PRINTING ALIGNMENT LAYERS ON LCD SUBSTRATES WITHIN INK JET PRINTING APPARATUS
An apparatus for printing a liquid crystal alignment layer of uniform thickness on a substrate of an LCD and a method for its use include an ink jet head that prevents the formation of stripes in the alignment layer as a result of variations in thickness of the alignment layer. The apparatus includes an alignment layer ink ejecting unit that includes an orifice unit having a plurality of orifices, and a plurality of control units, each including a piezoelectric element that controls the flow of ink through a corresponding one of the orifices. Each of the orifices includes a plurality of ink ejection passages through which the ink is ejected, and each of the passages terminates at nozzle, or ink ejection hole.
1 . An alignment layer printing apparatus, comprising:
an alignment layer ink ejecting unit, including an orifice unit having a plurality of orifices through which the ink is ejected, each orifice including a plurality of ink ejection passages, each passage terminating in an ink ejection hole.
2 . The apparatus of claim 1 , wherein each of the orifices further includes a main passage receiving the ink, and wherein the plurality of ink ejection passages branch off from the main passage.
3 . The apparatus of claim 1 , wherein the ink ejecting unit further comprises an ink supply unit having a plurality of ink supply passages supplying the ink to the orifices.
4 . The apparatus of claim 3 , further comprising a plurality of control units, each controlling the flow of the ink through a corresponding one of the orifices.
5 . The apparatus of claim 4 wherein each of the control units includes a piezoelectric element.
6 . The apparatus of claim 5 , further comprising a plurality of variable resistors, each adjusting a voltage applied to a corresponding one of the piezoelectric elements.
7 . The apparatus of claim 5 , wherein the plurality of piezoelectric elements are disposed on the ink supply unit, and the ink supply unit is disposed on the orifice unit.
8 . The apparatus of claim 7 , wherein the ink supply unit comprises: a first ink supply member having an aperture into which a corresponding one of the piezoelectric elements moves when actuated; and, a second ink supply member having an ink supply passage with a selected size and disposed under the first ink supply member.
9 . The apparatus of claim 8 , wherein the ink supply unit further comprises a third ink supply member having an ink supply passage with a selected size and disposed under the second ink supply member.
10 . The apparatus of claim 1 , wherein at least some of the ink ejection passages include right-angle bends.
11 . The apparatus of claim 1 , wherein at least some of the ink ejection passages are inclined at an angle relative to a direction in which the alignment layer ink is ejected.
12 . The apparatus of claim 1 , wherein the ink ejection holes are spaced apart from one another by a distance of from between about 250 to about 375 μm
13 . The apparatus of claim 1 , wherein the orifices are arranged in a plurality of rows and arranged such that the orifices of one row are staggered with respect to the orifices in an adjacent row.
14 . A method for printing an alignment layer on a substrate of an LCD, the method comprising:
preparing the substrate to be printed with an alignment layer; and,
ejecting an alignment layer ink onto the substrate using an alignment layer ink ejecting unit including an orifice unit having a plurality of orifices through which the ink is ejected, each orifice including a plurality of ink ejection passages, each passage terminating in an ink ejection hole.
15 . The method of claim 14 , further comprising:
preliminarily drying the substrate on which the alignment layer ink is ejected; and,
baking the substrate.
16 . The method of claim 14 , wherein the alignment layer ink includes a solution mixed with polyimide.