Method and apparatus for a high density array printer using hot melt inks

In a high density array printer for printing dots on a substrate with a phase change ink that is solid at room temperature, and liquid at some temperature above room temperature, said printer including a printing plate having an array of through holes of capillary dimension between a printing face and an opposing ink receiving face thereof, with individual and selectively operable heaters mounted in the interior walls of said through holes near the printing face and remote from the receiving face of said printing plate, the printer further including a container of said plate change ink for receiving said printing plate, a method of printing comprising:

• (a) heating said container to liquify the phase change ink therein;
• (b) immersing the ink receiving side of said printing plate into said ink for a time period permitting said through holes to fill with ink via capillary action;
• (c) removing said plate from said ink;
• (d) cooling said plate for solidifying the ink in said holes;
• (e) selectively energizing different ones of said heaters, for melting the ink in the respective holes near said printing face while maintaining in a solid phase the ink near the receiving face of the holes, whereby as the ink melts therein it expands in a direction away from the remaining solid ink in the selected holes, respectively, and protrudes from each one of the selected holes on the printing face of said printing plate;
• (f) laying a substrate into intimate contact with the surface of said printing face, whereby ink protrusions are received by said substrate for printing a desired pattern of dots thereon;
• and
• (g) removing said substrate from said printing face in completion of the printing cycle.

A high density array printing apparatus for printing a desired pattern of dots on a substrate with a phase change ink, said ink being solid at room temperature and liquid at elevated temperatures from room temperature, said apparatus comprising:

• a printing plate having a top "orifice" surface, and a bottom "chamber" surface, and a plurality of holes of capillary dimension through said orifice and chamber surfaces, providing an array of ink chamber/orifices in said printing plate;
• a plurality of selectively energizeable individual heating means mounted on the walls of said holes, respectively, near the orifice surface of said printing plate, for heating selected ones of said holes in portions remote from the chamber surface of said printing plate;
• container means for holding and heating said phase change ink to a liquid state, thereby providing a pool of liquified ink;
• and
• control means for energizing selected ones of said heating means, whereby printing is accomplished by immersing the chamber surface of said printing plate into the pool of liquified ink for a period of time allowing said holes to fill with ink via capillary action, the printing plate being thereafter removed from the pool of ink and allowed to cool for solidifying the ink in said holes, said control means then being operated to energize selected ones of said heating means for causing the ink in the respective holes to melt near the orifice surface of said printing plate, the ink expanding as it melts in a direction away from the solid ink still remaining in the respective holes near the chamber surface, causing the ink to protrude out of the holes on the orifice surface, thereby forming a desired pattern of protruding ink, thereon, for transfer to a substrate brought into contact with the orifice surface.