Printing alignment layers on lcd substrates within ink jet printing apparatus

Abstract

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.