Hygro-Mechanical Analysis of LCD Panels

Liquid crystal displays (LCDs) are getting larger, and the homogeneity of an LCD panel is becoming very important for the quality of the display. Inhomogeneity in an LCD panel can be caused by inhomogeneity of its materials and the defective production process, warpage of the panel due to changes in the temperature and humidity, and so on. In this study, we developed a scheme of hygro-mechanical analysis to reduce the warpage of an LCD. First, we measured the diffusion coefficients and Henry’s law coefficients of the respective components of an LCD using a thermo-gravimetric analyzer (TGA) under controlled humidity. We then measured the coefficients of moisture expansion (CME) of the componenets using a humidity-controlled thermo-mechanical analyzer (TMA). We analyzed the hygro-mechanical deformations of the respective components, a polarizing plate and an LCD panel using the finite element method (FEM) with measured diffusion coefficients, Henry’s law coefficients and the CMEs of the respective components. The analyzed deformations of the respective components corresponded quantitatively with the deformations measured experimentally. However, the analyzed deformation of the polarizing plate did not correspond with the measured deformation perfectly. A polarizing plate is made by sandwiching a polarizer by two sheets of protective film; the effect of the thin boundary layer between the polarizer and its protecting film was ignored in this analysis. The effect of this boundary layer on the diffusion of moisture may have caused the difference between the analysis and the measurement. The expected warpage of the analyzed LCD corresponded qualitatively with the measured warpage. In LCD panels, glass plates and polarizing plates are bonded using pressure-sensitive adhesive. Slippage between the glass plates and the polarizing plates may occur during the deformation of an LCD. We investigated the warpage of LCDs with two types of protecting film and different directions of polarizing plates using the developed technique of FEM analysis.

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Hygromechanical Analysis of Liquid Crystal Display Panels

Journal of Electronic Packaging ◽

10.1115/1.4025527 ◽

2013 ◽

Vol 135 (4) ◽

Cited By ~ 1

Author(s):

Toru Ikeda ◽

Tomonori Mizutani ◽

Kiyoshi Miyake ◽

Noriyuki Miyazaki

Keyword(s):

Boundary Layer ◽

Liquid Crystal ◽

Numerical Analysis ◽

Diffusion Coefficients ◽

Liquid Crystal Display ◽

Fem Analysis ◽

Contact Condition ◽

Henry's Law ◽

Henry’S Law ◽

The Difference

Liquid crystal displays (LCDs) are getting larger, and the homogeneity of an LCD panel is becoming very important for the quality of the display. Inhomogeneity in an LCD panel can be caused by inhomogeneity of its materials and the defective production process, warpage of the panel due to changes in the temperature and humidity, and so on. In this study, we developed a scheme of hygromechanical analysis to reduce the warpage of an LCD. First, we measured the diffusion coefficients and Henry's law coefficients of the respective components of an LCD using a thermogravimetric analyzer (TGA) under controlled humidity. We then measured the coefficients of moisture expansion (CME) of the components using a humidity-controlled thermomechanical analyzer (TMA). We analyzed the hygromechanical deformations of the respective components, a polarizing plate and an LCD panel using the finite element method (FEM) with measured diffusion coefficients, Henry's law coefficients and the CMEs of the respective components. The analyzed deformations of the respective components corresponded quantitatively with the deformations measured experimentally. However, the analyzed deformation of the polarizing plate did not correspond with the measured deformation perfectly. A polarizing plate is made by sandwiching a polarizer between two sheets of protection film. We ignored the effect of the thin boundary layer between the polarizer and its protecting film in this analysis, and the effect of this boundary layer on the diffusion of moisture may have caused the difference between the analysis and the measurement. The expected warpage of the analyzed LCD corresponded qualitatively with the measured warpage. However, the numerical analyzed strains near the edge of the LCD panel strongly shifted to the compression side compared to the experimental measured strains. A possible reason for this shift was the difference in the boundary condition at the edge of the LCD panel between the numerical analysis and the experimental measurement. The actual edge of the LCD panel was fastened by a bezel, and the contact condition between the LCD panel and the bezel was ambiguous. To perform a quantitative analysis, we will need to investigate the contact condition between the LCD panel and the bezel and introduce it to the numerical analysis. This is left for a future study. We qualitatively investigated the warpage of LCDs with two types of protecting film and different directions of polarizing plates using the developed technique of FEM analysis.

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Sorption and surface diffusion in porous glass

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1952.0124 ◽

1952 ◽

Vol 213 (1113) ◽

pp. 250-265 ◽

Cited By ~ 53

Keyword(s):

Surface Diffusion ◽

Porous Glass ◽

Diffusion Coefficients ◽

Hysteresis Loops ◽

Transient State ◽

Substantial Contribution ◽

Henry's Law ◽

Henry’S Law ◽

Type Iv ◽

Adsorbed Films

Sorption, gas-phase diffusion in the region of molecular streaming, and surface diffusion in very dilute adsorbed films have been studied quantitatively for a number of gases in membranes of porous glass. The sorption of oxygen, nitrogen, argon, sulphur dioxide and ammonia near their liquefying temperatures resulted in type IV isotherms with very characteristic hysteresis loops. From the isotherms porosity, surface area and mean pore radius were evaluated. Heats of sorption, Δ H , have been obtained in very dilute adsorbed films and in films where v/v m approaches or exceeds one. These heats showed the porous glass to be an energetically non-uniform sorbing surface. The Henry’s law region of sorption was studied and Henry’s law sorption constants evaluated at 273, 290, 323 and 343° K for the most dilute adsorbed films of oxygen, nitrogen, argon, krypton, methane and ethane. Nearly all this information is essential for measurements of surface diffusion by the transient state method of Barrer & Grove (1951). The micropore structure was so fine that non-sorbed gases diffused within the porous glass only by molecular streaming at pressures up to half an atmosphere or more. Effects of sorption upon this diffusion were inappreciable for helium, neon and possibly hydrogen; for oxygen, nitrogen, argon, krypton, methane and ethane the influence of sorption upon timelags and diffusion coefficients became progressively more marked. In the steady state of flow there was little evidence of surface diffusion when, in the most dilute adsorbed films, Henry’s law is obeyed. On the other hand, in the transient state of flow, surface diffusion makes a substantial contribution to flow. Reasons are given for the difference in the extent to which surface mobility can be detected in the two states of flow. Consistent values of the surface diffusion coefficients, D 8 , were obtained for oxygen, nitrogen, argon, krypton, methane and ethane. These values of D 8 were compatible with the Arrheniusequation D 8 = D 0 exp ( – E / RT ) over the temperature range of 273 to 343° K investigated. The ratio of E to Δ H for very dilute adsorbed films lay between 0·5 and 0·6, and should in order of magnitude be characteristic of a heterogeneous sorbing surface. The numerical values of D 8 have been compared with D for liquids, and analyzed in terms of entropy and energy of activation.

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