Inkjet Printing For Advanced Functional Coatings


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Xennia's Tim Phillips describes the challenges and opportunities for using inkjet technology to deposit functional coatings, especially for printed electronics and solar energy applications. This talk was presented at the Advanced Functional Printing Conference, Dusseldorf, Germany in March 2011.

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Inkjet Printing For Advanced Functional Coatings

  1. 1. INKJET PRINTING FOR ADVANCED FUNCTIONAL COATINGS Dr Tim Phillips Xennia Technology Ltd Presented at the Advanced Functional Printing Conference Dusseldorf, Germany, March 2011
  2. 2. Outline 1. Introduction 2. Example application - solar energy coatings 3. Inkjet versus other manufacturing techniques 4. Application examples 5. Application requirements 6. Summary
  3. 3. Xennia helps customers lower operating costs, increase productivity and simplify mass customised productionby revolutionising manufacturing processes
  4. 4. Background Xennia is the world’s leading industrial inkjet solutions provider 14 year history, over 300 customer development programmes World class reputation underpinned by a strong IP portfolio Unique expertise in inkjet chemistry with strong engineering capability Headquartered in UK, sales offices in US and China Awarded Queen’s Award for Enterprise in 2010 Offering reliable inkjet process solutions: Inkjet modules and inks for OEM partners with market access Printing systems and inks for end users through our distributors
  5. 5. From inkjet ideas production realityFeasibility studies Process development System design Production solutions
  6. 6. Xennia develops & supplies digital solutions based on inkjet modules, systems and inks for industrial applications
  7. 7. Inkjet manufacturing Use inkjet to: Apply coatings Create manufacturing processes Manufacture products Inkjet printing difficult materials Pigments (including inorganic), phosphors, metals Polymers Functional materials Key inkjet ink technologies Pigment and polymer dispersion Solvent based and UV cure chemistries
  8. 8. Solar energy generation Huge potential for energy generation 840 W/m2 reaches Earth’s surface during daylight e.g. 1600 TW strikes continental USA All electricity needs met with 10% efficient devices covering 2% of area (Interstate highways currently cover 1.5% of area) Solar energy harvesting Thermal – heat from sun heats water Used for hot water and swimming pools Photovoltaic – energy from sun used to generate electricity Can be used for any purpose
  9. 9. Solar photovoltaics Types of photovoltaic (PV) (solar cells) available Conventional (inorganic) 1st generation – crystalline Si 2nd gen – poly-Si, a-Si, CdTe or CIGS Input energy creates electron-hole pairs Separated by internal field Generates photocurrent Organic (small molecule or polymer) Heterojunction design incorporates: Electron transport layer (ETL) and hole transport layer (HTL) Input energy creates excitons ETL/HTL interface drives dissociation into electrons and holes ‘Standard’ materials P3HT and C60 derivatives
  10. 10. Solar photovoltaics Key figures of merit for PV Efficiency Percentage of incident energy converted into electrical energy Includes collection efficiency as well as conversion efficiency Cost Measured in $ (or €)/Wp Current typical cost 2-8$/Wp Need to reduce significantly Lifetime Minimum 3-5 years Desirable 20-25 years
  11. 11. Key cost drivers Key to reducing cost of PV Lower cost materials Lower cost manufacturing Continuous Additive (no waste) Flexible
  12. 12. Coating techniques Traditional semiconductor techniques Thermal/electron beam evaporation CVD/MOCVD etc Other coating techniques Spin coating Spray coating Printing Flexo/gravure printing Screen printing Inkjet printing
  13. 13. Traditional techniques Thermal/electron beam evaporation Material is heated and evaporates Deposits onto substrate and layer grows CVD/MOCVD Material made into volatile compound Compound decomposes to deposit material Spin coating Material in solution spun on flat surface Uniform coating with evaporation of solvent Spray coating Solution sprayed on surface Solvent evaporates
  14. 14. Technology comparisonTechnology Applicability Scalability Productivity Materials Film Process Multiple Wastage quality type layers?Thermal Inorganic/ Low Low (batch) Moderate High Subtractive Yes butevaporation small slow(vacuum) moleculeCVD (low Inorganic/ Low Low (batch) Moderate High Subtractive Yes butpressure) small slow moleculeSpin-coating Polymer/small Low Low (batch) Poor Medium Subtractive Yes but molecule slowSpray-coating Polymer/small High High Poor Low Subtractive Yesor doctor moleculebladeScreen or Inorganic/ Medium Very high Moderate Medium Additive Yes butgravure polymer/small damage?printing moleculeInkjet printing Inorganic/ High High Good Medium Additive Yes polymer/small molecule Gas phase versus solution phase deposition
  15. 15. Technology comparison Strengths Weaknesses Non-vacuum Film quality not as good as TE/EB/CVD Highly scalable Compatible with continuous/reel-to-reel process on flexible substrates Compatible with multi-layer printing Additive process Opportunities Threats Creation of a low-cost organic PV solution Transformation of other manufacturing processes
  16. 16. Inkjet deposition Production inkjet coating deposition requires High throughput High reliability  high productivity Excellent ink chemistry Functional performance Reliable printing Costs must make sense for application
  17. 17. Inkjet ink formulation Many PE inks require dispersion of particles Stable Need to overcome tendency to agglomerate Ionic or steric stabilisation – chemical stability Dispersion process Mill particles with dispersing agent Agglomeration Breaks up agglomerates and coats with agent 20% Delta Back Scattering 0:00 Physical stability 15% 10% 0:05 0:10 5% 0:15 Balance between Brownian and gravitational motion 0% 0:20 -5% 0:25 -10% 0:30 Mixing versus settling -15% -20% 0:35 0:40 -25% Dense and/or large particles  settling 0:45 -30% 0:50 -35% -40% 0:55 20mm 40mm 60mm Overcome with agitation/recirculation
  18. 18. Example materials Adhesives Inorganic pigments Abrasive materials Inorganic phosphors and lanthanides Aggressive acids and alkali materials Magnetic materials (MICR) Anti-scratch materials/clear coats Media coating materials Biomedical antibodies, reagents and enzymes Metal solutions and dispersions Bronze, aluminium and molybdenum powders OLED and LEP materials Ceramic pigments Organic soluble and dispersed dyes Colloidal and emulsion materials Sintered metals and ceramics Conductive graphite Textile pigments and dyes Conductive metals Titanium dioxide Conductive polymers Ultra high purity materials Decorative metallic pigments UV cure pigment inks Electrochromic materials UV cure structural polymers
  19. 19. Ink requirements Specific application requires specific ink Functional applications require very specialised inks Vital requirements for ink Printed ink must display required functional performance Ink must print reliably under production conditions Second requirement often forgotten Ink development requires testing Extensive/integrated Functional performance Inkjet performance
  20. 20. Low cost manufacturing Inkjet has the potential to allow low cost manufacturing of PV Can create a new market dynamic for solar energy production Need to deposit PV materials Contacts
  21. 21. Low cost PV Low cost, flexible PV allows Lower cost of ‘conventional’ power generation PV Easier installation Return on investment reasonable for mass market Enable new applications not currently possible/significant Power generation for mobile devices Power generation for signage Power generation in clothing
  22. 22. Applications example Power generating grass PV incorporated into synthetic grass Light absorbing layer can be coloured Absorbing grass is green! Make compatible with existing consumer products Allows power generation from existing areas Lower cost of lighting public and private areas
  23. 23. Applications example Power generating garments PV incorporated into clothing Military and civilian Absorbing materials in all colours Allows power generation from clothing Powering phones, radios, iPods, GPS Powering active camouflage
  24. 24. Applications example Power generating fabrics PV incorporated into tents, awnings, etc Multiple colours Allows power generation to campsites, homes and buildings Powering portable devices Lower cost of lighting public and private areas
  25. 25. Outlook Potential Solar power generation everywhere! Based on low cost production Challenges Increase efficiency OPV ~1/3 efficiency of conventional Increase stability OPV relatively unstable
  26. 26. Photovoltaics market Photovoltaic market growing significantly 20-25% per annum $30Bn industry generating 32GW Faster introduction impeded by costs Impact from Subsidies Regulations (e.g. specified renewables percentage) Emissions taxes Low cost solutions have massive potential
  27. 27. Inkjet PV Inkjet deposition ready to replace conventional techniques 2008: First organic solar cell fabricated with inkjet Commercialised inkjet PV production in 2009 Report 1.5m wide, 40m/min Inkjet printed electronics expected to grow €62M in 2008 €3,079 in 2013 Source: Plus Plastic Electronics, Pira International
  28. 28. Printing systemsfor functional coatings Range of requirements for functional inkjet printing systems Development systems Ink and process development/testing Batch processing systems Testing, prototyping, pilot production Batch production, high precision Continuous production systems High throughput production Rigid and flexible substrates 3D surfaces?
  29. 29. Functional inks Conductive Silver nanoparticle, copper UV catalytic (CIT), PEDOT Resistive Carbon black (pressure sensitive), carbon nanotube Semiconductor (under development) Electrochromic Displays Index matched filter inks Etch resist Laser ablateable Adhesives/hardcoats
  30. 30. EU collaborations Xennia is a member of two large new collaborative EU projects LOTUS – Three year project, commencing 1st Jan 2010 Development of conductive inkjet printing inks and sintering processes compatible with RTR printing for general application to printed electronics Xennia’s partners are TNO/Holst, Hebrew University of Jerusalem, ECN, Fraunhofer, Fredrich Schiller University Jena, Imperial College London, KSW Microtec, Agfa, Philips Lighting NOVA-CIGS – 3.5 year project, commencing 1st Jan 2010 Development of printed CIGS solar cell technology Xennia’s partners are Umicore, ZSW, Wuerth Elektronik Research GmbH, FLISOM AG, VTT, Technische Universität Chemnitz, EMPA Xennia is always looking for new opportunities for collaborative projects
  31. 31. SummaryInkjet is an excellent technology for many functional applicationsInk and process design is paramountXennia provides solutions for industrial inkjet applications Ink/fluid development and production Production system design/manufacture/installation/supportXennia wants to build partnerships