Numerical and Experimental Analysis of Intermittent Line-and-Space Patterns in Thermal Nanoimprint

Abstract

Time-evolutional analyses of an intermittent line-and-space patterning in thermal nanoimprint were performed both experimentally and numerically. The constitutive model of polymers in finite element numerical analyses was a viscoelastic model based on the generalized Maxwell model and the Williams-Landel-Ferry (WLF) law so that polymer deformation was strain-history and temperature dependent. We performed uniaxial vibrational tests and numerical inverse analyses to identify material properties of the viscoelastic model for cyclo-olefin-polymer (COP). We also carried out a series of experiments and numerical simulations of an intermittent line-and-space patterning at various pressure-holding times. Both experiments and simulations presented characteristic polymer deformation which never appear in continuous line-and-space patterning. The numerical simulation well agreed with experiments and revealed complicated distributions of stress and pressure during the imprinting that were difficult to be directly observed in thermal nanoimprint experiments.

Numerical Analysis of Pattern Shape Deformation in UV Imprint Due to Curing Shrinkage

“…Also, the time history of the volume change of UV resin after UV exposure is similar to that of thermo-plastic resin under cooling contraction. Focusing on these analogies and referring to the methods for thermal imprint process simulation [16,17], the proposed method uses a thermoviscoelastic constitutive model to represent the mechanical behavior of the UV resin.…”

“…The material constitutive model of the UV resin in this study is a thermo-viscoelastic material based on the generalized Maxwell model that has a virtual temperature-time shift factor function (A(θ virt )). The stress/strain formulation of the thermo-viscoelastic materials in a time-dependent analysis is detailed in the references [16,21] and is omitted in this paper. A(θ virt ) is identified by the time domain complex shear modulus at various frequencies G * (t; f).…”

“…Meanwhile, in the area of thermal imprint, there are some prior numerical researches [11][12][13][14][15][16][17], and several of them consider both the time-dependent deformation and thermal contraction of the thermoplastic resin. Hirai et al [15] proposed a numerical method for the thermal imprint process using a hyperelastic material model in the framework of solid mechanics.…”

“…Hirai et al [15] proposed a numerical method for the thermal imprint process using a hyperelastic material model in the framework of solid mechanics. As an extension of Hirai's approach, Onishi and Takagi et al [16,17] showed the effectiveness of a thermoviscoelastic model in thermal imprint process simulation. In Fig.…”

Experimental and numerical analyses on recovery of polymer deformation after demolding in the hot embossing process

“…[4][5][6] It has been proved that the tool have ability to analyze time-dependent polymer deformation. There have been reported several numerical analyses of the hot embossing ͑or thermal imprint͒ process.…”