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Hitachi Chemical materials for wearable devices
Keywords: Flexible, Assembly, Encapsulation
To materialize the Shindo-Hitachi Chemical joint concept proposal of flexible assembly for wearable devices, Hitachi Chemical introduces five types of full area coating encapsulants. All types have in common, thinness, lightness, flexibility, and high reliability. From liquid type to film type, UV-cure type to thermal-cure type, to those with high transparency rates, high heat resistance and high elongation, this material lineup will enable wearable producers select a material that meets their demands. Hitachi Chemical has conducted various tests to measure the practicability and reliability of this flexible assembly concept. Up to this date, the following perspectives have been considered: water, sweat, stress and heat resistance, chip protection, and stretch ability. Positive results were examined in all tests. All five encapsulants provide industry-accepted IPX7 standard water resistance, while no corrosion was monitored after artificial sweat (JISL0848) was applied to the comb electrode, dried at 40C for an hour, and then soaked under conditions of 65C / 90%RH / 168h. As for the bending test, one end of the flexibly assembled device was fixed to a PVC pipe with a diameter of 22, 26, and 32mm, while a weight of 500g was attached to the other end. The pipe was rolled back and forth numerous times to evaluate the bendability of the device and chip protection strength of the coating material. Type 5 produced the best result, providing protection when tested with the narrowest 22mm diameter PVC pipe. All types inspected passed the Bias HAST test under conditions of 110C / 85%RH / 5V / 100h, while two types showed good heat resistance in the HTSL test (125C / 600h). In terms of stretch ability, recovery of the encapsulants after 50% elongation was monitored. A sample size of 50mm x 5mm with a thickness of 100-300um was stretched at a elongation rate of 5 mm/s, and the best recovery rates measured were 91% and 87%, both with TPU. In addition, Hitachi Chemical is currently developing wireless power transfer and advanced thermal insulation materials for wearable devices. As a member of the A4WP alliance, Hitachi Chemical can support wearable devices go wireless by producing A4WP compliant flexible flat coils with a minimum coil size of 8mm x 20mm, as well as implementing a hybrid wireless power transfer capable of providing visual transfer or NFC for identification/payment. Overheating issues of smart glasses is another issue Hitachi Chemical can help overcome. Currently under development are two types of insulation sheets which are both light weight and possess low thermal conductivity. Hitachi Chemical believes these materials will make wearables become more wearable.
Go Yatabe,
Hitachi Chemical Co.,Ltd.
Chiyoda-ku, Tokyo

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