U.S. patent application number 12/181643 was filed with the patent office on 2009-02-05 for polymer film splicing method and device, and stretching method.
This patent application is currently assigned to FUJIFILM CORPORATION. Invention is credited to Shinsuke AOSHIMA.
Application Number | 20090032166 12/181643 |
Document ID | / |
Family ID | 40337015 |
Filed Date | 2009-02-05 |
United States Patent
Application |
20090032166 |
Kind Code |
A1 |
AOSHIMA; Shinsuke |
February 5, 2009 |
POLYMER FILM SPLICING METHOD AND DEVICE, AND STRETCHING METHOD
Abstract
An off-line stretching device includes a film supply chamber, a
tenter section, a relaxation chamber, a cooling chamber, and a
winding chamber. The film supply chamber includes a splicing
section, where a rear end of a preceding film and a front end of a
trailing film are overlapped to be spliced to each other by thermal
welding. The thermal welding is performed from above and below the
film while a temperature of welding heads of a heat sealer,
contacting with the film, is kept at a level equal to or less than
a decomposition temperature of the preceding and trailing films.
The spliced film is stretched in the tenter section and subjected
to heat treatment for stress relaxation in the relaxation chamber,
to shrink in a film width direction. Since the shrinkage amount of
a spliced area and that of a peripheral area become equal to each
other, the occurrence of wrinkles in the spliced area and tears of
the film in the peripheral area can be prevented. Additionally,
since a heat transfer distance between a film surface and a film
splicing surface can be shortened, the heating from above and below
the film enables high-speed welding.
Inventors: |
AOSHIMA; Shinsuke;
(Minami-ashigara-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
FUJIFILM CORPORATION
Tokyo
JP
|
Family ID: |
40337015 |
Appl. No.: |
12/181643 |
Filed: |
July 29, 2008 |
Current U.S.
Class: |
156/73.5 ;
156/580 |
Current CPC
Class: |
B29C 65/4895 20130101;
B29C 66/91411 20130101; B29C 66/83221 20130101; B29C 66/71
20130101; B29C 65/5057 20130101; B29C 66/71 20130101; B29C 66/91421
20130101; B29C 55/08 20130101; B29C 65/305 20130101; B29C 65/38
20130101; B29C 66/8322 20130101; B29C 66/91921 20130101; B29C 65/08
20130101; B29C 55/20 20130101; B29C 65/18 20130101; B29C 66/0342
20130101; B29C 66/1122 20130101; B29C 66/344 20130101; B29C
66/91231 20130101; B29C 66/91645 20130101; B29C 66/919 20130101;
B29C 66/73711 20130101; B29K 2001/12 20130101; B29K 2001/00
20130101; B29C 66/43 20130101; B29C 66/81417 20130101; B29C
66/91423 20130101; B29C 66/71 20130101; B29C 66/9141 20130101; B29C
66/71 20130101; B29C 66/81419 20130101; B29C 66/73715 20130101;
B29K 2001/14 20130101 |
Class at
Publication: |
156/73.5 ;
156/580 |
International
Class: |
B29C 65/06 20060101
B29C065/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 2007 |
JP |
2007-197725 |
Sep 19, 2007 |
JP |
2007-242414 |
Claims
1. A splicing method of a polymer film comprising the steps of:
overlapping a rear end of a preceding polymer film and a front end
of a trailing polymer film; pressing welding heads against a
portion in which said preceding and trailing films are overlapped
with each other from each side in a film overlapping direction
while sandwiching said portion between said welding heads; and
welding said films while keeping a temperature of said welding
heads contacting said film at a temperature equal to or less than a
decomposition temperature of said polymer film, to splice said rear
end and said front end to each other.
2. A splicing method of a polymer film as defined in claim 1,
wherein said polymer film is a cellulose ester film.
3. A splicing device of a polymer film comprising: a welding head
provided at each side of a portion in which a rear end of a
preceding polymer film and a front end of a trailing polymer film
are overlapped with each other in a film overlapping direction; a
shifter for moving said welding heads in said film overlapping
direction between a pressing position and a retracted position,
said welding heads sandwiching and pressing a portion in which said
preceding and trailing films are overlapped with each other in said
pressing position, and said welding heads being retracted from said
pressing position in said retracted position; and a heating
controller for heating said welding heads contacting said preceding
and trailing films at a temperature equal to or less than a
decomposition temperature of said polymer film after said welding
heads is shifted to said pressing position by said shifter.
4. A splicing device of a polymer film as defined in claim 3,
wherein said polymer film is a cellulose ester film.
5. A polymer film stretching method comprising: splicing a rear end
of a preceding polymer film and a front end of a trailing polymer
film by welding a portion in which said rear end of said preceding
film and said front end of said trailing film are overlapped with
each other; transporting continuously said polymer film after being
spliced; heating and stretching said transported polymer film by
holding side ends of said polymer film with use of plural clips in
a film width direction; and subjecting said polymer film after
being stretched to heat treatment for stress relaxation while
continuously transporting said polymer film, such that a shrinkage
amount of a spliced area of said preceding and trailing polymer
films and a shrinkage amount of an area around said spliced area
becomes approximately equal to each other in said film width
direction.
6. A polymer film stretching method as defined in claim 5, wherein
said welding is performed with use of heat caused by a heat
sealer.
7. A polymer film stretching method as defined in claim 5, wherein
said welding is performed with use of heat caused by ultrasonic
vibration of an ultrasonic splicer.
8. A polymer film stretching method as defined in claim 5, wherein
said welding is performed with use of a polymer solvent.
9. A polymer film stretching method comprising: splicing a rear end
of a preceding polymer film and a front end of a trailing polymer
film by adhering a splicing tape having an adhesive layer and no
base to a portion in which said rear end of said preceding film and
said front end of said trailing film are overlapped with each
other; transporting continuously said polymer film after being
spliced; heating and stretching said transported polymer film by
holding side ends of said polymer film with use of plural clips in
a film width direction; and subjecting said polymer film after
being stretched to heat treatment for stress relaxation while
continuously transporting said polymer film, such that a shrinkage
amount of a spliced area of said preceding and trailing polymer
films and a shrinkage amount of an area around said spliced area
becomes approximately equal to each other in said film width
direction.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a polymer film splicing
method and device, and a polymer film stretching method.
BACKGROUND OF THE INVENTION
[0002] Recently, in accordance with rapid development and
popularization of liquid crystal display (LCD) or the like, the
demand for a cellulose ester (cellulose acylate) film, in
particular, a triacetyl cellulose (TAC) film used as a protective
film for the LCD or the like, has been increasing. According to the
increase in the demand for the TAC film, the improvement in
productivity thereof has been desired. The TAC film is produced as
follows. A dope containing the TAC and a solvent is cast through a
casting die onto a support continuously moving to form a casting
film thereon. The casting film is dried or cooled to be solidified.
The solidified casting film is peeled from the support to form a
wet film. The wet film is dried and wound as a film. According to a
solution casting method described above, it is possible to form a
film containing less foreign materials and having more excellent
optical properties in comparison with a film forming method by
melt-extrusion.
[0003] In the solution casting method, as the support onto which
the dope is cast, a band and a drum are used. The drum can achieve
improvement in a casting speed more readily in comparison with the
band. In order to solidify the casting film on the support, the
casting film is dried, or cooled so as to turn into gel.
Additionally, in order to adjust the optical properties of the TAC
film, in particular retardation thereof, the TAC film is
stretched.
[0004] The optimum film producing speed and the optimum stretching
speed are different from each other. The film producing speed
requires more time than the stretching speed. Therefore, in the
case that the stretching speed is adjusted in accordance with the
film producing speed, it is impossible to stretch the film enough
to improve the optical properties. Accordingly, it is proposed that
the film is stretched in an off-line manner independently from a
solution casting line (see Japanese Patent Application Laid-open
No. 2002-311240, for example).
[0005] In a case where the film is stretched in an off-line manner
independently from the solution casting line as disclosed in
Japanese Patent Application Laid-open No. 2002-311240, for the
purpose of efficiently performing the stretching process, the TAC
film is preferably stretched continuously. In this case, in order
to supply the film continuously, a portion in which a rear end of a
preceding polymer film and a front end of a trailing polymer film
are overlapped with each other is heated to be welded. Thereby, the
preceding film and the trailing film are spliced to each other (see
Japanese Utility Model Applications Laid-open No. 53-020268 and
53-051864, for example).
[0006] However, as disclosed in Japanese Utility Model Applications
Laid-open No. 53-020268 and 53-051864, when a heater is disposed
above or below the portion in which the preceding and trailing
polymer films are overlapped with each other, in the case that the
temperature of the heater is raised or in the case that the contact
time between the heater and the film is increased for the purpose
of enhancing the welding, the temperature of the heated film
exceeds the degradation temperature of the polymer in the film in
some cases. The polymer film, in particular, cellulose ester film
has the melting point of 300.degree. C. and the decomposition
temperature of more than 300.degree. C. Since the melting point and
the decomposition temperature are close to each other, in the case
that the welding temperature is set higher for the purpose of
welding the film sufficiently, pitting occurs on the welded portion
of the polymer films or the degradation of the polymer proceeds due
to the overheating of the polymer film. Accordingly, there is a
problem that it is impossible to achieve sufficient splicing
strength.
[0007] In an off-line stretching device, the TAC film is subjected
to a splicing process for splicing a preceding film and a trailing
film, a stretching process for stretching the spliced TAC film by
holding the side ends thereof with use of plural clips in a film
width direction while heating the TAC film continuously
transported, and a relaxation process for subjecting the TAC film
thus stretched to heat treatment for stress relaxation (for
example, see U.S. application serial number No. 12/058,631
corresponding to Japanese Patent Application No. 2007-084424). In
the splicing process, as an easy splicing device, a single-sided
splicing tape is used. In general, the single-sided splicing tape
has a sheet as a base and an adhesive layer formed on one surface
of the base. The base material of the base is different from that
of the TAC film.
[0008] Further, the TAC film subjected to the stretching process
and heat treatment for stress relaxation in the off-line stretching
device shrinks in the film width direction after the heat treatment
for stress relaxation. The thermal shrinkage amount of the base of
the single-sided splicing tape and the thermal shrinkage amount of
the film are different from each other. Therefore, as shown in FIG.
11, in the case that a preceding film 3a and a trailing film 3b are
overlapped with each other and a single-sided splicing tape 60 is
adhered thereon so as to extend in a film width direction B in
order to splice the preceding film 3a and the trailing film 3b, the
shrinkage amount of a spliced area 61 is larger than that of an
area around the spliced area 61 (peripheral area). As a result,
wrinkles 62 occur in the spliced area 61.
[0009] When the wrinkles 62 occur in the spliced area 61, the
wrinkles 62 also occur in the peripheral area. The area having the
wrinkles 62 can not be used as a product and need to be discarded.
Therefore, there is a problem that the area as a product is
decreased. Further, in some cases, the TAC film breaks due to the
occurrence of wrinkles 62, thus causing a problem. The
above-described problems are not limited to the TAC film, and also
applied to other polymer films.
[0010] Accordingly, there is a problem that it is not possible to
obtain sufficient splicing strength in the case that the splicing
is performed by welding, and further wrinkles occur on the film
which is subjected to welding, splicing, stretching, and the heat
treatment for stress relaxation.
SUMMARY OF THE INVENTION
[0011] To solve the above problems, a first object of the present
invention is to provide a splicing method and device for more
infallibly splicing polymer films by thermal welding even though
the polymer film such as cellulose ester film is easily thermally
decomposed. A second object of the present invention is to provide
a polymer film stretching method capable of preventing occurrence
of wrinkles in a film spliced area after a heat treatment for
stress relaxation.
[0012] To achieve the first object, according to the present
invention, there is provided a splicing method of a polymer film
including the steps of: overlapping a rear end of a preceding
polymer film and a front end of a trailing polymer film; pressing
welding heads against a portion in which the preceding and trailing
films are overlapped with each other from each side in a film
overlapping direction while sandwiching the portion between the
welding heads; and welding the films while keeping a temperature of
the welding heads contacting the film at a temperature equal to or
less than a decomposition temperature of the polymer film, to
splice the rear end and the front end to each other. Note that the
polymer film may be a cellulose ester film.
[0013] Further, according to the present invention, there is
provided a splicing device of a polymer film including: a welding
head provided at each side of a portion in which a rear end of a
preceding polymer film and a front end of a trailing polymer film
are overlapped with each other in a film overlapping direction; a
shifter for moving the welding heads in the film overlapping
direction between a pressing position and a retracted position, the
welding heads sandwiching and pressing a portion in which the
preceding and trailing films are overlapped with each other in the
pressing position, and the welding heads being retracted from the
pressing position in the retracted position; and a heating
controller for heating the welding heads contacting the preceding
and trailing film at a temperature equal to or less than a
decomposition temperature of the polymer film after the welding
heads is shifted to the pressing position by the shifter. Note that
the polymer film may be a cellulose ester film.
[0014] According to the film splicing method of the present
invention, the portion in which the preceding and trailing films
are overlapped with each other is heated from both sides, and
therefore it is possible to shorten the heat transfer distance
between the film surface and the film splicing surface. Further,
while the temperature of the portion in which the preceding and
trailing films are overlapped with each other is kept at a level
equal to or less than a decomposition temperature of the film, the
overlapped portion can be welded. Accordingly, it is possible to
surely perform high-speed welding of the films each having a
melting point and decomposition point close to each other such as a
polymer film, in particular, cellulose ester film while preventing
occurrence of pitting.
[0015] Additionally, since it is possible to shorten the heat
transfer distance between the film surface and the film splicing
surface, it is also possible to decrease heating amount for the
welding. Thereby, electricity supplied to the heater can be
decreased to achieve improvement in energy conservation.
[0016] To achieve the second object, according to a polymer film
stretching method of the present invention, a portion in which a
rear end of a preceding polymer film and a front end of a trailing
polymer film are overlapped with each other is welded. Thereby, the
preceding film and the trailing film are spliced to each other. The
spliced polymer films are continuously transported. Side ends of
the spliced polymer film are held with use of plural clips to be
stretched in a film width direction while the polymer film is being
heated. While being continuously transported, the stretched polymer
film is subjected to a heat treatment for stress relaxation such
that a shrinkage amount of a spliced area of the preceding and
trailing polymer films and a shrinkage amount of an area around the
spliced area are approximately equal to each other in the film
width direction. Note that the welding is performed with use of
heat caused by an ultrasonic splicer or a heat sealer, or a polymer
solvent.
[0017] Further, according to a polymer film stretching method of
the present invention, a splicing tape having an adhesive layer and
no base is adhered to a portion in which a rear end of a preceding
polymer film and a front end of a trailing polymer film are
overlapped with each other. Thereby, the preceding film and the
trailing film are spliced to each other. The spliced polymer films
are continuously transported. Side ends of the spliced polymer film
are held with use of plural clips to be stretched in a film width
direction while the polymer film is being heated. While being
continuously transported, the stretched polymer film is subjected
to a heat treatment for stress relaxation such that a shrinkage
amount of a spliced area of the preceding and trailing polymer
films and a shrinkage amount of an area around the spliced area are
approximately equal to each other in the film width direction.
[0018] According to the polymer film stretching method of the
present invention, the portion in which the rear end of the
preceding polymer film and the front end of the trailing polymer
film are overlapped with each other is welded, and thereby the
preceding film and the trailing film are spliced to each other,
such that the shrinkage amount of the spliced area of the preceding
and trailing polymer films and the shrinkage amount of the area
around the spliced area after the heat treatment for stress
relaxation are approximately equal to each other in the film width
direction. Therefore, after the heat treatment for stress
relaxation, no wrinkles occur in the film spliced area and no tears
occur in the area around the spliced area.
[0019] Additionally, according to the polymer film stretching
method of the present invention, the preceding film and the
trailing film are spliced with use of the double-sided adhesive
tape having the adhesive layer and no base such that the shrinkage
amount of the spliced area of the preceding and trailing polymer
films and the shrinkage amount of the area around the spliced area
after the heat treatment for stress relaxation are approximately
equal to each other in the film width direction. Therefore, after
the heat treatment for stress relaxation, no wrinkles occur in the
film spliced area and no tears occur in the area around the spliced
area.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] One with ordinary skill in the art would easily understand
the above-described objects and advantages of the present invention
when the following detailed description is read with reference to
the drawings attached hereto:
[0021] FIG. 1 is a plan view illustrating an off-line stretching
device according to an embodiment of the present invention;
[0022] FIG. 2 is a plan view illustrating a preceding film, a
trailing film, and a heat sealer;
[0023] FIG. 3 is a perspective view illustrating the preceding
film, the trailing film, and welding heads;
[0024] FIG. 4 is a side view illustrating a procedure of a welding
process with use of the welding heads;
[0025] FIG. 5 is a view illustrating the preceding film and the
trailing film;
[0026] FIG. 6 is a plan view illustrating a tenter section;
[0027] FIG. 7 is a front view illustrating a clip;
[0028] FIG. 8 is a side view illustrating an ultrasonic
splicer;
[0029] FIG. 9 is a perspective view illustrating the preceding film
whose rear end is coated with acetone, and the trailing film;
[0030] FIG. 10 is a perspective view illustrating the preceding
film, the trailing film, and a double-sided splicing tape; and
[0031] FIG. 11 is a view illustrating a film subjected to a
stretching process and heat treatment for stress relaxation in a
conventional manner.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Embodiments of the present invention are described
hereinbelow. The present invention, however, is not limited to the
following embodiments.
Embodiment 1
[0033] As shown in FIG. 1, an off-line stretching device 2 is used
for stretching a TAC film 3 (hereinafter referred to as film 3),
and includes a film supply chamber 4, a tenter section 5, a
relaxation chamber 6, a cooling chamber 7, and a winding chamber 8
disposed in this order from a upstream side along a film
transporting direction A. A film roll 9 produced in a solution
casting apparatus is loaded in the film supply chamber 4. The film
roll 9 is obtained by winding the film 3 around a core in a roll
manner. The film 3 is fed from the film roll 9 loaded in the film
supply chamber 4 to the tenter section 5. In the tenter section 5,
the film 3 is continuously stretched in a film width direction
while being heated. The stretched film 3 passes through the
relaxation chamber 6 and the cooling chamber 7 to be cooled. The
cooled film 3 is wound in the winding chamber 8. In the tenter
section 5, the film 3 is stretched in the film width direction by
100.5% to 300%. In each of the film supply chamber 4, the tenter
section 5, the relaxation chamber 6, the cooling chamber 7, and the
winding chamber 8, there is provided an edge position controller
(EPC) (not-shown) for controlling such that the film 3 is
transported in a precise manner without meandering.
[0034] The film supply chamber 4 includes a turret-type film
feeding device 10 and a splicing section 11. The film feeding
device 10 includes a turret arm 13 provided with a mounting shaft
12 at each end. The film roll 9 is loaded to each of the mounting
shafts 12. The turret arm 13 makes half a rotation intermittently.
In the intermittent rotation by 180.degree., one of the mounting
shafts 12 is set at a film feeding position 16 (at a side of the
splicing section 11), and the other thereof is set at a core
replacement position 17. The film 3 is fed to the splicing section
11 from a film roll 9 mounted to the mounting shaft 12 located at
the film feeding position 16. When the film 3 located at the film
feeding position 16 is used up, the turret arm 13 rotates, and an
empty roll is removed from the mounting shaft 12 located in the
core replacement position 17, and then a new film roll 9 is mounted
thereto. Upon completing feeding of the film 3 from the film roll 9
loaded to the mounting shaft 12 located at the film feeding
position 16, the turret arm 13 rotates by 180.degree. to set the
film roll 9 loaded to the other mounting shaft 12 at the film
feeding position 16, thus feeding the film 3. Concurrently, the
rear end of the preceding film 3a fed first and the front end of
the trailing film 3b fed from the new film roll 9 are spliced to
each other in the splicing section 11.
[0035] A reservoir 29 is disposed between the film supply chamber 4
and the tenter section 5 to constitute a loop of the film 3 having
a length longer than the length necessary for the film splicing,
process. Accordingly, since the film 3 housed in the reservoir 29
is fed to the tenter section 5 at the time of splicing the
preceding film and trailing film, it is possible to perform the
splicing process of the film 3 without stopping the operation of
the tenter section 5.
[0036] As shown in FIG. 2, the splicing section 11 includes a
support roller 51 for supporting the preceding film 3a and a
support roller 52 for supporting the trailing film 3b. In order to
supply the film 3 continuously to the tenter section 5, in the
splicing section 11, a rear end of a preceding film 3a fed in first
and a front end of a trailing film 3b fed following the preceding
film 3a are overlapped with each other to be spliced by thermal
welding with use of a heat sealer 20. (Not that, welding means
melting and connecting the films by applying heat.) As shown in
FIG. 4A, for example, the heat sealer 20 includes an upper welding
head 21 and a lower welding head 22 provided so as to sandwich a
transporting path of the film 3 therebetween. The upper welding
head 21 has a heater 23 exposed from its lower surface, and the
lower welding head 22 has a heater 24 exposed from its upper
surface. A shift mechanism 56 causes each of the upper welding head
21 and lower welding head 22 to move between a heating position and
a retracted position. The heaters 23 and 24 are caused to contact
with the film 3 at the heating position. The heaters 23 and 24 are
caused to be retracted from the film 3 at the retracted position.
The temperature of each of the heaters 23 and 24 is controlled by
heat controllers 25 and 26 and sensors (not shown)
respectively.
[0037] As shown in FIG. 3, the splicing section 11 includes four
support rollers 51, 52, 71, and 72. The number of the support
rollers is not limited four, and any number of support rollers may
be provided as long as they can support the film. As shown in the
drawing, the width of each of the support rollers 51, 52, 71, and
72, and the welding heads 21 and 22 is made longer than that of the
film 3 to be transported.
[0038] The process for splicing the preceding and trailing films
with use of the heat sealer 20 is described hereinafter. FIG. 4
shows a procedure of welding the portion in which the preceding
film 3a and the trailing film 3b are overlapped with each other
with use of the welding heads 21 and 22. FIG. 4A shows a state in
which the preceding film 3a passes through the splicing section 11.
When the feeding of the film 3a from the film roll 9 is finished as
shown in FIG. 1, the rear end of the preceding film 3a is stopped
at the welding position (also referred to as heating position) of
the splicing section 11 as shown in FIG. 4B. The upper welding head
21 is located above the welding position, and the lower welding
head 22 is located below the welding position.
[0039] Next, in the film feeding device 10 shown in FIG. 1, the new
film roll 9 is set at the film feeding position 16, and the
trailing film 3b is fed therefrom. After the rear end of the
preceding film 3a and the front end of the trailing film 3b are
overlapped at the welding position, as shown in FIG. 4C, the
feeding of the trailing film 3b is stopped.
[0040] Next, as shown in FIG. 4D, the upper welding head 21 moves
downwards and the lower welding head 22 moves upwards, to sandwich
the portion in which films 3a and 3b are overlapped with each other
therebetween. In accordance with that, each of the heaters 23 and
24 is set to a predetermined temperature by the temperature
controller 25 and 26. The temperature is set such that the film 3
is welded but not decomposed, for example, within the range of
150.degree. C. to 299.degree. C. The portion in which the films 3a
and 3b are overlapped with each other is heated by the welding
heads 21 and 22 respectively provided above and below the portion,
and the portion is partially melted to be spliced with each other,
to form the welded portion (spliced area) 28. The portion is heated
for a desired period of time, and thereafter the heating is
stopped. The portion is naturally cooled while being nipped
therebetween for a desired period of time. Thereby, the rear end of
the preceding film 3a and the front end of the trailing film 3b are
spliced with each other on the welded portion 28. Note that instead
of natural cooling, a cooling device may be provided at each of the
welding heads 21 and 22 in order to cool the overlapped portion in
a press-contact manner.
[0041] Next, as shown in FIG. 4E, the upper welding head 21 moves
upwards and the lower welding head 22 moves downwards, and thereby
both welding heads 21 and 22 are respectively set to the retracted
position away from the welding position. Then, the films 3a and 3b
start to be fed.
[0042] As described above, the portion in which the films 3a and 3b
are overlapped with each other is heated from both upper and lower
sides, and therefore the heat transfer distance between the surface
of the heated film and the film splicing surface can be shortened
to approximately half in comparison with a case where only one head
is used for welding of the films in a conventional manner.
Accordingly, the films can be welded while the temperature of the
portion in which the films 3a and 3b are overlapped with each other
is kept at a level equal to or less than the decomposition
temperature of the polymer. Additionally, it is also possible to
prevent occurrence of pitting on the welded portion and degradation
of the polymer in the polymer film having a melting point of the
polymer and decomposition point thereof close to each other.
[0043] Note that instead of using the welding heads 53 and 54
provided so as to extend along the film width direction, a pair of
welding rollers containing heaters may be disposed so as to
sandwich the portion in which the rear end of the preceding film 3a
and the front end of the trailing film 3b are overlapped with each
other in a film overlapping direction such that the pair of welding
rollers are rolled in contact with the overlapped portion in the
film width direction. Note that, the film overlapping direction is
a direction so as to sandwich the films from above and below in a
vertical direction, as indicated by arrows X in FIG. 2, for
example.
[0044] In a case where the preceding and trailing films 3a and 3b
are spliced to each other with use of the heat sealer 20 as shown
in FIG. 5, in the film 3 subjected to the stretching process and a
heat treatment for stress relaxation, a shrinkage amount of the
spliced area 28 and a shrinkage amount of an area around the
spliced area 28 (hereinafter referred to as peripheral area) are
equal to each other, and a width of the spliced area 28 after
shrinkage (after heat treatment for stress relaxation) and a width
of the peripheral area after shrinkage become equal to each other.
Note that the stretching process and the heat treatment for stress
relaxation are described in detail later.
[0045] Further, in a case where the preceding and trailing films 3a
and 3b are spliced to each other with use of the heat sealer 20 as
described above, since different materials are not contained in the
spliced area 28, the spliced area 28 can be reused as a material of
the film. Note that, instead of the heat sealer 20, an impulse
sealer can be used for thermal-welding and splicing of the
films.
[0046] As shown in FIG. 6, in the tenter section 5, the film 3 is
stretched in the film width direction B while being transported in
the film transporting direction A. The tenter section 5 includes a
first rail 31, a second rail 32, a first chain (endless chain) 33
guided by the first rail 31, and a second chain (endless chain) 34
guided by the second rail 32.
[0047] The first chain 33 is bridged over a driving sprocket wheel
35 and a driven sprocket wheel 36, and the second chain 34 is
bridged over a driving sprocket wheel 37 and a driven sprocket
wheel 38. The driving sprocket wheels 35 and 37 are disposed at a
side of tenter outlet 66, and caused to rotate by a not-shown
driver. The driven sprocket wheels 36 and 38 are disposed at a side
of tenter inlet 65.
[0048] The first chain 33 and the second chain 34 are provided with
plural clips 39 at a predetermined interval. While holding the side
edges of the film 3, the clips 39 move along the rails 31 and 32,
to stretch the film 3 in the film width direction B. The clips 39
start holding the film 3 at a point PA, and release the film 3 at a
point PB. The clips 39 start stretching the film 3 at a point PC,
and finish stretching the film 3 at a point PD. Under the
stretching process, the film width Wpa at the point PA, the film
width Wpb at the point PB, the film width Wpc at the point PC, and
the film width Wpd at the point PD satisfy a formula:
Wpa=Wpc.ltoreq.Wpd=Wpb. Although the stretching ratio of the film 3
is appropriately changed in accordance with the desired optical
properties or the like, the film 3 is preferably stretched in the
film width direction B by 100.5% to 300%.
[0049] The tenter section 5 is disposed in a drying chamber
(not-shown). The tenter section 5 is divided into a preheating zone
5a, a heating/stretching zone 5b, and a heat treatment for stress
relaxation/stretching relaxation zone 5c in this order from the
downstream side in the film transporting direction A. The film 3 is
preheated while being transported with the film width kept at Wpa
in the preheating zone 5a. The distance between the pair of clips
39 does not change, and the film 3 is not stretched by the clips 39
in the film width direction B. In the heating/stretching zone 5b,
the film 3 is heated, and the distance between the pair of clips 39
gradually increases from Wpc to Wpd. In the heat treatment for
stress relaxation/stretching relaxation zone 5c, the film 3 is
heated while being transported with the film width kept at Wpd, to
be subjected to the heat treatment for stress relaxation, and the
film 3 is stretched by the clips 39 in the film width direction B.
The distance between the pair of clips 39 gradually decreases or
does not change, and the film 3 is subjected to the stretching
relaxation (heat treatment for stress relaxation).
[0050] As shown in FIG. 7, the clip 39 consists of a clip main body
80 and a rail attachment portion 81. The clip main body 80 consists
of a frame 82 having an approximately inverted U shape and a
flapper 83. The flapper 83 is rotatably mounted to the frame 82 by
a mounting shaft 82a. The flapper 83 shifts between a film holding
position (closed position) and a film releasing position. At the
film holding position, the flapper 83 stands approximately
vertically. At the film releasing position, a releasing member 70
contacts with an engaging head 83a and rotates in an oblique
direction. The flapper 83 is generally biased under its own weight
or by a spring (not shown) so as to be set at the film holding
position. The film 3 is held between a film holding surface 82b and
a flapper lower surface 83b at the film holding position.
[0051] The rail attachment portion 81 consists of an attachment
frame 84, and guide rollers 85, 86, and 87. The attachment frame 84
is provided with the first chain 33 or the second chain 34. The
guide rollers 85 to 87 respectively contact with each support
surface of the driving sprocket wheels 35 and 37 (see FIG. 6) or a
support surface of the first rail 31 or the second rail 32, and
thereby rotates. As a result, the clip main body 80 does not fall
from the driving sprocket wheels 35 and 37, and the rails 31 and
32, and is guided along the first and second rails 31 and 32.
[0052] The releasing member 70 of the clip 39 is disposed so as to
be close to the sprocket wheels 35 to 38 (see FIG. 6). At the
driven sprocket wheels 36 and 38 at the side of tenter inlet 65
(see FIG. 6), the releasing member 70 contacts with the engaging
head 83a of the clip 39 to release the engaging head 83a in front
of the film holding position PA, and thereby the side ends of the
film 3 can be transported to the tenter section 5. When the film 3
passes through the film holding position PA, the releasing member
70 moves away from the engaging head 83a, and the clips 39 is moved
away from the releasing position to be set at the film holding
position. Thus, the side ends of the film 3 are held. Similarly, at
the driving sprocket wheels 35 and 37 at the side of the tenter
outlet 66, the clips 39 are set to the releasing position by the
releasing member 70 at the film releasing position PB, and thereby
the holding of the side ends of the film 3 are canceled.
[0053] Returning to FIG. 1, the film 3 is stretched in the tenter
section 5 and sent to a slitting device 40. The side edges of the
film 3, which were held by the clips 39, are cut off at a
predetermined cutting line by the slitting device 40, and the side
edges thus cut away as slits are cut into pieces by a cut blower
41. The side edges thus cut into pieces are sent to a crusher 42 by
a not-shown blowing device and crushed into chips by the crusher
42. The chips are reused for preparing the dope, thus resulting in
improvement in cost.
[0054] The side edges of the preceding film 3a and the trailing
film 3b are reused. In a case where the preceding film 3a and the
trailing film 3b are spliced with use of the splicing tape, it is
necessary to remove the splicing tape from the side edges to reuse
the side edges. However, in a case where the preceding film 3a and
the trailing film 3b are spliced with use of the heat sealer 20,
since the splicing section 11 contains no substances different from
those of the film 3 and the splicing section 11 can be reused in
the material recycle, the edges in the spliced state can be used
directly. Thus, it is possible to save trouble of removing the
splicing tape at the time of reusing, and increase operability in
recovering of the side edges. Further, it is possible to simplify
the structure of the off-line stretching device 2. The film 3 whose
side edges are cut away by the slitting device 40 is sent to the
relaxation chamber 6.
[0055] The relaxation chamber 6 includes plural rollers 43, and the
film 3 is transported by the rollers 43 in the relaxation chamber
6. Air at a desired temperature is blown to the relaxation chamber
6 by a blower (drying air duct) (not-shown) to subject the film 3
to heat treatment for stress relaxation. The temperature of the air
is preferably in the range of 20.degree. C. to 250.degree. C. The
temperature of the film 3 is gradually decreased.
[0056] The film 3 subjected to the heat treatment for stress
relaxation is sent to the cooling chamber 7 to be cooled to
30.degree. C. or less, and then sent to the winding chamber 8. The
winding chamber 8 includes a winding device 47 provided with a
winding roller 44 and a press roller 45. The film 3 sent to the
winding chamber 8 is wound by the winding roller 44 while being
pressed by the press roller 45.
[0057] The film 3 can be formed by any well-known solution casting
method. For example, the TAC film disclosed in Japanese Patent
Laid-Open Publication No. 2005-104148 can be used. In particular,
for the purpose of improving the film producing speed, the present
invention is applied to the TAC film formed as follows. Dope
containing TAC and a solvent is cast onto a cooled peripheral
surface of the casting drum to form a casting film. After being
cooled and turning into gel, the casting film is solidified. The
solidified casting film is peeled as a wet film from the casting
drum and sent to a pin tenter to be dried and form a film. The film
is wound in a roll manner and housed to obtain the TAC film.
Thereby, according to the present invention, it is possible to
efficiently form the TAC film having excellent optical
properties.
Embodiment 2
[0058] Although the preceding film 3a and the trailing film 3b are
spliced to each other with use of the heat sealer 20 in the
splicing section 11 in Embodiment 1, alternatively, as shown in
FIG. 8, an ultrasonic splicer 50 can be used to splice the
preceding film 3a and the trailing film 3b.
[0059] The ultrasonic splicer 50 mechanically vibrates the film 3,
for example, 20,000 to 28,000 times/sec at the amplitude of 0.03
mm, to heat and weld the film 3. The ultrasonic splicer 50 includes
two transducers 57, a horn 59, and a transmitter 53. A permanent
magnet 54 is disposed between the transducers 57. A coil 55 is
bridged over each of the transducers 57. The transmitter 53 causes
the coil 55 to drive the transducers 57. The transducer 57 converts
electrical vibration to mechanical vibration. The horn 59 amplifies
the mechanical vibration caused by the transducer 57 to apply
energy to the rear end of the preceding film 3a and the front end
of the trailing film 3b (vibrate the rear end of the preceding film
3a and the front end of the trailing film 3b) mounted on a mounting
base 56. The rear end of the preceding film 3a and the front end of
the trailing film 3b are heated by the vibration to be welded and
spliced to each other.
Embodiment 3
[0060] Although the preceding film 3a and the trailing film 3b are
spliced to each other with use of the heat sealer 20 in the
splicing section 11 in Embodiment 1, alternatively, as shown in
FIG. 9, the splicing may be performed with use of acetone as one of
the solvents contained in the dope used in forming the TAC
film.
[0061] Acetone is applied to the spliced area 28 at the rear end of
the preceding film 3a by spraying, and then the front end of the
trailing film 3b is put on the rear end of the preceding film 3a.
Thereafter, the rear end of the preceding film 3a and the front end
of the trailing film 3b are spliced to each other by the acetone in
a press-contact manner.
Embodiment 4
[0062] Although the preceding film 3a and the trailing film 3b are
spliced to each other with use of the heat sealer 20 in the
splicing section 11 in Embodiment 1, alternatively, as shown in
FIG. 10, a double-sided splicing tape 58 having no base of No.
5919ML produced by NITTO DENKO CORPORATION may be used to splice
the preceding film 3a and the trailing film 3b. The double-sided
splicing tape 58 having no base is adhered to the spliced area 28
of the preceding film 3a, and the trailing film 3b is adhered
thereon, to splice the preceding film 3a and the trailing film
3b.
[0063] Although the TAC film is used as the polymer film according
to the first to fourth embodiments, the present invention is not
limited to the TAC film. The present invention is also applicable
to other cellulose ester films, for example, cellulose acetate
propionate film, and various kinds of polymer films.
Example
[0064] The film 3 stretched in the tenter section 5 was subjected
to heat treatment for stress relaxation in the relaxation chamber
6. After the heat treatment for stress relaxation, the film 3
shrunk in the film width direction B.
[0065] The film 3 obtained by splicing the rear end of the
preceding film 3a and the front end of the trailing film 3b
according to each of the splicing methods in Embodiments 1 to 4 was
subjected to the stretching process and heat treatment for stress
relaxation in the off-line stretching device 2. Then, the film
width of the spliced area 28 after shrinkage (heat treatment for
stress relaxation) and the film width of the peripheral area after
shrinkage were measured to obtain results shown in Examples 1 to 4.
Note that the preceding film 3a and the trailing film 3b were TAC
films and had a product width of 80 .mu.m. The width of the film 3
before the stretching was 640 mm, and the width of the film 3 after
the stretching was 862 mm. After the stretching, in order to remove
the deformed portion of the film 3 caused by being held by the
clips 39, the side edges of the film 3 were cut off by the slitting
device 40 such that the width of the film 3 became 660 mm. The film
3 whose side edges were cut away was subjected to heat treatment
for stress relaxation in the relaxation chamber 6. Moreover, as
shown in FIG. 11, the preceding film 3a and the trailing film 3b
were overlapped with each other, and a single-sided splicing tape
60 with a base of No. 31B produced by NITTO DENKO CORPORATION was
adhered thereto so as to extend in the film width direction B, thus
obtaining the result shown in Comparative Example. The other
conditions of Comparative Example are the same as those in Examples
1 to 4.
[0066] The results of the experiments are shown in Table 1. In
Table 1, P (Pass) represents a state of a film after shrinkage, in
which there occurred no wrinkles in the spliced area 28 and there
occurred no tears in the peripheral area. F (Fault) represents a
state of a film after shrinkage, in which there occurred wrinkles
in the spliced area 28 or there occurred tears in the peripheral
area.
TABLE-US-00001 TABLE 1 Width of Width of spliced area peripheral
State of film after area after after shrinkage shrinkage shrinkage
Example 1 650 mm 650 mm P Example 2 650 mm 650 mm P Example 3 650
mm 650 mm P Example 4 650 mm 650 mm P Comparative 625 mm 650 mm F
Example
[0067] The film width before shrinkage: 660 mm
[0068] For thermal welding of the spliced area 28, the heat sealer
20 was used in Example 1, the ultrasonic splicer 50 was used in
Example 2, the acetone was used in Example 3, the double-sided
splicing tape 58 having no base was used in Example 4. As a result
of the experiments, in Examples 1 to 4, the shrinkage amount of the
spliced area 28 was equal to that of the peripheral area. The film
width of the spliced area 28 was equal to that of the peripheral
area. Therefore, there occurred no wrinkles in the spliced area 28,
and thus leading to excellent results. Further, there occurred no
tears in the peripheral area, and thus leading to excellent
results.
[0069] As described above, the rear end of the preceding film 3a
and the front end of the trailing film 3b are spliced to each other
by thermal welding with use of the heat sealer 20 or the ultrasonic
splicer 50, by welding with use of acetone, or by joining with use
of the double-sided splicing tape 58 having no base, and thereby it
is possible to make the shrinkage amount of the spliced area 28 and
the shrinkage amount of the peripheral area equal to each other.
Accordingly, it is possible to prevent occurrence of wrinkles in
the spliced area 28 and tears in the peripheral area. Thus, it is
possible to increase the area of the film capable of being used as
a product in comparison with the films formed in a conventional
manner.
[0070] Further, since it is possible to make the film width of the
spliced area 28 after shrinkage and the film width of the
peripheral area after shrinkage equal to each other, the control
for preventing meandering of the film 3 and transporting the film 3
precisely with use of the EPC can be secured in comparison with the
case where the film width of the spliced area 28 and the film width
of the peripheral area are different from each other as shown in
FIG. 11.
[0071] The present invention is not to be limited to the above
embodiments, and on the contrary, various modifications will be
possible without departing from the scope and spirit of the present
invention as specified in claims appended hereto.
* * * * *