Study on Surface Modification of PEN Filmby Remote Ar Microplasma
A. Umeda, M. Blajan and K. Shimizu
Innovation and Joint Research Center, Shizuoka University, 3-5-1 Johoku, Hamamatsu, 432-8561, Japan
E-mail：shimizu@cjr.shizuoka.ac.jp

1. Introduction

4.2 XPS analysis
X-ray photoelectron spectrometer (XPS) was used toanalyze chemical changes of the sample surface.

Polymer materials have a wide field of application for
example in food industry, medical equipments, electronic,in information technology industry, etc. Plasma treatment
has been studied to improve the PEN(polyethylenenaphthalate) surface characteristics. For industry
application, plasma process in atmospheric pressure isdesired to minimize the cost and process time.
Microplasma which is atmospheric pressure non thermal
require relatively
low discharge voltage. Surface
treatment of PEN film by atmospheric microplasma wasinvestigated.

Table 1 XPS analysis on PEN films.
Atomic concentration [%]Sample2. Atmospheric microplasma

Fig.4 An example of Marx generator circuit.

Atmospheric microplasma is a type of dielectric barrierdischarge which has a discharge gap in the order of micro
meters. A schematic image of the miroplasma electrodes(hole size of 1.1 mm)and surface treatment process of
PEN film is presented in Fig.1.

Fig. 4 shows an example of Marx generator circuit.
When the switches(Tr2) are opened, the capacitors
linked in parallel connection are charged at a given
voltage E.

SpacerElectrodeO/C ratio
CON

Untreated

77.95

21.95

0.1

0.28

Treated byhumid Ar

69.45

30.16

0.39

0.43

Untreated

C-C
C-H

By turning on the switches, the capacitors discharge inseries connection. The voltage will have the value E
multiplied with the number of capacitors.

PEN film

4. Results and discussion
4.１ Changes in surface wettability

Carrier gas

Surface wettability was evaluated by measuring static
contact angle with a drop of distilled water on thesample PEN film surface.

Microplasma

76°

21°

(a)Before treatment(b)After treatment
Fig.5 Images of contact angle of a waterdrop
on PEN film.

Contact angle [degree]

90

2.5

80
27060

1.5

50
40

13020Contact angle
Power consumption

1001

1.1

1.20.5

Power consumption [W]Fig.1 A Schematic image of microplasma electrodes
and surface treatment process of PEN film.

Fig.2 Image of microplasma during discharge.
Two metal circular plates covered with dielectricmaterials are faced together with a spacer (thickness100 um) in between. By applying an alternative voltage,streamers generate to form glow-like plasma (Fig.2).

3. Experimental setup

PEN film
Contact angle meter
Water
Current probe

XPSAr
Gas cylinder

Fig.3 An Experimental setup
Fig.3 shows the experimental setup. Argon gas wassupplied by a gas cylinder. Argon gas had some humidity
due to water inside flask. We used a Marx generator whichgenerates negative pulsed for generating microplasma.
Innumerable streamers were generated between theelectrodes, which generate various radicals. In series ofexperiments those active species could affect a targetsurface.

O=C

Treated by humid Ar plasma

O=C(Treatment time 5sec, distance between electrodes and PEN
film1 mm, gas flow rate 5 L/min, gas humidity 0 %RH)

Fig.6 shows characteristics between discharge voltage
and contact angle. Decrease of contact angle wasobserved with the increase of discharge voltage.

Dry Ar plasma60

Fig.9 XPS O1s peaks of PEN films.

Fig.8 shows the decrease of C-H bond and C-C bondthat are hydrophobic functional group. Fig. 9 shows theincrease of O-H bond and O=C bond that are hydrophilic
functional group. These changes contributed to improvinghydrophilic property of the PEN surface.
This could be the result of the metastable excited argon
atoms responsible for attacking the C-H or C-C bondleading to the production of carbon radicals on the PENsurface. Since the carbon radicals could react withoxygen, nitrogen, water vapor in the atmospheric air andcarrier gas, hydrophilic functional group increased afterplasma treatment.

70Humid Ar plasma

50403020105. Conclusions

00Oscilloscope

O-H

O-H

Fig.6 Discharge voltage versus discharge powerand contact angle.

Contact angle [degree]

Gas

Untreated

1.3

80Electrodes

Fig.8 XPS C1s peaks of PEN films.

0Discharge voltage [kV]HV probe

C-C
C-H

Front view

Cross-section view

Flow meter

Treated by humid Ar plasma

102030Treatment time [sec]Fig.7 Relationship between treatment timeand contact angle.
(Discharge voltage -1.3 kV,
distance between electrodes and PEN film1 mm,
gas flow rate 5 L/min, gas humidity 0 %RH and 63 %RH)

Fig.7 shows characteristics between treatment timeand contact angle. Initial contact angle of PEN film wasabout 76゜. The minimum contact angle of about 21゜ wasobtained by the treatment time of 5 sec and the gas
humidity of 63 %RH.

(1)Surface of PEN film was modified by atmosphericmicroplasma at a discharge voltage of -1.3 kV .
(2)The minimum contact angle of about 21゜ wasobtained by the treatment time 5 sec withhumid Ar.
(3)It was confirmed that humid Ar plasma was more
effective in surface treatment than dry Ar plasma.
(4)Decrease of hydrophobic functional group andincrease of hydrophilic functional group wereobserved after microplasma treatment on thePEN film.