www.allnex.com
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
• 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
• 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
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)
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
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
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
Notice: Trademarks indicated with the ®, ™ or * are registered, unregistered or pending trademarks of Allnex Belgium SA or its directly or indirectly affiliated Allnex Group companies.
Disclaimer: Allnex Group companies (“Allnex”) decline any liability with respect to the use made by anyone of the information contained herein. The information contained herein represents Allnex's best knowledge thereon without constituting any express or implied guarantee or warranty of any kind (including, but not limited to, regarding the accuracy, the completeness or relevance of the data set out herein). Nothing contained herein shall be construed as conferring any license or right under any patent or other intellectual property rights of Allnex or of any third party. The information relating to the products is given for information purposes only. No guarantee or warranty is provided that the product and/or information is adapted for any specific use, performance or result and that product and/or information do not infringe any Allnex and/or third party intellectual property rights. The user should perform its own tests to determine the suitability for a particular purpose. The final choice of use of a product and/or information as well as the investigation of any possible violation of intellectual property rights of Allnex and/or third parties remains the sole responsibility of the user.
© 2016 Allnex Belgium SA. All Rights Reserved
26 October 2017