CO2 Laser free-shape cutting of flexible glass substrates
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CO2 Laser Free-Shape Cutting of Flexible Glass Substrates Xinghua Li, Sean Garner September 25, 2012

• Flexible Glass Substrates • CO2 Laser Free-shape Cutting • Summary Corning Willow Glass

Flexible Glass Applications Continuing to Emerge Significant advances occurring in device designs and processes • Device applications include: – Display (e-paper, color filter, OLED, LCD) – Touch sensor – Photovoltaic – Lighting • Processes include: high-resolution and high-registration patterning and printing • “Flexible electronics” devices typically focused on thin, light, or conformal • Glass substrate opportunities progressing toward flexible sheets and web Flexible Glass Sheets

Flexible Glass Enables High-Quality Electronics Substrate choice critical for device fabrication & performance • Substrate integrates designs, materials, & processes – Essential for overall optimization – Glass enables improved resolution, registration, performance & lifetime • Corning Willow Glass compatible with sheet-fed and R2R processes – Thickness 200 m – Alkali-free borosilicate composition – Optimized for device substrate and hermetic barrier applications Flexible glass barrier Flexible glass substrate © 2012 Corning Incorporated

Glass Enables Device Performance Optimization Willow glass offers high-quality surface & optical properties Surface Roughness 3 2 • Glass enables optimized combinations of R2R and sheet-fed fabrication steps • Flexible glass benefits include: – Hermeticity – Optical transmission – Surface roughness Optical Transmission Glass - 50 m - 100 m - 600 m

Glass Enables Fabrication Process Optimization Willow glass offers dimensional stability & process compatibility Registration of 4.7-inch Backplane Array Flexible glass benefits device fabrication • Thermal capability • Dimensional stability • Chemical compatibility • Flexible glass enables layer-layer registration • R2R processes • Sheet-fed processes Flexible Glass – Upper Left Thermal & Dimensional Stability for R2R Stress (MPa) Flexible Glass – Lower Right S. Garner, et al., “Flexible Glass Substrates for Organic TFT Active Matrix Electrophoretic Displays,” IEEE J. Disp. Technol., in...

Willow Glass Enables Thin, Light, Conformal Displays Capability demonstrated with 100 m glass substrates Active Matrix Segmented Color LCD, 4” diag., <170 m thick, qVGA S. Hoehla, et al., “Active Matrix Color-LCD on 75 m Thick Flexible Glass Substrates,” IEEE J. Disp. Technol., vol. 8, pp. 309-316, 2012. EPD, 4.7” diag., <270 m thick, 170dpi P-Y. Lo, et al., “Flexible Glass Substrates for Organic TFT Active Matrix Electrophoretic Displays,” SID 2011. Color ChLCD, 5” diag., <210 m thick, 80ppi Color EKD, 3.5” diag., 3-layer stacked, <0.7mm K-W. Wu, et al., “Color ChLC E-paper Display with...

High Edge Quality is Essential for Reliable Substrates Flexible nature of ultrathin glass substrates requires high edge quality • Strength limiting defects occurred primarily on as-cut edges

CO2 Laser Cutting of Flexible Glass Substrates Cutting is achieved through propagating a full-body crack • CO2 laser cutting uses tensile stress to propagate a crack along cutting path • Tensile stress is generated by CO2 laser heating and subsequent cooling process – Heating: CO2 laser – Cooling: Water Jet, Mist Jet, air convection • The tensile stress can be estimated using • For borosilicate glass, tensile stress on the order of 100 MPa is generated by the process

CO2 Laser Enables High Speed Glass Cutting Strong absorption requires laser beam shaping to avoid glass overheating Wavelength (um) © 2012 Corning Incorporated

CO2 Laser Cutting of Flexible Glass Elongated Laser Beam Approach (prior art) • An elongated CO2 beam (with an optional cooling spot), can be used to cut thin glass using the full-body cutting technique. – Repetitive initiation requirements make the process complex – Difficult to implement in free-shape cutting

CO2 Laser Free-shape Cutting Fast scanning beam approach • This technique cuts devices of arbitrary shape from a sheet of glass in one step by using – optical scanning of a round laser beam – ambient air convective cooling – full body cutting • This technique: – minimizes potential contamination from applied coolant – eliminates breaking step needed for laser scribe Device • Using flexible nature of glass makes extraction easier

CO2 Laser Free-shape Cutting Samples of arbitrary 2D shape can be cut • Fast laser beam scanning approach enables free-shape cutting of thin glass Rectangle with round corners Wafer with a flat notch Rectangular part with square corners

CO2 Laser Free-shape Cutting High edge strength & scalable to multiple device cutting • 2-pt bend test results • Multiple glass articles cutting capability

Summary • CO2 laser free-shape cutting is capable of producing glass articles with arbitrary 2D shapes • CO2 laser cutting produces glass articles with high edge quality at high speed