・ In the case of liquid crystal display (LCD), eachelement is as small in size as several tens of µm. However, due to the large overall size, a huge number of elements of several tens of µm in size are arranged.In the case of the LCD shown in Fig.1, fine patterns at a pitch of several tens of µm are fabricated on the entire surface.

・ In the production technology for such fabrication, positioning with accuracy on the order of µm is essential for the X-Y table to arrange several hundred thousand to several millions of elements in a horizontal pattern.

・ A typical X-Y table is configured with robots moving in a straight line along the two (2) axes, X and Y.

・ In practice, however, the pulse generators adopted on the X- and Y-axes vary from the performance stated in the products-specifications . The differences in the timing of pulse generation appear in the form of accumulated errors in the repeatability of positioning accuracy on the order of µm (Fig.2, 3).

・ Even if individual errors are on the order of nm(nanometer), the extent of differences, when viewed with the human eye, looks like uneven irregularities, and thus the fabricated products may be defined unacceptable.

・ As a solution, such circuit design has been adopted that relies on one-pulse generator for controlling the pulse timing for all robots moving in a straight line for position alignment (Fig.4).

Precautions

・ In order to make the adopted solution effective, it is essential to control the accuracy of straight movement of the straight-line moving robots and the precision of the position alignment scales to the level equivalent to the required positioning accuracy.