Alignment films (generally polyimide films) applied on glass substrates and rubbed onto the substrates are used to align liquid crystals uniformly. However, it is very difficult to quantitatively evaluate the effect of this rubbing. However, it is very difficult to quantitatively evaluate the effect of this rubbing, and a method to evaluate rubbing films by measuring the amount of birefringence has been discussed. In this article, we will introduce the results of a study on the effect of rubbing using birefringence.\n
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In this experiment, we prepared samples of two different alignment film materials and thicknesses. There are two types of rubbing methods: right-angle rubbing and diagonal rubbing. In this experiment, we prepared samples by using the right-angle rubbing method with the table speed and indentation amount as parameters.
![\"rubmeth\"](\"https:\/\/uniopt.co.jp\/wp-content\/uploads\/2014\/05\/rubmeth.gif\")
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- Sample :
Glass substrate: Material size, thickness; 20 x 25 mm, 1.1 mm
Alignment film: Spinner coating thickness; 1000, 200 \u00c5
Alignment film material:
\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0A1 : Alicyclic polyamide (similar to soluble polyimide) Firing 200\u00b0C, 60 min.
\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0A2 : Aromatic polyamide (polyamic acid) Fired at 250\u00b0C, 60 min.<\/li>\n - Rubbing conditions :
Table speed : 10\uff0c20\uff0c60\uff0c120 mm \/ sec.
Push-in amount : 0.3\uff0e0.5\uff0c0.7 mm
Number of passed : 1\u56de
Substrate angle : 0\u309c
Number of rolls, diameter, rotation speed, rotation direction, angle : 1 roll, 148 mm\u03c6, 500 rpm, positive rotation, 0\u00b0.<\/li>\n<\/ul>\n<\/li>\n
\nEvaluation method
A measurement area is set up around the point to be evaluated (3 x 3 mm in this case), and the measurement laser beam is scanned in a stepwise manner over the area (16 points in this case) to measure the retardation Re and retardation axis azimuth angle \u03a6. The laser beam is scanned stepwise over the area (16 points in this case) to measure retardation Re and retardation axis azimuth angle \u03a6.![\"mesmeth\"](\"https:\/\/uniopt.co.jp\/wp-content\/uploads\/2014\/05\/mesmeth.gif\")
From the retardation Re and retardation axis orientation angle \u03a6 obtained from the measurement
(1)\u00a0 Average value of retardation Re(x)
(2) Standard deviation (3\u03c3) of the retardation axis orientation angle \u03a6
to quantitatively evaluate the effect of rubbing.<\/p>\n
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IntroductionAlignment films (generally polyimide films) applied on glass substrates and rubbed onto the substr … Continue reading