U.S. patent application number 10/716158 was filed with the patent office on 2005-05-19 for induction splicing of photographic film strips.
Invention is credited to Dontula, Narasimharao, Johnston, Brian H., Kordovski, Luba, Smith, Thomas M..
Application Number | 20050103430 10/716158 |
Document ID | / |
Family ID | 34522979 |
Filed Date | 2005-05-19 |
United States Patent
Application |
20050103430 |
Kind Code |
A1 |
Smith, Thomas M. ; et
al. |
May 19, 2005 |
INDUCTION SPLICING OF PHOTOGRAPHIC FILM STRIPS
Abstract
A method is described for splicing together overlapping ends of
first and second lengths of photographic film strips of common film
strip width, comprising positioning a bonding element between an
overlapping end of the first length of photographic film and a
corresponding overlapped end of the second length of photographic
film, and heating the bonding element to effect an adhesive bond
between such film ends, wherein the bonding element comprises an
induction heating receptive support and thermoplastic adhesive
layers on each side of the support, and wherein the heating of the
bonding element is performed by induction heating. The present
invention allows for the preparation of photographic film splices,
consisting of either homogeneous or dissimilar film bases, using a
bonding element and induction heating to provide smooth yet strong
splices. In particular, the invention enables successful splicing
of acetate support (e.g., cellulose triacetate (CTA)) based films
and polyester support (e.g., polyethylene terephthalate (PET))
based films either to themselves or each other. The invention
provides a method of forming composite rolls of motion picture film
containing different film bases as well as eliminating the need for
emulsion skiving, and the use of toxic, flammable film cements when
splicing CTA films.
Inventors: |
Smith, Thomas M.;
(Spencerport, NY) ; Johnston, Brian H.;
(Pittsford, NY) ; Dontula, Narasimharao;
(Rochester, NY) ; Kordovski, Luba; (Rochester,
NY) |
Correspondence
Address: |
Paul A. Leipold
Patent Legal Staff
Eastman Kodak Company
343 State Street
Rochester
NY
14650-2201
US
|
Family ID: |
34522979 |
Appl. No.: |
10/716158 |
Filed: |
November 18, 2003 |
Current U.S.
Class: |
156/157 ;
156/159; 156/273.9 |
Current CPC
Class: |
G03D 15/043 20130101;
Y10T 428/19 20150115 |
Class at
Publication: |
156/157 ;
156/159; 156/273.9 |
International
Class: |
B65H 019/00; B65H
069/02 |
Claims
1. (canceled)
2. A method for splicing together overlapping ends of first and
second lengths of photographic film strips of common film strip
width, comprising positioning a bonding element between an
overlapping end of the first length of photographic film and a
corresponding overlapped end of the second length of photographic
film, and heating the bonding element to effect an adhesive bond
between such film ends, wherein the bonding element comprises an
induction heating receptive support and thermoplastic adhesive
layers on each side of the support and wherein the heating of the
bonding element is performed by induction heating, wherein the
first and second lengths of photographic film strips are motion
picture film strips of width from 8 to 70 mm, the film strips
contain imaged scene frames, the bonding element is from 0.5 to 3
mm in width and from 8 to 70 mm in length and less than or equal to
about 200 .mu.m thick, and the bonding element is positioned
lengthwise across the film strip width in an area between the
imaged scene frame areas, and wherein the peel strength of the
resulting prepared splice exceeds 1.0 kg/35 mm width and the
tensile strength of the resulting prepared splice exceeds 18 kg/35
mm width.
3. A method according to claim 2, wherein the bonding element has a
thickness of from about 5 .mu.m to about 100 .mu.m.
4. A method according to claim 2, wherein the bonding element has a
thickness of from about 5 .mu.m to about 50 .mu.m.
5. A method according to claim 2, wherein the bonding element has a
thickness of from about 5 .mu.m to about 30 .mu.m.
6. A method according to claim 2, wherein the bonding element
comprises a metal foil support having a thickness of from about 5
.mu.m to about 100 .mu.m and thermoplastic adhesive layers of from
about 1 to about 10 .mu.m coated on each side of the support.
7. A method according to claim 6, wherein the metal foil has a
thickness of from about 10 .mu.m to about 50 .mu.m.
8. A method according to claim 6, wherein the bonding element
comprises a metal foil support having a thickness of from about 10
.mu.m to about 25 .mu.m and thermoplastic adhesive layers of from
about 1 to about 5 .mu.m coated on each side of the support.
9. A method according to claim 2, wherein the bonding element
comprises a metal foil support having a thickness of from about 5
.mu.m to about 100 .mu.m and pre-formed adhesive films which are
laminated to both sides of the metal foil.
10. A method according to claim 9, wherein the pre-formed adhesive
films comprise self-supported adhesive films of less than or equal
to about 50 .mu.m in thickness having a thermal activation
temperature of greater than 75.degree. C., an ultimate elongation
of less than 400%, and a 2% secant modulus of less than 120
N/mm.sup.2.
11. A method according to claim 9, wherein the pre-formed adhesive
films comprise self-supported adhesive films of less than or equal
to about 25 .mu.m in thickness having a thermal activation
temperature of greater than 75.degree. C., an ultimate elongation
of less than 400%, and a 2% secant modulus of less than 120
N/mm.sup.2.
12. A method according to claim 2, wherein the metal foil comprises
aluminum foil.
13. A method according to claim 2, wherein the induction heating
receptive support of the bonding element comprises a polymeric film
support with layers of electrically conductive or magnetic metal
vacuum-deposited on both surfaces of the polymeric film.
14. A method according to claim 13, wherein the polymeric support
comprises polyethylene terephthalate having a thickness of from
about 5 .mu.m to about 50 .mu.m and each vacuum-deposited metal
layer has a thickness of from about 1000 to about 8000
Angstroms.
15. A method according to claim 14, wherein the polymeric support
has a thickness of from about 6 .mu.m to about 20 .mu.m and each
vacuum-deposited metal layer has a thickness of from about 4000 to
about 6000 Angstroms.
16. A method according to claim 13, wherein the metal layers
comprise silver.
17. A method according to claim 2, wherein the first and second
lengths of photographic film strips each independently comprises an
acetate based film strip or a polyester based film strip.
18. A method according to claim 2, wherein one of the first and
second lengths of photographic film strips comprises an acetate
based film strip and the other of the first and second lengths of
photographic film strips comprises a polyester based film
strip.
19. (canceled)
Description
FIELD OF THE INVENTION
[0001] This invention relates to a method of utilizing
induction-heating technology to splice together photographic film
strips, and especially motion picture films having dissimilar
polymeric supports. In particular, the invention relates to
materials and methods that will allow successful splicing of
acetate support (e.g., cellulose triacetate (CTA)) based films and
polyester support (e.g., polyethylene terephthalate (PET)) based
films either to themselves or to each other.
BACKGROUND OF THE INVENTION
[0002] Motion picture photographic films used in producing a
release print (the film projected in movie theaters) include camera
origination film, intermediate film, and the release print film.
Current practice for most motion picture production involves the
use of at least four photographic steps. The first step is the
recording of the scene onto a camera negative photographic film.
While the original negative (typically after editing) may be
printed directly onto a negative working print film in a second
step to produce a direct release print, most motion picture
productions use an additional two intermediate steps. Typically,
the original camera negative film is printed onto a negative
working intermediate film, such as Eastman Color Intermediate Film,
yielding a master positive. The master positive is subsequently
printed again onto an intermediate film providing a duplicate
negative. Finally, the duplicate negative is printed onto a print
film forming the release print. In practice, several duplicate
negative copies are produced from the master positive, and each of
the duplicate negatives may then be used to make hundreds of print
film copies. This multistep process helps save the integrity of the
valuable original camera negative film in preparing multiple
release prints. In certain situations, usually involving special
effects, intermediate film may be used an additional two or more
times in preparing the final duplicate negatives to be used in
printing the release prints. In this case, the first duplicate
negative is used to print onto intermediate film to produce a
second master positive, which is in turn used to produce a second
duplicate negative. The second duplicate negative may be then used
for printing the release prints.
[0003] The wide variety of potential film products available for
the above-mentioned processes can be produced on either of two
commonly employed polymeric supports: cellulose triacetate (CTA)
and polyethylene terephthalate (PET). It is becoming more common
for specific film codes to be available on only one of these
supports as opposed to either. Currently, acetate-based films, and
the older, less common cellulose nitrate-based films, are spliced
to themselves using film cements comprising organic solvents
designed to partially solubilize the cellulose-based film supports.
Satisfactory cement splicing requires careful scraping away of the
emulsion layers of the lower film component prior to application of
the film cement in order to allow intimate support contact. It is
also important to allow sufficient clamping time in the splicer.
Current recommendations are fifteen to thirty seconds under modest
heat and pressure prior to handling of the splice. Because a cement
splice does not attain full strength for several hours, care is
required when handling the film if immediate use is contemplated.
Not only is this splicing technique cumbersome, time consuming, and
a source of debris, but there are also health, safety and
environmental concerns surrounding the components of the currently
employed film cements.
[0004] With the advent of PET-based film products, a new splicing
technique was required since this film support does not readily
lend itself to cement splicing. The polymer used as the support
base is not soluble in the solvents used in film cement and even
more toxic solvents would be required to produce the same type of
bonding with PET-based films. The most common method of splicing
PET-based film, when it was originally introduced, was the use of
pressure sensitive tapes. These tapes are costly, cumbersome, a
potential source of dirt and require application to imaged frames
adjacent to the splice itself.
[0005] A more convenient method of splicing PET-based films has
been with the use of ultrasonic energy to essentially "weld" the
two film members together. This splicing technique is typically
accomplished in an overlap configuration, and within an area that
will exclude perforations and/or an imaged frame. U.S. Pat. Nos.
3,574,037 and 4,029,538, and EP 0497 393, e.g., describe systems
and apparatus employing the use of ultrasonic sealing devices that
can be used to splice films, specifically motion picture films.
These patents, however, refer only to the splicing or welding of
polyester-based film products.
[0006] While the use of ultrasonic welding techniques has been
suggested for splicing of acetate based film strips, attempts to do
so have generally not been successful. Motion picture film splicers
that have been developed which utilize ultrasonic energy to splice
PET-based films together, e.g., when used to splice CTA-based
films, cause brittleness and diminished strength typically
resulting in splices that are far too weak and/or rough for
practical application. Such splices may exhibit levels of roughness
that are likely to damage adjacent areas of film when wound in roll
form. Additionally, the increased thickness produced by the molten
acetate material may prevent splices from smooth conveyance through
the tight tolerances encountered in film printing gates. Similarly,
using existing ultrasonic splicing devices to join CTA. and PET
film stocks produces the same rough, distorted surface of the
acetate film member. U.S. Pat. No. 3,700,532, e.g., notes some
typical problems associated with attempts to ultrasonically splice
acetate based film strips.
[0007] Japanese Kokais 57-072816 A and 57-073064 A describe
materials that can be utilized to bond components using induction
heating. These consist of thermoplastic resins coated on both sides
of metallic films. These publications, however, refer only to the
bonding media itself and not the adherends.
[0008] Japanese Kokai 55-119652 A teaches a method of splicing
together photographic paper using induction heating. Overlapped
sections of photographic paper webs are joined together by
preheating the surfaces, prepressing and then induction heating
under pressure to form a splice. This application relies on the
thermal fusing of resin-coated paper to itself and not the bonding
of photographic film products of differing polymeric
composition.
[0009] Similarly there are numerous patent publications, among them
Japanese Kokais 62-098307 A and 63-182610 A, that deal with the
splicing together of optical fibers by means of induction heating.
Again, the splice components are of homogeneous composition and the
application is non-photographic.
[0010] There are also many patent publications, typified by
Japanese Kokais 04-019139 A and 07-069369 A, that teach this
technology for the use of lidding attachment in the bottling
industry. The two patents referenced involve the use of an aluminum
foil layer or similar electrically conducting support, coated on
one surface with a thermoplastic resin layer having good adhesion
to the container material.
[0011] There are numerous other patent publications that describe
the use of induction heating to bond various materials together.
They range from bonding together shoe components (EP 0 919 151 A1),
to the assembly of automotive panels (Japanese Kokai 59-076220 A),
to the attachment of labels to metallic can bodies (Japanese Kokais
10-000683 A and 2001-047511 A).
[0012] To date no one has provided a method for successfully
splicing together motion picture film strips composed of dissimilar
polymeric supports that does not rely on the use of
pressure-sensitive tape. The prior art has also failed to provide a
method of splicing cellulosic-based motion picture film without the
need for removal of the emulsion layer and application of a
flammable and toxic solvent mixture.
SUMMARY OF THE INVENTION
[0013] In accordance with one embodiment of the invention, a method
is described for splicing together overlapping ends of first and
second lengths of photographic film strips of common film strip
width, comprising positioning a bonding element between an
overlapping end of the first length of photographic film and a
corresponding overlapped end of the second length of photographic
film, and heating the bonding element to effect an adhesive bond
between such film ends, wherein the bonding element comprises an
induction heating receptive support and thermoplastic adhesive
layers on each side of the support, and wherein the heating of the
bonding element is performed by induction heating.
[0014] The present invention allows for the preparation of
photographic film splices, consisting of either homogeneous or
dissimilar film bases, using a bonding element and induction
heating to provide smooth yet strong splices. In particular, the
invention enables successful splicing of acetate support (e.g.,
cellulose triacetate (CTA)) based films and polyester support
(e.g., polyethylene terephthalate (PET)) based films either to
themselves or each other. The invention provides a method of
forming composite rolls of motion picture film containing different
film bases as well as eliminating the need for emulsion skiving,
and the use of toxic, flammable film cements when splicing CTA
films.
DETAILED DESCRIPTION OF THE INVENTION
[0015] In accordance with this invention, materials and methods are
identified that will allow induction heating devices to be used to
splice either polyester-based films or acetate-based films either
to themselves or to each other and provide an adequate level of
splice strength and smoothness.
[0016] Induction bonding technology provides the capability of
bonding incompatible substrates, at high sealing rates, with
precise control over the bond area. By far the most common
applications of induction heating technology to date have been
directed towards food packaging and lidding materials. These
technologies typically employ a heat-sealable thermoplastic
adhesive layer on one side of a metal foil or metal coated (vacuum
deposited) polymeric web. The present inventors have found that the
induction heating process may be employed successfully for the
splicing of photographic film strips, and in particular motion
picture film strips, provided the adhesive is applied to both sides
of an induction heating receptive support. The process of the
invention is particularly advantageous in that it enables the
splicing of dissimilar motion picture films, which has been
particularly problematic in the art.
[0017] The key to induction heating bonding in accordance with the
invention is incorporation of a bonding element, which comprises an
induction heating receptive (typically metallic) support and a
thermoplastic adhesive layer on each side of the support. When
placed between two substrates and exposed to the electromagnetic
field of an induction coil, the bonding element generates
sufficient heat to either bring the surrounding surfaces to fusion
temperature or, sufficiently soften the adhesive material to allow
it to bond the surrounding surfaces together.
[0018] Induction heating in accordance with the invention may be
accomplished with use of a high power oscillator that supplies
alternating current to an induction work coil. An alternating
magnetic field is associated with the supplied current according to
Ampere's law. The energy associated with the magnetic field is
transferred to the bonding element by electromagnetic induction
(Lenz's law and Faraday's law). One or both of the following
phenomena therefore generate heat within the materials: hysteresis
losses, whereby a magnetic material tends to oppose a change in or
lag an applied oscillating field; and conduction losses, whereby
electrical conductors resist the flow of electrons associated with
an induced current (eddy currents).
[0019] Typically an electromagnetic field of 10 kHz to 15 MHz may
be employed, more preferably the frequencies of 2 MHz to 6 MHz are
employed. Low frequencies are typically employed for thicker
materials where deep heat penetration is required, while higher
frequencies are effective for smaller parts or shallower
penetration. The induction-heating coil, typically comprising
water-cooled copper tubing, is generally formed into different
shapes depending on the application and to maximize the heating
effect. One common shape that is used is a hairpin-shaped loop. The
coil is usually embedded in a nonmetallic fixture that aligns the
components with necessary pressure prior to bonding. The coil is
placed in close proximity to the bonding element and power is
pulsed to the unit, typically for a fraction of a second. Since
induction heating is highly directional, very small bonding areas
can be heated without affecting the surrounding areas. Furthermore,
power input can be regulated to achieve the temperatures needed for
bonding.
[0020] In accordance with a preferred embodiment of the invention,
induction heating may be used for splicing together acetate-based
film products with resultant strong and smooth splices. The ability
to splice acetate-based film using induction heating eliminates the
need for emulsion layer skiving as well as the use of flammable and
toxic solvent cements. In addition, it provides the capability for
joining together dissimilar film products. It also allows, e.g.,
for acetate-based film to be adequately spliced to polyester-based
film products, which until now has been impossible without the use
of pressure sensitive tape.
[0021] In accordance with the method of the invention, overlapping
ends of first and second lengths of photographic film strips of
common film strip width are spliced together by positioning a
bonding element between an overlapping end of the first length of
photographic film and a corresponding overlapped end of the second
length of photographic film, and heating the bonding element to
effect an adhesive bond between such film ends, wherein the bonding
element comprises an induction heating receptive support and
thermoplastic adhesive layers on each side of the support, and
wherein the heating of the bonding element is performed by
induction heating.
[0022] To enable effective splicing of motion picture film strips
(typically having film widths of from 8 to 70 mm) having imaged
scene frame areas without having the splice area negatively effect
the imaged frame areas, in accordance with a preferred embodiment
of the invention a bonding element is employed which is from 0.5 to
3 mm in width and from 8 to 70 mm in length and less than or equal
to about 200 .mu.m thick, and the bonding element is positioned
lengthwise across the film strip width in an area between the
imaged scene frame areas.
[0023] The bonding element preferably has a thickness of from about
5 .mu.m to about 100 .mu.m, more preferably from about 5 .mu.m to
about 50 .mu.m, and even more preferably from about 5 .mu.m to
about 30 .mu.m, in order to minimize thickness of the resulting
spliced area.
[0024] In accordance with a particular embodiment, the bonding
element employed in the process of the invention may comprise a
metal foil support having a thickness of from about 5 .mu.m to
about 100 .mu.m (more preferably from about 10 .mu.m to about 50
.mu.m, and even more preferably from about 10 .mu.m to about 25
.mu.m) and thermoplastic adhesive layers of from about 1 to about
20 .mu.m (more preferably from about 1 to about 10 .mu.m) coated on
each side of the support. The metal foil support may comprise any
induction heating receptive metal, although aluminum foil is
preferred for balance of cost and performance.
[0025] Alternatively, the induction heating receptive support of
the bonding element may comprise a polymeric film support with
layers of electrically conductive or magnetic metal
vacuum-deposited on both surfaces of the polymeric film. Polymeric
supports in accordance with such embodiment preferably may
comprise, e.g., polyethylene terephthalate film having a thickness
of from about 5 .mu.m to about 50 .mu.m (more preferably from about
6 .mu.m to about 20 .mu.m). Each vacuum-deposited metal layer in
such embodiment preferably has a thickness of from about 1000 to
about 8000 Angstroms (more preferably from about 4000 to about 6000
Angstroms), with silver being an example of a preferred deposited
metal layer.
[0026] Two coatable thermoplastic adhesive materials, which have
been identified as superior for use in bonding elements for use in
the method of the invention, include VITEL.TM. 3300B, produced by
Bostik and HYPALON.TM. 30, from DuPont Dow Elastomers. HYPALON.TM.
30 is a chlorosulfonated polyethylene resin having a molecular
weight (N) of 23,000. The polymer contains 43% (by weight) chlorine
and 1.1% (by weight) sulfur. It has a glass transition temperature
of 10.degree. C., and is soluble in aromatic and chlorinated
hydrocarbons, esters, and ketones. VITEL.TM. 3300B is a high
molecular weight, aromatic, linear saturated polyester resin having
a glass transition temperature of 11.degree. C. and a (Ring and
Ball) melt flow point of 125.degree. C. This is a typically
employed thermoplastic adhesive material with a suggested
activation temperature of at least 27.degree. C. It is most soluble
in oxygenated solvents such as ketones and esters.
[0027] In a further embodiment of the invention, the adhesive
layers may comprise pre-formed adhesive films that are laminated to
both sides of the induction heating receptive support, in
particular where the support comprises a metal foil. The pre-formed
adhesive films preferably comprise self-supported adhesive films of
less than or equal to about 50 .mu.m in thickness, more preferably
less than or equal to about 25 .mu.m in thickness, having a thermal
activation temperature of greater than 75.degree. C., an ultimate
elongation of less than 400%, and a 2% secant modulus of less than
120 N/mm.sup.2. Examples of such preferred pre-formed adhesive
films include INTEGRAL.TM. 709 and INTEGRAL.TM. 803 films available
from Dow Chemical Company.
EXAMPLES
[0028] The following examples are intended to illustrate the
present invention more practically but not to limit it in scope in
any way.
[0029] Film materials used to evaluate the effectiveness of
induction heating splicing represent a cross-section of Eastman
Kodak motion picture film products on both acetate and polyester
base. All films tested were unexposed, processed, 35 mm products.
The specific (EK) film codes and brief description are listed
below:
[0030] 2234--a polyester-based panchromatic negative film intended
for making duplicate negatives from master positives, or
internegatives from reversal originals.
[0031] 5234--an acetate-based version of 2234.
[0032] 2383--a polyester-based color print film.
[0033] 5279--an acetate-based color negative film.
[0034] Six-inch lengths of film were spliced together in various
combinations with various bonding elements and tested for tensile
strength, peel strength, and surface roughness on the spliced area.
The induction heating process utilized a system comprised of a NOVA
STAR.TM. 3L solid state induction power supply, a water-cooled
chilling unit, and a remote heating (sealing) station which
includes a coil mounted in a non-conductive clamping fixture. The
NOVA STAR.TM. unit has a frequency of 485 kHz, 3 kW power, and was
used in conjunction with a water-cooled single loop (hairpin)
copper coil mounted in a TEFLON.TM. bed. A second TEFLON.TM. bar
provided clamping pressure and held the film components in place
over the coil using air pressure. Unless otherwise indicated, all
bonding/splicing was carried out using an impulse time of 0.5
seconds at a 70% power level and approximately 140 kPa of clamping
pressure.
[0035] Tensile strength was measured by separation of the splice
sample on an Instron Tensile Tester (model 4301) at a separation
rate of 30 cm/min, at 22.degree. C. and 60% RH. Five replicate
samples were tested and the average reported.
[0036] Peel strength was measured on splices prepared with one film
member directly on top of the second member (as opposed to an
overlap splice), and separated in a "wishbone" configuration at a
separation rate of 30 cm/min. This testing was also done at
22.degree. C. and 60% RH. Five replicate samples were tested and
the average reported.
[0037] Surface roughness was measured using a Taylor Hobson
profilometer, by tracing across the leading and trailing edges of a
splice, perpendicular to the film width, and approximately 5 mm in
from the outside edges of the film. Roughness was reported as the
standard deviation of the height of the traced surface, in
micrometers. Roughness values reported represent the average of the
leading and trailing trace values.
[0038] Based on current splicing technology and discussions with
potential users, it is felt that a tensile strength of greater than
15 kg and peel strength of greater than 1.0 kg, coupled with a
surface roughness of less than 35 .mu.m should be sufficient for
all splicing applications. These values were established as aims
for acceptable use.
[0039] As a means of comparison, cement splices were prepared using
5234 acetate-based film. Cement splicing was done on a
Maier-Hancock, model 1635, splicer. The emulsion layer was scraped
away for the preparation of all splices and they were made with
Kodak Film Cement. Film cement splices were clamped for thirty
seconds with a splicing block temperature of approximately
43.degree. C. and tested no sooner than thirty minutes after being
made.
[0040] Comparison is also made to splices comprising 2234
polyester-based film made on a Model 3001 ultrasonic film splicer
from Metric Splicer & Film Company, Inc. There was no scraping
or removal of emulsion or backing layers prior to ultrasonic
splicing.
Example 1
[0041] A bonding element was prepared by coating thermoplastic
adhesive material (VITEL.TM. 3300B, produced by Bostik) onto each
side of standard food-grade aluminum foil from Alcoa (REYNOLDS
WRAP.TM.), which is approximately 18 .mu.m in thickness. VITEL.TM.
3300B is a high molecular weight, aromatic, linear saturated
polyester resin having a glass transition temperature of 11.degree.
C. and a (Ring and Ball) melt flow point of 125.degree. C. The
adhesive was applied from a 30% solution in 2-butanone. The
coatings were dried for 15 minutes at 65.degree. C. Dried coating
thickness was estimated to be approximately 6 .mu.m on either side
of the foil.
[0042] Pieces of coated foil were cut 2 mm wide by 35 mm long to
form film strip bonding elements, and sandwiched between
overlapping ends of strips of 5234 and 2234 films. Splices were
prepared by positioning the bonding element internal to the
overlapped film components, clamping the assembly directly over an
induction coil, initiating the sealing cycle (0.5 seconds impulse
at 70% power), and then releasing the pressure and removing the
splice. The induction heating sealed spliced samples have an
average peel strength of 1.6 kg/35 mm width.
[0043] Comparison cement splices made with 5234 acetate film
averaged 1.5 kg/35 mm width, and comparison ultrasonic splices made
with 2234 polyester film averaged 5.2 kg/35 mm width. Both the
cement splice and ultrasonic splice resulted in film tearing at the
reported values. Due to the fact the induction splices are
equivalent to cement splices, they should be adequate for practical
application.
Example 2
[0044] Splice samples were prepared similarly as in Example 1 using
different films, film combinations, and orientations and measured
for tensile strength. The bonding element and sealing parameters
are the same as noted in Example 1. The resulting tensile strength
averages are shown in Table 1. In Table 1, the film listed first is
the upper member of the splice; therefore the backside of this film
is bonded to the emulsion side of the lower film member.
1 TABLE 1 Film codes Tensil Strength (kg) 2383/2383 12.8 5279/5279
13.3 2383/5279 10.0 5279/2383 18.5 2234/2234 12.5 5234/5234 11.5
2234/5234 11.7 5234/2234 10.8 Aim 15.0 5234 Cement check 13.6 2234
Ultrasonic check 10.4
[0045] Most of the combinations, independent of film type or
orientation, exhibit a tensile strength of 10-13 kilograms, which
is comparable to the ultrasonic and cement splice checks and
therefore considered adequate for practical application. It is
demonstrated that similar or dissimilar films can be spliced in any
configuration or orientation and maintain a level of strength
comparable to existing splices.
Example 3
[0046] VITEL.TM. 3300B adhesive was applied to a polyethylene
terephthalate (PET) support that had been vacuum-metalized with a
thin layer of silver. The adhesive was coated on the silver surface
at a dry thickness of approximately 6 .mu.m. This material proved
to be very receptive to induction heating, but at the impulse time
and power levels previously employed (0.5 seconds and 70%
respectively), the film has a tendency to char. For this sample
only, the backside of 2234 acetate based film was bonded to a
sample of the metal layer and adhesive coated PET support by
induction heating similarly as in Example 1, but with the power
reduced to 30% and the impulse time increased to 2.0 seconds. The
peel strength of the adhesive coated surface to the backside of
2234 film averaged 4 kg/35 mm width, well above the aim
strength.
Example 4
[0047] A series of adhesive films from the Dow Chemical Company,
under the trade name INTEGRAL.TM., were evaluated for potential
application. Each film represents a different proprietary adhesive
material. Some are cast in a single layer and others are
co-extruded films of two different adhesive layers. Each film was
laminated to both sides of aluminum foil, having a thickness of 25
.mu.m, using a double-heated nip laminator. Roll temperatures of
150.degree. C. were used with a web speed of 30 cm/min under light
nip pressure. The materials prepared in this fashion were cut into
2 mm by 35 mm pieces and sandwiched between 2383 filmstrips.
Induction heating splice sealing was accomplished similarly as in
Example 1, at 0.5 seconds impulse time using 70% power. A list of
the adhesive films tested, along with select physical properties,
and the resultant peel and tensile strengths of the splice, are
shown in Table 2.
2 TABLE 2 Adhesive Film INTEGRAL INTEGRAL INTEGRAL INTEGRAL
INTEGRAL INTEGRAL 115 709 801 803 835 E100 Type single single
single layer coextruded coextruded coextruded layer layer Thickness
25 50 25 25 50 25 (um) Activation 87 85 71 102 102 102 Temp. (C.)
Elongation 425 200 400 340 400 100 (%) 2% Secant 186 107 123 100 86
207 Modulus (N/mm2) Peel 0.2 1.2 0.7 1.4 0.3 0.7 Strength (kg)
Tensile -- 26.2 13.9 19.4 -- 16.8 Strength (kg)
[0048] For each film, the thickness indicated is the thinnest gauge
that product is available in. The values for ultimate elongation
and modulus have been measured in the machine direction according
to ASTM procedure D 882. Both INTEGRAL.TM. 709 and INTEGRAL.TM. 803
are adequate candidates for this application. These two film
adhesives have an activation temperature greater than 75.degree. C.
coupled with an elongation of less than 400% and a modulus of less
than 120 N/mm.sup.2.
Example 5
[0049] In order to minimize total thickness in the splice area,
bonding elements were prepared similarly as in Example 4, but with
INTEGRAL.TM. 803 film laminated to both sides of a 12.5 .mu.m
aluminum foil. The material prepared in this fashion was cut into 2
mm by 35 mm pieces and sandwiched between 2383 filmstrips, and the
same laminating and splicing conditions as outlined above were
used. The resulting peel strength averaged 1.0 kg/35 mm width and
the tensile strength averaged 23.3 kg. Both strength aims are met
and the total bonding element thickness is 62.5 .mu.m.
Example 6
[0050] A sample consisting of 17.5 .mu.m aluminum foil coated on
both sides with a 2.5 .mu.m coating of thermoplastic adhesive layer
(total thickness of element 22.5 .mu.m) was obtained from
All-Foils, Inc. of Brooklyn Heights, Ohio. The proprietary
adhesive, referred to as HSX 3, has a recommended activation
temperature of 116.degree. C. The material was cut into 2 mm by 35
mm pieces and inserted between strips of 2383 film. Induction
heating sealing was done as described above at 70% power for 0.5
seconds impulse time. The strength of these splices and roughness
of the splice area are listed in Table 3, along with ultrasonic
splices made with 2383 as a comparison.
3TABLE 3 Peel Tensile Splice Strength (kg) Strength (kg) Roughness
(um) Induction w/HSX 3 1.0 16.1 9.3 2383 Ultrasonic Control 3.3
28.0 18.3 Aim >1 >15 <35
[0051] As indicated the induction-formed splice meets the desired
specifications established for strength and is considerably
smoother than a typical ultrasonic control splice.
[0052] This invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
* * * * *