Electricity: measuring and testing – Magnetic – Fluid material examination
Reexamination Certificate
2003-04-09
2004-03-23
Strecker, Gerard R. (Department: 2862)
Electricity: measuring and testing
Magnetic
Fluid material examination
C324S228000, C324S261000, C324S262000, C324S701000
Reexamination Certificate
active
06710591
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for measuring anchoring strength of liquid crystal and to a measurement system therefor.
BACKGROUND ART
Literature in relation to this technical field includes the following.
(1) Hiroshi Yokoyama, “Principle and Practical Method for Measuring Interface Anchoring Strength: Focused on Strong Electric-Field Method,” Liquid Crystal, 4, 63 (2000).
(2) Hiroshi Yokoyama, “Thermodynamics of Interface Anchoring of Liquid Crystal,” Liquid Crystal, 3, 25 (1999).
(3) H. Yokoyama: Mol. Cryst. Liq. Cryst., 165, 265 (1988).
(4) H. Yokoyama and H. A. van Sprang: J. Appl. Phys., 57, 4520 (1985).
Anchoring at a substrate-liquid crystal interface is determined by three anchoring energy coefficients defined by the following expression (1):
Δγ
=
1
2
W
p
δθ
2
+
1
2
W
a
δφ
2
+
W
pa
δθδφ
(
1
)
where &thgr; is a zenith angle that a director forms with respect to the substrate normal line (z axis), &phgr; is an azimuth angle, and &ggr; is interface free energy (see the above-mentioned literature (1) and (2)).
Over the years, there have been developed methods for measuring anchoring energy, which affects the photoelectric response of liquid crystal and which is the most fundamental physical property of orientation film (see the above-mentioned literature (3) and (4)).
For measurement of strength of zenith angle anchoring, a strong electric-field method utilizing the scaling law of Frank elasticity has been developed. This method enables highly accurate extraction of characteristics of interface anchoring without being affected by bulk characteristics such as elastic constant and dielectric constant.
The strong electric-field method is used for nematic liquid crystal having a positive dielectric anisotropy. In this method, a vertical electric field is applied to a cell; and an optical retardation R that remains in the vicinity of the substrate interface at that time is measured as a function of voltage in a high voltage region where voltage is greater than the Freedericksz transition voltage.
The retardation R is the total sum of contributions from individual points; i.e., is represented by the following expression:
R
=
2
π
λ
∫
0
∞
Δ
n
eff
(
θ
)
ⅆ
z
(
2
)
where &lgr; is the wavelength of light, and &Dgr;n
eff
(&thgr;) is effective birefringence of light at the respective point.
DISCLOSURE OF THE INVENTION
According to the theory of elasticity, in general, there holds the scaling law in which not only retardation, but also other summable physical property values change in proportion to the reciprocal of the density of electric flux applied to a cell.
Moreover, in bulk, liquid crystal is oriented along the direction of an electric field, and no retardation is generated for a light ray passing through the liquid crystal in parallel to the electric field (R→ for V→∞). The strong electric-field method is based on these two characteristics.
Meanwhile, for azimuth angle anchoring, no summable physical property which automatically vanishes at the limit of a strong electric field is known. Therefore, the strong electric-field method cannot be applied to azimuth angle anchoring as is. Therefore, at present, there are used only several easier methods in which influences of bulk are removed through comparison with simulation results.
Further, in the case of zenith angle anchoring as well, there exist various factors which hinder R→0, such as discrepancy between a light ray and an electric field and a residual retardation of the substrate; and for strong anchoring their influences cannot be ignored.
An object of the present invention is to provide a method for measuring anchoring strength of liquid crystal through measurement of magnetic-field-induced torque, which, unlike conventional methods such as the strong electric-field method, uses a strong magnetic field, is therefore based on a clear principle, does not require bias correction, and enables measurement for liquid crystal of an arbitrary shape, as well as a measurement system for the measuring method.
To achieve the above object, the present invention provides the following.
[1] A method for measuring anchoring strength of liquid crystal, characterized by applying a strong magnetic field to a liquid crystal cell, and measuring magnetic-field-induced torque to thereby measure the anchoring strength of liquid crystal.
[2] The method for measuring anchoring strength of liquid crystal as described above in [1], wherein the strong magnetic field is about 10 T.
[3] A system for measuring anchoring strength of liquid crystal, characterized by comprising an optical system for radiating light onto a liquid crystal cell; means for applying a strong magnetic field to the liquid crystal cell; and means for measuring magnetic-field-induced torque.
[4] The system for measuring anchoring strength of liquid crystal as described above in [3], further comprising means for adjusting the angle of the liquid crystal cell.
REFERENCES:
patent: 4965518 (1990-10-01), Agarwala
patent: 5427713 (1995-06-01), Wartenberg et al.
patent: 5571448 (1996-11-01), Wartenberg et al.
patent: 6242060 (2001-06-01), Yoneya et al.
patent: 10-246693 (1998-09-01), None
Hiroshi Yokoyama Ekisho, vol. 4, No. 1, pp. 63-72 2000.
Takashi Sugiyama et al.: “A simple model for pretilted nematic liquid crystal medium and its torsional surface coupling strength” Japanese Journal of Applied Physics, vol. 29, No. 10, pp. 2045-2051 10/90.
Hiroshi Yokoyama Ekisho, vol. 3, No. 1, pp. 25-33 1999.
H. Yokoyama: “Surface anchoring of nematic liquid crystals” Mol. Cryst. Liq. Cryst., vol. 165, pp. 265-316 1988.
H. Yokoyama: “A novel method for determining the anchoring energy function at a nematic liquid crystal-wall interface from director distortions at high fields” J. Appl. Phys., vol. 57, No. 10, pp. 4520-4526 May 15, 1985.
Japan Science and Technology Corporation
Strecker Gerard R.
LandOfFree
Method and system for measuring anchoring strength of liquid... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for measuring anchoring strength of liquid..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for measuring anchoring strength of liquid... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3213494