WO 2012/136466 A1
This patent relates to using ink jet for printing etch masks, resist masks, conductive tracks and similar applications where high positional accuracy is required. In these applications drops are printed wet on wet in lines and sharp edges are normally required.
Here the problem is shown. On the left the position of printed droplets forming a line is shown. The print direction is B. In the middle the resulting line outline is shown. Note that due to surface tension, wetting and spreading effects the start of the line has moved forwards, and the line width is wider at the beginning than the middle. A similar effect occurs at the end of the line too. Therefore the line is shorter than it should be and the edge is not straight.
The solution, shown on the right, is to vary the pitch 28’ at which drops are deposited at the line ends. To begin with the drops are deposited further apart than the normal pitch, then closer together, and then back to the standard pitch. The lines shown are labelled i=3, 7, 11, 15, 19, 23, 27 etc. representing the original drop centre positions. By adjusting the drop positions to i=1, 6, 11, 16, 20, 23, 27 etc. then a straight line of the correct length is printed.
To achieve this, first test lines are printed and the line lengths and profiles are measured. An algorithm is then used to calculate the accumulated drop volume for a series of positions. From this the corrected drop positions can be calculated.