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26 October 2017

Boosting cure speed and performance of coatings & inks when using LED light sources

Kevin Poelmans

Steven Cappelle

MAJOR MARKET TRENDS IN UV LED

• According to research, global UV-LED Market is projected to grow at a CAGR Of 8.9% over 2016-2020. (Gos Reports Center; Nov 2016)

• UV LEDs - Technology, Manufacturing and Application Trends 2016 (YoleDeveloppement; Jul 2016)

• UV Days 2017 (IST Metz; May 2017) => UV LED market size in 2021 ~ 980 M$=> ~ 90% UV Curing

26 October 2017 2

26 October 2017 3

MAJOR MARKET TRENDS IN UV LED - DRIVERS

Compact & scalable design of product lineInstantaneous turning on and offConstant outputEase of handling heat-sensitive substrates

Reduced electricity consumptionIncreased lifetime – LED chips last ~ 30 000 operating hoursReduced maintenance

No hazardous UVC & UVB wavelengthsLow operating temperaturesNo O3 and no Hg

Additional driver = ROHS II:

- ROHS2 = Directive 2011/65/EU (Restriction of Hazardous Substances) of European Parliament & of Council of 8 June 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment

- Active in 2019

- UV lamp manufacturers have done little to nothing to prevent a ban. They are now trying to get an extension and there will be probably a 5 year extension for UV lamps. Looking at the directive, this would mean until 22 July 2024

26 October 2017 4

MAJOR MARKET TRENDS IN UV LED - DRIVERS

Growth of UV LED in different market segments, fastest in Graphics followed by Industrial coatings

Graphics Market is switching towards UV LED

- Estimation by 2020: 300 offset presses & 150 flexo presses (source: EuPIA)

- Still some (technical) challenges today: higher (total) costs, incomplete surface cure, yellowing (OPV),…

• Flexo UV LED: brand new + converting of Flexo UV presses

• Litho UV LED: new UV LED presses to replace conventional sheetfed presses

retrofitting conv presses (faster delivery prints > internet orders)

• Digital UV inkjet market: preferred curing is UV LED

• UV LED OPV: in combination with LED litho or flexo; ongoing developments

26 October 2017 5

MAJOR MARKET TRENDS IN UV LED

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Technical challenges

• Narrow emission spectrum

• Restricted choice of available effective photo initiators (through cure PIs)

• More trouble with oxygen inhibition = lack of surface cure

26 October 2017

UV LED – EMISSION SPECTRUM

26 October 2017

LED 395 nm

26 October 2017 8

UV LED – PHOTOINITIATOR WAVELENGTH ABSORPTION

Not a lot of new dedicated commercial PIs coming to market

UV LED

UV-A UV-V

Coating

Substrate

315 – 400nm

400 – …nm

BulkThrough

O2O2

O2O2

O2

O2O2 O2

O2O2

O2O2

O2O2 O2O2

O2

O2O2

O2

O2

O2

O2

O2

O2O2

O2O2

O2O2

O2O2

O2 O2 O2

O2O2

O2O2

O2

O2

O2O2

O2O2

O2 O2O2

O2O2

O2

O2

O2O2

O2O2

O2

O2O2

O2O2

O2O2O2

O2 O2O2 O2 O2

O2 O2

O2O2O2O2

O2

O2

O2O2

26 October 2017 9

OXYGEN INHIBITION IN CLEARCOAT (OPV)

UV LED

UV-A UV-V

Coating

Substrate

315 – 400nm

400 – …nm

BulkThrough

O2O2

O2O2

O2

O2O2 O2

O2O2

O2O2

O2O2 O2O2

O2

O2O2

O2

O2

O2

O2

O2

O2O2

O2O2

O2O2

O2O2

O2

O2 O2

O2O2

O2O2

O2

O2

O2O2

O2O2

O2 O2O2

O2O2

O2

O2

O2O2

O2O2

O2

O2O2

O2

O2

O2

O2

O2O2

O2 O2O2

O2 O2

O2

O2

O2O2O2

O2

O2

O2O2

O2

26 October 2017 10

OXYGEN INHIBITION IN INK

26 October 2017 11

Method

Inert Gas blanket

Waxes

Protective Films

Increase PI Concentration

Increase LED power

Chemical modification:

(Abstractable) Hydrogen

donors

Oligomer + UV LED PI

Oligomer ●

Olig –O-O ●

UV LEDlight

Oxygen

Less reactiveSpecies for radical polymeristation

Olig –O-O-H + R ●

R – Olig ●

+ Oligomer

+ Oligomer

Polymer

+ R – H(Hydrogen donor)

Thiols > Amines > Ethers

Hydrogen donor:

KEEPING OXYGEN FROM INTERFERING

ACTUAL ISSUES WITH CURRENT PRODUCTS

• Thiol based:

- Smell

- Cost

- Stability in formulations

• Ether based:

- outdoor performance

- mechanical properties

• Amine based:

- Color/Yellowing

- Labeling

- Plasticizer

26 October 2017 12

Need for next generation LED booster

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Next generation LED booster

26 October 2017

• LED booster principle:

- Increase surface cure by attacking slow propagating peroxyl radicals & generating fast propagating ones.

- UV LED transformer: UV formulation -> UV LED formulation: still need adequate PI

- Efficient chemistries: thiols or amines

• Amino acrylate chemistry:

- High amine content

- Integrated in network after cure

- Polymeric form: REACH exempt, potential positive effect on migration (LM?)

- Cost effective

26 October 2017

UV LED BOOSTER CHOICE & PRINCIPLES

amines

Based on these choices and principles:

• 3 prototypes developed with specific features

• All 2-functional Polymeric Aza-Michael addition products

26 October 2017

UV LED BOOSTER PROTOTYPES

PrototypeLED03A

PrototypeLED03B

PrototypeLED03C

Amine content 4.2 meq N/g 4.3 meq N/g 2.9 meq N/g

Acr DB content 2.1 meq =/g 2.2 meq =/g 1.9 meq =/g

Viscosity 6900 mPa.s 2100 mPa.s 440 mPa.s

Color 1.6 G 0.5 G 0.5 G

Key features High amine contentRenewable content

Cyclic polyols

High amine contentLow color

Low migration potential

Low viscosityLow color

• Pilot UV LED Unit: - 365 nm 8W/cm² air-cooled Firejet (Phoseon)- 395 nm 8W/cm² water-cooled RX Fireline (Phoseon)- Mounted on 1 conveyor- Distance to substrate 1 cm

• Coatings & inks application:- Leneta charts & plastic substrates- Layer thickness depending on application:

- Clear coating: 15µ- Ink: 4 µ

• Evaluation:- Surface cure: thumb twist, fingernail mar or carbon black @ line speed- Yellowing- Stain resistance

26 October 2017

APPLICATION & TEST CONDITIONS IN LAB TRIALS

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Clear coating OPV application

UV LEDOPV FORMULATION: EFFECT ON CURE SPEED & YELLOWING

REFERENCE BOOSTED 1 BOOSTED 2

Epoxy Acrylate 15.2 13.6 12.8

TPGDA 39.4 35.2 33.1

TMPTA 39.4 35.2 33.1

BOOSTER / 10 15

PI blend 6 6 6

0

5

10

15

20

25

30

0

10

20

30

40

50

60

70

Surf

ace

cu

re in

m/m

in

Db

t(0h)

t(4h)

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Flexo ink application

26 October 2017

REF MODIFIED C MODIFIED C’

Polyester acrylate (4f) 26,7 25 23,4

Diluting acrylate (PO-2f) 26,7 25 23,3

Diluting acrylate (3,5f) 26,6 25 23,3

LED Booster - 5 10

PIGMENT (C: PAC 15:4) 20 20 20

PI package 6 6 6

Wetting & dispersing additive

3,8 3,8 3,8

Defoamer additive 0,48 0,48 0,48

CYAN FLEXO FORMULATION

Viscosities @ shear rate 3A 3B 3C 3A’ 3B’ 3C’

Shear rate 1.1 (mPa.s) 803 3140 2250 1410 3280 2660 1370

Shear rate 92.5 (mPa.s) 572 1080 1020 853 1550 1400 1030

Shear rate 2500 (mPa.s) 439 694 678 573 1010 907 712

Shortness index 2500 1.82 4.52 3.32 2.46 3.25 2.93 1.92

0

5

10

15

20

25

Cyan Magenta Yellow

Normalized reactivity

REACTIVITY NOT TAKING WORKING VISCOSITY IN ACCOUNT

Normalized reactivity

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

9,0

10,0

REFERENCE+ 5% LED

03A+ 5% LED

03B+ 10% LED

03C

Yellow Cyan Magenta

O.D

. 2,6

1

REACTIVITY TAKING WORKING VISCOSITY IN ACCOUNT

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Inkjet ink application

26 October 2017

Example Yellow ink Pigment paste

Ebecryl 151® 68,4

Stabilizer 1

Pigment wetting additive package 5,6

PIGMENT (Y: DGR) 25

Example Yellow ink REFERENCE IJ SPF

MODIFIED IJ SPF1

MODIFIED IJ SPF2

MODIFIED IJ SPF3

Pigment paste 20 20 20 20

Ebecryl 152® 72,5 62,5 62,5 62,5

TPO-L 6 6 6 6

DETX 1,5 1,5 1,5 1,5

LED 03A 10

LED 03B 10

LED 03C 10

UV LED MODIFICATION OF ALLNEX UV INKJET SPF

0

5

10

15

20

25

REF + 10% LED03A

+ 10% LED03B

+ 10% LED03C

Reactivity (m/min)

UV LED MODIFICATION OF ALLNEX UV INKJET SPF: REACTIVITY

0,6

0,7

0,8

0,9

1

1,1

1,2

30

40

50

60

70

80

90

100Gloss 20°Optical DensityViscosity (500Hz)

UV LED MODIFICATION OF ALLNEX UV INKJET SPF: OTHER SPECS

30

40

50

60

70

80

90

100

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Conclusions and outlook

CONCLUSIONS & OUTLOOK

Conclusions:

• New prototypes all afford increased reactivity under UV LED conditions in different end applications

• In the OPV application yellowing actually better than without Booster added

• In ink applications we see no detrimental inpact on color strength & in inkjet application even more vibrant colors

• 3rd prototype LED03C most formulation lattitude (effects on viscosity & rheology)

Outlook:

• Further development of prototypes: Migration properties, fine-tuning synthesis,…

• No convenient solution for Litho application: further development of LED booster for litho

26 October 2017

www.allnex.com

26 October 2017

Thank you

Jurgen Van HolenSteven Cappelle

Luc De WaeleMichel Malfliet

Carmen Van VaerenberghSabine Larno

disclaimer

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26 October 2017