In2O3:Sn (ITO) transparent conducting coatings of high optical quality have been obtained on glass and several plastic substrates by spin and dip coating processes followed by a low temperature processing (T < 130°C). The sols are made of crystalline nanoparticles redispersable in an alcohol and modified by adding a binder to favour the coalescing of the particles and to allow the deposition of thick single layers (>400 nm). The smallest stable resistivity so far obtained is &rho; = 

Aegerter, Michel A.

Al-Dahoudi, Naji

In2O3:Sn (ITO) transparent conducting coatings of high optical quality have been obtained on glass and several plastic substrates by spin and dip coating processes followed by a low temperature processing (T 400 nm). The smallest stable resistivity so far obtained is &rho; = 

Universaar

Wet coating deposition of ITO coatings on plastic substrates

Scientific documents from the Saarland University,

Wet Coating Deposition of ITO Coatings on Plastic Substrates
N. AL-DAHOUDI AND M.A. AEGERTER∗
Institut fuer Neue Materialien—INM, Department of Coating Technology, Im Stadtwald, Gebaeude 43,
66123 Saarbruecken/Germany
aegerter@inm-gmbh.de
Abstract. In2O3:Sn (ITO) transparent conducting coatings of high optical quality have been obtained on glass and
several plastic substrates by spin and dip coating processes followed by a low temperature processing (T < 130◦C).
The sols are made of crystalline nanoparticles redispersable in an alcohol and modified by adding a binder to favour
the coalescing of the particles and to allow the deposition of thick single layers (>400 nm). The smallest stable
resistivity so far obtained is ρ = 9 × 10−2 cm (sheet resistance of 1.6 k for a 570 nm thick single layer). The
transparency in the visible range is high, T ≈ 87%, the abrasion resistance is in agreement with DIN 58-196-G10
and the hardness according to ASTM D 3363-92a is 1H. A spray process allows to obtain antiglare-conducting
coatings with an adjustable gloss of 60 to 80 GU and an optical resolution >8 lines/mm.
Keywords: sol-gel, electrical coatings, conductivity, indium tin oxide, ITO, plastic substrate, antiglare coating,
antistatic coatings, low temperature processing
1. Introduction
Transparent conducting coatings are widely used as
electrodes in optoelectronic devices, as IR reflecting or
heatable layer, for electromagnetic shielding or dissi-
pating static, etc. Among the most important material
are n-type oxide semiconductors (TCO) such as in-
dium tin oxide (ITO) and fluorine or antimony doped
tin dioxide (FTO, ATO) [1].
There is today a great interest to coat systems which
do not withstand high temperature such as plastic sub-
strates or already preformed glass devices. These above
materials can only be deposited by physical deposition
techniques [2]. However wet coating deposition pro-
cesses such as spray, dip and spin coating are also well
adapted techniques to coat even large substrates us-
ing a cheaper infrastructure if organic precursors fully
polymerizable at low temperature can be incorporated
in the sol formulation (organic-inorganic hybrids). For
TCO coatings one possible issue is the use of hybrid
sols containing a high amount of already conducting
crystalline oxide nanoparticles [3].
∗To whom all correspondence should be addressed.
The paper reports on recent progress to obtain ITO
coatings processed at temperature as low as 130◦C
and their optical, electrical, mechanical and textural
characteristics.
2. Experimental
2.1. Precursors and Sols
In2O3:Sn nanopowders with primary size adjustable up
to about 20 nm and having the cubic In2O3 phase were
prepared by a controlled growth technique. The de-
tailed preparation can be found in [3–5]. The powders
can be fully redispersed in alcohol and water. Their
density is 6.45 g/cm3 corresponding to 92% of the
theoretical density of In2O3. They have been already
used to develop nanoparticulate coatings on glass with
sintering at high temperature [6, 7].
The sols used to obtain transparent conducting coat-
ings consist of an ethanolic solution containing 25 wt%
redispersed ITO nanoparticles modified by adding un-
der ultrasonic treatment hydrolyzed 3-methacryloxy-
propyltrimethoxysilane (MPTS). Polymethylmetacry-
694 Al-Dahoudi and Aegerter
late (PMMA), polycarbonate (PC) and glass substrates
were coated by spin and dip coating process. The
resulting films were first cured by UV irradiation
with an average intensity of 105 mW/cm2 for 110 s
(Beltron) and then heated in air or reducing atmo-
sphere at 130◦C up to 20 hours. A further annealing
under forming gas or N2 atmosphere was performed
at 130◦C during 3 hours to improve their electrical
properties.
The same sols were used to obtain antiglare conduct-
ing coatings, but were sprayed at room temperature for
a period of 15 to 20 seconds using a SATA mini-jet
spray gun (0.5 mm nozzle, 3 bar) on polycarbonate or
glass substrates. The coatings, a few µm thick, were
then polymerized using the same process.
2.2. Characterization of the Coatings
2.2.1. Textural Properties. The surface morphology
of the coatings was analyzed using a white light inter-
ferometer (WLI) and AFM (Zygo Newview 5000) and
Scanning Electron Microscopy (SEM-JEOL 6400).
Coating cross sections were observed by high reso-
lution Transmission Electron Microscopy (HR-TEM-
Philips, 200 KeV).
2.2.2. Optical Properties. Optical transmission and
reflection were determined using a Variant Cary 5 E
spectrophotometer in the wavelength range 300 to
3000 nm. IR spectroscopy was performed with a
Bruker IFS 66V instrument. Haze, clarity and gloss
were measured using a ByK Gardner plus and a
micro-TRI reflectometer.
2.2.3. Mechanical Properties. The thickness (t) of
the coating was determined using a Tencor P10 pro-
filometer. The abrasion resistance and the adhesion of
the coatings was tested according to DIN 58196 and
their hardness according to ASTM D3363-92a.
2.2.4. Electrical Properties. The sheet resistance
(R) was measured by a 4 points technique or a contact-
less measurement device (Lehigton Electronic Inc.).
The resistivity was calculated from ρ = R · t .
3. Results and Discussion
3.1. Transparent Conducting Coating
The evolution of the sheet resistance of a 570 nm thick
single layer of pure ITO and MPTS/ITO (6 vol%)
102
103
104
105
106
107
EDCBA
R
 
 
[  
 
 
]
 Pure ITO
 ITO/MPTS
Figure 1. Sheet resistance of 570 nm thick MPTS/ITO (6 vol%)
coatings measured after different heat treatments in air: 130◦C, 15 h.
(A) as deposited; (B) as deposited + heat treatment in air at 130◦C
during 10 h; (C) as deposited + UV irradiation (110 s, 105 mW/cm3);
(D) process C + heat treatment in air at 130◦C/30 h; (E) process
D + reducing in forming gas at 130◦C/3 h.
coatings deposited on a 3 mm thick PC substrate is
shown in Fig. 1 after different annealing treatments.
Whatever the treatment is, R for pure ITO remains
high (>1 M) and the coating adhesion is very poor.
Cured MPTS/ITO coatings were found to exhibit a min-
imum of R for a composition volume ratio of 6%.
After deposition, the sheet resistance is high, about 10
M. A heat treatment in air at 130◦C only slightly de-
creases R down to 7×105 . IR spectroscopy shows
that a well defined Si O Si network (1050 cm−1
band) is not achieved and that the presence of ITO
particles impedes the polymerization and condensa-
tion processes [6]. A UV treatment drastically reduces
the sheet resistance down to 8 k. The C C band
(1036 cm−1) is completely eliminated and the C = 0
band (1716 cm−1) is strongly reduced so that a well
defined Si O Si network link the conducting parti-
cles together leading to a much better conductivity. A
further annealing in a reducing atmosphere at 130◦C
still lowers this value down to 800 .
These values, measured just after the processing of
the coatings, are only stable when the coatings are kept
in vacuum or in a protective atmosphere such as nitro-
gen or argon (Fig. 2). When kept in air the sheet resis-
tance however slightly increases with time to reach a
stable value of 1650  in air (20◦C, 40% RH).
The mechanisms leading to these variations are not
yet clear, but are certainly related to the composition
and the morphology of the coatings. Besides the poly-
merization process of MPTS an important effect of both
the UV and the reducing treatment is to diminish the
concentration of chemisorbed oxygen species on the
ITO Coatings on Plastic Substrates 695
0 50 100 150 200
600
800
1000
1200
1400
1600
1800
after
reducing
treatment
Vacuum, N2, Ar
air  20°C, 40% RH
R
 
 
[  Ω
 
 
 
]
Time [ hrs. ]
Figure 2. Time evolution of the sheet resistance of 570 nm thick
MPTS (6 vol%)/ITO coatings left in a protective atmosphere (vac-
uum, N2, Ar) in vacuum and air. The coatings have been initially
post annealed in a reducing atmosphere.
surface of the ITO particles, which act as free electron
traps surface states. This leads to an increase of the
carrier concentration and consequently to a large re-
duction of R . As the coatings are porous (see below),
oxygen from air slowly diffuses back into the coat-
ing and is again chemisorbed at the surface grains as
charged species. This leads to an electron transfer from
the particles to the adsorbed species inducing a high
band bending increasing the potential barrier height
and consequently the resistivity. Without the presence
of oxygen, the values of R are stable.
The surface morphology of the coatings observed by
SEM (Fig. 3) consists of loosely packed globular grains
(raspberry like) about 100 nm in size formed by the
aggregation of the ITO nanoparticles linked together by
a small strip of polymerized MPTS (dark regions). The
coating roughness measured by WLI on a 53×70 µm2
area with a lateral resolution of 600 nm is Ra = 0.85
nm, with a peak-to-valley maximum value of RPV =
15 nm. When measured with a higher resolution on a
1 × 1 µm2 area (AFM), the values are Ra = 4 nm and
RPV = 28 nm.
The optical transmission and reflection spectra of
a 3 mm thick PC substrate uncoated and one coated
with a 500 nm hybrid ITO layer is shown in Fig. 4.
A high transmission of about 87% is observed in the
visible range. The influence of the carrier is clearly
seen by the strong absorption occurring in the near IR
range (900 nm < λ < 2000 nm) and the increase of the
reflection for λ > 2µm.
Figure 3. SEM picture of the surface (top) and HR-TEM cross-
section (bottom) of a MPTS/ITO coating UV cured (110 s) and heat
treated at 130◦C, 15 h.
The mechanical properties of the coatings deposited
on PC substrate have been studied by various test. The
adhesion is in agreement with the Tape test procedure
(DIN 58196-K2). No scratch (class 1) was observed
after 10 rubbing cycles with an eraser under a load
of 10 N (DIN 58196-G10). The hardness measured
using the Pencil test ASTM D 3363-92a is 1H. Higher
value were observed when the amount of MPTS was
increased, but such coatings present also a higher value
of the sheet resistance.
3.2. Antiglare Conducting Coatings
Antiglare conducting coatings have been obtained by
spray coating followed by the same post deposition
treatments. The spray gun delivers droplets with an
696 Al-Dahoudi and Aegerter
Table 1. Typical gloss, haze, clarity, resolution and abrasion resis-
tance of antiglare coatings deposited on plastic and glass substrates
and cured by UV irradiation.
Haze Clarity Resolution Abrasion
Gloss @ 60◦ (%) (%) (USAF chart) resistance (9.8 N)
60–70 ≤10 75–90 ≥8 lines/mm DIN 58196-G10
500 1000 1500 2000 2500 3000
0
20
40
60
80
100
R
T
 coated substrate
 uncoated substrate
T,
 R
  %
Wavelength [nm]
Figure 4. UV-near IR transmission (T) and reflection (R) measured
against air of a 500 nm thick MPTS/ITO coating deposited on a 3 mm
thick polycarbonate (PC) substrate and of an uncoated PC substrate.
Figure 5. Glaze of a white object placed in front of a AS-AG
coated plastic (left) and an uncoated one (right). The picture of the
building placed 2 cm behind the substrates is clearly visible in both
configurations.
average size of 25 µm. When arriving on the cold
substrate they spread and form a rough surface which
can be polymerized following the same treatments (UV
irradiation + heating at T ≈ 130◦C). The thickness of
the coatings can range up to a few µm.
The surface morphology of such coatings consist of
10 to 100 µm features confirming an average roughness
of Ra = 0.2 µm with peak to valley of 0.8 µm. Similar
sheet resistance values and mechanical properties can
be obtained. Table 1 shows the results of the optical
properties of the coatings.
Figure 5 shows the optical effect of such coatings.
The image of the entrance of INM placed 2 cm behind a
coated and a non-coated substrate is clearly visible and
the glare of the object placed in front of the substrates
is strongly reduced at the coated side.
4. Conclusions
Stable hybrid pastes and sols allowing the deposition of
conducting, antistatic and antiglare-antistatic coatings
fully processable at low temperature (T < 130◦C) have
been developed. They have been obtained by modify-
ing an ethanolic suspension of redispersed crystalline
ITO nanoparticles with a hydrolyzed silane (MPTS)
acting as a binder. Single layers as thick as 570 nm can
be obtained by spin or dip coating processes on plastic
(PMMA, PC) and glass substrates. The curing process
involves a UV irradiation (105 mW/cm2, 110 s) fol-
lowed by a heat treatment at T = 130◦C during 15 h
and then a reducing treatment in forming gas. 570 nm
thick coatings exhibit a high transparency (T ≈ 87%)
and a stable sheet resistance as low as 1.6 k (resis-
tivity ρ = 9×10−2 cm). The abrasion resistance is in
agreement with DIN 58196-G10 class 1, the adhesion
passes the tape test DIN 58196-K2 and the pencil hard-
ness is 1 H according to ASTM D 3363-92c. The sur-
face roughness is low, Ra ≈ 1 nm. Antistatic coatings
with similar sheet resistance presenting an antiglare
effect (GU ∼ 65) have been obtained on the same sub-
strates by a spray process at room temperature followed
by UV irradiation and N2 annealing. All these coat-
ings are stable under UV or visible light irradiation
and consequently their properties are presently better
than those obtained with commercial conductive poly-
mers [8]. The process can be applied to coat at low
temperature (T < 130◦C) flat or slightly curved sub-
strates such as CRT, LCD, PDP, touch screen panels,
discharge plates in clean environment, etc.
References
1. H.L. Hartnagel, A.L. Dawar, A.K. Jain, and G. Jagdish, Semi-
conducting Transparent Thin Film (IOP Publishing, Bristol and
Philadelphia, 1995).
2. H.K. Pulker, Coatings on Glass, 2nd edn. (Elsevier, 1999).
3. C. Goebbert, M.A. Aegerter, D. Burgard, R. Nass, and H. Schmidt,
ITO Coatings on Plastic Substrates 697
Proc. Materials Research Society, MRS, Nanostructured Powders
and their Industrial Application 520, 293 (1998).
4. C. Goebbert. M.A. Aegerter, D. Burgard, R. Nass, and H. Schmidt,
J. Mater. Chem. 9, 253 (1999).
5. N. Al-Dahoudi, H. Bisht, C. Goebbert, T. Krajewski, and M.A.
Aegerter, Thin Solid Film 392, 299 (2001).
6. C. Goebbert, R. Nonninger, M.A. Aegerter, and H. Schmidt, Thin
Solid Film 351, 79 (1999).
7. C. Goebbert, H. Bisht, N. Al-Dahoudi, R. Nonninger, M.A.
Aegerter, and H. Schmidt, Journal of Sol-Gel Science and
Technology 19, 201 (2000).
8. Baytron P Technical Information.


Acronym

Wet Coating Deposition of ITO Coatings on Plastic SubstratesN. AL-DAHOUDI AND M.A. AEGERTER∗Institut fuer Neue Materialien—INM, Department of Coating Technology, Im Stadtwald, Gebaeude 43,66123 Saarbruecken/Germanyaegerter@inm-gmbh.deAbstract. In2O3:Sn (ITO) transparent conducting coatings of high optical quality have been obtained on glass andseveral plastic substrates by spin and dip coating processes followed by a low temperature processing (T < 130◦C).The sols are made of crystalline nanoparticles redispersable in an alcohol and modified by adding a binder to favourthe coalescing of the particles and to allow the deposition of thick single layers (>400 nm). The smallest stableresistivity so far obtained is ρ = 9 × 10−2 cm (sheet resistance of 1.6 k for a 570 nm thick single layer). Thetransparency in the visible range is high, T ≈ 87%, the abrasion resistance is in agreement with DIN 58-196-G10and the hardness according to ASTM D 3363-92a is 1H. A spray process allows to obtain antiglare-conductingcoatings with an adjustable gloss of 60 to 80 GU and an optical resolution >8 lines/mm.Keywords: sol-gel, electrical coatings, conductivity, indium tin oxide, ITO, plastic substrate, antiglare coating,antistatic coatings, low temperature processing1. IntroductionTransparent conducting coatings are widely used aselectrodes in optoelectronic devices, as IR reflecting orheatable layer, for electromagnetic shielding or dissi-pating static, etc. Among the most important materialare n-type oxide semiconductors (TCO) such as in-dium tin oxide (ITO) and fluorine or antimony dopedtin dioxide (FTO, ATO) [1].There is today a great interest to coat systems whichdo not withstand high temperature such as plastic sub-strates or already preformed glass devices. These abovematerials can only be deposited by physical depositiontechniques [2]. However wet coating deposition pro-cesses such as spray, dip and spin coating are also welladapted techniques to coat even large substrates us-ing a cheaper infrastructure if organic precursors fullypolymerizable at low temperature can be incorporatedin the sol formulation (organic-inorganic hybrids). ForTCO coatings one possible issue is the use of hybridsols containing a high amount of already conductingcrystalline oxide nanoparticles [3].∗To whom all correspondence should be addressed.The paper reports on recent progress to obtain ITOcoatings processed at temperature as low as 130◦Cand their optical, electrical, mechanical and texturalcharacteristics.2. Experimental2.1. Precursors and SolsIn2O3:Sn nanopowders with primary size adjustable upto about 20 nm and having the cubic In2O3 phase wereprepared by a controlled growth technique. The de-tailed preparation can be found in [3–5]. The powderscan be fully redispersed in alcohol and water. Theirdensity is 6.45 g/cm3 corresponding to 92% of thetheoretical density of In2O3. They have been alreadyused to develop nanoparticulate coatings on glass withsintering at high temperature [6, 7].The sols used to obtain transparent conducting coat-ings consist of an ethanolic solution containing 25 wt%redispersed ITO nanoparticles modified by adding un-der ultrasonic treatment hydrolyzed 3-methacryloxy-propyltrimethoxysilane (MPTS). Polymethylmetacry-694 Al-Dahoudi and Aegerterlate (PMMA), polycarbonate (PC) and glass substrateswere coated by spin and dip coating process. Theresulting films were first cured by UV irradiationwith an average intensity of 105 mW/cm2 for 110 s(Beltron) and then heated in air or reducing atmo-sphere at 130◦C up to 20 hours. A further annealingunder forming gas or N2 atmosphere was performedat 130◦C during 3 hours to improve their electricalproperties.The same sols were used to obtain antiglare conduct-ing coatings, but were sprayed at room temperature fora period of 15 to 20 seconds using a SATA mini-jetspray gun (0.5 mm nozzle, 3 bar) on polycarbonate orglass substrates. The coatings, a few µm thick, werethen polymerized using the same process.2.2. Characterization of the Coatings2.2.1. Textural Properties. The surface morphologyof the coatings was analyzed using a white light inter-ferometer (WLI) and AFM (Zygo Newview 5000) andScanning Electron Microscopy (SEM-JEOL 6400).Coating cross sections were observed by high reso-lution Transmission Electron Microscopy (HR-TEM-Philips, 200 KeV).2.2.2. Optical Properties. Optical transmission andreflection were determined using a Variant Cary 5 Espectrophotometer in the wavelength range 300 to3000 nm. IR spectroscopy was performed with aBruker IFS 66V instrument. Haze, clarity and glosswere measured using a ByK Gardner plus and amicro-TRI reflectometer.2.2.3. Mechanical Properties. The thickness (t) ofthe coating was determined using a Tencor P10 pro-filometer. The abrasion resistance and the adhesion ofthe coatings was tested according to DIN 58196 andtheir hardness according to ASTM D3363-92a.2.2.4. Electrical Properties. The sheet resistance(R) was measured by a 4 points technique or a contact-less measurement device (Lehigton Electronic Inc.).The resistivity was calculated from ρ = R · t .3. Results and Discussion3.1. Transparent Conducting CoatingThe evolution of the sheet resistance of a 570 nm thicksingle layer of pure ITO and MPTS/ITO (6 vol%)102103104105106107EDCBAR  [    ] Pure ITO ITO/MPTSFigure 1. Sheet resistance of 570 nm thick MPTS/ITO (6 vol%)coatings measured after different heat treatments in air: 130◦C, 15 h.(A) as deposited; (B) as deposited + heat treatment in air at 130◦Cduring 10 h; (C) as deposited + UV irradiation (110 s, 105 mW/cm3);(D) process C + heat treatment in air at 130◦C/30 h; (E) processD + reducing in forming gas at 130◦C/3 h.coatings deposited on a 3 mm thick PC substrate isshown in Fig. 1 after different annealing treatments.Whatever the treatment is, R for pure ITO remainshigh (>1 M) and the coating adhesion is very poor.Cured MPTS/ITO coatings were found to exhibit a min-imum of R for a composition volume ratio of 6%.After deposition, the sheet resistance is high, about 10M. A heat treatment in air at 130◦C only slightly de-creases R down to 7×105 . IR spectroscopy showsthat a well defined Si O Si network (1050 cm−1band) is not achieved and that the presence of ITOparticles impedes the polymerization and condensa-tion processes [6]. A UV treatment drastically reducesthe sheet resistance down to 8 k. The C C band(1036 cm−1) is completely eliminated and the C = 0band (1716 cm−1) is strongly reduced so that a welldefined Si O Si network link the conducting parti-cles together leading to a much better conductivity. Afurther annealing in a reducing atmosphere at 130◦Cstill lowers this value down to 800 .These values, measured just after the processing ofthe coatings, are only stable when the coatings are keptin vacuum or in a protective atmosphere such as nitro-gen or argon (Fig. 2). When kept in air the sheet resis-tance however slightly increases with time to reach astable value of 1650  in air (20◦C, 40% RH).The mechanisms leading to these variations are notyet clear, but are certainly related to the compositionand the morphology of the coatings. Besides the poly-merization process of MPTS an important effect of boththe UV and the reducing treatment is to diminish theconcentration of chemisorbed oxygen species on theITO Coatings on Plastic Substrates 6950 50 100 150 20060080010001200140016001800afterreducingtreatmentVacuum, N2, Arair  20°C, 40% RHR  [  Ω   ]Time [ hrs. ]Figure 2. Time evolution of the sheet resistance of 570 nm thickMPTS (6 vol%)/ITO coatings left in a protective atmosphere (vac-uum, N2, Ar) in vacuum and air. The coatings have been initiallypost annealed in a reducing atmosphere.surface of the ITO particles, which act as free electrontraps surface states. This leads to an increase of thecarrier concentration and consequently to a large re-duction of R . As the coatings are porous (see below),oxygen from air slowly diffuses back into the coat-ing and is again chemisorbed at the surface grains ascharged species. This leads to an electron transfer fromthe particles to the adsorbed species inducing a highband bending increasing the potential barrier heightand consequently the resistivity. Without the presenceof oxygen, the values of R are stable.The surface morphology of the coatings observed bySEM (Fig. 3) consists of loosely packed globular grains(raspberry like) about 100 nm in size formed by theaggregation of the ITO nanoparticles linked together bya small strip of polymerized MPTS (dark regions). Thecoating roughness measured by WLI on a 53×70 µm2area with a lateral resolution of 600 nm is Ra = 0.85nm, with a peak-to-valley maximum value of RPV =15 nm. When measured with a higher resolution on a1 × 1 µm2 area (AFM), the values are Ra = 4 nm andRPV = 28 nm.The optical transmission and reflection spectra ofa 3 mm thick PC substrate uncoated and one coatedwith a 500 nm hybrid ITO layer is shown in Fig. 4.A high transmission of about 87% is observed in thevisible range. The influence of the carrier is clearlyseen by the strong absorption occurring in the near IRrange (900 nm < λ < 2000 nm) and the increase of thereflection for λ > 2µm.Figure 3. SEM picture of the surface (top) and HR-TEM cross-section (bottom) of a MPTS/ITO coating UV cured (110 s) and heattreated at 130◦C, 15 h.The mechanical properties of the coatings depositedon PC substrate have been studied by various test. Theadhesion is in agreement with the Tape test procedure(DIN 58196-K2). No scratch (class 1) was observedafter 10 rubbing cycles with an eraser under a loadof 10 N (DIN 58196-G10). The hardness measuredusing the Pencil test ASTM D 3363-92a is 1H. Highervalue were observed when the amount of MPTS wasincreased, but such coatings present also a higher valueof the sheet resistance.3.2. Antiglare Conducting CoatingsAntiglare conducting coatings have been obtained byspray coating followed by the same post depositiontreatments. The spray gun delivers droplets with an696 Al-Dahoudi and AegerterTable 1. Typical gloss, haze, clarity, resolution and abrasion resis-tance of antiglare coatings deposited on plastic and glass substratesand cured by UV irradiation.Haze Clarity Resolution AbrasionGloss @ 60◦ (%) (%) (USAF chart) resistance (9.8 N)60–70 ≤10 75–90 ≥8 lines/mm DIN 58196-G10500 1000 1500 2000 2500 3000020406080100RT coated substrate uncoated substrateT, R  %Wavelength [nm]Figure 4. UV-near IR transmission (T) and reflection (R) measuredagainst air of a 500 nm thick MPTS/ITO coating deposited on a 3 mmthick polycarbonate (PC) substrate and of an uncoated PC substrate.Figure 5. Glaze of a white object placed in front of a AS-AGcoated plastic (left) and an uncoated one (right). The picture of thebuilding placed 2 cm behind the substrates is clearly visible in bothconfigurations.average size of 25 µm. When arriving on the coldsubstrate they spread and form a rough surface whichcan be polymerized following the same treatments (UVirradiation + heating at T ≈ 130◦C). The thickness ofthe coatings can range up to a few µm.The surface morphology of such coatings consist of10 to 100 µm features confirming an average roughnessof Ra = 0.2 µm with peak to valley of 0.8 µm. Similarsheet resistance values and mechanical properties canbe obtained. Table 1 shows the results of the opticalproperties of the coatings.Figure 5 shows the optical effect of such coatings.The image of the entrance of INM placed 2 cm behind acoated and a non-coated substrate is clearly visible andthe glare of the object placed in front of the substratesis strongly reduced at the coated side.4. ConclusionsStable hybrid pastes and sols allowing the deposition ofconducting, antistatic and antiglare-antistatic coatingsfully processable at low temperature (T < 130◦C) havebeen developed. They have been obtained by modify-ing an ethanolic suspension of redispersed crystallineITO nanoparticles with a hydrolyzed silane (MPTS)acting as a binder. Single layers as thick as 570 nm canbe obtained by spin or dip coating processes on plastic(PMMA, PC) and glass substrates. The curing processinvolves a UV irradiation (105 mW/cm2, 110 s) fol-lowed by a heat treatment at T = 130◦C during 15 hand then a reducing treatment in forming gas. 570 nmthick coatings exhibit a high transparency (T ≈ 87%)and a stable sheet resistance as low as 1.6 k (resis-tivity ρ = 9×10−2 cm). The abrasion resistance is inagreement with DIN 58196-G10 class 1, the adhesionpasses the tape test DIN 58196-K2 and the pencil hard-ness is 1 H according to ASTM D 3363-92c. The sur-face roughness is low, Ra ≈ 1 nm. Antistatic coatingswith similar sheet resistance presenting an antiglareeffect (GU ∼ 65) have been obtained on the same sub-strates by a spray process at room temperature followedby UV irradiation and N2 annealing. All these coat-ings are stable under UV or visible light irradiationand consequently their properties are presently betterthan those obtained with commercial conductive poly-mers [8]. The process can be applied to coat at lowtemperature (T < 130◦C) flat or slightly curved sub-strates such as CRT, LCD, PDP, touch screen panels,discharge plates in clean environment, etc.References1. H.L. Hartnagel, A.L. Dawar, A.K. Jain, and G. Jagdish, Semi-conducting Transparent Thin Film (IOP Publishing, Bristol andPhiladelphia, 1995).2. H.K. Pulker, Coatings on Glass, 2nd edn. (Elsevier, 1999).3. C. Goebbert, M.A. Aegerter, D. Burgard, R. Nass, and H. Schmidt,ITO Coatings on Plastic Substrates 697Proc. Materials Research Society, MRS, Nanostructured Powdersand their Industrial Application 520, 293 (1998).4. C. Goebbert. M.A. Aegerter, D. Burgard, R. Nass, and H. Schmidt,J. Mater. Chem. 9, 253 (1999).5. N. Al-Dahoudi, H. Bisht, C. Goebbert, T. Krajewski, and M.A.Aegerter, Thin Solid Film 392, 299 (2001).6. C. Goebbert, R. Nonninger, M.A. Aegerter, and H. Schmidt, ThinSolid Film 351, 79 (1999).7. C. Goebbert, H. Bisht, N. Al-Dahoudi, R. Nonninger, M.A.Aegerter, and H. Schmidt, Journal of Sol-Gel Science andTechnology 19, 201 (2000).8. Baytron P Technical Information.

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Wet coating deposition of ITO coatings on plastic substrates

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