Optical properties of solvent-cast polarizer films for liquid-crystal displays: A viscoelastic modeling framework

Greener, J.; Lei, Herong; Elman, James F.; Chen, Janglin

doi:10.1889/1.2121067

Cited by 12 publications

(14 citation statements)

References 12 publications

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“…Kohn suggested that ultrathin and pinhole‐free PI films could be made with the solution casting processes. Several authors have also studied the optical birefringence of TAC films …”

Section: Introductionmentioning

confidence: 99%

“…Several authors have also studied the optical birefringence of TAC films. 16,22,23 Three major steps involved in solution casting are liquid film casting, solvent removal, and the peeling of dried films from the steel belt. Despite the importance of solution casting in polymer processing operations, the fundamental analysis of this process appears to be limited.…”

Section: Introductionmentioning

confidence: 99%

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Operating window of solution casting. II. Non‐Newtonian fluids

Huang

Wang

Liu

et al. 2014

J of Applied Polymer Sci

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The operating windows of the solution casting of two polymeric liquids were evaluated experimentally. The experimental setup and procedure were the same as used previously for the casting of Newtonian fluids (Journal of Applied Polymer Science 2013, 129, 507–516). Aqueous carboxymethylcellulose/glycerol solutions exhibited pure shear‐thinning behavior at low polymer concentrations but became viscoelastic at high polymer concentrations, whereas polyacrylamide/glycerol solutions showed viscoelastic behavior over a wide range of concentrations. The shear‐thinning behavior, in conjunction with a low level of elasticity, of the casting solution was found to be useful in expanding the stable operating windows. However, an opposite effect on the operating windows was found for highly elastic solutions. The non‐Newtonian effect on the maximum stable casting speed was prominent only when the capillary number exceeded unity. Defects outside of the operating window were mostly similar to those observed in Newtonian solution casting. For highly concentrated solutions, a new rough surface defect was observed. This defect could be attributed to polymer chain entanglement, alignment, or breakup. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41411.

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“…Kohn suggested that ultrathin and pinhole‐free PI films could be made with the solution casting processes. Several authors have also studied the optical birefringence of TAC films …”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Operating window of solution casting. II. Non‐Newtonian fluids

Huang

Wang

Liu

et al. 2014

J of Applied Polymer Sci

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“…Juergen and Siemann 19 replaced the melt extrusion process by the solvent casting process so that the isotropic properties of polyarylate film products can be significantly improved. Recently, several authors exam-ined the optical properties of the cast TAC, [20][21][22][23][24] PI, 11,25 and other polymer films. [26][27][28] Nakayama et al 20 controlled TAC film's in-plane birefringence and out-of-plane birefringence.…”

Section: Introductionmentioning

confidence: 99%

Operating window of solution casting, part I: Newtonian fluids

Huang

Wang

Tsai

et al. 2012

J of Applied Polymer Sci

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An experimental study was carried out to investigate the fluid mechanics of solution casting. Newtonian glycerol solutions were used as test fluids and were casted on the polyethylene terephthalate films. The focus of this study is on the evaluation of the operating window, i.e., a region for stable and uniform processing. Different types of defects such as stable or unstable poolings, vibrating edges, and air entrainment outside the operating windows were observed. The effects of two different start-up approaches on the operating window were studied. One of the key operating parameters is the maximum casting velocity V max for stable operation. The fluid viscosity is the most critical parameter on V max . It was found that if the gap between the slot die exit and the moving film substrate is smaller than 600 lm, V max might go down and then go up as the fluid viscosity increases. On the other hand, if the gap is larger than 600 lm, V max will decrease as the fluid viscosity increases. Competition of two different types of defects, i.e., unstable pooling and air entrainment, can decide V max, as evidenced by the observation on the fluid motion and dynamic contact angles of different cases. The importance of different forces on V max was also analyzed.

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“…When a polymer is cast from solution to form a very thin (< 8 μm) solid layer, it produces a characteristic out-of-plane birefringence, which is closely associated with its intrinsic birefringence, provided the drying of the film is sufficiently fast [2,3]. This birefringence component represents the relative alignment of polymer molecules parallel to the film plane and is defined as:…”

Section: Introductionmentioning

confidence: 99%

P‐108: Birefringence Dispersion of Polymer Films As Applied to Optical Compensation in LCD

Greener

Rao

Elman

2007

Symp Digest of Tech Papers

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Minimizing color shift effects in a liquid crystal display (LCD) requires close attention to the optical dispersion of compensation layers used to increase the contrast ratio and viewing angle of the display. This paper describes our attempt to systematize and characterize the birefringence dispersion of solvent-cast polymer films and relate it to the "native" out-ofplane birefringence (Δn th ) of the polymer and its structure. Results for a wide range of polymers show general correlation between the dispersion parameter DP Δn [≡Δn(450)/Δn (590)] and Δn th . For all positively birefringent polymers, DP Δn is always > 1, suggesting "normal" dispersion at any level of Δn th , while for negatively birefringent polymers DP Δn > 1 only when |Δn th | > ~0.003. Below this critical value, DP Δn < 1, i.e., the polymer is reverse-dispersive. The results are explained in terms of the Cauchy coefficients for the corresponding polymers, and they suggest that the dispersion of birefringence cannot be controlled independently of the birefringence of the polymer film.SID 07 DIGEST • 607 ISSN/007-0966X/07/3801-0607-$1.00 © 2007 SID

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Optical properties of solvent-cast polarizer films for liquid-crystal displays: A viscoelastic modeling framework

Cited by 12 publications

References 12 publications

Operating window of solution casting. II. Non‐Newtonian fluids

Operating window of solution casting. II. Non‐Newtonian fluids

Operating window of solution casting, part I: Newtonian fluids

P‐108: Birefringence Dispersion of Polymer Films As Applied to Optical Compensation in LCD

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