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UV Laser Etching of Polymer Films for the Alignment of Liquid Crystals

IP.com Disclosure Number: IPCOM000102912D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 45K

Publishing Venue

IBM

Related People

Sun, TI: AUTHOR [+2]

Abstract

Liquid crystal displays such as twisted nematic (TN) and guest-host (either dichroic dyes in nematic or cholesteric) displays require a uni-directional alignment of the liquid crystal (LC) on the substrates. Commonly used methods include the oblique evaporation of dielectric material such as silicon oxide onto the substrate and rubbing the polymer-coated substrates. The method of the oblique evaporation is a more expensive processing which it is also difficult to achieve a low pretilt angle. In TN or dichroic-dyes-in-nematic displays, a low pretilt angle is necessary to achieve a high contrast ratio in the display. Commercially available TN panels have used rubbed polyimide- coated substrates for the alignment of LC to achieve a low pretilt angle of about one degree.

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UV Laser Etching of Polymer Films for the Alignment of Liquid Crystals

      Liquid crystal displays such as twisted nematic (TN) and
guest-host (either dichroic dyes in nematic or cholesteric) displays
require a uni-directional alignment of the liquid crystal (LC) on the
substrates.  Commonly used methods include the oblique evaporation of
dielectric material such as silicon oxide onto the substrate and
rubbing the polymer-coated substrates.  The method of the oblique
evaporation is a more expensive processing which it is also difficult
to achieve a low pretilt angle.  In TN or dichroic-dyes-in-nematic
displays, a low pretilt angle is necessary to achieve a high contrast
ratio in the display. Commercially available TN panels have used
rubbed polyimide- coated substrates for the alignment of LC to
achieve a low pretilt angle of about one degree.

      The yield of thin-film-transistor (TFT) driven LC displays is a
crucial factor for that device to compete with CRT displays in the
marketplace.  To align a LC on a TFT-on-glass substrate, the
conventional method of rubbing the polyimide overcoat might damage
the TFT underneath, and thus lower the fabrication yield.  It has
been found that a uv laser, such as KrF laser at 248 nm, passing
through a mask may be used to etch the polyimide to form fine grooves
for the alignment of the LC.  Etching through the polyimide layer can
be prevented by adjusting the laser power.  The possibility of damage
to the TFT underne...