44‐3: Novel COP Optical Film with Durability for Flexible Displays

Inoue, Kyosuke; Yoda, Kenji; Murakami, Toshihide; Kikukawa, Masaru; Komoto, Sogo

doi:10.1002/sdtp.11718

Cited by 2 publications

(2 citation statements)

References 3 publications

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“…Compared to existing optical methods, the surface-labeled grating method is more versatile with respect to targeted materials because the label is merely attached to any surfaces as required; in the case of the others, targeted materials have to exhibit crystallinity or optical anisotropy, which significantly limits the types of measurable materials. [24][25][26][27][28][29] To demonstrate this versatility, we measured the surface bending strains of three representative samples: a cyclo-olefin polymer (COP) film exhibiting amorphousness and no optical anisotropy, [32] a polyimide (PI) film with colored appearance, and a glass plate as an amorphous inorganic material (Figure 3b). To prove the accuracy of this method, we used the modified Elastica theory which is an analytical model of curvature for a single-layer bent film that we recently reported.…”

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confidence: 99%

Nanoscale Analysis of Surface Bending Strain in Film Substrates for Preventing Fracture in Flexible Electronic Devices

Taguchi

Akamatsu

Kuwahara

et al. 2021

Adv Materials Inter

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be circumvented by exploiting an elementary mechanics that surface bending strain decreases linearly with a thickness of a substrate. For example, flexible substrates with a thicknesses of 10 µm experience peak surface strain of only 0.1% upon bending to the radius of curvature of 5 mm, and this strain remains well below the fracture limits of semiconductors (≈1%), metals (1-2%), and hard coatings (1-3%); indeed, the use of a substrate within a range below tens of micrometers enables comparable growth, resulting in high-performance durable flexible devices for epidermal, implantable, and wearable applications (Figure 1b). [10-20] On the other hand, the development of foldable electronics devices that have thicknesses of hundreds of micrometers is an emerging challenge. This highlights the ever-growing importance of the substrates strategically designed to reduce surface strain without thinning (Figure 1a right and 1b). However, it is not yet possible to measure nanoscale surface bending strain in real time: none of the currently available advanced methods fulfill all of the necessary spatial-temporal resolution, accuracy, precision, and a wide range of measurable materials. Electrical strain sensors including strain gauges exemplify the most common strain analytical method. [21-23] Although they provide surface bending strains of materials targeted in real time, their With the rapid development of flexible electronics and soft robotics, there is an emerging topic of preventing fracture in materials and devices integrated on largely bending film substrates of >100 µm thickness. The high demand for strategically reducing strain in bending materials requires a facile method that enables one to accurately and precisely analyze the surface bending strain in a wide variety of materials. This study proposes the surface-labeled grating method that is the fundamental and efficient technique for measuring surface bending strains merely by labeling a thin, soft grating onto various film substrates composed of flexible polymeric and rigid inorganic materials. The surface strain with a single-nanoscale (<1.0 nm) can be quantified in real time with no need of material information such as Poisson's ratio, Young's modulus, and film thickness. The fracture limit of a hard coating overlying flexible substrates is successfully determined by the accurate and precise quantification of surface bending strains. Furthermore, a multilayer film substrate with surface bending strain reduced by 50% prevents fractures of hard coatings and organic thin film transistors (OTFTs) since the strains remain below the fracture limit under large bending.

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confidence: 99%

Nanoscale Analysis of Surface Bending Strain in Film Substrates for Preventing Fracture in Flexible Electronic Devices

Taguchi

Akamatsu

Kuwahara

et al. 2021

Adv Materials Inter

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“…4,5) In order to manufacture optical films with designed anisotropy, that is, well-defined retardation and optic axis, it is crucial to control residual birefringence of flexible film. 11) Specifically, in the case of liquid crystal display (LCD), the in-plane birefringence of film alters polarization state of the light emitted from backlight source. 1,12,13) Thus, evaluation of the in-plane birefringence of flexible films in a wide spectral range including the visible region is important.…”

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confidence: 99%

Wavelength dependent in-plane birefringence of transparent flexible films determined by using transmission ellipsometry

Yang

Hong

Kim

2018

Jpn. J. Appl. Phys.

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We introduce a simple method to determine the in-plane birefringence of transparent flexible films by using transmission spectroscopic ellipsometry. The pseudo-ellipsometric constants which can represent their sample azimuthal angle dependent characteristics are introduced. The effect of in-plane birefringence and sample azimuthal angle on the pseudo ellipsometric constants is calculated using Jones matrix formalism, and the observed sample azimuthal angle dependence of measured pseudo-ellipsometric data is well understood. Wavelength dependence of in-plane birefringence is expressed in terms of the Sellmeier dispersion equation. The best fit pseudo-ellipsometric spectra to the measured ones at the sample azimuthal angles of every 15°from 0 to 90°are searched. The dispersion coefficients of the Sellmeier equation and the azimuthal angle of the optic axis are determined for polycarbonate (PC), poly(ethylene naphthalate) (PEN), poly(ethylene terephthalate) (PET), polyimide (PI), and colorless polyimide (CPI) films.

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44‐3: Novel COP Optical Film with Durability for Flexible Displays

Cited by 2 publications

References 3 publications

Nanoscale Analysis of Surface Bending Strain in Film Substrates for Preventing Fracture in Flexible Electronic Devices

Nanoscale Analysis of Surface Bending Strain in Film Substrates for Preventing Fracture in Flexible Electronic Devices

Wavelength dependent in-plane birefringence of transparent flexible films determined by using transmission ellipsometry

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