etching & texturing polymer films - aimcal• chemical • atmospheric process – wet baths –...

© 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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