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Introduction to Ink Design
Introduction to Ink Design
• Critical aspects of Ink jet ink design• Ink properties• Ink types
– Aqueous– Oil-based– Solvent-based– Phase change– UV curable
Inkjet ink design
Complexity
Ingredients
High
Up to 10
High
Up to 15
High
Up to 10
Med
~ 6
Med
~ 4
ApplicationFunctionality Med High High Med Low
Purity
Filtered Inkper micron
High
<0.5
Med
<3.0
Med
<1.0
Med
<1.0
High
<0.2
Reliability
Ink dropsper nozzle
High
> 1010
High
> 1011
High
> 1010
High
> 109
High
> 109
CIJ OfficeTIJ
Officepiezo
CIJ Multi DODPiezo
Ink Property Binary deflection
Ink jet ink requirements
CIJ Valve jet
OfficeTIJ
Officepiezo
CIJ Multi DODPiezo
Ink Property Binary deflection
Viscosity/cP ~ 1.5 3 - 8 8 - 12 < 2 ~ 1.5 ~ 1.5
Surface Tension/ dynes/cm
> 35 25 - 40 > 32 > 24 > 35 > 35
Max. size
/ microns
1 3 1 5 1 0.2
Conductivitymicro siemens
Yes> 500
Yes> 1000
No No No No
Salt levelsChlorides/ppm
< 100 < 100 < 100 < 100 < 10 < 10
Ink jet ink requirements
• Viscosity and Surface Tension properties dominate droplet formation
– Dynamic properties are most important– Dynamic properties are very different in the nozzles
region• Laboratory measurements are not key for design
– These measurements characterise low shear properties of an ink
– During the nozzle region ink experience high shear conditions
Droplet formation and jet stability
Image quality & durability
Wetting of capillary channels
Flow through the nozzle
Understanding the inkjet process
High Speed IJ Technology
Printhead Development
App
aren
t Res
olut
ion
Low
High
Speed
Low High
Industrial Printheads
Desktop Printheads 600 - 1200 dpi180 m /min
Printhead Developments: Resolution - Drop Volume
• Ink droplet volume: limits definition of printed features (in absence of substrate modification)
• Most Industrial Printheads not achieved <6pl
2pl 20pl 80pl
16μ 34μ 53μ
Resolution: High Low
Printhead Developments: Speed
Variable Droplet Size
Higher frequency
Higher Nozzle Density
Page wide array
P (Image Quality)
Line
Spe
ed m
/min
Cactus SeedCactus Seed
200+
100
50
25
64800 180000 720000
9 734 72 456 34
Text and Barcode
CIJ DOD
P (Image Quality)
Line
Spe
ed m
/min
Cactus SeedCactus SeedCactus SeedCactus Seed
200+
100
50
25
64800 180000 720000
9 734 72 456 34
Text and Barcode
9 734 72 456 34
Text and Barcode
CIJ DOD
P = (resolution)2 * No. of greyscale levels
Printhead
Maintenance Station
Scanning
Page Wide Array
Scanning vs. Fixed Head IJ Printing
IJ Productivity: Full Colour Printing
Sca
nnin
g
Hea
dsFi
xed
Hea
d11 m2/hr of Printed output
120m2/hr
940m2/hr
Role Of Ink in High Speed PrintingInk Formulation challenges
1. Ink Jet Stage - Ultra high reliability
2. Ink behaviour on substrate 3. Performance Properties of image post ink
evaporation, absorption, reaction
•All aspects of the printing process need to be optimised to deliver a satisfactory process
For example, for a 30 min job @ 24m/min:• each nozzle must deliver reproducibly up to 10 million
ink droplets without interruption
What do we mean by Ultra High Reliability?
Extremely high jetting stability - “Turn it on & it works”
Delivering Ink Reliability:
Needs consider ink design, chemical and process technology to optimise performance in head of choice
•Basic ink operating window
•Component Design
•Operability testing and waveform matching
•Ink Path Issues
Component Design: Some key factors
Drop Regularity:
Ultra Stable Pigment dispersion with tight particle size control (<200nm) for drop regularity.
Also requires understanding of how to control dynamic surface tension, wetting and visco-elastic properties.
>10μm<200nm
IJ vs Typical Analogue Dispersion
20-30μm
Ink Component Design: Some key factors
Open time :
Ink components must be designed not to clog nozzles
0 500 1000 1500
Minutes
Aqueous Desktop
Solvent
Aqueous Industrial
Oil
UVIn
k C
lass
Ink Jet Open Time
Typical Open Time
Acceptable Open Time for Single Pass Printing
Important aspects of ink design- ink flow through the print head
• Ink flow through the print head– Wetting of different materials throughout the
head– Wetting capillary channels effectively
• Minimise sensitivities of air– Entrapped air– Pressure differences
Ink ReservoirInk Manifold Multiple printheads
Important aspects of ink design- ink flow through the print head
• Creating a stable meniscus
– Wetting / non-wetting faceplates• Aid to maintenance systems
– Balance surface tension forces of the meniscus and gravity feed from ink supply
Range of ink jet ink types
• Common characterisation of ink type is by carrier base
• Commercial Inks:– Water based inks – Solvent based inks – “Oil” based inks – Phase change inks – UV curable based inks
Printhead Technologies and Ink Types
Aqueous
Solvents
Hot Melt
UVCurables
CIJ OfficeTIJ
Officepiezo
CIJ Multi DODPiezo
DODShared
wall
Ink TypeBinary deflection
Inkjet Ink Formulations
Ingredients• Liquid carriers
– water, solvents, oils• Binders
– polymers• Colorants
– dyes & pigments• Additives
– surfactants– conductivity salts
Critical Materials• Colorants• Binders
Influence– jet performance– reliability– stability– application
performance