Development of silver and CNT inks for applications in ... · PDF filefor applications in...

Düsseldorf, 2012-05-15

Development of silver and CNT inks for applications in printed electronics Stefanie Eiden

100nm

Corporate Center

Bayer AG

Service Areas Business Areas

Group Management Board

Holding Company

Bayer Business Services

Bayer Technology Services

Currenta

Bayer

HealthCare

Bayer

CropScience

Bayer

MaterialScience

Bayer Technology Services

- a Bayer Group Company

Düsseldorf, 15.5.2012 S.Eiden

Bayer Technology Services Full Year 2010

Employees* 2,700

Sales** (2010) EUR 420 million

Managing Director Dr. Dirk Van Meirvenne

Employees in full-time equivalents

Including goods and services delivered within the Bayer Group

*

**


BTS Technology Platforms

"DPP-Tool"

-100

0

100

200

300

400

500

Tem

pera

ture

[°C

]

Enthalpy

Source

Sink

Hot Utility

Cold Utility

D31 D6 D3

D31-Gen.

D6-Gen. D3-Gen.

Cooling water/Air R(-20)

Technology

Platforms

Processing

In-silico

Technologies

Nanotechnology

Biotechnology

Process

Synthesis

Catalysis Synthesis

Product

Design

Bedarfsplanung

Campaign-

design

Process

Management

Systems

Düsseldorf, 15.5.2012 S.Eiden page 4

200

nm

Materials Structuring at Nano and

Micro Scale

Composites Encapsulation Formulations

100nm

Reinforced plastics

Anti-static plastics

Barrier

UV-, Corrosion-

Protection

Scratch Resistance

Flame Retardancy

Fluorescent inks

Conductive Inks

d(00l)

d(00l)


The Vision of Printed Electronics

• Seamlessly integrated

• Flexible form factors

• Expected to be a 100

Bn$ market in 2020

(device level) image: Nokia

Source: NOKIA

page 6 Düsseldorf, 15.5.2012 S.Eiden

Market Potential of Printed Inorganic

Electronics

Likely impact of inorganic printed technology to 2017

element

device

inorganic

hybrid

organic

highest

potential for

dominant

chemistry

page 7

Düsseldor

f,

15.5.2012

S.Eiden

Silver particles for printed electronics

Unmet need

• Thin, highly conductive structures on

flexible substrates

Challenges

• High conductivity at low sintering

temperature (140°C)

• Low costs (reduced consumption of silver)

• Mass production (printed electronic)

• Transparency

• Highly flexibility


Synthesis of Silver nanos


Ag2O-Sol

Precipitation

AgNO3 solution + NaOH + surfactant

Ag-Sol

Reduction

Ag2O + reducing agent

2

Ag-Sol

Reduction and precipitations

AgNO3 + reducing agent + (surfactant)

1 Sterically stabilized particles

Electrostatically stabilized particles - - - - - - -

- -

Tailored silver particles:

Effect on particle size and size distribution

Parameter screening:

Process (batch, conti) striring conditions

Surfactants

Reduction agent

Temperature

Concentration of reactants

Length of polymer chain


Aim: High conductivity

Effect of particle size

Effect of particle size distribution

Effect of surfactant

Effect of surfactants

0,0

0,2

0,4

0,6

0,8

1,0

1,2

300 400 500 600 700 800

Wavelenght [ nm ]

no

rm. E

xti

nc

tio

n

PVP Dysperbyk 190

100nm

50nm

Width of the UV peak depend on the size and size distribution


Summary: effects on particle size


polymer chain (PVP K15,

Luvitec® K90)

reagents concentration

(AgNO3, NaOH, formaldehyde,

PVP, Luvitec®)

temperature (20 – 90° C)

prewarming (20 – 90 °C)

Process

the longer polymer chain, the particles are bigger

higher concentration of AgNO3 and NaOH, particle size is bigger

higher concentration of AgNO3 and NaOH, more aggregates

higher concentration of polymer, the particle size is smaller

the higher reaction temperature, the particles are bigger

Prewarming of AgNO3 and NaOH decreases polydispersity

Higher the stirring speed, particle size is smaller

Procedure Results

Particle properties effect conductivity


• Tailored particles

bimodal distribution

high packing density

low sintering temperature

low amount of surfactants

improved adhesion on substrates

by tailored surfactant

High conductivity

= 10% of bulk silver

100nm

Silver sol production process

Microreactor setup

400 L vessel with diafiltration unit

Continuous process with a capacity of 10 t silver sol per year


Ag2O-Sol

1 Precipitation

AgNO3 solution + NaOH + surfactant

Ag-Sol

Reduction

Ag2O + reducing agent 2

AgNO3 solution

NaOH solution

+ surfactant

Ag2O sol

Sample taking

Reducing agent

Heating

Ag nano sol

1 2

Purification

Washing

Concentration

Purified Ag-Sol

3

Bayink® has the best application

characteristics…

2 µm

Application advantages

Formulations for digital and

contactless printing

High resolution (<10 µm)

High conductivity at low sintering T

Various sintering processes

possible (microwave, photonic, …)


2 µm

Crack-free film of Bayink® TPS

after sintering at 180°C

3.8 µm

4.6 µm

Good adhesion and flexibility

on PC (APEC)

Application advantages Excellent adhesion properties







Applicable on many substrates

– Polymers: PC, PET..

– ITO

– Glass

Adhesion and wetting behavior

adjustable by formulation

Aerosol jet printing on ITO

(Optomec)

20 µm resolution

… and excellent adhesion properties...











– ITO

– Glass



Lower material cost

Lower process cost

no fume-hood required

Not harmful to most surfaces

Environmentally friendly

Long shelf life & high ink stability

Water-based ink formulation

…coupled with superior water-based

formulations…











– ITO

– Glass



Upscaled process of sol in place

Lower material cost

Lower process cost

no fume-hood

Not harmful to most surfaces

Environmentally friendly

Long shelf life & high ink stability

Low cost

– Manufacturing plant

– Automation possible

Allows production of up to 10 tons

per year

Water-based ink formulation

…and the only commercially scalable

production process


Summary: Silver

Synthesis of tailored particles shown

Effect of synthesis parameter on

the particle size and particle size

distribution

Suitable bimodal particles for

printed electronics

formulation adapted on the

physical properties for printing

applications


100nm

Development of

CNT inks/ pastes

Requirements and approaches for screen

printing

Requirements for conductive inks

High viscosity, e.g. c. 100 Pa.s at 1 – 10 s-1.

Low surface tension (depends on wettability of substrate)

Small coarse fraction, ideally no or few particles over 2 µm

in order to avoid clogging of the screen

High concentration (to give thick, highly conductive lines)

High conductivity

Approaches

Evaluation of different dispersion processes

Testing of different surfactants

Effect on conductivity

Effect on particle size

Ink formulation

Particle Size is crucial!!

Screen-printing formulations developed, at high CNT-concentration

Particle size distribution of DUD 1763 100315-590 nach Ansatz

by laser diffraction (MS 2000 Hydro S) in Water with different ultrasound treatment

0

10

20

30

40

50

60

70

80

90

100

0,01 0,1 1 10 100 1000 10000

particle size x [µm]

cu

mm

ula

tiv

e p

art

s o

f v

olu

me

Q 3

[%

]

ohne Ultraschall

ohne Ultraschall

ohne Ultraschall

nach 15 s Ultraschall



screen

pore

sizes

CNT-ink size

distribution

Effect of surfactant on particle size

5% CNT-Dispersionen in Wasser; 4% Hilfsmittel

Viscosity of CNT dispersions

Sodium lignosulfonate,

desufonated

Sodium lignosulfonate

Carboxymethyl cellulose

Poly-N-vinylpyrrolidone

Sodium dodecylbenzene

sulfonate

Polystyrene sulfonate

sodium salt

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Sodium lignosulfonate,

desufonated

Sodium lignosulfonate

Polystyrene sulfonate sodium salt

Carboxymethyl cellulose

Poly-N-vinylpyrrolidone

Sodium dodecylbenzene sulfonate

Specific conductivity in S/m

Conductivities

Comparison of specific conductivity

values

• large influence of dispersing agent

Mechanism CNT and surfactant


PSSA

Printing

Drying

Printing

Drying

PVP

replusion

Bayink® TP CNT - water-based CNT Dispersion

Good adhesion and

flexibility

solid content 5 % (customized)

particle size d90 ~ 1 µm

viscosity 200 - 700 mPas

density ~ 1,0 g/mL

pH 6 - 7

specific conductivity ~ 5000 S/m

temperature stabilty (CNT) 600 °C

Screen printing,

also Flexographic,

Gravure and doctor

blading

application process:

Pattern printed with Bayink TP CNT TEM of CNT Dispersion

Ink-jet ink formulation

Dispersing agent identified which:

• stabilizes at high CNT concentration: 5%

• allows for agglomerate free dispersion

• delivers low viscosity 0,010 Pa.s at high CNT concentration (> 6 wt.%)

with agglomerates

after agglomerate removal


Summary

Development and build up of a high energy dispersion process

10% solid content of CNT

Dispersion of single CNTs

Tailored viscosity

Development of Inks

Screen-printable ink

Ink-jet printable ink with very high CNT content

Conductivity is 3 times higher as graphite pastes opens applications in new fields


Thank you!

Development of silver and CNT inks for applications in ... · PDF filefor applications in...

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