Barrier Films and Adhesives for Display Applications CCR OLED Workshop, June 8, 2011, U of MN
3M Company Overview Sales: $23.1 B Net income: $3.2 B R&D investment $1.3 B (5.6% to sales) International sales $14.6 B (63% of company total) Companies in more than 60 countries Sales in nearly 200 countries Six Market Leading Businesses ~ 75,000 employees ~ 10,000 technical employees 55,000+ products 45 established Technology Platforms > 2000 patents issued in 2009 40,000 issued and pending patents Consumer and Office Display and Graphics Fiber Optic Solutions Electro and Communications Safety, Security and Protection Services Health Care Industrial and Transportation 2
Display and Graphics Business Innovative Solutions for light management and visual communications Sales: $3.1 billion Optical Systems Traffic Safety Commercial Graphics Touch Systems 3
Barrier Products Under Development. Barrier Film (optional light extraction) Optically Clear PSA Cover Film Barrier Adhesive Cover Film with Adhesive Device Optional Transparent Conductor Barrier Film (optional light extraction) Substrate Film 4
.Creating a Flexible Encapsulation System Barrier Film Optically Clear Barrier PSA Device Optional Transparent Conductor Barrier Film -Enabling Fully Flexible Displays and Solid State Lighting -Can also be used on rigid devices 5
3M Barrier Products Roadmap OLED TV OLED Lighting Time HH OLED E-paper Printed OLED 10-2 10-3 10-4 10-5 10-6 6 Barrier Performance, g/m 2 -day
3M Barrier Film Technology All vacuum roll to roll process Barrier properties are provided by oxide/polymer pairs: Top coat polymer Oxide 1 One Dyad Base polymer Substrate High barrier properties are obtained by using multiple dyads: H 2 O Multi-Layering creates a tortuous path through defects for water and oxygen 7
Multilayer vacuum web process: Web Substrate Base polymer Oxide Polymer Oxide Polymer Polymer Chill Drum Polymer One Dyad Vacuum Chamber Oxide 8
Optical Absorption UV-Visible Spectra 5 mil Film 100 90 %T 80 70 PET r356 r356 /A47 PSA 60 50 300 350 400 450 500 550 600 650 700 750 800 nm 9
Preliminary Barrier Film Specifications < 10-3 g/m 2 -day WVTR Barrier (FTB3-125 and FTB3-50) Suitable for E-Paper >87%T in the visible range, <2.5% haze PET substrate Can incorporate AG/HC A4 sheets or 300mm wide rolls < 10-5 g/m 2 -day WVTR Barrier Under development, suitable for OLEDs PET substrate Non-birefringent substrates under development A4 sheets or 300mm wide rolls 10
Barrier Adhesives 3M has focused on transfer adhesive films: Pressure Sensitive Adhesives (PSAs) Non-reactive towards common device materials PSAs are used in aircraft, automobiles and buildings as structural adhesives 11
Adhesion Testing Steel T-Peel Adhesive (25 µm PSA) Barrier Film Shear Barrier PSA Typical Values T-peel: 25 to 35 oz/in (27-38 N/100 mm) Shear: about 400 minutes (½ x ½ inch overlap) 1 Kg 12
Adhesive Bulk WVTR Using Mocon Permatran 150 (accumulation mode), 90% RH differential, ASTM E398. Adhesive laminated between water permeable film supports: Porous Support Adhesive Porous Support 10% RH 100% RH RH Probe Barrier PSA WVTR (normallized to 1 mil) WVTR for 1 mil OCA g/m2-day 18 16 14 12 10 8 6 4 2 0 5 10 15 20 25 30 35 40 45 Temperature (C) g/m2-day 1000 900 800 700 600 500 400 300 200 100 0 0 5 10 15 20 25 30 35 40 45 Temperature (C) 13 For a 25 µm thick Barrier PSA: For 25 µm thick typical OCA: (optically clear adhesive) WVTR at 20 C 1.9 g/m 2 -day 182 g/m 2 -day WVTR at 25 C 3.4 g/m 2 -day 292 g/m 2 -day
Adhesive Thermal Stability 120 TGA Instrument: AutoTGA 2950 V5.4A 600 100 80 400 Weight (%) 60 Temperature ( C) 40 200 20 0 0 0 10 20 30 40 50 60 70 Time (min) Universal V4.5A TA Instruments 14 10% weight loss at about 300 C, little or no loss up to 200 C
Adhesive Optical Properties (25 µm Barrier PSA) UV Absorbing PSA 100 90 80 70 60 %T 50 40 30 20 10 2%T at 380 nm 0 300 350 400 450 500 550 600 650 700 750 800 nm 15
Preliminary Barrier PSA Specifications FTBA-25 25 µm standard thickness, ~10-50 µm also possible Between liners or pre-applied to barrier film A4 sheets or up to 650mm wide rolls 2-4 g/m 2 -day bulk adhesive WVTR (Mocon 150) >87%T in the visible range, <2.5% haze UV cutoff feature; <2%T @380nm Stable to 200C Peel and shear properties typical of optical laminating adhesives 16
WVTR - Mocon and HTO Methods Dry N 2 @ 10 sccm Barrier side PET side 100% humidity Sponge soaked in water Temperature Controlled Mocon test cell N 2 + H 2 O Out to detector Same basic technique Different detectors Different detection limits 3M 1-dyad films are- Below Mocon detection 10-5 by HTO permeation of sample R094 final result: 2E-05 g/sqm/d @ 100% RH; 22 C 1.00E-02 1.00E-03 permeation [g/sqm/d] 1.00E-04 1.00E-05 1.00E-06 1.00E-07 17 Tritiated Water test cell 0:00:00 24:00:00 48:00:00 72:00:00 96:00:00 duration [h] 120:00:00 144:00:00 168:00:00 192:00:00
WVTR 3M Mass Spec Method Key features Precise, small volume sampling valve Accumulation Mode No pressure gradient Calibrate with known gas standards Monitor several gases simultaneously US Patents 7,552,620 and 7,555,934 18
WVTR 3M Mass Spec Method Tested system versus Oxygen Certification Films- 19 Now exploring Helium as the challenge gas Fast, < 4 hour test time Measuring defect density? Need to correlate He transmission rate with WVTR
WVTR 3M Calcium Test Method Use thin film of Calcium as an indicator for moisture Ca + 2 H 2 O Ca(OH) 2 + H 2 Encapsulate Calcium and monitor loss Optical Density or Transmission Metal mirror clear oxide Resistivity Conductive metal insulating oxide 3M using optical density measurements and image analysis 20
Calcium Test Example EPD Laminated Barrier/HC Films Aphelion Study 337 - OD Loss over time (Average) 100% 90% 80% 70% OD Loss (%) 60% 50% 40% 30% 20% 10% Control 342 Concept 2 Damp Heat Concept 2 Thermal Shock Concept 2 Heat Soak 0% 0 50 100 150 200 250 Hours in Humidity Chamber (60C / 90% RH) Can also track- Number of pinholes Pinhole area Ca pixel area 21
Deriving WVTRs from Ca Data 50 x 50 mm glass 40 x 40 mm barrier & adhesive 7 x 7 mm Ca pixels, 1000Å thick Place in 60/90 environmental chamber and monitor Ca optical density loss Amount of Calcium in sample is known Reaction stoichiometry is known: Ca + 2 H 2 O Ca(OH) 2 + H 2 Area of barrier film/adhesive is known Assume Ca half optical density corresponds to consumption of half the Ca in sample Assume an acceleration factor of 20 - generally accepted that 1 hour at 60/90 is equivalent to 24 hours at ambient Water required to consume one half of the Ca (Area of barrier & adhesive) (Time to half optical density) = WVTR of the film plus adhesive g/m 2 -day 22
Deriving WVTRs from Ca Data Ca loss vs WVTR (log-log) WVTR (g/m2-day) 1.00E-06 1.00E-05 1.00E-04 1.00E-03 Time to Ca half density at 60/90-10 hr = 1 x 10-3 g/m 2 -day WVTR 100 hr = 1 x 10-4 g/m 2 -day WVTR 1000 hr = 1 x 10-5 g/m 2 -day WVTR 10000 hr = 1 x 10-6 g/m 2 -day WVTR - at ambient conditions 1.00E-02 1 10 100 1000 10000 Time to 50% OD (hours) 23
Large Area Ca Test Under Development Early FTB3-125 sample Early FTB3-125 sample Recent FTB3-50 sample Recent FTB3-125 sample 0 hrs @ 60/90 28hrs @ 60/90 97hrs @ 60/90 24 150 x 50 mm glass and barrier film & adhesive 140 x 40 mm calcium area Can reveal patterns of defects and scratches Apply image analysis techniques Shows steady improvement in barrier film performance
Amazon Kindle E-Book 25
Barrier Laminates for E-Paper Displays AG HC PET Substrate Barrier PSA 1 PET Barrier Film Barrier PSA 2 e-paper front plane TFT backplane on glass or plastic Film requirements 10-2 g/m 2 -day WVTR Low pinhole defect density 3H pencil hardness Antiglare (5-10% haze) 200-300 µm thick Optional PSA 2 UV cutoff at 380 nm 3M Film WVTR g/m 2 - day at 50C Avg %T 550 nm Avg %T 450-650nm Avg %T 380 nm Avg %Haze Clarity Pencil Hardness A < 0.005 89.47 89.55 0.14 9.79 63.05 3H B < 0.005 90.86 89.45 1.86 8.66 64.80 3H C < 0.005 91.49 91.33 1.85 8.59 65.46 3H 26
Shelf Tags with 3M Barrier Film Pervasive Display, Inc. ECO-Signs (www.pervasivedisplays.com) Deployed in Grocery stores in Taiwan 2 shelf label Wireless data refresh 27
Moisture & Oxygen Cause OLED Dark Spots: Barrier film with conventional PSA Barrier film with barrier PSA 28 From Schaer et al., Adv. Funct. Mater. 2001, 11, 116-21
Conventional OLED encapsulation Rigid encapsulation: glass(metal) cap + adhesive + desiccant Replace epoxy with 3M barrier PSA stainless steel or glass cap desiccant (BaO or CaO) Replace rigid substrate and cap with 3M Barrier Film 29
OLED Flexible Barrier Requirements Flexible barriers offer advantages Thin & rugged rigid devices Fully flexible devices Simple lamination encapsulation processing Enables roll-to-roll processing 10-6 g/m 2 -day WVTR Generally accepted as the OLED barrier target Calculation based on aluminum cathode corrosion May be dependent on device design and cathode choice Thin film encapsulation and desiccants can compensate for higher WVTR barriers OLED displays using circular polarizers need non-birefringent barriers 3M is pursuing non-birefringent transparent barrier films TAC, COP, PC. OLED lighting may be able to use PET Adhesive needs What WVTR is required? How to incorporate desiccant into flexible encapsulation schemes? Epoxy edge seal plus desiccant seems to work for glass-glass OLED encapsulation 30
Why 10-6 g/m 2 day? Number based on consumption calculation for a 2000Å thick aluminum cathode 2Al(s) + 3H 2 O(g) 2Al 2 O 3 + 3H 2 (g) Calculated WVTR vs Percent Cathode Consumed 1E-4 WVTR (g/m 2 day) 1E-5 3 year 5 year 10 year For a 10-4 barrier, about 20% of the cathode would be consumed in 3 years and about 67% in 10 years Aluminum Cathode 1E-6 0 10 20 30 40 50 60 70 80 90 100 31 Percent cathode consumed
Ca WVTRs Showing 10-6 Barrier Performance Time to 50% Ca Optical Density 0.5 Hours at 60/90 0 200 400 600 800 1000 1200 1400 1600 0.45 2 mil PET Ca Optical Density Loss 0.4 0.35 0.3 0.25 0.2 0.15 0.1 Film 1 Film 2 Film 3 Film 4 Film 5 Barrier 1 mil barrier PSA Barrier 2 mil PET 1 mil barrier PSA Ca Glass Film 4 0.05 FTB3-125 and 50 10-5 g/m 2 -day 10-6 g/m 2 -day 2 mil PET Barrier 1 mil barrier PSA 2 mil PET Film 5 Barrier 1 mil barrier PSA Ca Glass 32 Film 1 Film 2 Film 4 Film 5 Pictures of samples after 136 hours at 60/90
Edge Effects How critical is moisture ingress from exposed film or adhesive edges? Knowing bulk WVTR properties calculate contribution from each component in device of interest: Barrier Substrate Barrier Layers Adhesive Device Possible H 2 O Ingress sites Substrate 33
Adhesive Bondline WVTR Calculations Water 1 x 1 m Barrier Film Glass 25 µm x 2 mm Adhesive Calculate the amount of water passing through a 2 mm wide bond line of a 1 by 1 meter device Compare result to the barrier film WVTR In this example- The amount of water entering the through the bond line is 5 x 10-6 g/day 3M s barrier PSA is well matched to OLED barrier film requirements in large device sizes. 34
Bondline WVTR Calculations Smaller Devices Device perimeter and area do not scale linearly with device size Calculate the water leakage due to film and bondline Different film WVTRs, bondline widths, and circular device sizes Determine where the water leakage rates for the film and bondline are the same: 1 mm Bondline and 1 x 10-4 g/m 2 -day Film g/day water ingress 0.000002 0.0000018 0.0000016 0.0000014 0.0000012 0.000001 7 x 7 cm 0.0000008 0.0000006 Bondline 0.0000004 Barrier Film 0.0000002 0 0 50 100 150 200 Bond line requirements can be calculated for essentially any device size and shape Device size, cm 2 3 mm Bondline and 1 x10-5 g/m 2 -day Film g/day water ingress 0.0000025 0.000002 0.0000015 22 x 22 cm 0.000001 Bondline 0.0000005 Barrier Film 0 0 500 1000 1500 2000 2500 Barrier property mismatch can be addressed with desiccants, thin film encapsulation, more stable display materials and electrodes Device size, cm 2 35
Desiccant Effect Boron oxide thermally evaporated over Ca coupons Improves Ca durability at 60C/90%RH Improves OLED device lifetimes B 2 O 3 + 3 H 2 O 2 B(OH) 3 Boron Oxide forms clear glassy film; can be in the optical path Average Ca Density loss @ 60/90 0.60 Optical Density Loss (0-1) 0.50 0.40 0.30 0.20 0.10 No desiccant 100Å Boron Oxide 250Å Boron Oxide 500Å Boron Oxide Barrier Film Barrier Adhesive B 2 O 3 Ca Glass 36 0.00 0 5 10 15 20 Days
Summary 3M is developing a family of barrier products Wide range of applications Targeting EPD and OLED markets Encapsulation system Barrier Film Adhesive Value add features; AG/HC, UV cutoff Sampling and R&D sales now, EPD barriers commercial in Q4 2011 A4 sheets, 300mm wide rolls Wide width production coater in early 2012 Up to 2 meter wide Unique WVTR test methods developed Calcium image analysis and Mass Spec 37
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