U.S. patent application number 10/512413 was filed with the patent office on 2005-10-20 for linearly easy-to-rupture thermoplastic resin film, and method and device for manufacturing the resin film.
Invention is credited to Kagawa, Seiji, Kagawa, Yoichiro.
Application Number | 20050233102 10/512413 |
Document ID | / |
Family ID | 29267549 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050233102 |
Kind Code |
A1 |
Kagawa, Seiji ; et
al. |
October 20, 2005 |
Linearly easy-to-rupture thermoplastic resin film, and method and
device for manufacturing the resin film
Abstract
A method for forming substantially parallel linear scratches on
a thermoplastic resin film, comprising bringing the film into
sliding contact with a means having a lot of fine projections for
forming linear scratches, and pressing the film onto the
linear-scratch-forming means from the opposite side of the
linear-scratch-forming means by a film-pressing means, in a region
in which the film is in sliding contact with the
linear-scratch-forming means.
Inventors: |
Kagawa, Seiji; (Saitama-ken,
JP) ; Kagawa, Yoichiro; (Saitama-ken, JP) |
Correspondence
Address: |
BROWDY AND NEIMARK, P.L.L.C.
624 NINTH STREET, NW
SUITE 300
WASHINGTON
DC
20001-5303
US
|
Family ID: |
29267549 |
Appl. No.: |
10/512413 |
Filed: |
October 25, 2004 |
PCT Filed: |
April 25, 2003 |
PCT NO: |
PCT/JP03/05354 |
Current U.S.
Class: |
428/43 ;
428/156 |
Current CPC
Class: |
B30B 3/005 20130101;
B29C 59/04 20130101; B29C 59/007 20130101; Y10T 428/24479 20150115;
B29C 2059/027 20130101; Y10T 428/15 20150115; B29L 2007/001
20130101 |
Class at
Publication: |
428/043 ;
428/156 |
International
Class: |
B65D 065/28 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 2002 |
JP |
2002-125045 |
Claims
1. An easy-to-straight-tear thermoplastic resin film having
substantially parallel linear scratches formed on at least one
entire surface, whereby it is easily torn substantially straight
from any point along said linear scratches.
2. The easy-to-straight-tear thermoplastic resin film according to
claim 1, wherein the depth of said linear scratches is 1 to 40% of
the thickness of said film.
3. The easy-to-straight-tear thermoplastic resin film according to
claim 1, wherein the depth of said linear scratches is 0.1 to 10
.mu.m.
4. The easy-to-straight-tear thermoplastic resin film according to
claim 1, wherein the width of said linear scratches is 0.1 to 10
.mu.m.
5. The easy-to-straight-tear thermoplastic resin film according to
claim 1, wherein intervals of said linear scratches are 10 to 200
.mu.m.
6. The easy-to-straight-tear thermoplastic resin film according to
claim 1, further having a multiplicity of uniformly located fine
penetrating and/or non-penetrating pores.
7. The easy-to-straight-tear thermoplastic resin film according to
claim 1, wherein said film is a single-layer film or a laminate
film.
8. The easy-to-straight-tear thermoplastic resin film according to
claim 7, wherein said laminate film comprises at least one film
layer having said linear scratches, and a sealant film layer.
9-10. (canceled)
11. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein said fine particles have
a Mohs' hardness of 5 or more.
12. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 11, wherein said fine particles are
fine diamond particles.
13. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein said pressing is by a
film-pressing means comprising an air-blowing means.
14. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 13, wherein the pressure of an
airflow blown onto said film is 0.05 to 5 kgf/cm.sup.2.
15. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 13, wherein air is blown from a
blower or a nozzle.
16. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein said pressing is by a
film-pressing means comprising a brush brought into sliding contact
with said film.
17. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 16, wherein said brush have hairs
having a recovery-from-bending ratio of 70% or more, a diameter of
0.1 to 1.8 mm and a length of 1 to 8 cm, and a density of 100 to
500/cm.sup.2 on the brush-sliding surface.
18. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 16, wherein said brush is in sliding
contact with said film at a pressure of 0.01 to 5 kg/cm.sup.2 on
said brush-sliding surface.
19. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein said roll has an outer
diameter of 2 to 20 cm.
20. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein a tension of 0.01 to 5
kgf/cm width is applied to said film in sliding contact with said
roll or plate.
21. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein the moving speed of said
film is 10 to 500 m/minute.
22. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein linear scratches are
formed in the moving direction of said film with the position of
said roll or plate being fixed in the width direction of said
film.
23. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 22, wherein the rotation axis of said
roll is parallel with the width direction of said film, and wherein
said roll has a lower peripheral speed than the moving speed of
said film and an opposite rotation direction to the moving
direction of said film.
24. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 23, wherein the peripheral speed of
said roll is 1 to 50 m/minute.
25. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein an endless pattern belt
comprising small rolls or plates having a large number of hard fine
particles on the surfaces in parallel, which is longer than the
width of the film, is arranged in the width direction of said film,
such that each small roll or plate can be in sliding contact with
said film; and wherein said endless pattern belt is rotated to
continuously bring said small rolls or plates into sliding contact
with said film, whereby said linear scratches are formed on said
film slantingly to its moving direction.
26. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 25, wherein said pressing is by a
film-pressing means comprising an endless brush comprising a large
number of hairs on an endless belt, which is longer than the width
of the film; wherein said endless brush is disposed in parallel
with said endless pattern belt via said film; and wherein said
endless brush is rotated to continuously bring said hairs into
sliding contact with said film, such that the direction of said
hairs slidably moving on said film is opposite to the direction of
said small rolls or plates slidably moving on said film.
27. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein at least two rolls or
plates each having an axial direction in the width direction of
said film are arranged in parallel in the moving direction of said
film; wherein vertically movable guide means for independently
moving said rolls or plates in the width direction of said film is
provided; wherein each roll or plate is slidably movable on said
film from one end to the other; wherein said rolls or plates are
repeatedly subjected to a cycle of moving away from said film after
reaching the other end and returning to the original position; and
wherein the movement of said rolls or plates is controlled such
that at least any one of rolls or plates is always in sliding
contact with said film over its entire width, whereby said linear
scratches are formed on said film slantingly to its moving
direction.
28. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 27, wherein said rolls are rotated at
a lower peripheral speed than the moving speed of said film in an
opposite direction to the moving direction of said film.
29. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein at least two roll trains
each comprising small rolls having a large number of fine hard
particles on the surface, which are mounted to supports in
parallel, are arranged in the width direction of said film, said
roll trains independently moving along vertically movable guide
means in the width direction of said film; wherein each roll train
slidably moves on said film from one end to the other, and is
repeatedly subjected to a cycle of moving away from said film after
reaching the other end and returning to the original position,
during which the movement of said roll trains is controlled such
that at least any one of said roll trains is always in sliding
contact with said film over its entire width, whereby said linear
scratches are formed on said film slantingly to its moving
direction.
30. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 29, wherein the axial direction of
each small roll in said roll trains is substantially in alignment
with the longitudinal direction of said film.
31. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein an endless pattern belt
comprising small rolls or plates having a large number of fine hard
particles on the surfaces in parallel, which are longer than the
width of the film, is arranged slantingly to its moving direction
such that each small roll or plate can be in sliding contact with
said film on said film; and wherein said endless pattern belt is
rotated in an upstream direction of said film to continuously bring
said small rolls or plates into sliding contact with said film,
whereby said linear scratches are formed on said film substantially
in its width direction.
32. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 31, wherein said film-pressing means
is an endless brush comprising a large number of hairs on an
endless belt, which is longer than the width of the film; wherein
said endless brush is arranged in parallel with said endless
pattern belt via said film; and wherein said endless brush is
rotated such that the direction of said hairs slidably moving on
said film is opposite to the direction of said small rolls or
plates slidably moving on said film, thereby continuously bringing
said hairs into sliding contact with said film.
33. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein at least two rolls each
having an axial direction slanting to the moving direction of said
film and vertically movable guide means for independently moving
said rolls are arranged; wherein each roll slidably moves on said
film from one end to the other, and is repeatedly subjected to a
cycle of moving away from said film after reaching the other end
and returning to the original position, during which the movement
of said rolls is controlled such that at least any one of said
rolls is always in sliding contact with said film over its entire
width, whereby said linear scratches are formed on said film
substantially in its width direction.
34. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 33, wherein each roll is rotated at a
lower peripheral speed than the moving speed of said film in an
opposite direction to the moving direction of said film.
35. The method for producing an easy-to-straight-tear thermoplastic
resin film according to claim 64, wherein at least two roll trains
each comprising small rolls having a large number of fine hard
particles on the surfaces, which are mounted to supports in
parallel, are arranged on said film slantingly to its moving
direction; wherein vertically movable guide means for independently
moving said roll trains in the width direction of said film
are-arranged; wherein each roll train slidably moves on said film
from one end to the other, and is repeatedly subjected to a cycle
of moving away from said film after reaching the other end and
returning to the original position, during which the movement of
said roll trains is controlled such that at least any one of said
roll trains is always in sliding contact with said film over its
entire width, whereby said linear scratches are formed on said film
substantially in its width direction.
36-37. (canceled)
38. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, wherein said fine
particles have a Mohs' hardness of 5 or more.
39. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 38, wherein said fine
particles are fine diamond particles.
40. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, wherein said
film-pressing means is an air-blowing means.
41. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 40, wherein the
pressure of an airflow blown onto said film is 0.05 to 5
kgf/cm.sup.2.
42. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 40, wherein said
air-blowing means is a blower or a nozzle.
43. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, wherein said
film-pressing means is a brush brought into sliding contact with
said film.
44. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 43, wherein said brush
has hairs having a recovery-from-bending ratio of 70% or more, a
diameter of 0.1 to 1.8 mm and a length of 1 to 8 cm, and a density
of 100 to 5 kg/cm.sup.2 on the brush-sliding surface.
45. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 43, wherein said brush
is in sliding contact with said film at a pressure of 0.01 to 5
kg/cm.sup.2 on said brush-sliding surface.
46. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, wherein said roll
has an outer diameter of 2 to 20 cm.
47. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, comprising a means
for applying a tension of 0.01 to 5 kgf/cm width to said film in
sliding contact with said linear-scratch-forming means.
48. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, comprising means to
move the film at 10 to 500 m/minute.
49. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, means to form
linear scratches in the moving direction of said film with the
position of said rolls or plates fixed in the width direction of
the film.
50. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 49, wherein the
rotation axis of said roll is parallel with the width direction of
said film; and wherein said roll is rotated at a lower peripheral
speed than the moving speed of the film in an opposite direction to
the moving direction of the film.
51. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 50, wherein the
peripheral speed of said roll is 1 to 50 m/minute.
52. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, comprising an
endless pattern belt comprising small rolls or plates having a
large number of fine hard particles on the surfaces in parallel,
which are longer than the width of the film; wherein each small
roll or plate is arranged in the width direction of said film such
that it is in sliding contact with said film; and wherein said
endless pattern belt is rotated so that said small rolls or plates
are continuously brought into sliding contact with said film,
whereby said linear scratches are formed on said film slantingly to
its moving direction.
53. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 52, wherein said
film-pressing means is an endless brush comprising a large number
of hairs on an endless belt, which is longer than the width of the
film; wherein said endless brush is arranged in parallel with said
endless pattern belt via said film; and wherein said endless brush
is rotated such that the direction of said hairs slidably moving on
said film is opposite to the direction of said small rolls or
plates slidably moving on said film, whereby said hairs are
continuously in sliding contact with said film.
54. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, comprising at least
two rolls or plates each having an axial direction in the width
direction of said film, which are arranged in parallel with the
moving direction of said film; and vertically movable guide means
for independently moving said rolls or plates in the width
direction of said film; wherein each roll or plate slidably moves
on said film from one end to the other, and is repeatedly subjected
to a cycle of moving away from said film after reaching the other
end and returning to the original position, during which the
movement of said rolls or plates is controlled such that at least
any one of rolls or plates is always in sliding contact with said
film over its entire width, whereby said linear scratches are
formed on said film slantingly to its moving direction.
55. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 54, wherein said rolls
are rotated at a lower peripheral speed than the moving speed of
said film in an opposite direction to the moving direction of said
film.
56. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, comprising at least
two roll trains in the width direction of said film, each of which
comprises small rolls having a large number of fine hard particles
on the surfaces and mounted to supports in parallel; and vertically
movable guide means for independently moving said roll trains in
the width direction of said film; wherein each roll train slidably
moves on said film from one end to the other, and is repeatedly
subjected to a cycle of moving away from said film after reaching
the other end and returning to the original position, during which
the movement of said roll train is controlled such that at least
any one of said roll trains is always in sliding contact with said
film over its entire width, whereby said linear scratches are
formed on said film slantingly to its moving direction.
57. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 56, wherein the axial
direction of each small roll in said roll train is substantially in
alignment with the longitudinal direction of said film.
58. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, comprising an
endless pattern belt comprising small rolls or plates having a
large number of fine hard particles on the surface in parallel,
which are longer than the width of the film; wherein each small
roll or plate is arranged slantingly to the moving direction of
said film such that it can be in sliding contact with said film;
and wherein said endless pattern belt is rotated in an upstream
direction of said film such that said small rolls or plates are
continuously in sliding contact with said film, whereby said linear
scratches are formed on said film substantially in its width
direction.
59. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 58, wherein said
film-pressing means is an endless brush comprising a large number
of hairs on an endless belt, which is longer than the width of the
film; wherein said endless brush is arranged in parallel with said
endless pattern belt via said film; and wherein said endless brush
is rotated such that the direction of said hairs slidably moving on
said film is opposite to the direction of said small rolls or
plates slidably moving on said film, whereby said hairs are
continuously in sliding contact with said film.
60. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, comprising at least
two rolls each having an axial direction slanting to the moving
direction of said film, vertically movable guide means for
independently moving said rolls, and a mechanism for controlling
said support member, wherein each roll slidably moves on said film
from one end to the other, and is repeatedly subjected to a cycle
of moving away from said film after reaching the other end and
returning to the original position, during which the movement of E
said roll is controlled such that at least any one of said rolls is
always in sliding contact with said film over its entire width,
whereby said linear scratches are formed on said film substantially
in its width direction.
61. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 60, wherein each roll
is rotated at a lower peripheral speed than the moving speed of
said film in an opposite direction to the moving direction of said
film.
62. The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to claim 65, comprising at least
two roll trains each comprising small rolls having a large number
of fine hard particles on the surfaces, which are mounted to
supports in parallel; wherein said roll trains are arranged
slantingly to the moving direction of said film; wherein said
apparatus comprises vertically movable guide means for
independently moving said roll trains in the width direction of
said film; and wherein each roll train slidably moves on said film
from one end to the other, and is repeatedly subjected to a cycle
of moving away from said film after reaching the other end and
returning to the original position, during which the movement of
said roll trains is controlled such that at least any one of said
roll trains is always in sliding contact with said film over its
entire width, whereby said linear scratches are formed on said film
substantially in its width direction.
63. The easy-to-straight-tear thermoplastic resin film according to
claim 6, wherein said fine pores have an average opening diameter
of 0.5 to 100 .mu.m.
64. A method for forming substantially parallel linear scratches on
a thermoplastic resin film, comprising bringing said film into
sliding contact with a roll or plate having a multiplicity of hard
fine particles on its surface, and pressing said film onto said
roll or plate.
65. An apparatus forming substantially parallel linear scratches on
a thermoplastic resin film, comprising (a) a means for moving said
film, (b) a roll or a plate having a multiplicity of fine hard
particles on its surface, and (c) a film-pressing means disposed
near said roll or plate, the said film-pressing means being adapted
to press the film onto the roll or plate while the film is brought
into sliding contact with said roll or plate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a thermoplastic resin film
easy to straight tear in one direction, and a method and apparatus
for producing such a film.
BACKGROUND OF THE INVENTION
[0002] In recent progress of barrier-free items, easy opening is
considered to be an important function for wrapping films. Typical
methods for making the wrapping bags easily openable include a
method of providing the wrapping bags with cutting-start points
such as V-shaped notches, etc. in their edge portions (heat-sealing
portions), and methods needing no cutting-start points such as a
magic cut method, a fancy cut method and a method of providing the
wrapping bags with fine pores.
[0003] The magic cut and the fancy cut comprise providing the
wrapping bags with fine scratches in their edge portions and
bending portions in place of notches. However, even with the magic
cut or the fancy cut, it has been difficult to open the wrapping
bags straight in directions not aligned with the molecular
orientation of plastic films. Further, when cut lines progress in
conventional easy-to-open wrapping bags beyond their edge portions
to regions in which contents are included, the cut lines are likely
to unintentionally go toward the regions having contents even
though plastic films for the bags have molecular orientation,
resulting in falling, dropping or scattering of the contents.
[0004] Working for making a plastic film porous (porous working) is
to form a lot of fine penetrating or non-penetrating pores on the
entire surface of the film. Thus, wrapping bags of films subjected
to the porous working can be opened from any position without
notches regardless of the directions of the films. Accordingly,
even if an opening operation is temporarily stopped, the bags can
be opened to the end. However, because films for wrapping food,
etc. are required to have moistureproofness, the film subjected to
the porous working should be laminated as an outermost film.
[0005] JP 2002-80705 A discloses an easy-to-tear, biaxially
stretched polyester film, which can be easily torn straight.
However, when used for applications of wrapping films requiring
moistureproofness, the biaxially stretched polyester films should
not be used alone but laminated with polyolefin films, etc., to
provide wrapping films.
[0006] Vapor-deposited transparent films are widely used as
gas-barrier films to wrap food, medicine, high-precision electronic
parts, etc. However, because the vapor-deposited transparent films
are composed of thermoplastic resin films vapor-deposited with
metals, metal oxides, etc. and coated with resins, they have
insufficient easy-to-tear characteristics even though the plastic
base films have easy-to-tear characteristics.
[0007] For instance, cut tapes are attached to wrapping films for
triangular rice balls sold at convenience stores and the like to
enable cutting in a strip shape. To adhere the cut tapes to the
films, transfer methods are usually used. As a result, the films
cannot be moved at a high speed in the production of the wrapping
films, resulting in low productivity and high production cost.
OBJECTS OF THE INVENTION
[0008] Accordingly, an object of the present invention is to
provide an inexpensive thermoplastic resin film easily torn
straight in one direction regardless of the orientation of the
original film, free from the above-mentioned defects of the
conventional films.
[0009] Another object of the present invention is to provide a
method for producing such a film.
[0010] A further object of the present invention is to provide an
apparatus for producing such a film.
SUMMARY OF THE INVENTION
[0011] As a result of intensive research in view of the above
objects, the inventors have found that a thermoplastic resin film
having substantially parallel linear scratches at least on one
surface has easy-to-straight-tear characteristics, and that the
linear scratches are formed by a linear-scratch-forming means such
as a roll, a plate, etc. with a lot of fine projections on the
surface, which is in sliding contact with the film at a proper
pressure.
[0012] Thus, the easy-to-straight-tear thermoplastic resin film of
the present invention has substantially parallel linear scratches
formed at least on one surface, so that it is easily torn straight
from any point along the linear scratches.
[0013] The depth of the linear scratches is preferably 1 to 40% of
the thickness of the easy-to-straight-tear thermoplastic resin
film. It is preferable that the depth of the linear scratches is
0.1 to 10 .mu.m, that the width of the linear scratches is 0.1 to
10 .mu.m, and that the intervals of the linear scratches are 10 to
200 .mu.m.
[0014] The easy-to-straight-tear thermoplastic resin film of the
present invention may further have a lot of fine penetrating and/or
non-penetrating pores uniformly. The easy-to-straight-tear
thermoplastic resin film of the present invention may be a
single-layer film or a laminate film. The laminate film preferably
has at least one film layer having the linear scratches, and a
sealant film layer.
[0015] The production method of the easy-to-straight-tear
thermoplastic resin film of the present invention comprises
bringing the film into sliding contact with a means having a lot of
fine projections for forming linear scratches, and pressing the
film onto the linear-scratch-forming means from the opposite side
of the linear-scratch-forming means by a film-pressing means, in a
region in which the film is in sliding contact with the
linear-scratch-forming means, whereby substantially parallel linear
scratches are formed on the film.
[0016] A roll or plate having a lot of hard fine particles on its
surface is preferably used as the linear-scratch-forming means. The
fine particles are preferably particles having a Mohs' hardness of
5 or more, particularly fine diamond particles.
[0017] In one preferred embodiment of the present invention, the
film-pressing means is an air-blowing means. Air blowing makes it
possible to apply a substantially uniform pressure onto the film
surface in sliding contact with the linear-scratch-forming means.
The pressure of an airflow blown onto the film is preferably 0.05
to 5 kgf/cm.sup.2. Preferable as an air-blowing means is a blower
or a nozzle.
[0018] In another preferred embodiment of the present invention,
the film-pressing means is a brush brought into sliding contact
with the film. The brush preferably has hairs having a
recovery-from-bending ratio of 70% or more, a diameter of 0.1 to
1.8 mm, and a length of 1 to 8 cm. The brush hairs brought into
sliding contact with the film have a density of 100 to 500/cm.sup.2
on the brush-sliding surface. The brush is preferably in sliding
contact with the film at a pressure of 0.01 to 5 kgf/cm.sup.2 on
the brush-sliding surface.
[0019] The outer diameter of the roll is preferably 2 to 20 cm. A
tension of 0.01 to 5 kgf/cm (width) is preferably applied to the
film in sliding contact with the linear-scratch-forming means. The
moving speed of the film is preferably 10 to 500 m/minute.
[0020] In a further preferred embodiment of the present invention,
the linear scratches are formed in the film-moving direction by the
roll or plate, whose position is fixed with respect to the width
direction of the film. It is preferable that the rotation axis of
the roll is parallel with the width direction of the film, and that
the roll is rotated at a lower peripheral speed than the moving
speed of the film in an opposite direction to the moving direction
of the film. The peripheral speed of the roll is preferably 1 to 50
m/minute. The roll is preferably longer that the film width to have
contact with the film over its entire width.
[0021] In a still further preferred embodiment of the present
invention, an endless pattern belt longer than the width of the
film comprises small rolls or plates having a lot of hard fine
particles on the surface in parallel. The endless pattern belt is
arranged in the width direction of the film such that each small
roll or plate can be in sliding contact with the film. The endless
pattern belt is rotated such that the small rolls or plates are in
sliding contact with the continuous film to form linear scratches
on the film slantingly to the moving direction of the film. The
film-pressing means is an endless brush comprising a large number
of hairs on an endless belt, which is longer than the width of the
film; the endless brush being disposed in parallel with the endless
pattern belt via the film. The endless brush is preferably rotated
such that the direction of the hairs moving in sliding contact with
the film is opposite to the direction of the endless pattern belt
moving in sliding contact with the film, whereby the brush hairs
are continuously in sliding contact with the film.
[0022] In a still further preferred embodiment of the present
invention, at least two rolls or plates each having an axial
direction in the width direction of the film are arranged in the
moving direction of the film, and vertically movable guide means
for independently moving the rolls or plates are arranged in the
width direction of the film, each roll or plate slidably moving on
the film from one end to the other, and being repeatedly subjected
to a cycle of moving away from the film after reaching the other
end and returning to the original position, during which the
movement of the rolls or plates is controlled such that at least
any one of rolls or plates is always in sliding contact with the
film over its entire width, whereby linear scratches are formed on
the film slantingly to its moving direction. The rolls are
preferably rotated at a lower peripheral speed than the moving
speed of the film in an opposite direction to the moving direction
of the film.
[0023] In a still further preferred embodiment of the present
invention, at least two roll trains each comprising small rolls
having a large number of fine hard particles on the surfaces, which
are mounted to supports in parallel, are arranged in the width
direction of the film; and vertically movable guide means for
independently moving the roll trains are arranged in the width
direction of the film; each roll train slidably moving on the film
from one end to the other, and being repeatedly subjected to a
cycle of moving away from the film after reaching the other end and
returning to the original position, during which the movement of
the roll trains is controlled such that at least any one of the
roll trains is always in sliding contact with the film over its
entire width, whereby linear scratches are formed on the film
slantingly to its moving direction. The axial direction of each
small roll in the roll train is preferably substantially in
alignment with the longitudinal direction of the film.
[0024] In a still further preferred embodiment of the present
invention, an endless pattern belt comprising small rolls or plates
having a large number of fine hard particles on the surface in
parallel, which are longer than the width of the film, is arranged
slantingly to its moving direction such that each small roll or
plate can be in sliding contact with the film on the film, and the
endless pattern belt is rotated in an upstream direction of the
film to continuously bring the small rolls or plates into sliding
contact with the film, whereby the linear scratches are formed on
the film substantially in its width direction. The film-pressing
means is an endless brush comprising a large number of hairs on an
endless belt, which is longer than the width of the film, the
endless brush being arranged in parallel with the endless pattern
belt via the film, and the endless brush being rotated such that
the direction of the hairs slidably moving on the film is in
opposite to the direction of the endless pattern belt slidably
moving on the film, thereby continuously bringing the hairs into
sliding contact with the film.
[0025] In a still further preferred embodiment of the present
invention, at least two rolls each having an axial direction
slanting to the moving direction of the film, and vertically
movable guide means for independently moving the rolls are
arranged, each roll slidably moving on the film from one end to the
other, and being repeatedly subjected to a cycle of moving away
from the film after reaching the other end and returning to the
original position, during which the movement of the roll is
controlled such that at least any one of the rolls is always in
sliding contact with the film over its entire width, whereby the
linear scratches are formed on the film substantially in its width
direction. Each roll is preferably rotated at a lower peripheral
speed than the moving speed of the film in an opposite direction to
the moving direction of the film.
[0026] In a still further preferred embodiment of the present
invention, at least two roll trains each comprising small rolls
having a large number of fine hard particles on the surfaces, which
are mounted to supports in parallel, are arranged slantingly to the
moving direction of the film; and vertically movable guide means
for independently moving the roll trains are arranged in the width
direction of the film; each roll train slidably moving on the film
from one end to the other, and being repeatedly subjected to a
cycle of moving away from the film after reaching the other end and
returning to the original position, during which the movement of
the roll trains is controlled such that at least any one of the
roll trains is always in sliding contact with the film over its
entire width, whereby the linear scratches are formed on the film
substantially in its width direction.
[0027] The apparatus for producing an easy-to-straight-tear
thermoplastic resin film according to the present invention
comprises (a) a means for moving a thermoplastic resin film, (b) a
linear-scratch-forming means having a lot of fine projections,
which is brought into sliding contact with the film to form
substantially parallel linear scratches, and (c) a means for
pressing the film from the opposite side of the
linear-scratch-forming means in a region in which the film is in
sliding contact with the linear-scratch-forming means.
[0028] The linear-scratch-forming means is preferably a roll or a
plate having a lot of hard fine particles on the surface. The fine
particles are preferably particles having a Mohs' hardness of 5 or
more, particularly fine diamond particles.
[0029] In one preferred embodiment of the present invention, the
film-pressing means is an air-blowing means. Preferable as an
air-blowing means is a blower or a nozzle. The pressure of an
airflow blown onto the film is preferably 0.05 to 5
kgf/cm.sup.2.
[0030] In another preferred embodiment of the present invention,
the film-pressing means is a brush brought into sliding contact
with the film. The brush preferably has hairs having a
recovery-from-bending ratio of 70% or more, a diameter of 0.1 to
1.8 mm, and a length of 1 to 8 cm. The brush hairs are brought into
sliding contact with the film at a density of 100 to 500/cm.sup.2
on the brush-sliding surface. The brush is preferably in sliding
contact with the film at a pressure of 0.01 to 5 kgf/cm.sup.2 on
the brush-sliding surface.
[0031] The outer diameter of the roll is preferably 2 to 20 cm. A
tension of 0.01 to 5 kgf/cm (width) is preferably applied to the
film in sliding contact with the linear-scratch-forming means. The
moving speed of the film is preferably 10 to 500 m/minute.
[0032] In a further preferred embodiment of the present invention,
the linear scratches are formed in the film-moving direction by a
roll or plate, whose position is fixed with respect to the width
direction of the film. It is preferable that the rotation axis of
the roll is parallel with the width direction of the film, and that
the roll is rotated at a lower peripheral speed than the moving
speed of the film in an opposite direction to the moving direction
of the film. The peripheral speed of the roll is preferably 1 to 50
m/minute.
[0033] In a still further preferred embodiment of the present
invention, the linear-scratch-forming means is an endless pattern
belt comprising small rolls or plates having a large number of fine
hard particles on the surface in parallel, which are longer than
the width of the film; each small roll or plate is arranged in the
width direction of the film such that it can be in sliding contact
with the film; and the endless pattern belt is rotated so that the
small rolls or plates are continuously brought into sliding contact
with the film, whereby the linear scratches are formed on the film
slantingly to its moving direction. The film-pressing means is an
endless brush comprising a large number of hairs on an endless
belt, which is longer than the width of the film; the endless brush
being arranged in parallel with the endless pattern belt via the
film; and the endless brush being rotated such that the direction
of the hairs slidably moving on the film is opposite to the
direction of the small rolls or plates slidably moving on the film,
whereby the hairs are continuously in sliding contact with the
film.
[0034] In a still further preferred embodiment of the present
invention, the apparatus comprises at least two rolls or plates
each having an axial direction in the width direction of the film,
which are arranged in parallel with the moving direction of the
film; and vertically movable guide means for independently moving
the rolls or plates in the width direction of the film; each roll
or plate slidably moving on the film from one end to the other, and
being repeatedly subjected to a cycle of moving away from the film
after reaching the other end and returning to the original
position, during which the movement of the rolls or plates is
controlled such that at least any one of rolls or plates is always
in sliding contact with the film over its entire width, whereby the
linear scratches are formed on the film slantingly to its moving
direction. The rolls are preferably rotated at a lower peripheral
speed than the moving speed of the film in an opposite direction to
the moving direction of the film.
[0035] In a still further preferred embodiment of the present
invention, the apparatus comprises at least two roll trains in the
width direction of the film, each of which comprises small rolls
having a large number of fine hard particles on the surface and
mounted to supports in parallel; and vertically movable guide means
for independently moving the roll trains in the width direction of
the film; each roll train slidably moving on the film from one end
to the other, and being repeatedly subjected to a cycle of moving
away from the film after reaching the other end and returning to
the original position, during which the movement of the roll train
is controlled such that at least any one of the roll trains is
always in sliding contact with the film over its entire width,
whereby the linear scratches are formed on the film slantingly to
its moving direction. The axial direction of each small roll in the
roll train is preferably substantially in alignment with the
longitudinal direction of the film.
[0036] In a still further preferred embodiment of the present
invention, the linear-scratch-forming means is an endless pattern
belt comprising small rolls or plates having a large number of fine
hard particles on the surface in parallel, which are longer than
the width of the film; each small roll or plate being arranged
slantingly to the moving direction of the film such that it can be
in sliding contact with the film; and the endless pattern belt
being rotated in an upstream direction of the film such that the
small rolls or plates are continuously in sliding contact with the
film, whereby the linear scratches are formed on the film
substantially in its width direction. The film-pressing means is
preferably an endless brush comprising a large number of hairs on
an endless belt, which is longer than the width of the film; the
endless brush being arranged in parallel with the endless pattern
belt via the film; and the endless brush being rotated such that
the direction of the hairs slidably moving on the film is opposite
to the direction of the small rolls or plates slidably moving on
the film, whereby the hairs are continuously in sliding contact
with the film.
[0037] In a still further preferred embodiment of the present
invention, the apparatus comprises at least two rolls each having
an axial direction slanting to the moving direction of the film,
and vertically movable guide means for independently moving the
rolls, each roll slidably moving on the film from one end to the
other, and being repeatedly subjected to a cycle of moving away
from the film after reaching the other end and returning to the
original position, during which the movement of the roll is
controlled such that at least any one of the rolls is always in
sliding contact with the film over its entire width, whereby the
linear scratches are formed on the film substantially in its width
direction. Each roll is preferably rotated at a lower peripheral
speed than the moving speed of the film in an opposite direction to
the moving direction of the film.
[0038] In a still further preferred embodiment of the present
invention, the linear-scratch-forming means is at least two roll
trains each comprising small rolls having a large number of fine
hard particles on the surfaces, which are mounted to supports in
parallel; the roll trains being arranged slantingly to the moving
direction of the film; the apparatus comprising vertically movable
guide means for independently moving the roll trains in the width
direction of the film; and each roll train slidably moving on the
film from one end to the other, and being repeatedly subjected to a
cycle of moving away from the film after reaching the other end and
returning to the original position, during which the movement of
the roll trains is controlled such that at least any one of the
roll trains is always in sliding contact with the film over its
entire width, whereby the linear scratches are formed on the film
substantially in its width direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a schematic side view showing an example of an
apparatus for forming linear scratches on a film in a moving
direction thereof;
[0040] FIG. 2 is a partial, enlarged plan view showing the
direction of a compressed air blown onto a film surface in sliding
contact with a pattern roll in the apparatus shown in FIG. 1;
[0041] FIG. 3 is a partial, enlarged, cross-sectional view showing
a film in sliding contact with a pattern roll in the apparatus
shown in FIG. 1;
[0042] FIG. 4(a) is a front view and a right side view showing an
example of a nozzle;
[0043] FIG. 4(b) is a front view and a right side view showing
another example of a nozzle;
[0044] FIG. 4(c) is a schematic view showing the direction of a
compressed air blown onto a pattern roll from a nozzle with a hood
and the winding of a film around the pattern roll;
[0045] FIG. 5 is a schematic view showing another example of an
apparatus for forming linear scratches on a film in a moving
direction thereof;
[0046] FIG. 6 is a perspective view showing an example of an
apparatus for forming linear scratches on a film slantingly to its
moving direction;
[0047] FIG. 7(a) is a partial, enlarged plan view showing a film in
sliding contact with an endless pattern belt in the apparatus shown
in FIG. 6;
[0048] FIG. 7(b) is a schematic side view taken from the direction
(A) in FIG. 7(a);
[0049] FIG. 8 is a schematic side view showing another example of
an apparatus for forming linear scratches on a film slantingly to
its moving direction;
[0050] FIG. 9 is a partial enlarged plan view showing a film in
sliding contact with a roll train in the apparatus shown in FIG.
8;
[0051] FIG. 10(a) is a partial enlarged plan view showing a further
example of an apparatus for forming linear scratches on a film
slantingly to its moving direction;
[0052] FIG. 10(b) is a schematic side view taken from the direction
(B) in FIG. 10(a);
[0053] FIG. 11 is a partial, enlarged plan view showing an example
of an apparatus for forming linear scratches on a film
perpendicularly to a moving direction thereof;
[0054] FIG. 12 is a partial, enlarged plan view showing another
example of an apparatus for forming linear scratches on a film
perpendicularly to a moving direction thereof;
[0055] FIG. 13 is a partial, enlarged plan view showing a further
example of an apparatus for forming linear scratches on a film
perpendicularly to a moving direction thereof;
[0056] FIG. 14(a) is a partial, enlarged plan view showing a still
further example of an apparatus for forming linear scratches on a
film perpendicularly to a moving direction thereof;
[0057] FIG. 14(b) is a schematic side view taken from the direction
(C) in FIG. 14(a);
[0058] FIG. 15 is a view showing a model of measuring the surface
roughness of the easy-to-straight-tear thermoplastic resin film of
the present invention by an AFM;
[0059] FIG. 16 is a graph illustrating an AFM image of the
easy-to-straight-tear polyester film in Example 1; and
[0060] FIG. 17 is a graph illustrating one cross section of the AFM
image of the easy-to-straight-tear polyester film in Example 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0061] [1] Method for Forming Linear Scratches
[0062] The easy-to-straight-tear thermoplastic resin film of the
present invention is produced by forming substantially parallel
linear scratches by bringing a continuously running thermoplastic
resin film into sliding contact with a means for forming linear
scratches, which has a lot of fine projections. The method and
apparatus for producing the easy-to-straight-tear thermoplastic
resin film of the present invention will be explained below in
detail referring to the drawings.
[0063] (1) Formation of Linear Scratches on Film in Moving
Direction
[0064] FIG. 1 is a schematic side view showing an example of an
apparatus for forming linear scratches on a film 1 in a moving
direction, which comprises a roll 2 having a lot of fine
projections on the surface (hereinafter referred to as "pattern
roll") as a means for forming linear scratches, and an air-blowing
nozzle 3 as a film-pressing means. A film 1 unwound from a reel 11
having an original film passes between nip rolls 12 and is brought
into contact with a pattern roll 2 to be provided with linear
scratches. The thermoplastic resin film provided with
easy-to-straight-tear characteristics passes through nip rolls 13
and guide rolls 14 and 15, and is then wound around a reel 16.
[0065] As shown in FIG. 2, the pattern roll 2 is fixed with its
rotation axis in parallel with the width direction of the film 1,
and longer longitudinally than the width of the film 1, such that
the film 1 is in sliding contact with the pattern roll over its
entire width.
[0066] The nip rolls 12 and 13 disposed upstream and downstream of
the pattern roll 2 as tension-controlling rolls give tension to the
film 1 moving over the pattern roll 2. Further as shown in FIG. 2,
the air at a predetermined pressure is blown from a nozzle 3
disposed on the opposite side of the pattern roll 2 onto the film 1
in sliding contact with the pattern roll 2, so that the film 1 is
pressed onto the sliding surface (hereinafter referred to as
"roll-sliding surface" unless otherwise particularly mentioned) of
the pattern roll 2 at a uniform force. Uniform linear scratches are
thus formed on the surface of the film. Using the nozzle 3, the
film 1 is pressed onto the pattern roll 2, such that non-uniform
contact with the roll-sliding surface due to the uneven thickness
of the film 1 can be suppressed.
[0067] Because the pattern roll 2 has a lower peripheral speed than
the moving speed of the film 1, it is preferable to rotate the
pattern roll 2 in an opposite direction to the moving direction of
the film 1. This can prevent the film from being wrinkled and dust
generated by the formation of linear scratches from remaining on
the surface of the pattern roll 2, thereby forming linear scratches
of proper length and depth. In the present invention, the moving
speed of the film 1 is preferably 10 to 500 m/minute. The
peripheral speed of the pattern roll 2 (rotation speed in an
opposite direction to the moving direction of the film 1) is
preferably 1 to 50 m/minute.
[0068] A usable pattern roll 2 is described, for instance, in JP
2002-59487 A. This pattern roll comprises a lot of fine particles
having Mohs' hardness of 5 or more attached to a surface of a metal
roll by an electrodeposition method or by an organic or inorganic
binder. The metal roll is made of iron, iron alloys, etc. The metal
roll preferably has a plating layer of nickel or chromium. The fine
particles having Mohs' hardness of 5 or more are, for instance,
cemented carbide particles such as tungsten carbide, silicon
carbide particles, boron carbide particles, sapphire particles,
cubic boron nitride (CBN) particles, natural or fine synthetic
diamond particles, etc. Fine synthetic diamond particles having
large hardness and strength are particularly desirable. The
particle size of the fine particles is properly determined
depending on the depth and width of linear scratches formed. In the
present invention, the fine particles desirably have a particle
size of 10 to 100 .mu.m with unevenness of 5% or less. How many
fine particles are attached to the roll surface is properly
selected such that the formed linear scratches have desired
intervals. To form uniform linear scratches, the fine particles are
preferably attached to 50% or more of the roll surface. A specific
example of the pattern roll 2 may be a pattern roll having a lot of
fine synthetic diamond particles fixed with a nickel
electrodeposition layer to the surface of an iron roll at an area
ratio of 50% or more. The outer diameter of the pattern roll 2 is
preferably 2 to 20 cm, more preferably 3 to 10 cm.
[0069] The pattern roll 2 may also be a needle roll having metal
needles embedded in the surface of a metal roll regularly in a
lattice pattern with extremely small intervals. In addition to the
pattern roll 2, the means for forming linear scratches may be a
pattern plate having many fine particles having Mohs' hardness of 5
or more as described above on the surface of a plate body.
[0070] FIG. 3 is a partial enlarged cross-sectional view showing
the film 1 in sliding contact with the pattern roll 2 to form
linear scratches. When an edge of at least one fine particle 4 on
the surface of the pattern roll 2 bites the roll-sliding surface,
one long linear scratch is formed until the edge of the biting fine
particle 4 separates away from the roll-sliding surface, because
the moving speed of the film 1 is larger than the peripheral speed
of the pattern roll 2 rotating in an opposite direction as
described above.
[0071] A nozzle having pluralities of blowing orifices 31 shown in
FIG. 4(b) may be used as the air-blowing means, in place of a
nozzle having a strip-shaped blowing orifice 31 shown in FIG. 4(a),
which is the same as shown in FIGS. 1 to 3. In addition, when a
compressed air is blown from a nozzle having a hood 32 covering the
pattern roll 2 as shown in FIG. 4(c), the compressed air ejected
from the blowing orifice 31 is not easily diffused until it reaches
a position at which the film 1 is in sliding contact with the
pattern roll 2, so that the contact force of the film 1 to the
pattern roll 2 becomes further uniform on the roll-sliding surface.
The pressure of the compressed air flow blown from such air-blowing
means is preferably 0.05 to 5 kgf/cm.sup.2, so that the contact
force of the film 1 to the pattern roll 2 becomes uniform on the
roll-sliding surface. The more preferred pressure of the compressed
air flow is 0.1 to 2 kgf/cm.sup.2. The distance from the blowing
orifice 31 to the roll-sliding surface is preferably 10 to 50 cm.
The compressed air needs only uniformly impinge onto a region
covering at least a surface of the roll. However, if the blowing
orifice 31 of the blower or the nozzle were larger than necessary,
too much amount of the compressed air is unpreferably needed to
obtain a proper gas pressure.
[0072] The winding of the film 1 around the fixed pattern roll 2 is
preferably conducted such that an angle .theta. between the winding
direction of the film 1 and the unwinding direction of the film 1
is in a range of 60.degree. to 170.degree. as shown in FIG. 4(c).
This makes the length and depth of linear scratches easily
adjustable. The angle .theta. is preferably in a range of
90.degree. to 150.degree.. To set the angle .theta. at a desired
value, the vertical position of the pattern roll 2 may be changed
such that the positional relation of the pattern roll 2 to the nip
rolls 12 and 13 are properly adjusted. Depending on the way of
winding the film 1 around the pattern roll 2 and the outer diameter
of the pattern roll 2, a tension given to the film 1 by the nip
rolls 12 and 13 and the pressure of a gas ejected from the nozzle 3
may be properly adjusted to obtain linear scratches with the
desired length and depth. In the present invention, a tension
(tension per width) given to the film by the nip rolls 12 and 13 is
preferably in a range of 0.01 to 5 kgf/cm width.
[0073] In place of the air-blowing means, a brush may be in sliding
contact with the opposite side of the roll-sliding surface, to give
a uniform contact force to the roll-sliding surface. The brush
hairs are preferably movable on a surface of the film 1, on which
the brush slides, (hereinafter referred to as "brush-sliding
surface" unless otherwise described), at a lower speed than the
moving speed of the film 1 in an opposite direction to the moving
direction of the film 1. Thus, as shown in FIG. 5, the brush is
preferably a rotatable roll brush 5 having a lot of hairs radially
extending from a brush shaft (rotation shaft), which is longer than
the width of the film 1 and fixed in parallel with the width
direction of the film 1, such that the brush is in sliding contact
with the film 1 over its entire width.
[0074] The outer diameter of the rotatable roll brush 5 is
preferably 5 to 10 cm. The hairs 51 of the rotatable roll brush 5
preferably have a recovery-from-bending ratio of 70% or more, a
diameter of 0.1 to 1.8 mm, and a length of 1 to 5 cm. The hairs 51
of the rotatable roll brush 5 preferably have a density of 100 to
500/cm.sup.2 on the brush-sliding surface. The
recovery-from-bending ratio is determined as follows: First, two
looped hair fibers having a length of about 26 cm are crossed like
a chain with an upper loop fixed to a hook, and a load (g) as heavy
as half of the denier of the hair fiber is applied to a lower loop
for 3 minutes, and a sample having a length of about 3 cm is cut
out of a pair of loops bent like pine leaves, and left to stand for
60 minutes. An open angle (.theta.) of the sample is measured to
calculate the recovery-from-bending ratio by the equation of
(.theta./180).times.100 (%). Though not particularly restrictive,
the tip ends of the hairs 51 are preferably substantially in a
U-shape or in a tapered shape. The materials of the hairs 51 are
preferably synthetic resins such as polypropylene, nylon, acrylic
resins, polyethylene, etc., though not particularly
restrictive.
[0075] The rotatable roll brush 5 is preferably in sliding contact
with the film 1 at a pressure of 0.01 to 5 kgf/cm.sup.2 on the
brush-sliding surface. The peripheral speed of the rotatable roll
brush 5 (rotation speed in an opposite direction to the moving
direction of the film 1) is preferably 1 to 50 m/minute.
[0076] The length and depth of linear scratches are adjusted to
obtain the desired level of the easy-to-straight-tear
characteristics, by properly changing the moving speed of the film
1, the peripheral speed of the pattern roll 2, the size of the fine
diamond particles 4, the outer diameter of the pattern roll, the
gas pressure from the nozzle 3, the pressure of the rotatable roll
brush 5, a tension given to the nip rolls 12 and 13, etc.
[0077] (2) Formation of Slanting Linear Scratches on Film
[0078] FIG. 6 shows an example of an apparatus for forming linear
scratches on the film 1 slantingly to the moving direction of the
film 1. The same reference numerals are assigned to the same
members or portions as in FIG. 1. The apparatus shown in FIG. 6
comprises an endless pattern belt 6 comprising a lot of small
pattern rolls 21 connected as a means for forming linear scratches,
and an endless brush 7 comprising a lot of hairs 71 implanted to an
endless belt as a film-pressing means. FIG. 7(a) is a partial
enlarged plan view showing the endless pattern belt 6 rotating in
the width direction of the film 1 in the apparatus shown in FIG. 6,
and FIG. 7(b) is a schematic cross-sectional view taken from the
direction (A) in FIG. 7(a).
[0079] The endless pattern belt 6 is rotated in the width direction
of the film 1 as shown in FIGS. 7(a) and 7(b), such that small
pattern rolls 21 are in sliding contact with the continuous film 1
to form linear scratches on the film 1 slantingly to its moving
direction. The endless pattern belt 6 is preferably constituted by
a larger number of the pattern rolls 21 at a high density. The
length and outer diameter of each small pattern roll 21 are both
preferably 5 to 10 cm.
[0080] The angle of the slanting linear scratches to the moving
direction of the film can be changed by properly adjusting the
peripheral speeds of the endless pattern belt 6 and the moving
speed of the film 1. The peripheral speed of the endless pattern
belt 6 is usually 1 to 100 m/minute. Small pattern rolls 21 are
rotated in an opposite direction to the moving direction of the
endless pattern belt 6 on the roll-sliding surface at a peripheral
speed of 1 to 50 m/minute as in the case of the pattern roll 2
described in (1) above.
[0081] The endless brush 7 is preferably rotated, such that the
direction of the hairs 71 moving in sliding contact with the film 1
is opposite to the direction of the endless pattern belt 6 moving
in sliding contact with the film 1. Thus, the endless brush 7 and
the endless pattern belt 6 are rotated in the same direction. The
hairs 71 of the endless brush 7 are preferably as long as 4 to 8
cm. The preferred requirements of the hairs 71 of the endless brush
7 concerning a recovery-from-bending ratio, a diameter, a density
on the brush-sliding surface, a tip shape and a material are the
same as those of the rotatable roll brush 5 described in (1) above.
The pressure of the endless brush 7 on the brush-sliding surface
may be 0.01 to 5 kgf/cm.sup.2, the same as in the rotatable roll
brush 5 described in (1) above. The pressure at which the endless
brush 7 comes into sliding contact with the film 1 may be
controlled by properly adjusting the vertical position of the
endless brush 7 by rotating a height-controlling knob 73. The
peripheral speed of the endless brush 7 is preferably 1 to 50
m/minute. The peripheral speed of the endless brush 7 may be
controlled by properly adjusting the rotation speed of a motor 74.
The endless pattern belt 6 and the endless brush 7 are preferably
longer than the width of the film 1 in their moving directions,
such that the film 1 is brought into sliding contact with the
endless pattern belt 6 and the endless brush 7 over its entire
width.
[0082] FIG. 8 shows another example of an apparatus for providing
the film 1 with linear scratches slantingly to the moving
direction. The same reference numerals are assigned to the same
members or portions as in FIG. 1. The apparatus shown in FIG. 8
comprises a roll train 8a comprising a lot of small pattern rolls
22a mounted to a guide rail (support) 81a in parallel, and a roll
train 8b comprising a lot of small pattern rolls 22b mounted to a
guide rail (support) 81b in parallel, as means for forming linear
scratches, as shown in FIG. 9
[0083] Support shafts 91a and 91b supporting the pattern rolls 22a
and 22b are movable up and down, and the roll trains 8a and 8b are
movable straight along the guide rails 81a and 81b, respectively,
in the width direction of the film 1. The guide means comprising
the support shafts 91a and 91b movable up and down and the guide
rails 81a and 81b can independently move the roll trains 8a and 8b
in the width direction of the film 1. Accordingly, the roll trains
8a and 8b move from one end of the film 1 to the other end thereof
in a slidably contacting manner, and then separate from the film 1
and return to the original position, and this cycle is repeated.
During this cycle, the movement of the roll trains 8a and 8b is
controlled such that at least any one of the roll trains is always
in sliding contact with the film 1 over its entire width, thereby
forming linear scratches on the film slantingly to its moving
direction. As the guide means, instead of making the support shafts
91a and 91b not movable up and down relative to the guide rails 81a
and 81b, the guide rails 81a and 81b may move up and down.
[0084] The longitudinal length and outer diameter of each pattern
roll 22a, 22b may be about 5 to 10 cm. Intervals between the
adjacent pattern rolls 22a, 22b are preferably narrower than the
width of each pattern roll, such that the pattern rolls are
disposed at a high density. Each roll train 8a, 8b is longer than
the width of the film 1.
[0085] The apparatus shown in FIG. 8 comprises the same endless
brushes 7a and 7b as in the apparatus shown in FIG. 6 as
film-pressing means, and the endless brushes 7a and 7b are opposing
to the roll trains 8a and 8b in parallel via the film 1. Support
members 72, 72 supporting the endless brushes 7a and 7b are movable
up and down. Accordingly, the vertical movement of the endless
brush 7a is controlled such that both the endless brush 7a and the
roll train 8a are brought into sliding contact with the film 1
simultaneously, and the vertical movement of the endless brush 7b
is controlled such that both the endless brush 7b and the roll
train 8b are brought into sliding contact with the film 1
simultaneously. Thus, a constant contact force is always applied to
the roll-sliding surface.
[0086] The endless brushes 7a and 7b are preferably rotated such
that the moving direction of their hairs in sliding contact with
the film 1 is opposite to the moving direction of the roll trains
8a and 8b in sliding contact with the film 1. The preferred
requirements of the hairs of the endless brushes 7a and 7b
concerning a recovery-from-bending ratio, a diameter, a length, a
density on the brush-sliding surface, a tip shape and a material,
and the preferred requirements of the endless brushes 7a and 7b
concerning a pressure onto the brush-sliding surface and a
peripheral speed may be the same as those of the endless brush 7 in
the apparatus shown in FIG. 6.
[0087] The angle of the slanting linear scratches to the moving
direction of the film may be changed by properly adjusting the
speed of the roll trains 8a and 8b in sliding contact with the film
1 and the moving speed of the film 1. The pattern rolls 22a and 22b
are rotated in an opposite direction to the moving direction of the
roll trains 8a and 8b on the roll-sliding surface. Their peripheral
speed may be the same as that of the pattern rolls 2 described in
(1) above.
[0088] FIGS. 10(a) and 10(b) show another example of an apparatus
for forming linear scratches slantingly to the moving direction of
the film 1. In this embodiment, two pattern rolls 23a and 23b each
having a larger longitudinal length than the width of the film 1
are disposed in parallel in two rows in the moving direction of the
film 1. The longitudinal length of each pattern roll 23a and 23b is
preferably 2 times the width of the film 1 or more.
[0089] Support shafts 92a and 92b supporting the pattern rolls 23a
and 23b are movable up and down, and the pattern rolls 23a and 23b
are movable straight along guide rails 82a and 82b in the width
direction of the film 1. The pattern rolls 23a and 23b can move
independently in the width direction of the film 1 by a guide means
comprising the vertically movable 92a and 92b and the guide rails
82a and 82b. Accordingly, the pattern rolls 23a and 23b move from
one end of the film 1 to the other end thereof in a slidably
contacting manner, and then separate from the film 1 and return to
the original position, and this cycle is repeated. During the
cycle, the movement of the pattern rolls 23a and 23b can be
controlled such that at least any one of the pattern rolls is
always in sliding contact with the film 1 over its entire width,
thereby forming linear scratches slanting to the moving direction
of the film. The angle of the slanting linear scratches to the
moving direction of the film can be changed by properly adjusting
the sliding speed of the pattern rolls 23a and 23b and the moving
speed of the film 1.
[0090] The apparatus shown in FIG. 10 comprises, as film-pressing
means, endless brushes 7a and 7b movable up and down and opposing
the pattern rolls 23a and 23b in parallel via the film 1 like the
apparatus shown in FIG. 8.
[0091] Though the apparatuses shown in FIGS. 6 to 10 comprise the
endless brushes as film-pressing means, they may comprise the
air-blowing means described in (1) above.
[0092] (3) Formation of Linear Scratches on Film in Width
Direction
[0093] FIG. 11 shows an example of an apparatus for forming linear
scratches on a film 1 in its width direction. The same reference
numerals are assigned to the same members or portions as in FIG. 6.
The apparatus shown in FIG. 11 is the same as shown in FIGS. 6 and
7 except that an endless pattern belt 6 is disposed slantingly to
the moving direction of a film (no endless brush shown). Using the
apparatus having the structure shown in FIG. 11, linear scratches
can be formed on the film 1 in its width direction, by properly
adjusting operation conditions such as the moving speed of the film
1, the angle of the endless pattern belt 6 to moving direction of
the film 1, the peripheral speed of the pattern belt 6, etc.
[0094] FIG. 12 shows another example of an apparatus for forming
linear scratches on the film 1 in a width direction. In this
embodiment, an endless pattern belt 6a comprising a lot of small
pattern rolls 21a and an endless pattern belt 6b comprising a lot
of small pattern rolls 21b are disposed symmetrically to the center
line 17 of the film 1 as a symmetry axis and slanting to the moving
direction of the film. The same endless brushes (not shown) as in
the apparatus shown in FIG. 6 are preferably disposed as
film-pressing means in parallel with endless pattern belts 6a and
6b via a film 1.
[0095] Using the apparatus having the structure shown in FIG. 12,
linear scratches can be formed on the film 1 in its width
direction, by properly adjusting operation conditions such as the
moving speed of the film 1, the angles of the endless pattern belts
6a and 6b to the center line 17 of the film 1, the peripheral
speeds of the endless pattern belts 6a and 6b, etc.
[0096] FIG. 13 shows another example of an apparatus for forming
linear scratches on the film 1 in its width direction. The
apparatus shown in FIG. 13 is the same as shown in FIG. 9, except
that the same roll trains 8a and 8b as shown in FIG. 9 are disposed
slantingly to the width direction of the film 1 (no endless brushes
shown). Using the apparatus having the structure shown in FIG. 13,
linear scratches can be formed on the film 1 in its width
direction, by properly adjusting operation conditions such as the
moving speed of the film 1, the angles of the roll trains 8a and 8b
relative to the moving direction of the film 1, the sliding speeds
of the roll trains 8a and 8b, etc.
[0097] FIGS. 14(a) and 14(b) show another example of an apparatus
for forming linear scratches on the film 1 in a width direction.
FIG. 14(b) shows a left side of the apparatus shown in FIG. 14(a)
[taken from the direction (C) in FIG. 14(a)]. The apparatus in this
embodiment comprises two pattern rolls 24a and 24b each having a
longitudinal axis slanting to the moving direction of the film 1.
The longitudinal length of each pattern roll 24a and 24b is
preferably at least two times the width of the film 1 or more.
[0098] Support shafts 93a and 93b supporting the pattern rolls 24a
and 24b are movable up and down, and the pattern rolls 24a and 24b
are movable straight along guide rails 83a and 83b at a
predetermined angle relative to the center line 17 of the film 1.
The pattern rolls 24a and 24b can move independently at a
predetermined angle relative to the center line 17 of the film 1,
by a guide means comprising the vertically movable 93a and 93b and
the guide rails 83a and 83b. Because the pattern roll 24b is longer
than the pattern roll 24a, the pattern rolls 24a and 24b can cross
each other during moving in opposite directions. The pattern rolls
24a and 24b thus move from one end of the film 1 to the other end
thereof in a slidably contacting manner, and separate from the film
1 and return to the original position, and this cycle is repeated.
Linear scratches can be formed on the film in its width direction,
by controlling the movement of the pattern rolls 24a and 24b such
that at least any one of the pattern rolls is always in sliding
contact with the film 1 over its entire width.
[0099] As shown in FIG. 14(b), rotatable roll brushes 5a and 5b are
movable up and down in parallel, and move as the pattern rolls 83a
and 83b move along the roll-sliding surface of the film 1. One of
the rotatable roll brushes 5a and 5b is longer than the other in a
longitudinal direction, so that they can cross each other during
moving in opposite directions. A contact force is thus always
applied to the film 1 in sliding contact with the pattern roll 83a
or 83b. The preferred requirements of the hairs 51 of the rotatable
roll brushes 5a and 5b concerning a recovery-from-bending ratio, a
diameter, a length, a density on the brush-sliding surface, a tip
shape and a material may be the same as those of the rotatable roll
brush 5 described in (1) above.
[0100] In the apparatuses shown in FIGS. 11 to 14, linear scratches
can be formed on the film 1 slantingly to its moving direction, by
properly adjusting operation conditions, etc. Though the
apparatuses shown in FIGS. 11 to 14 comprise the endless brushes as
film-pressing means, they may comprise the air-blowing means
described in (1) above.
[0101] [2] Thermoplastic Resin Film
[0102] Though not particularly limited, examples of thermoplastic
resin films usable for producing the easy-to-straight-tear
thermoplastic resin film of the present invention include
single-layer films made of polyolefins such as polyethylene and
polypropylene; polyesters such as polyethylene terephthalate,
polybutylene terephthalate and polyethylene naphthalate; polyvinyl
chlorides; fluororesins; polyamides; polycarbonate; polyimides;
polyetheretherketone; polyetherketone; elastomers; polyurethanes;
polyethersulfone; polyphenylene sulfide; polyamideimides, etc. The
thermoplastic resin films may be stretched monoaxially or
biaxially, if necessary.
[0103] The above thermoplastic resin film may be vapor-deposited
with metals, metal oxides, etc. or coated with resins to provide
vapor-deposited transparent films. Specific examples thereof
include silica-deposited polyethylene terephthalate films,
alumina-deposited polyethylene terephthalate films, etc.
[0104] The above thermoplastic resin film may comprise a layer of
common polyolefins and a sealant layer of special polyolefins.
Specifically, they are low-density polyethylene (LDPE),
medium-density polyethylene (MDPE), high-density polyethylene
(HDPE), cast polypropylene (CPP), linear-low-density polyethylene
(LLDPE), very-low-density polyethylene (VLDPE), ethylene-vinyl
acetate copolymers (EVAs), ethylene-acrylic acid copolymers (EAAs),
ethylene-methacrylic acid copolymers (EMAAs), ethylene-ethyl
acrylate copolymers (EEAs), ethylene-methylmethacrylate copolymers
(EMMAs), ethylene-methyl acrylate copolymers (EMAs), ionomers
(IOs), etc. To further improve moisture resistance and gas barrier,
the thermoplastic resin film preferably comprises an intermediate
layer formed by an aluminum foil, a silica-deposited polyethylene
terephthalate film, an alumina-deposited polyethylene terephthalate
film, etc.
[0105] In the production of a laminate film, the above
thermoplastic resin film or vapor-deposited transparent film is
preferably formed with linear scratches described in [1] above, and
then laminated with a sealant film with or without the above
intermediate film. The lamination may be carried out by a known
method, for instance, by extrusion with an adhesive layer
therebetween. The adhesive layer is preferably made of
polyethylene.
[0106] The thermoplastic resin film may be a film having a lot of
fine pores, which is called "porous film." Fine pores are
preferably formed before forming the linear scratches described
above. The fine pores may be penetrating or non-penetrating the
thermoplastic resin film. The fine pores preferably have an average
opening diameter of 0.5 to 100 .mu.m, and they exist at a density
of about 500/cm.sup.2 or more. The upper limit of the density of
the fine pores is not particularity restricted as long as
technically possible. In the production of the laminate film, the
sealant film may be formed with a lot of fine pores described
above, if necessary, to improve the easy-to-tear characteristics of
the laminate film.
[0107] To form the fine pores on the thermoplastic resin film, the
methods disclosed in Japanese Patent 2,063,411 and JP 2002-059487
A, for instance, may be used. In the method for producing a long
porous sealant film disclosed in Japanese Patent 2,063,411, a long
sealant film is caused to pass between a first roll having fine
particles with sharp edges and a Mohs' hardness of 5 or more on the
surface (the same as the pattern roll 2 described in [1] (1)
above), and a second roll having a smooth surface, with pressure
applied to the film passing therebetween adjusted uniform over its
entire width in contact with the roll, to form a lot of penetrating
or non-penetrating pores having a diameter of 50 .mu.m or less at a
density of 500/cm.sup.2 or more on the long sealant film with sharp
edges of a lot of particles on the first roll surface.
[0108] [3] Easy-To-Straight-Tearing Thermoplastic Resin Film
[0109] Because the easy-to-straight-tear thermoplastic resin film
of the present invention has a lot of substantially parallel linear
scratches at least on one surface, it can be easily torn straight
from any point along the linear scratches. It thus has
easy-to-straight-tear characteristics in one direction regardless
of the orientation of the original film. A wrapping bag formed from
the easy-to-straight-tear thermoplastic resin film of the present
invention can be opened in a strip shape without tapering while
keeping a constant width.
[0110] The depth of linear scratches on the easy-to-straight-tear
thermoplastic resin film is preferably 1 to 40% of the film
thickness, to meet both requirements of high strength and good
easy-to-straight-tear characteristics. The linear scratches formed
by the method described in [1] above are preferably as deep as 0.1
to 10 .mu.m and as wide as 0.1 to 10 .mu.m, and their intervals are
preferably 10 to 200 .mu.m.
[0111] The method for measuring the depth, width and intervals of
the linear scratches will be explained below referring to the
drawings. FIG. 15 schematically illustrates the cross section of
the easy-to-straight-tear thermoplastic resin film of the present
invention rectangularly to the linear scratches, which is taken
from an image of surface roughness measured by an atomic force
microscope (AFM). The depth of a linear scratch L.sub.1 is a
distance d between a reference line P and the bottom of the linear
scratch L.sub.1. The width of the linear scratch is a distance
D.sub.1 between intersections P.sub.1 and P.sub.2, at which the
reference line P crosses the walls of the linear scratch. The
interval of linear scratches is a distance D.sub.2 between the
bottoms of parallel linear scratches L.sub.1 and L.sub.2.
[0112] The film having linear scratches in its moving direction
(longitudinal direction) may be used for wrapping bags for stick
cookies. Because the wrapping bags formed by the
easy-to-straight-tear thermoplastic resin film of the present
invention having linear scratches in a longitudinal direction can
be opened in a strip shape without tapering while keeping a
constant width, the cookies are not damaged. Though wrappings
formed by a biaxially stretched polypropylene films (OPP films) for
rice balls, etc. are provided with cutting tapes (tear tapes) in
alignment with the opening width, the easy-to-straight-tear
thermoplastic resin film of the present invention having linear
scratches in a longitudinal direction does not need a tear tape,
because it can be opened while keeping the opening width.
[0113] The film having linear scratches slanting to its moving
direction may be used for wrapping bags of powdery medicine,
seasonings for lunch boxes, etc. A wrapping bag formed by the
easy-to-straight-tear thermoplastic resin film of the present
invention having slanting linear scratches can be easily torn
slantingly in a corner thereof.
[0114] The film having linear scratches in a width direction
(transverse direction) may be used for stick-shaped wrapping bags
of powdery instant food, etc. Using the easy-to-straight-tear
thermoplastic resin film of the present invention having linear
scratches in a transverse direction, increasingly demanded
stick-shaped wrapping bags can be produced at a low cost.
[0115] The present invention will be explained in more detail
referring to Examples below without intention of restricting the
present invention thereto.
EXAMPLE 1
[0116] A polyester (PET) film having a thickness of 12 .mu.m was
brought into sliding contact with a 5-cm-diameter pattern roll with
fine synthetic diamond particles having a diameter of 100 .mu.m to
produce an easy-to-straight-tear polyester film having linear
scratches in its moving direction, under the conditions that the
film speed was 50 m/minute, that the peripheral speed of the
pattern roll rotating in an opposing direction to the film was 10
m/minute, that the pressure of air blown from a nozzle was 1
kgf/cm.sup.2, and that a tension given to the film by nip rolls was
0.5 kgf/cm width.
[0117] A surface of the resultant easy-to-straight-tear polyester
film was observed by AFM. FIGS. 16 and 17 are the drawings of AFM
images. FIGS. 16 and 17 show different portions of the film, and
FIG. 17 shows a cross section of the observed portion. As is clear
from FIGS. 16 and 17, linear scratches of 0.1 to 1 .mu.m in depth,
0.5 to 5 .mu.m in width and 10 to 50 .mu.m in interval were formed
on the polyester film. It is clear that because the linear
scratches were formed by scraping by fine synthetic diamond
particles, film portions on both sides of the grooves were
plastically deformed to bulge by pressure when the linear scratches
(grooves) were formed.
[0118] It was confirmed that the resultant easy-to-straight-tear
polyester film was torn straight at least in a longitudinal length
of an A4 size or so.
[0119] Because the easy-to-straight-tear thermoplastic resin film
of the present invention can be easily torn straight in one
direction regardless of the orientation of the original film as
described above, it is useful for wrapping bags requiring various
types of easy opening. With the method and apparatus for producing
the easy-to-straight-tear thermoplastic resin film of the present
invention, it is possible to produce such easy-to-straight-tear
thermoplastic resin films at a low cost.
* * * * *