Coating method for liquid crystal alignment film of tft-lcd

Abstract

A coating method for liquid crystal alignment film of TFT-LCD including: forming a layer of hydrophobic film on a TFT / CF substrate corresponding to a non-display area, the hydrophobic film separates the TFT / CF substrate into a plurality of rectangular opened areas which are separated from each other, each of the rectangular opened areas corresponds to a display area and its outer frame is formed by the hydrophobic film; and coating of a liquid of a material of an alignment film along a boundary of the rectangular opened area. Accordingly, edge waves caused by spreading of drips of the material of the alignment film can be reduced, so that a precision of printing of the alignment film can be controlled effectively.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a manufacturing technique of liquid crystal display device and more particularly to a coating technique for liquid crystal alignment film of LCD.BACKGROUND OF THE INVENTION[0002]PI (polyimide) film is a layer of even alignment film on a surface of TFT (Thin Film Transistor) substrate and CF (Color Filter) substrate, it makes liquid crystal molecules to be arranged according to a certain pre-tilt angle in order to control a passing direction of light, and achieve a display purpose by applying an appropriate driving voltage. Currently, there are mainly two coating methods of coating technique for PI film: PI roller coating and PI inkjet.[0003]Referring to FIG. 1, a process for transfer-printing technique mainly includes: a polyimide (PI) solution is ejected from a PI nozzle 4 and it drips on a turning metal roller 3, a scraper 5 is used to scrape excessive PI solution, the metal roller 3 turns and is in contact with a plate ...

AI Technical Summary

Benefits of technology

This method effectively reduces edge waves and enhances the precision of the alignment film printing, resulting in a PI film with straighter edges and improved product quality by leveraging the non-wetting and wetting properties of the hydrophobic and hydrophilic interfaces.

Problems solved by technology

The roller coating technique has the following drawbacks: cumbersome equipment, poor mobility, large consumption of consumables (dummy base plates and printing plates), thickness film which is difficult to adjust, complicated operation, low PI usage percentage, high operating costs and common deficiencies easily caused by polluted printing plates.

This technical method has the following drawbacks: large uneven area of edges of the film thickness, small nozzle hole which is easy to be clogged, interval difference of the nozzle hole 9 and uneven spreading which will produce deficient products with uneven inner lines and inner surfaces.

The most serious deficiency is that, the PI drip 8 is unable to be spread evenly to form a film when a segmental difference of the base plate surface is too large, as a result, product quality is substantially decreased and even large quantity of products is rejected.

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