Adhesive-Free Lamination Technique using a Plasma Surface ...

Adhesive-Free Lamination Technique using a Plasma Surface Treatment
at Atmospheric Pressure
Masuhiro Kogoma 1 , Atsushi Manabe 2 , and Kunihito Tanaka 1
1 Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University,
7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan
2 Research and Development Center, Fujimori Kogyo Co. Ltd.,
1-10-1 Sachiura, Kanazawa-ku, Yokohama, Kanagawa 236-0003, Japan
Abstract: A new adhesive-free lamination technique with the N 2 /He atmospheric pressure
glow discharge (APGD) was investigated. On the plasma treatment of PET/LDPE and
NY/LDPE, we got higher adhesive strength than that of the target required value when we
used RF discharge.
Key words: Adhesive-free lamination, APGD
1. Introduction
The laminated polymer films are widely used for the
packaging materials of foods, cosmetics, pharmaceutical
products and so on. These laminated films are generally
pasted two or more kinds of polymer films with an organic
adhesive diluted by an organic solvent. The adhesives
and/or solvents, which remain between the films,
sometimes exude into the package content. And the organic
solvent is cause of the environmental pollution in
the manufacturing plant as a volatile organic compound
(VOC). Thus, a new adhesive-free lamination technique is
desired. In this study, we tried to develop an adhesive-free
lamination technique using the atmospheric pressure glow
plasma surface treatment and thermo-compression.
2. Experimental
The popular lamination materials, poly ethylene terephthalate
(PET), nylon (NY), polyethylene (LDPE) and
polypropylene (PP) films, were used for the adhesive-free
lamination. These films were treated by N 2 /He, APG
Rotary pump
Polymer Film
Stainless
electrode
Exhaust
Shower head
gas inlet
HV
N 2 +He
Cu mesh
electrode
Pyrex glass
reactor
Fig. 1 Schematic diagrams of the reactor a) using 100kHz
power source
plasma using the reactor shown in Fig. 1 and 2.
The films is rolled and fitted on the inner electrode in
Fig. 1. Then, the treated films were laminated by the
thermo-compression (140 ~ 180ºC, 0.4 MPa, 10 s). The
adhesive strength (AS) of the laminated film was measured
with a 180º peel tensile tester. When we measured
the AS, PET or NY film was fixed on a steel plate, and
LDPE or PP was pulled. The reactor a) and b) were
used for long (a; 10 ~ 90 s) and quite short (b; 1 ms ~ 10
s) time treatment experiments, respectively. The treatment
time with the reactor b) was varied by changing the velocity
of the slider. The details of the discharge conditions
are shown in table 1.
The chemical state of the films was determined by XPS
(ULVAC-Phi Co., Ltd., ESCA-5800ci); light source was
monochromatic Al K α ray and take-off angle was 5º.
Table 1. The discharge conditions.
Discharge Frequency / kHz
(LF), / MHz (RF)
100 (LF), 13.56 (RF)
Discharge Power / W 100 or 10
N 2 Flow Rate / sccm 0 or 20
He Flow Rate / slm 5
Pressure
atmospheric pressure
Deposition time
15 ~ 90s or 1 ms ~ 10 s
Sample film
Insulator
Electrode
N 2 /He gas
HV
Electrode
Plasma area
Slider
Fig. 2 Schematic diagrams of the reactor b) using LF
(100 kHz) and RF (13.56MHz). Power: 10, 20 W, Discharge
time: 1 ms ~1 s

3. Results and discussion
The AS of each combination of the films is shown in
table 2. All combinations of untreated films were not
stuck only by the heat-press. While the AS values of the
treated films did not exceed the industrial required values,
they showed hopeful high values.
Fig. 3 shows the treatment time dependence of the AS
of PET/LDPE treated in reactor a). Since this result was
one of the previous study results and PET was pulled in
the 180º peel test, these AS values were bigger than that
of table 2. As shown in Fig. 3, we obtained no clear dependence
of the AS on the treatment time. Thus, we tried
to use the reactor b) which was able to treat the films for a
quite short time.
Fig. 4 is the AS of PET/LDPE treated with the reactor
b). The AS at 10 s was stronger than that of table 2. This
reason was considered that the discharge density of the
reactor b) (52 Wcm -3 ) was higher than that that the reactor
a) (6.3 Wcm -3 ). Fig. 5 shows the AS of PET/LDPE treated
with the reactor b) with different discharge power. The
maximum AS value is attained at shorter treatment time in
higher power (20W) compared with lower power (10W)
treatment. But still the maximum value is lower than that
of required value (RV).
This result indicated that several tens of milliseconds
treatment time in high density plasma suffices for the adhesive-free
lamination technique. So we need high density
and short time treatment using high frequency discharge
such as RF pulse modulated discharge.
Fig. 6 shows the variation of the adhesive strength of
PET/LDPE as a plasma treatment time with different discharge
frequency in the same power (10W). The adhesive
strength was improved only by RF discharge even in the
same power. They indicated that enough adhesive strength
300
Table 2. The adhesive strength of each combination
treated with 100 kHz discharge.
Adhesive strength / Nm -1
Films Plasma gas
UT PT RV
PET/LDPE N 2 /He
87 300
NY/LDPE N 2 /He 434 500
0
PET/PP He 98 300
NY/PP He 186 500
*UT, untreated; PT, plasma treated; RV, required value.
*Reactor, a); treatment time, 15 s; Power, 100 W, 100
kHz.
Adhesive strength / Nm -1
250
200
150
100
50
0
0.001 0.01 0.1 1 10
Treatment time / s
Fig.4. The variation of the adhesive strength as a function
of the N 2 /He plasma treatment time. Sample, PET/LDPE;
reactor, b); Power; 10 W, 100 kHz.
Adhesive strength / Nm -1
200
100
0
0 20 40 60 80 100
Treatment time / s
Fig 3. The variation of the adhesive strength as a function
of the N 2 /He plasma treatment time. Sample, PET/LDPE;
reactor, a); Power; 100 W; 100 kHz, N 2 , 50 sccm.
Adhesive strength / Nm -1
300
250
200
150
100
50
0
20W
10W
0.001 0.01 0.1 1
Plasma treatment time / s
Fig.5 Adhesion strength as a function of treatment time
with different discharges power. 100kHz, 10W, 20W.

for use as packaging materials was attained with RF discharge.
Fig. 7 shows PET/LDPE and NY/LDPE adhesive
strengths as a function of treatment time with different
power of RF discharge. The aim adhesion strengths for
both PE and NY were broken by the adhesion maximums.
In comparison of Fig. 6 and Fig. 7, the adhesion maximum
time of PET/LDPE is decreased with increasing of
the power. This means that we will attain rapider treatment
in higher power RF discharge. However in 20W, NY
treatment, we cannot treat longer than 50ms because heat
softening of the sample will be occurred by plasma heating.
So we need cooling electrode to decrease the temperature
of the sample surfaces when we increase the power
higher than 20 W.
Fig. 8 shows the adhesive strengths of PET/PP and
NY/PP as a function of treatment time. Both NY and PET
adhesion with PP are not over take the aims in their peaks
even using the RF discharge. If the thermo adhesion occurred
by low molecular PP produced by plasma exposing
of the surface, we have to use about 1.5 times of the
plasma power than that of PE treatment as shown in Table
3, because -CH 3 side chain should be lost before main
chain cutting with plasma energy. From the reason, more
intensive power should be needed to increase the adhesive
strength of PP. So the new electrode system will be desired.
To investigate the adhesive-free lamination mechanism,
XPS spectra of the treated LDPE in the valence band region
were measured. Fig. 9 shows the XPS balance band
spectra of LDPE untreated and treated surfaces by N 2 /He
plasma with different times. In the untreated PE, we can
find a wide and strong peak from 1 to 2ev on the binding
energy which assigned as C-C bond in PE main chain
[1-2]. In the 10ms and 50ms treated PE, the C-C bond
peak is decreased with increasing of the treatment time.
This means that the molecular weight of PE will be decreased
with increasing of plasma exposing time. We
supposed that some low molecular weight PE were consisted
on the film surface and that they acted as an adhesive
for the heat-press lamination.
The thickness of the turned layer is less than few nm
which measured by using the angle resolved measurement
of XPS valence band.
4. Conclusion
We successfully developed the adhesive-free lamination
technique using N 2 /He atmospheric pressure glow
discharge plasma. In case of the adhesion of PET/
L-LDPE and NY/LDPE, we got higher adhesive strength
than that of the target required value when we used RF
discharge.
However the adhesion of PET/PP and NY/PP, we could
not attain the RV even in RF discharge. We expect that
we need higher power density to enhance the adhesion
strength of PP using new cooled electrodes.
Adhesive strength / Nm -1
800
600
400
200
0
Aim strength
for PET/PE
100 kHz
RF(13.56MHz)
0.001 0.01 0.1 1
Plasma treatment time / s
Fig. 6 PET/LDPE adhesive strength as a function of
plasma treatment time with different frequency. Discharge
power, 10 W.
Adhesive strength / Nm -1
800
600
400
200
0
PET/PE
20 W
Aim strength
for NY/PE
Aim strength
for PET/PE
NY/PE
20 W
NY/PE
10 W
0.001 0.01 0.1 1
Plasma treatment time / s
Fig. 7 PET/LDPE and NY/LDPE adhesive strengths vs.
treatment time with different power of RF discharge.
Adhesive strength / Nm -1
600
400
200
0
Aim strength forNY/PP
Aim strength for PET/PP
PET /PP
NY/PP
0.001 0.01 0.1 1
Plasma treatment time / s
Fig. 8 The adhesive strengths of PET/PP and NY/PP as a
function of treatment time.

Intensity (a.u.)
60
50
C-C bond
40
30
20
10
Untreated
0
50 40 30 20 10 0
Binding Energy (eV)
Treatment time
10 ms
50 40 30 20 10 0
Binding Energy (eV)
AS, 108 Nm -1 AS, 206 Nm -1
Treatment time
50 ms
50 40 30 20 10 0
Binding Energy (eV)
FIG. 9. The XPS spectra of untreated and the N 2 /He plasma treated LDPE in the valence band region. Reactor; b); Power;
10W, 100 kHz.
5. References
[1] J. Delhalle, J. M. Andre, S. Delhalle, J. J. Pireaux, R.
Caudano and J. J. Verbist, J. Chem. Phys., 60, 595 (1974).
[2] R. Foerch, G. Beamson and D. Briggs, Surf. Interface
Anal., 17, 842 (1991).
Table 3. Number of chemical bond in polymer unit of PE
and PP to be dissociated by plasma energy.
LDPE PP
Number of C-C bond 2 3
Number of C-H bond 4 6
Possibility of main chain cutting
with same energy
33.3% 22.2%