VP ITO – for electrically conductive coatings and other applicationsTechnical Information 1362

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Contents1 Introduction – what is Indium Tin Oxide? 4

2 Applications 42.1 Transparent antistatic coatings and fi lms for fl at panel displays and clean-room window panes 42.2 Transparent electrically conductive coatings based on VP ITO TC8 62.3 Transparent NIR absorbing additive for 2D-laser marking/printing, 3D-sub-surface laser engraving and laser welding of transparent polymers 72.4 Heat Management for windows in automobiles and buildings 9

3 Product Properties 103.1 Powder Properties 103.2 Dispersion Properties 11

4 Packaging and Storage 11

5 Product Safety 11

6 Measurement methods 11

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1 Introduction – what is Indium Tin Oxide?

VP ITO – Nanostructured Indium Tin OxideIndium Tin Oxide (ITO) is a transparent conductive oxide (TCO) which has been in widespread use for quite some time. ITO is for example used to produce transparent but at the same time electrically conductive coatings, which are vital elements in every kind of display such as LCDs, TFTs etc. Currently the most used production process for these kinds of coatings is a sputtering process to create thin high conductive, fragile coatings using very expen-sive and energy consuming machinery.

VP ITO now provides the opportunity to create electri-cally conductive coatings with excellent optical properties by using simple coating or printing techniques. With this approach not only the equipment and energy costs can be reduced, but also the material yield improved.

ITO containing coatings on glass or plastics are highly transparent and feature electrical conductivity, antistatic properties and IR absorption. Additionally, these proper-ties are complimented by enhanced scratch resistance and fl exibility of the coatings. Such characteristics open up numerous potential applications, for example, in optoelec-tronic components such as fl at panel displays. Other fi elds of application are antistatic coatings for aircra or automo-bile windows, and heat absorbing transparent coatings.

Evonik Industries AG off ers its know-how for adapting available formulations to diff erent systems. Surface modi-fi cation and the provision of test dispersions facilitate rapid testing of the suitability of ITO in a given applica-tion in the fi rst developmental stage.

Table 1

VP ITO is available as:VP ITO TC8 Powder form for antistatic and electrically

conductive applications

VP ITO IR5 Powder form for IR applications

VP Disp. ITO TC8 DE

20 wt.% ITO dispersion in ethanol. Standard recommendation for UV cured electrically conductive and antistatic coatings

VP Disp. ITO IR5 DE

20 wt.% ITO dispersion in ethanol for UV cured IR absorbing coatings

VP Disp. ITO IR5 DMEK

40 wt.% dispersion in methyl ethyl ketone for temperature cured IR absorbing coatings

VP Disp. ITO LRC Ready-to-use UV curable lacquer for transpar-ent and scratch resistant antistatic coating (106 Ω/sq.)

VP Disp. ITO LTH2 Ready-to-use temperature curable lacquer for transparent and electrically conductive coating (≥ 500 Ω/sq.)

VP Disp. ITO LIR Ready-to-use UV curable Lacquer for transpar-ent IR absorption with up to 98 % reduction of IR radiation > 900 nm

Further dispersions of VP ITO in water and / or solvents and ready-to-use lacquers are available upon request.

VP = Versuchsprodukt; = Developmental Product

2 Applications2.1 Transparent antistatic coatings and films for flat

panel displays and clean-room window panesAntistatic transparent surfaces have gained increasing interest in recent years. The use of fi lms and plastic glaz-ing is increasingly replacing typical glass applications. Due to a certain degree of surface conductivity, glasses experience few problems with electrostatic charges. Plas-tics, however, become heavily charged in dry or air-con-ditioned rooms. As a result, discharges that can disrupt electronic components or displays may occur. Consider-ably more dust contamination of the plastic surfaces is also observed. Likewise standards for optical transpar-ency and clarity are becoming higher and higher with the increased use of plastic fi lms on TV screens and displays. The outer fi lm facing the viewer of displays is o en treated with rapidly degrading antistatic chemicals a er installation. Light-sensitive colored conductive polymers that result in an antistatic surface are also an alternative, however they can cause a distorted color perception.

The use of coating formulations based on our VP ITO products does not have these drawbacks. They are stable and exhibit high grade functionality.

Coatings with the new antistatic transparent VP ITO coating formulations enables PET, TAC and PMMA and other substrates to be provided in a single step with three attractive functions:

• Antistatic properties (105 – 108 Ω/sq.) together with • high transparency • color fastness • high UV resistance

• High mechanical stability and scratch resistance (up to 5 H)

• High chemical resistance

Picture 1: Coating on Plexiglas® sheet

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The coating is provided at low cost on conventional fi lm coating systems. With this coating system, Evonik Indus-tries AG provides customers with the advantages result-ing from many years of intensive research: maximum transparency, scratch resistance and antistatic properties with minimum VP ITO use.

Figure 1 shows an example of a UV curing acrylic coating on a Plexiglas® sheet featuring a transparency of 90 % (DIN 5033/5036), a haze of 0.5 % and a surface resis-tivity of 108 Ω/sq. This coating passes the steel wool scratch test.

Table 3 shows a comparison between Evonik VP Disp. ITO LRC and diff erent products available in the market.The performance of VP Disp. ITO LRC shows clear advantages. VP ITO is also available predispersed in water or solvents, in addition to the pure powder, for custom development of coating systems.

These nanostructured VP ITO dispersions can be further processed into heat-curing or UV curing coatings which are applied in conventional coating processes (blade, spray, dipping, pouring or spin coating). There is a great deal of latitude in the choice of component geometries that can be coated, aff ording a wide range of possibilities in fi elds of application such as antistatic scratch proofi ng of

• aircra windows • safety goggles • motorcycle helmets

Evonik Industries AG has developed application instruc-tions and guiding formulations for the use of ITO contain-ing coatings or dispersions. Acrylic coatings have been prepared, for example, using VP Disp. ITO TC8 DE, a 20 % ethanolic dispersion based on VP ITO TC8. The acrylic coating was applied with 12 µm blade and cured with a UV lamp. In this instance, the ITO concentration is 20 wt. % related to the solid coating.

Table 2

PropertiesVP Disp. ITO LRC

VP Disp. ITO LUV1

VP Disp. ITO LUV2

Surface Resistivity1 Ω/sq. ≥ 105 108 106

Light Transmission2 % 90 90 90

Haze3 % < 1 < 1 < 5

Abrasion Resis-tance*4 Haze

% < 2 < 3 < 6

Surface Resistivity after Abrasion**5

107 109 107

Pencil Hardness***6 3 – 5 H 3 H 2 H

Sensitive against NaOH NaOH NaOH

Formability of sheets no no no

Formability of films yes yes yes

Comparison of coating properties using different ITO based technologies.Parameters that can be achieved with UV curable lacquers by Evonik. * Taber Abraser, 500 g, CS10, 100 cyles, PC ** Scratching Test: Equipment Graf, green pad 3 M, 250 passes *** Tested on PMMA

Surface Resistivity [Ω/sq.]

Penc

il H

ardn

ess

106105104

2H

H

B

3H

Antistatic (superior antistatic)Dissipative

Antistatic

Figure 1

Solution to Customer

The performance of vEvonik Industries AG products, e. g. VP Disp. ITO LRC, VP Disp. ITO LUV1 and VP Disp. ITO LUV2 meet the high quality level of ready-to-use lacquer systems.

Good overall optical performance: Transmittance > 90 %.Relationship between pencil hardness of the surface and electrical surface resistivity.

Table 3

VP Disp. ITO LRC Supplier A Supplier B

Surface Resistivity Ω/sq. ≥ 105 106 – 107 106 – 108

Light Transmission % 90 80 > 75slightly blue

Haze % < 1 < 1 < 5

Abrasion Resistance* Haze

% < 2 26 14

Surface Resistivity after Abrasion**

107 1011 1012

Pencil Hardness*** 3 – 5 H B7 B8

Sensitive against NaOH NaOH, Acetone, MEK

NaOH, Acetone, MEK

Formability of sheets no yes yes

Formability of films yes no no

Comparison between VP Disp. ITO LRC and competitive materials. * Taber Abraser, 500 g, CS10, 100 cyles, PC** Scratching Test: Equipment Graf, green pad 3 M, 250 passes*** Tested on PMMA

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2.2 Transparent electrically conductive coatings based on VP ITO TC8

Sputtered ITO is the most commonly used transparent conductive oxide on the market. It combines superior conductivity together with good optical performance. At the same time sputtered ITO also has many disadvantages such as the lack of fl exibility of the coated substrates. Additionally only fl at substrates can be eff ectively coated using sputtering technology and the preparation of patterned electrodes is very diffi cult and time consum-ing- o en requiring 6 – 8 steps to create a pattern. In this process up to 90 % of the formerly deposited ITO is removed and only 10 % is fi nally used as an electrode.

ITO lacquers and inks have already been available on the market for some time, however the performance of the material was not within the range of sputtered ITO. The idea behind an ITO ink is that by using printing technol-ogy it could be a two step approach to create transparent electrodes for various applications. By simply printing the electrode in the correct location followed by a curing step it is possible to save a lot of ITO material and production time. In addition it is now possible to create a fl exible electrically conductive coating which cannot be achieved with sputtered ITO layers.

With the development of VP ITO, our customers are able to create their own transparent electrodes using printing technology. By incorporating VP ITO into a binder system the material can be printed using the customer process and cured either by using temperature or UV light. In table 4 you fi nd a short summary of what electrical and optical properties can be reached by using a simple VP ITO dispersion in a temperature cured binder system measured in light.

Due to these characteristics, products based on VP ITO TC8 can be used in all kind of display applications, for example, touch or fl at panel displays.

Table 4

VP Disp. ITO LTH2

Surface Resistivity1 Ω/sq. ≥ 500

Light Transmission2 % ca. 88

Haze3 % < 2

Pencil Hardness6 2B

Sensitive against Acetone, MEK, NaOH

Bending / Formability yes

The best values reached to date for coatings on PET are about 400 Ω/sq. as shown in fi gure 2.

On glass substrates values about 320 Ω/sq. have been achieved as shown in fi gure 3.

Figure 2

Figure 3

Time

Shee

t Res

istam

ce [Ω

/sq.

]

120011001000

900800700600500400300200

VP Disp. ITO LTH2 (1) VP Disp. ITO LTH2 (2)VP Disp. ITO LTH2 (3)

Time

Shee

t Res

istam

ce [Ω

/sq.

] 800700600500400300200

VP Disp. ITO LTH2 (1)VP Disp. ITO LTH2 (3)

VP Disp. ITO LTH2 (2)VP Disp. ITO LTH2 (4)

Development of Sheet Resistance [Ω/sq.] on PET over time (several months). Coating of several identical VP Disp. ITO LTH2 coat-ings on PET film.

Development of Sheet Resistance [Ω/sq.] on glass over time (several months). Coating of several identical VP Disp. ITO LTH2 coatings on glass

All measured coatings show a very stable surface resis-tivity over time if stored in light. By using VP ITO it is possible to create highly conductive and fl exible coatings which could be used for example in displays such as touch panels.

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2.3 Transparent NIR absorbing additive for 2D-laser marking/printing, 3D-sub-surface laser engrav-ing and laser welding of transparent polymers

Transparent polymers which are treated with VP ITO IR5 can be used for laser marking and engraving, without loosing the overall properties of the pure polymer. The key advantages of laser marking are:

• Contact free procedure • Eco-friendliness since no organic solvents are necessary

• No drying needed • Biocompatibility • High reliability of the process • Abrasion resistance of the mark since it is inside the polymeric compound

• Possibility to have unique marks on every item / article

Possible applications for this material are e. g. all kind of medical equipment, where the use of glue is not permit-ted or where the polymer must be crystal clear to see the liquid inside.

With suffi cient intensity, the energy of the laser beam can be utilized to selectively heat, melt or carbonize the poly-meric matrix. This provides versatile potential uses: rapid inside marking of transparent plastics, selective engraving or laser-induced welding of transparent plastics.

VP ITO IR5 particles can be incorporated into a variety of diff erent binder systems and polymers by using the pure powder or customized dispersions. With this procedure, the particles are invisible in the polymeric matrix and don’t create any haze. In addition, no color diff erence occurs compared to the undoped polymer, unlike to poly-mers which are treated with organic IR absorbers.

Picture 2: Laser welded parts using ITO modified TROGAMID® CX7323. Left: in polarized light, Right: visible lightNo color caused by the transparent and colorless NIR absorber.

Transparent nanocomposites have been developed for diff erent kinds of polymers, such as PA (Polyanilin), PMMA (Polymethacrylate = Plexiglas®), PC (Polycarbon-ate) and PP (Polypropylene) in addition to other materials which may be available upon request.

Transmission spectrum of pure and ITO modified Trogamid® CX7323.Ready-to-use inorganic NIR absorber ITO composite for transparent polymers.

Transmission spectrum of pure and ITO modified Plexiglas®.Ready-to-use inorganic NIR absorber ITO composite for transparent polymers.

Figure 4

Figure 5

200 400Wavelength [nm]

600 800 1000 1200 1400 1600

Tran

smiss

ion

[%]

100908070605040302010

0

Visible lightunmodified

Nd: YAG-LaserITO modified

Incr

easin

g co

ncen

tratio

n of

NIR

abso

rber

200 400Wavelength [nm]

600 800 1000 1200 1400 1600

Tran

smiss

ion

[%]

100908070605040302010

0

Visible lightunmodified

Nd: YAG-LaserITO modified

Incr

easin

g co

ncen

tratio

n of

NIR

abso

rber

8

Figure 6

VP ITO IR5 nanostructured particles can be homoge-neously distributed in the polymer matrix. The better dispersed and distributed the particles are, the lower the haze which will be created. In addition the energy uptake is more homogeneous, preventing local overheating of the organic material (see. Picture 3).

By focusing the laser beam where the mark should be created, the nanostructured fi ller absorbs the energy of the laser and creates diff erent discontinuities in the polymer, depending on the polymeric material used. This discontinuity results in a refractive index change of the material or in a carbonization of the polymer and creates thus a visible mark in the transparent material.

Well dispersed laser-sensitive additives

Agglomerated laser sensitive additives

Example of well dispersed particles (red balls) and poorly dispersed par-ticles. The well dispersed material creates only minimum Haze and has also an optimal energy uptake from the laser. In contrast, the agglomer-ated material causes Haze and has an inhomogeneous energy uptake resulting in poor resolutions of the marking.

Picture 3: Inhomogeneous NIR absorber distribution leads to local overheating and bad resolution.

In addition to 2D-laser engraving, 3D-laser engraving is also possible. For this process an article will be scanned providing the data for the generation of the dot cloud of the article. The dots then can be generated using a highly focused, frequency doubled Nd:YAG laser (532 nm).

Principle of laser marking using VP ITO IR5 as an IR absorbing additive.

Focused Laser

absorption by additive

foaming white

carbonization black

Discontinuity in refractive index or carbonization makes marking visible

unmodified TROGAMID®

modified TROGAMID®

Picture 6: Example for 2D-laser marking with modified Trogamid® resulting in higher contrast and better contour sharpness.

Picture 4: Example for 2D-laser marking with modified Plexiglas® resulting in higher contrast and better contour sharpness.

CAD-data dot-cloud

Picture 5: Process of the generation of the dot cloud for the 3D-laser marking process.

Picture 6: Examples of 3D-sub-surface laser engraving.

unmodified PLEXIGLAS®

ITO modified PLEXIGLAS®

Figure 7

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2.4 Heat Management for windows in automobiles and buildings

There are many fi lms or coatings available on the market for sun protections to reject heat caused by the IR radia-tion from the sun. These products are typically tinted dark, extremely refl ective or use a metal layer. The appli-cation in house strongly requires an eff ective heat barrier with very few tinting without infl uencing the natural daylight brightness. For car fi lms, these tinted products are also not very suitable because of impaired night time vision.

Films based on metallic layers have the disadvantage that they interfere with radio waves and thus minimize the reception of mobile phones. In addition they are vulner-able to corrosion especially in an environment with high humidity.

Thanks to the combination of optical transparency and IR absorption, VP ITO IR5 off ers the opportunity to pro-duce highly transparent, colorless coatings or fi lms with very good protection against heat radiation from the sun. Incorporated in a wide variety of transparent plastics and clear coatings, VP ITO IR5 permits not only the selective absorption of IR laser light but also the thermal radiation invisible to the human eye.

Figure 8

Heat radiation (IR radiation) will be absorbed

Visible light

Heat (IR) absorbing coating or polymer using ITO

Spectrum

Transparent substrate

The application of VP ITO IR5 in transparent fi lm coat-ings makes it possible to provide glass installed in build-ings or vehicles with better solar absorption properties while maintaining optical transparency (no darkening). Figure 9 shows the infrared transmission spectrum of a typical coating on Plexiglas® in comparison to the uncoat-ed material.

How eff ective a coating or a polymer comprising VP ITO IR5 is at reducing thermal transmission is shown in fi g-ure 10. There the temperature development of a room behind an uncoated and coated glass window was mea-sured. The fi gure shows not only a temperature diff er-ence of up to 13 degrees Celsius but also a much slower increase in the temperature as well.

How does VP ITO IR5 work?

Wave length [nm]

Tran

smitt

ance

& R

eflec

tanc

e [%

] 90.0080.0070.0060.0050.0040.0030.0020.0010.00

0.00250

Transmittance

500 750 1000 1250 1500 1750 2000 2250 2500

Figure 9

IR transmission spectrum of a coated PMMA sheet.

VP ITO IR5 Coating on PET

T [°

C]

50454035302520

0 20 40 60 80 100 120 140

Without IR Protection Time [min]VP ITO IR5 Coating on PET

Figure 10

Comparison of temperature development between coated and uncoated glass windows.

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Table 5 shows the most important values concerning heat protection. The relative heat stop performance can have values between one (uncoated glass) and two (black glass). The closer to two the more energy is rejected, but visible light transmittance should be as high as possible. The Global Radiation Transmitted should have a very low value. The lower this value the less energy passes a win-dow. For the Global Radiation Refl ected it is the other way around. The higher the value the less energy passes the window. As a result you will fi nd that the eff ect of Evonik IR absorbing coatings or polymers is comparable to sputtered ITO. In addition it has the advantage that it can be coated on or incorporated in transparent poly-mers. In this way existing insulating windows can be upgraded to sun protective glasses by simply installing a window fi lm with VP ITO IR5 without replacing the whole window.

Table 5

Sputtered ITOon insulatingglass

VP ITO IR5 coated on single glass

VP ITO IR5 coated on insulating glass

Light transmission (visible range)

% 77 79 71.5

Light reflection (visible range)

% 12 8.9 14.6

Relative heat stop performance

τ/g 1.26 1.23 1.32

Total energy transmission

% 0.61 0.64 0.54

Global Radiation Transmitted

% 0.52 0.54 0.48

Global Radiation Reflected

% 0.25 0.07 0.11

The measured heat protection indicators show that providing a window with a VP ITO IR5 film can compete with all sun protection systems on the market.

3 Product Properties3. 1. Powder PropertiesITO in pure form is a fi ne blue powder. The color is an indicator of the quality of the product. Yellow or gray ITO has a distinctly lower electrical conductivity. At tem-peratures over 200 °C in the presence of oxygen, VP ITO loses its blue color and also its conductivity.

Table 6 shows some typical values of the product in powder form.

Table 6

Property Unit VP ITO

Specific surface are m2 / g ≥ 35

pH 3 – 5.5

color blue

electrical resistivity Ω cm 1 – 2

Powder properties, typical values.

When processing and handling the material, all of the usual precautions for fi ne powders must be taken and the instructions in the safety data sheet must be adhered to.

Picture 7 shows a TEM photo of the product in the coat-ing layer.

Picture 7: TEM photo of a cross section ITO-charged coating on a PMMA film.

PMMA

1,5 µm

0,2 µm

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3.2 Dispersion PropertiesAll ITO products in powder form are particularly easy to disperse with the use of high shear force, allowing for excellent transparency of the product.

Dispersions based on VP ITO TC8 enable the production of highly transparent, colorless coatings and feature electrical conductivity and antistatic properties. These properties are additionally complimented by enhanced scratch resistance of the coatings depending on the used binder matrix. Such characteristics open up numerous potential applications, for example, in optoelectronic components such as fl at panel displays. Other fi elds of application are antistatic coatings for aircra , clean room glazing or covering for machinery.

Dispersions based on VP ITO IR5 enable the produc-tion of highly transparent, colorless coatings featuring IR absorbing properties on polymers and glass. These prop-erties are additionally complimented by enhanced scratch resistance of the coatings depending on the used binder matrix. Such characteristics open up numerous potential applications, for example, as heat absorbing coatings in architectural application or car industry or in the area of transparent and colorless laser markable coatings and polymers.

Dispersions of VP ITO are a bluish liquid. The solid con-tent varies and depends on the solvent. It ranges from 20 to 50 wt. %. The dispersions show also at 50 wt. % still a low viscosity and can easily be combined with suitable binders or polymers.

Dispersions are available in a big variety of diff erent sol-vents such as alcohols (ethanol, isopropanol, n-butanol, ethylene glycol), ketones (ethyl methyl ketone), ethers (Dowanol PPH) and water. Further solvents are available upon request.

4 Packaging and StorageITO (powder) samples are delivered in 50 g glass bottles. Packaging for larger amounts and containers is available upon request. Dispersions and coating material are also delivered in glass bottles. It is recommended to store the product in a dry place and away from heat and frost and to process it within six months a er production. Slight sedimentation is normal and can be eliminated by shaking or stirring.

5 Product SafetyA safety data sheet accompanies every fi rst (sample) delivery of our products. You can obtain a safety data sheet and further information from our department Prod-uct Safety at any time.

6 Measurement methods

Measured Properties Used Methods

1 Surface Resistivity (Ω/sq.) DIN EN 100015/1

2 Light Transmission (%) DIN 5033/5036

3 Haze (%) ASTM D-1003

4 Abrasion Resistance (Haze %) Taber Abraser, 500 g, CS10, 100 cyles, PC ASTM D-1044/90

5 Surface Resistivity after Abrasion

Scratching Test: Equipment Graf, green pad 3M, 250 passes

6 Pencil Hardness DIN EN 13523-4

This information and any recommendations, tech-nical or otherwise, are presented in good faith and believed to be correct as of the date prepared. Recipients of this information and recommenda-tions must make their own determination as to its suitability for their purposes. In no event shall Evonik assume liability for damages or losses of any kind or nature that result from the use of or reliance upon this information and recommenda-tions. EVONIK EXPRESSLY DISCLAIMS ANY REPRESENTATIONS AND WARRANTIES OF ANY KIND, WHETHER EXPRESS OR IMPLIED, AS TO THE ACCURACY, COMPLETENESS, NON-INFRINGEMENT, MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PUR-POSE (EVEN IF EVONIK IS AWARE OF SUCH PURPOSE) WITH RESPECT TO ANY INFORMA-TION AND RECOMMENDATIONS PROVIDED. Reference to any trade names used by other companies is neither a recommendation nor an endorsement of the corresponding product, and does not imply that similar products could not be used. Evonik reserves the right to make any chang-es to the information and/or recommendations at any time, without prior or subsequent notice.

07-2

015

Europe / Middle-East / Africa / Latin AmericaEvonik Resource Effi ciency GmbHBusiness Line SilicaRodenbacher Chaussee 463457 Hanau-WolfgangGermany +49 61 81 59-8118 +49 61 81 59-78118ask-si@evonik.comwww.evonik.comwww.sipernat.com

North America

Evonik Corporation299 Jeff erson RoadParsippany, NJ 07054USA +1 800 233-8052 +1 973 929-8502ask-si-na a@evonik.com

Asia / Pacifi c

Evonik (SEA) Pte. Ltd.Business Line Silica3 International Business Park#07 – 18 Nordic European CentreSingapore 609927 +65 6 809-6877 +65 6 809-6677ask-si-asia@evonik.com