radtech na 2014 dr. mike j. idacavage, steve lundahl and ... formulation/idacavage... · radtech na...
TRANSCRIPT
RadTech NA 2014 Dr. Mike J. Idacavage, Steve Lundahl and Steve Appel
PL Industries May 12th, 2014
Agenda
• Photoinitiator Basics • Challenges with LED Curing
– Surface Cure – Yellowing
• Comparative Systems – Med Pressure Hg vs. LED
• Pigmented (thick & thin) • Clears (thick & thin)
Lamp Comparison
• Traditional UV Lamps - Arc lamps use an electric arc inside a mercury gas to excite atoms, which then decay, emitting photons. Microwave lamps excite the gas via microwave emission.
• UV LED Semiconductors (UV LED) emit a narrow bandwidth of light at the junction where doped semiconductor positive holes join with negative electrons when voltage is applied.
Formulating a UV Curable System
Matching PI with UV lamp
• Different UV lamps emit energy in different parts of the spectrum
• Its important to match absorbance of the PI with the output of the lamp for highest efficiency
UV-LED Output vs. Mercury Lamp
Challenges in LED Curing • Surface Cure
o UV-C promotes surface cure while UV-A promotes depth of cure
o Photoinitiators have very low absorption in UV-C range
• Yellowing
o Photoinitiators that absorb in UV-C range have a higher tendency to yellow (problem in clears)
Surface Cure PI’s
• Benzophenone/Amine combinations
• α-hydroxy ketones
• Benzil dimethyl-ketal
• No absorbance in the UV-A Region
Deep Cure PI’s
• Phosphine oxides
• α-Amino ketones
• Thiaxanthones
• Camphoquinone (visible)
• All deep cure photoinitiators tend to yellow
Pigmented Systems
Offset Printing Inks (thin films)
Medium pressure Hg Formula Epoxy Acrylate 35
Polyester Acrylate 15
GPTA 20
Pigment 15
Additives 5
STD DRK PI System 10
LED Formula Epoxy Acrylate 35
Polyester Acrylate 15
GPTA 20
Pigment 15
Additives 5
LED PI Package A 7
LED PI Package B 3
Absorbance of PI Packages
Challenge of Matching Absorption • Exceptions to the Rule
• There does not have to be a strong peak overlapping the LED transmission IF the quantum efficiency of the PI is strong.
Offset Inks Maximum Cure Speed (FPM)
Med. Pressure Hg Lamp LED Lamp
Standard Hg Ink Set Standard Hg Ink Set LED Ink Set
Yellow 175 40 130
Magenta 180 40 150
Cyan 180 35 100
Black 180 40 90
Medium pressure Hg testing conducted using a 200W/In lamp. LED testing completed with an 8W/cm 395 nm lamp.
Pigmented Systems
Inkjet Inks (thicker films)
Medium pressure Hg Formula
EOHDDA 50
EOTMPTA 12.5
Monofunctional Acrylate 12.5
Pigment Dispersion 10
STD DRK PI System 15
LED Formula EOHDDA 50 EOTMPTA 12.5 Monofunctional Acrylate 12.5 Pigment Dispersion 10 LED PI Package A 10 LED PI Package B 5
Inkjet Inks Maximum Cure Speed (FPM)
Med. Pressure Hg Lamp LED Lamp
Standard Hg Ink Set Standard Hg Ink Set LED Ink Set
Yellow 115 15 30
Magenta 115 20 30
Cyan 110 15 20
Black 100 15 20
Clear Coatings
Medium Pressure Hg Formulas
Thin Films
Epoxy Acrylate 38
TPGDA 10
EOTMPTA 25
HDDA 15
Additives 1
Benzophenone 4
MDEA 6
PL-CPK 1
Thick Films
Epoxy Acrylate 39
TPGDA 10
EOTMPTA 25
HDDA 15
Additives 1
PL-100 10
Clear Coatings
LED Formula
Thick Films
Epoxy Acrylate 39
TPGDA 10
EOTMPTA 25
HDDA 15
Additives 1
LED PI Package A 10
Clear Coatings Maximum Cure Speed (FPM)
Med. Pressure Hg Lamp LED Lamp
Standard Hg Coating Standard Hg Coating LED Coating
Thin Film (0.2 Mil) 120 No Cure 30
Thick Film (1.0 Mil) 130 No Cure 40
Yellowing Yellowness Index (ΔYi)
Film Description (ΔYi)
Thin Film UV Cure (0.2 mil) 0.76
Thin Film LED Cure (0.2 mil) 2.37
Thick Film UV Cure (1.0 mil) 2.55
Thick Film LED Cure (1.0 mil) 13.97
Conclusions
• Formulas must be modified for LED Curing
• High speed LED systems are achievable
• Pigmented systems are easier to develop as yellowing is less of a concern
• Yellowing is a problem in clear films and especially at higher coat weights
Thank You
Contact information: Steve Lundahl
VP of Technology
PL Industries, a Division of Esstech Inc.
24060 Greenway Rd.
Forest Lake, MN 55025
1-651-261-2611