etching & texturing polymer films - aimcal• chemical • atmospheric process – wet baths –...
TRANSCRIPT
© C.A.Bishop Consulting Ltd 2005
CONSULTING LTD
Etching & texturing polymer films
different options for patterned deposition or
encouraging nucleation.
Charles A. Bishop
C.A.Bishop Consulting Ltd
Agenda
• Background
• Comments on options for surfaces
• Texturing methods & descriptions
• Conclusions
Background
• Some envisioned structures need discontinuous coatings – island structures
• Plasmon effects
• Photonic crystal growth
• High surface area catalysts
• Sensors
Nucleationminimising surface energy
reduced surfaceenergy
lowest surfaceenergy
untextured surface
Influence of texture on nucleation
no texture -random
nucleation
simple groovespreferred nucleation
in grooves
crossed groovespreferred nucleation
in pyramid pits
TextureRandom
–Chemical etching
–Laser ablation/etching similar
–Plasma etching
–Hairy surface
Regular–Laser writing
–Printing
–Embossing
Texture• Chemical
• Atmospheric process – wet baths – wash & dry
• Laser ablation/etching• cones – aspect ratio affected by flux & angle
• Web process 1m wide ~ 1m/min– mid 90’s – may now be quicker – speed similar to sputtering
• Hairy & embossing• Atmospheric process
• Laser writing• Direct writing into substrate
• Writing into photopolymer requires developing
• Printing• Printing of vacuum oils done in vacuum
Orthochlorophenol etched polyester
Laser ablation/etching
Atomic force microscope picture of the surface structure developed on the ablated PET film at 0 and 85 degrees. Dyer et al. Hull Univ.
Laser ablation/etching
Scanning electron microscope picture of the developed conical structure on excimer laser irradiated polyimide at 74.4 mJ/cm2 fluence.
AFM picture of the developed conical structure on excimer laser irradiated polyester at 600 -1000 mJ/cm2 fluence. Rossier et al. Lausanne Polytechnic Langmuir 1999 15, 5173-5178
Tack melt hairy surface
substrate
Hot rolllocally softens the surface
& picks up strands ofpolymer
knifehairy surface
Embossing, printing & laser writing
Embossing can be thought of as the inverse of printing
Embossing produces holes to make the equivalent to the step that printing produces
embossing printing
Intersecting gratings
Intersecting gratings
Ruled grating have sharp pyramids
whereas the holographic grating produces sinewave type structure
Micrographs - holographic surfaces
~175nm
300nm pitch replicated holographic motheyeStructure produced by Holographix
Grating types & dimensions
Electron beam lithography can give gratings with dimensions down to 10’s nm - but expensive & slow for v.large area shim or needs very precise stitching & reorigination
Regular grating Sawtooth grating
Patterning
oilevaporator
gravureroll
Masking bands for simple down-web striping
Striped web Patterned web
aluminium evaporation
Demetallised image
350 microns
500 micronsminimum line~ 50 microns
These images takenfrom samplesprovided by Aerre
Laser agglomeration or reticulation
substrate Laser scans from spot to spot on thin film causing reticulation of the film into islands
This requires a good quality very thin continuous coatings to shrink into uniform size islands
Cleaning
The best cleaning only removes debris down to ~0.3 microns (300nm)
Periodicity of anti-reflection embossing
< 300nm to be invisible to eye
Island growth likely to be ~10nm ie. << 300nm
Clean + smoothing polymer = required minimum
Debris –
the need for cleaning
substrate
ITO ~~ 200nm
Light Emitting Polymer (LEP) - 50nm
Polymer transport layer - 50nm
Top metal electrode
Light output
0.3microns
dia
0.3microns
diaresidual debris is of the same size as the total thickness of OLED coatings or pitch of the embossed grating or track spacing of blue laser DVR
250nm
DVR blue laser 400nmtrack spacing 0.32 microns
Starting process steps
tackroll
Clean surface Polymer smoothing layer -to cover remaining debris
Emboss surfaceNucleation into micro/nano-embossed surface
Cleanroom &/or vacuum?
After surface cleaning rolls need to be kept from re-contamination ie cleanroom or vacuum
Cleanroom – conventional – proven
Vacuum – unproven – difficult
cleaning in vacuum – not yet developed
polymer deposition & curing – proven in vacuum
embossing in vacuum – not yet developed
integration of processes with high efficiency - unproven
© C.A.Bishop Consulting Ltd 2005
CONSULTING LTD
ConclusionsThere are many techniques available
Regular texturing dimensions currently large compared to dimensions of final coating
Techniques like cleaning & embossing not yet proven to work in vacuum
© C.A.Bishop Consulting Ltd 2005
CONSULTING LTD
Thank you for Thank you for your your
attentionattention
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