically, a metal foil winding roller. The
metal foil winding roller is axially supported by a supporting means (not shown) so
as to be capable of rotation around the axis. The metal foil winding roller is also
rotated by a drive means (not shown). The metal foil winding roller winds the metal
foil 2 with protrusion portions formed by the machining means 4 around the circumferential
surface of the metal foil winding roller while rotating.
The metal foil 2 with protrusion portions is manufactured by using the metal foil
machining apparatus 10 and pressure-molding a metal foil 8.
Examples
[0055] Hereinafter, the present invention will be described in detail with reference to
examples and comparative examples.
Example 1
[0056] A Nb:YAG laser was mounted onto a laser machining apparatus (available from Spectra
Physics KK.) as a laser oscillator. The intensity of laser light output from a machining
head was set to 23 µJ per instance of irradiation. Also, a condenser lens and a focal
length were adjusted so that the imaging magnification of the machining head was set
to 16 times. That is, the imaging size of the machining head would be 1/16 times the
size of the openings of a laser machining mask. The laser machining mask was obtained
by subjecting a stainless steel plate (SUS304) with a thickness of 0.3 mm, and dimensions
of 22 mm × 22 mm to electro-discharge machining so as to form laser-passing apertures
with an approximately rhombic shape. The diameter of the rhombic opening of the laser-passing
apertures (the length of the longer diagonal line) was 0.32 mm. The length of the
shorter diagonal line was 0.16 mm.
[0057] A forged steel roller (available from Daido Machinery Ltd., diameter: 50 mm, roller
width: 100 mm, Rockwell hardness in A scale of the forged steel: HRA 84.9, transverse
rupture strength of the forged steel: 4.0 GPa, forged steel composition (weight ratio):
carbon 1 %, silicon 0.24%, manganese 0.36%, chromium 1.46%, and the remaining ratio
of iron) was mounted between a roller rotating apparatus and a tailstock of the laser
machining apparatus, and the surface of the forged steel roller was irradiated with
laser light with an irradiation time of 50 nanoseconds and an irradiation interval
of 1 millisecond. After laser light irradiation, the laser light irradiated region
was moved in the longitudinal direction of the forged steel roller by 20 µm, or in
the circumferential direction by 29 µm, and laser light was directed thereto in the
same manner. Such movement in the circumferential direction was performed by rotating
the forged steel roller. After 5,400 recessed portions had been formed by moving the
laser light irradiated region in the circumferential direction, the laser light irradiated
region was moved in the longitudinal direction by 20 µm and rotated in the circumferential
direction by 14.5 µm and, then, an operation of forming 5,400 recessed portions in
the circumferential direction was repeated. A 90 mm region was machined by moving
in the roller width direction 4,500 times. In this manner, 24,300,000 recessed portions
were formed in a staggered arrangement and a metal foil machining roller of the present
invention was produced.
[0058] The opening shape of the formed recessed portions was an approximately rhombic shape,
and the opening diameter (the length of the longer diagonal line of the rhombic shape)
was 20 µm. The length of the shorter diagonal line of the rhombic shape was 10 µm.
The bottom face of the recessed portions had a dome shape, and the depth of the recessed
portions was about 12 µm. The pitch of the recessed portions in the longitudinal direction
(the width direction of the forged steel roller) was about 20 µm, and the pitch in
the transverse direction (the circumferential direction of the forged steel roller)
was about 29 µm.
[0059] Two such produced metal foil machining rollers were mounted onto a metal foil machining
apparatus 10. The pressure force of the press-contact nip portion of the metal foil
machining apparatus 10 was set to, in terms of linear pressure, about 14.7 kN · cm
(1500 kgt/cm), and a tough pitch copper foil with a width of 80 mm and a thickness
of 26 µm was allowed to pass through the press-contact nip portion and machined. In
the surface of the machined copper foil surface, protrusion portions corresponding
to the recessed portions of the metal foil machining rollers were formed. The average
height of ten protrusion portions was measured with a laser microscope (trade name:
VK-9500, available from Keyence Corporation) and found to be 7.0 µm. A 2000 m length
of the copper foil was machined by using 20 rollers, each roller being 100 m long.
As a result, the protrusion portions formed on the copper foil surface had approximately
the same shape and a height of 7.0 µm. The surface of the metal foil machining rollers
was observed with a laser microscope, as a result of which no occurrence of cracking
and chipping was observed.
Example 2
[0060] Metal foil machining rollers of the present invention were produced in the same manner
as in Example 1, except that a cemented carbide roller (available from Fuji Die Co.
Ltd., diameter: 50 mm, width: 100 mm, Rockwell hardness in A scale: HRA 90.0, transverse
rupture strength: 3.1 GPa, tungsten carbide particles and cobalt (binder) included)
was used.
A tough pitch copper foil with a width of 80 mm and a thickness of 26 µm was machined
in the same manner as in Example 1, except that two metal foil machining rollers obtained
above were mounted onto the metal foil machining apparatus 10, and the pressure at
the press-contact nip portion was changed from about 14.7 kN · cm (1500 kgf/cm) to
about 9.8 kN · cm (1000 kgf/cm). In the surface of the machined copper foil, protrusion
portions corresponding to the recessed portions of the metal foil machining rollers
were formed. The average height of ten protrusion portions measured with a laser microscope
(VK-9500) was 6.5 µm. A 1000 m length of the copper foil was machined by using 10
rollers, each roller being 100 m long. As a result, the protrusion portions formed
on the copper foil surface had an approximately uniform shape and a height of 6.7
µm. The surface of the metal foil machining rollers was observed with a laser microscope
after machining, as a result of which no occurrence of cracking and chipping was observed.
Subsequently, the copper foil was machined until 2000 m was machined in total. The
shape of protrusion portions formed on the copper foil surface was approximately the
same as that of the initial protrusion portions, and the protrusion portions had a
height of 6.5 µm. The surface of the metal foil machining rollers was observed with
a microscope, as a result of which some chipped portions in which tungsten carbide
particles had been lost were observed.
Example 3
[0061] Metal foil machining rollers of the present invention were produced in the same manner
as in Example 1, except that a cemented carbide roller (available from Fuji Die Co.
Ltd., diameter: 50 mm, width: 100 mm, Rockwell hardness in A scale: HRA 89.0, transverse
rupture strength: 3.3 GPa, tungsten carbide particles and cobalt (binder) included)
was used.
A tough pitch copper foil with a width of 80 mm and a thickness of 26 µm was machined
in the same manner as in Example 1, except that two metal foil machining rollers obtained
above were mounted onto the metal foil machining apparatus 10, and the pressure at
the press-contact nip portion was changed from about 14.7 kN · cm (1500 kgf/cm) to
about 9.8 kN · cm (1000 kgf/cm). In the surface of the machined copper foil, protrusion
portions corresponding to the recessed portions of the metal foil machining rollers
were formed. The average height of ten protrusion portions measured with a laser microscope
(VK-9500) was 6.3 µm. Furthermore, a 2000 m length of the copper foil was machined
by using 20 rollers, each roller being 100 m long. As a result, the shape of protrusion
portions formed on the copper foil surface was approximately the same as that of the
initial protrusion portions, and the average height of ten protrusion portions was
6.4 µm. The surface of the metal foil machining rollers after machining was observed
with a microscope, as a result of which no occurrence of cracking and chipping was
observed.
Example 4
[0062] Metal foil machining rollers of the present invention were produced in the same manner
as in Example 1, except that a forged steel roller (available from Daido Machinery
Ltd., diameter: 50 mm, width: 100 mm, Rockwell hardness in A scale: HRA 83.9, transverse
rupture strength: 5.5 GPa) was used. The composition of the forged steel was carbon
1.1%, silicon 0.22%, manganese 0.38%, chromium 1.76% and the remaining amount was
iron (weight ratio).
A tough pitch copper foil with a width of 80 mm and a thickness of 26 µm was machined
in the same manner as in Example 1, except that two metal foil machining rollers obtained
above were mounted onto the metal foil machining apparatus 10, and the pressure at
the press-contact nip portion was changed from about 9.8 kN · cm (1000 kgf/cm) to
about 19.6 kN · cm (2000 kgf/cm). In the surface of the machined copper foil, protrusion
portions corresponding to the recessed portions of the metal foil machining rollers
were formed. The average height of ten protrusion portions measured with a laser microscope
(VK-9500) was 5.8 µm. Furthermore, a 2000 m length of the copper foil was machined
by using 20 rollers, each roller being 100 m long. As a result, the shape of protrusion
portions formed on the copper foil surface was approximately the same as that of the
initial protrusion portions, and the average height of ten protrusion portions was
5.7 µm. The surface of the metal foil machining rollers after machining was observed
with a microscope, as a result of which no occurrence of cracking and chipping was
observed.
Example 5
[0063] Metal foil machining rollers of the present invention were produced in the same manner
as in Example 1, except that a die steel roller (available from Daido Machinery Ltd.,
diameter 50 mm, roller width: 100 mm, Rockwell hardness in A scale: HRA 81.2, transverse
rupture strength: 5.8 GPa) was used. The composition of die steel was carbon 1.4%,
silicon 0.4%, manganese 0.6%, chromium 11.2%, molybdenum 0.9%, vanadium 0.3% and the
remaining amount was iron.
A tough pitch copper foil with a width of 80 mm and a thickness of 26 µm was machined
in the same manner as in Example 4, except that two metal foil machining rollers obtained
above were mounted onto the metal foil machining apparatus 10. In the surface of the
machined copper foil, protrusion portions corresponding to the recessed portions of
the metal foil machining rollers were formed. The average height of ten protrusion
portions measured with a laser microscope (VK-9500) was 4.9 µm. Furthermore, a 2000
m length of the copper foil was machined by using 20 rollers, each roller being 100
m long. As a result, the shape of protrusion portions formed on the copper foil surface
was approximately the same as that of the initial protrusion portions, and the average
height of ten protrusion portions was 5.0 µm. The surface of the metal foil machining
rollers after machining was observed with a microscope, as a result of which no occurrence
of cracking and chipping was observed.
Comparative Example 1
[0064] Metal foil machining rollers were produced in the same manner as in Example 1, except
that a cemented carbide roller (available from Fuji Die Co., Ltd., diameter 50 mm,
width: 100 mm, Rockwell hardness in A scale: HRA 94.0, transverse rupture strength:
1.5 GPa, tungsten carbide particles and cobalt (binder) included) was used. In the
recessed portions in the circumferential surface of the metal foil machining rollers,
non-uniform opening shapes and opening diameters were observed. As to the opening
shape in particular, although openings with an approximately rhombic shape were observed,
there were a large number of openings with an elliptic shape.
[0065] A tough pitch copper foil with a width of 80 mm and a thickness of 26 µm was machined
in the same manner as in Example 1, except that two metal foil machining rollers obtained
above were mounted onto the metal foil machining apparatus 10, and the pressure at
the press-contact nip portion was changed from about 14.7 kN · cm (1500 kgf/cm) to
about 9.8 kN · cm (1000 kgf/cm). In the surface of the machined copper foil, protrusion
portions corresponding to the recessed portions of the metal foil machining rollers
were formed. That is, protrusion portions of non-uniform shape were formed. The average
height often protrusion portions measured with a laser microscope (VK-9500) was 7.2
µm. Furthermore, a 1000 m length of the copper foil was machined by using 10 rollers,
each roller being 100 m long. As a result, among the protrusion portions formed on
the copper foil surface, a large number of deformed protrusion portions were observed.
The average height of ten protrusion portions was 6.2 µm. The surface of the metal
foil machining rollers after machining was observed with a microscope, as a result
of which deformed recessed portions and a ruined roller surface due to loss by chipping
of tungsten carbide (WC) particles were observed.
Comparative Example 2
[0066] Metal foil machining rollers of the present invention were produced in the same manner
as in Example 1, except that a die steel roller (available from Daido Machinery Ltd.,
diameter 50 mm, width: 100 mm, Rockwell hardness in A scale: HRA 78.0, transverse
rupture strength: 8 GPa) was used. The composition of die steel was carbon 0.4%, silicon
1.1 %, manganese 0.5%, chromium 5.0%, molybdenum 1.0%, vanadium 1.0% and the remaining
amount was iron. In the recessed portions in the circumferential surface of the metal
foil machining rollers, non-uniform opening shapes and opening diameters were observed.
As to the opening shape in particular, although openings with an approximately rhombic
shape were observed, there were a large number of openings with an elliptic shape.
[0067] A tough pitch copper foil with a width of 80 mm and a thickness of 26 µm was machined
in the same manner as in Example 1, except that two metal foil machining rollers obtained
above were mounted onto the metal foil machining apparatus 10, and the pressure at
the press-contact nip portion was set to about 9.8 kN · cm (1000 kgf/cm), about 14.7
kN · cm (1500 kgf/cm) or about 19.6 kN · cm (2000 kgf/cm). In the surface of the machined
copper foils, protrusion portions corresponding to the recessed portions of the metal
foil machining rollers were formed. That is, protrusion portions of non-uniform shape
were formed. The average height of ten protrusion portions measured with a laser microscope
(VK-9500) was 2.2 µm (about 9.8 kN · cm), 2.3 µm (about 14.7 kN · cm) and 2.3 µm (about
19.6 kN · cm), from which it was found that the height of protrusion portions does
not increase even when the pressure at the press-contact nip portion is increased.
This is presumably because the metal foil machining rollers are flattened as the pressure
is increased, increasing the contact area between the roller surface and the copper
foil, so the load actually applied to the copper foil does not increase.
[0068] From the results of Examples 1 to 5 and Comparative Examples 1 and 2, it is dear
that, by using the metal foil machining roller of the present invention, a unit of
several tens of millions of protrusion portions with an approximately uniform shape
and a height of 4 µm or more can be formed over a copper foil with a length of 1000
m or more in a stable manner. The metal foil machining roller of the present invention
is a roller containing a metal material with a Rockwell hardness in A scale of HRA
81.2 to 90.0 and a transverse rupture strength of 3 GPa to 6 Gpa in which recessed
portions are formed.
With a metal foil machining roller containing a metal material with a Rockwell hardness
in A scale of HRA 81.2 or less or a transverse rupture strength of 3 Gpa or less,
it is dear that the roller is flattened, and protrusion portions with a height of
3 µm or more cannot be formed in a copper foil even when the pressure at the press-contact
nip portion is increased. In addition, with a metal foil machining roller containing
a metal material with a Rockwell hardness in A scale of HRA 90.0 or more or a transverse
rupture strength 6 Gpa or more, recessed portions are deformed due to the occurrence
of chipping and the roller surface is ruined, from which it is found that stable machining
is not possible.
Industrial Applicability
[0069] The metal foil machining roller of the present invention can be preferably used to
form protrusion portions on the surface of a variety of metal foils. In particular,
because the metal foil machining roller of the present invention exhibits a high level
of durability, it is possible to efficiently manufacture a metal foil with protrusion
portions with a very low defect rate even when mass-produced, so the present invention
is industrially advantageous.