P‐198: Optically Clear Adhesives Enabling Foldable and Flexible OLED Displays

Campbell, Christopher J.; Clapper, Jason R.; Behling, Ross E.; Erdogan, Belma; Beagi, Hollis Z.; Abrahamson, Joel T.; Everaerts, Albert

doi:10.1002/sdtp.12071

Cited by 30 publications

(26 citation statements)

References 5 publications

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“…The foldable display is a united panel containing a variety of layers and substrates. For a flexible OLED display, it is desirable to have either an OCA that perfectly mechanically decouples the layers from each other in bending (i.e., a material with no modulus) to minimize strain on critical layers or to have OCA that can tune the position of the neutral plane during the folding process [38]. Also, although the thickness of OCA is thinner than that of OCA for a rigid display for reducing strain caused by folding, the strong adhesion, flexibility, and durability to withstand hundreds of thousands of bends are required.…”

Section: Development In Display and Ocamentioning

confidence: 99%

“…When measuring the shear modulus of foldable OCA, Campbell et al suggest that the storage modulus should be maintained and has a low T g in the operating range (−20 to 80°C) [38]. Because, as presented in Figure 7, T g is shown at the primary reduction of storage modulus, lowering T g can result in modulus reduction below the operating range.…”

Section: Shear Modulusmentioning

confidence: 99%

“…The maintenance of the shear modulus ensures adhesion strength [38], strain recovery, and processability at high temperature. If the modulus decreased as the temperature rise, the adhesion strength and strain recovery are able to decrease by cohesion reduction.…”

Section: Shear Modulusmentioning

confidence: 99%

“…The decrease of modulus causes poor adhesion and mechanical durability in high temperature. So, they are researching that the foldable OCA has a stable modulus while maintaining a low T g [38].…”

Section: Researches Of Oca For Flexible Displaymentioning

confidence: 99%

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Pressure-Sensitive Adhesives for Flexible Display Applications

Lee¹,

Kim²,

Lee³

et al. 2020

Hybrid Nanomaterials - Flexible Electronics Materials

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Pressure-sensitive adhesives (PSA) have been used in electronics for not only attachment of two materials but also shock absorption, thermal and electrical conductivity, electromagnetic shielding, and optical property. Optically clear adhesives (OCA) have been used as a core material for optical performance of display. In addition to basic properties of OCA such as adhesion strength, transmittance, haze, and reliability, it has required dielectric constant, gap filling, and anticorrosion according to a substrate. However, the structural and functional changes of flexible display bring challenges to OCA that protects vulnerable components such as thin-film transistor, OLED, and thin-film encapsulation by stress dispersion and adjustment of a neutral plane. At the same time, flexibility and existing properties are essential. In this chapter, the development of components and performance of OCA, and evaluation methods will be discussed.

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Section: Development In Display and Ocamentioning

confidence: 99%

Section: Shear Modulusmentioning

confidence: 99%

Section: Shear Modulusmentioning

confidence: 99%

Section: Researches Of Oca For Flexible Displaymentioning

confidence: 99%

See 2 more Smart Citations

Pressure-Sensitive Adhesives for Flexible Display Applications

Lee¹,

Kim²,

Lee³

et al. 2020

Hybrid Nanomaterials - Flexible Electronics Materials

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show abstract

“…Indeed, OLEDs have been a promising candidate for commercializing flexible displays by considering their features such as thin structure, good planarity, excellent electroluminescent (EL) performances, and most importantly high mechanical flexibility. In recent times, several prototypes of the flexible display based on OLED have been reported . However, there are still some issues related to the fabrication of flexible OLEDs.…”

Section: Introductionmentioning

confidence: 99%

Thermally Evaporated Organic/Ag/Organic Multilayer Transparent Conducting Electrode for Flexible Organic Light‐Emitting Diodes

Bae

Kim

Lee

et al. 2019

Adv Elect Materials

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flexibility. In recent times, several prototypes of the flexible display based on OLED have been reported. [2][3][4] However, there are still some issues related to the fabrication of flexible OLEDs. Among the main concerns, securing transparent conducting electrode (TCE) with high mechanical flexibility as well as durability and good thermal stability are the most important issue. Generally, widely used TCE, Indiumtin-oxide (ITO) is not suitable for flexible display applications despite high transparency and conductivity due to its high rigidity. Therefore, to replace ITO, various types of flexible TCEs such as conducting metal oxide, [5][6][7] metal nanowire, [8,9] metal mesh, [10,11] carbon nanotube, [12,13] graphene, [14,15] and conducting polymers [16,17] have been reported.An ultrathin metal layer or sputter coinage metal, especially silver (Ag), with a thickness of about 10-14 nm is one of the noteworthy and alternative flexible TCEs because of its high transparency and low sheet resistance. The high ductility of the ultrathin metal layer makes it a flexible electrode to ensure high durability against the mechanical deformations. Moreover, it has a simple fabrication process which includes thermal deposition at room temperature using a fine metal mask without any patterning process for instance photo lithography. However, sole ultrathin Ag film with low resistivity and good uniformity cannot be formed accurately due to the Ag agglomeration, which induced by the stronger cohesion force between Ag clusters than the adhesion force of metal-substrate interface. [18][19][20][21] Typically, the Ag agglomeration aggravates the sheet resistance property owing to incomplete electrical path connection, as a result, low transmittance at the thickness of Ag with sufficiently low sheet resistance. To overcome this, metal oxide-based dielectricmetal-dielectric multilayer structures have been largely developed for optoelectronic devices. [22][23][24][25][26][27] Normally, the metal oxide-based binding/seed layer can reduce the coalescence between Ag clusters by increasing the interface adhesion force according to the bonding formation between Ag and oxygen. [21] However, metal oxide, especially molybdenum This paper reports an efficient, thermally stable, and high-performance flexible multilayer transparent conducting electrode (TCE) by sandwiching an ultrathin Ag layer between a thermally evaporated small-molecule organic wetting inducer, 1,4-bis(2-phenyl-1,10-phenanthrolin-4-yl)benzene and an organic antireflective capping layer, 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile for flexible organic light-emitting diodes (OLEDs). This TCE demonstrates a high transmittance of about 81.34% at 550 nm and very low sheet resistance of 9.51 Ω sq −1 with excellent thermal stability under high-temperature (100 °C for 72 h) conditions. These properties arise from the synergistic effect of coordinate bonding between the nitrogen of the phenanthroline moiety and the Ag atom which leads to a smooth and uniform Ag surface and the o...

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Controlling Neutral Plane of Flexible Substrates by Asymmetric Impregnation of Glass Fabric for Protecting Brittle Films on Foldable Electronics

Lee

et al. 2021

Adv Eng Mater

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Neutral plane strategies have been studied to reduce the tensile strain of brittle films in foldable electronics under bending. However, those strategies depend on the dimensions of components in devices, implying that they could be limited to application to various designs of devices. Herein, the glass fabric's position in a glass fabric–reinforced siloxane hybrid substrate is shifted to control the neutral plane of the substrate. Due to the stiffness difference between the glass fabric and epoxy siloxane hybrid matrix, the neutral plane of the substrate is affected by the position of the glass fabric. Therefore, the glass fabric is asymmetrically impregnated to be located at the substrate surface so as to shift the neutral plane of the substrate toward the surface. The effectiveness of the newly developed substrate is proved by comparison with a conventional colorless polyimide substrate. The neutral plane position and maximum tensile strain of the substrates are investigated by analytical calculation, digital image correlation analysis, bending test, and finite element method simulation. The results clearly show that the newly developed substrate–based structure can reduce the maximum tensile strain under bending. Consequently, the cracking of the brittle hard coating is effectively prevented.

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P‐198: Optically Clear Adhesives Enabling Foldable and Flexible OLED Displays

Cited by 30 publications

References 5 publications

Pressure-Sensitive Adhesives for Flexible Display Applications

Pressure-Sensitive Adhesives for Flexible Display Applications

Thermally Evaporated Organic/Ag/Organic Multilayer Transparent Conducting Electrode for Flexible Organic Light‐Emitting Diodes

Controlling Neutral Plane of Flexible Substrates by Asymmetric Impregnation of Glass Fabric for Protecting Brittle Films on Foldable Electronics

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