New Developments in Moisture Barrier Materials and Conductive Adhesives for Flexible Display Applications

T H E C U S T O M E R F O C U S E D E L E C T R O N I C S O L U T I O N P R O V I D E R New Developments in Moisture Barrier Materials and Conductive Adhesives for Flexible Display Applications Dr. Stijn Gillissen & Kurt Severyns Jan 2007

Presentation Overview 1. Moisture Barrier Materials 2. Challanges Imposed by Flexible Devices 3. Flexible Edge Sealants 4. Flexible Laminating adhesives 5. Flexible Electrically Conductive Adhesives 6. Conclusions

Moisture Barrier Materials Sealant Needs Protection from moisture / oxygen is needed in emerging display applications. Two different types of moisture barrier adhesives are needed. As Edge Sealant in OLED s (glass-glass or glass-metal) or E-paper displays As Laminating Adhesive in (flexible) OLED s using inorganic vapor deposited coatings : substrate : adhesive : display media : inorganic coating

Moisture Barrier Materials Emerson & Cuming s Product Range for Flat Panel Displays Emerson & Cuming supplies: -- UV & thermally curable paste moisture barrier sealants -- Barrier Laminating Adhesives (liquid & film) -- Electrically Conductive Adhesives Emerson & Cuming does not supply: -- high barrier films (Aclar, Saran, etc.) -- multilayer films (food packaging films PE/PVOH/PVDC, etc ) -- inorganic barrier materials

Challanges Imposed by Flexible Devices Key Sealant Properties Moisture permeability Adhesion Cure Speed Flexibility Outgassing Bondline thickness Moisture absorption Transparency

Challanges Imposed by Flexible Devices Bending of a rigid sealant results in cracking and delamination Rigid sealant can not cope with stress induced during the bending process. Cracking & delamination will occur. Before bending After bending Substrate Display Media Substrate Sealant Crack & Delamination (Cross section of typical display using edge sealant)

Challanges Imposed by Flexible Devices The challenge in formulating flexible sealants is to combine a high cross-link density with low E-modulus DMA measurement: E-Modulus (~ stiffness) of polymer material vs temperature High cross-link density is key property to get good moisture barrier in rigid sealants Modulus drop in Tg region = free volume and barrier properties 4500 Rigid Sealant E-modulus drop in Tg region. 3500 Storage Modulus (MPa) 2500 1500 500 Semi-Flexible Sealant Full flexible material Inherent polymer packing becomes much more important for flexible materials with low modulus andtg -500-100 -50 0 50 100 150 200 250 Temperature ( C) Universal V4.1D TA Instruments

Challanges Imposed by Flexible Devices The formulation of a flexible sealant requires high inherent polymer packing Permeability of a polymeric matrix can be derived from Fick s law: P = D x S Rigid material T g > T exposure P: Permeability coefficient D: Diffusivity coefficient S: Solubility coefficient Flexible material T g < T exposure Factor Diffusivity ( ) Low free volume High conversion (maximize cross-link density) Hydrophobicity High Filler loading Higher free volume / High packing density High Inherent polymer packing needed Hydrophobicity Selective use of fillers Diffusivity ( ) Diffusivity ( ) Solubility ( ) Diff.( ), Sol.( )

Challanges Imposed by Flexible Devices Bend test Capability to evaluate bending performance on device level Speed, diameter and cycles can be controlled bend test movie click here

Presentation Overview 1. Moisture Barrier Materials? 2. Challanges imposed by flexible devices 3. Flexible Edge Sealants 4. Flexible Laminating adhesives 5. Flexible Electrically Conductive Adhesives 6. Conclusions

Flexible Edge Sealants E&C offers thermally and UV curable edge sealant materials for e-paper and OLED displays E-paper edge sealants OLED edge sealants : substrate : adhesive : display media Benefits Superior Moisture Barrier Fast Thermal Cure (10 min 70 C) Low viscosity for fast processing Superior Moisture Barrier UV cure without thermal post cure

Flexible Edge Sealants Substrate Display Media Substrate E-paper Display Roadmap Sealant Rigid sealant Semi-Flexible sealant Full-flexible sealant 2007 2008 2009 2010

Flexible Edge Sealants Worklife in hours @ 25 C 1000 100 Rigid Display XUV80260 XUV80277 (Rigid ; 1 month) Substrate Display Media Substrate Sealant Bendable Display XUV80276 (Semi-flex ; 1 month) Flexible Sealant Roadmap Rollable Display XUV80303 (Flex ; 1 month) UV Cure 24 10 Eccoseal 7200 (Rigid ; 12 h) XE80308 (Semi-flex ; 24 h) TBD (Flex ; 24h) XE80284 (Semi-flex ; transparent; 5 h) XE80304 (Semi-flex ; high Tg; 5h) TBD (Flex ; 5h) Thermal Cure 1 2007 2008 2009

Flexible Edge Sealants Emerson & Cuming introduces XE80308, a bendable thermal cure moisture barrier sealant Key material properties: 70 C thermal cure (45 minutes) 24 hours worklife @ 25 C Water Vapor Permeation Rate < 10 g.mil/100in².day @ 50 C/100%RH (< 40 g/m².day for 100µm thick film) Semi- flexible: E-modulus @ 25 C : 2500 MPa Viscosity = 1.5 Pa.s (= 1500 cps) no thixotropy Storage at -20 C (6 months) Very good adhesion to glass, PET and metal White color

Flexible Laminating Adhesives Fully transparent materials UV-Vis measurements on cured films (100µm) Transparency as % T between 400 800 nm > 90% Also after 300h 85%RH/85 C transparency is maintained 100 90 80 70 60 %T 50 40 30 20 10 0 300 400 500 600 700 800 900 Wavelength (nm)

Flexible Laminating Adhesives High degree of flexibility XE80284 140 µm thick film on FR4 substrate bended over 2 cm cylinder XUV80303 250 µm thick free standing film XUV80303 250μm XE80284 143μm No delamination or cracking during bending

Flexible Laminating Adhesives Emerson & Cuming has developed thermally and UV curable laminating adhesives with excellent moisture barrier properties, transparency and flexibility. Product overview : substrate : adhesive : display media : inorganic coating Product Appearance after cure Viscosity range Pa.s @ 15 s -1 Cure Die Shear Strength (kg, glass on glass) Moisture Permeability g.mil/100 in².day Flexibility XUV 80276 Transparent 0.5 UV Cure 6 J/cm² 15 4-5 Semi Flexible XUV 80300-2 Transparent 164 (RT) UV Cure 2 J/cm² 6.4 ± 2.8 20 High Flexibility XUV 80303 Transparent 10-15 UV Cure 2 J/cm² 6.0 ± 1.5 8.5 High Flexibility XE 80284 Transparent 0.13 Thermal cure 1 hour at 70 C 47.5 8 Semi flexible

Flexible Laminating Adhesives Emerson & Cuming has developed Film Type Laminating Adhesives Prototype film type laminating adhesives are available: Need a UV cure after hot lamination Will stay tacky even after cure Materials are supplied between 2 PE release liners Film Carrier Film thickness Application Water Vapor Permeation (50ºC/100%RH) g mil/(100in 2 day) Water Transmission Rate (50ºC/100%RH) g/(m 2 day) Film thickness: 100μm Adhesion (T-peel ITO on PET), lb/in XF 80305-1 Polyester (125 and 50 micron) 50 micron Hot lamination (70-100 C), 20 psi followed by UV cure (1-2 J/cm 2 ) 5.8 22.8 1.40 XF 80305-2 Polyester (125 and 50 micron) 50 micron Hot lamination (70-100 C), 20 psi followed by UV cure (1-2 J/cm 2 ) 7.6 29.9 2.31

Flexible Electically Conductive Adhesives Background Emerson & Cuming also offers a number of isotropic conductive adhesives that are used for: Component attach, Electrical grounding, Battery attach,... Isotropic conductive adhesives conduct electricity in all directions (similar to solder). Isotropic conductive adhesive Anisotropic conductive adhesive

Flexible Electically Conductive Adhesives Emerson & Cuming offers 1-component, fast curing, flexible conductive adhesives Feature 1 component materials Stable electrical contact on Sn, SnPb and OSP coated Cu substrates Low temperature cure (as of 70 C) Very fast cure possible as of 100 C Benefit No mixing, ready to use Reliable electrical connection Use of temperature sensitive substrates High throughput production processes Product Viscosity (Pa.s) Volume resistivity (Ocm.cm) Typical cure temperature and time Worklife at 25 C E-Modulus at 25 C (MPa) Glass Transition Temerature ( C) Unique features CE 3103 WLV 15-25 8 x 10-4 120 C (10min) 150 C (3 min) 3 days 4500 (Rigid) 114 Fast cure, Stable Electrical contact on Sn, SnPb and OSP coated Cu XCA 3556 HF 30-40 7 x 10-4 80 C (1.5 min) 110 C (< 0.5min) 24 hours 650 (Flexible) 65 Very fast cure, Flexibility, Very good peel strength CE 3111 20-30 5 x 10-4 110 C (< 0.5min) 24 hours 4100 (Rigid) 90 Very fast cure

Conclusions To meet the challenges posed by flexible e-paper displays, Emerson & Cuming has developed 1-component sealants that are 24 h stable at RT Bendable Cure fast at 70 C Have excellent moisture barrier properties Emerson & Cuming has developed thermally and UV curable laminating adhesives with excellent moisture barrier properties, transparency and flexibility for use in combination with inorganic barrier coatings in OLED displays. Film type laminating adhesives prototypes exist. Emerson & Cuming offers 1-component, fast curing, flexible conductive adhesives

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