Device for making a master

A device for perforating a thermosensitive medium in accordance with an image signal to thereby make a master, said device comprising:

• a thermal head including a plurality of heat generating elements arranged on a thin film substrate in an array in a main scanning direction;
• lead electrodes provided on the thin film substrate and connecting said plurality of heat generating elements to an electric power source;
• a protection layer provided on the thin film substrate to cover said heat generating elements and said lead electrodes;
• a platen roller for pressing the thermosensitive medium against said thermal head while in rotation for thereby conveying said thermosensitive medium in a subscanning direction perpendicular to the main scanning direction, said plurality of heat generating elements selectively generating heat in accordance with the image signal to thereby perforate said thermosensitive medium;
• said thermal head including a stepped portion at a medium outlet side in the subscanning direction, an upper surface of said stepped portion being positioned lower than an upper surface of a portion of said protection layer which covers said lead electrodes;
• and
• said plurality of heat generating elements each having an edge which adjoins an end of said stepped portion, a distance between the edge of each of said plurality of heat generating elements and said end of said stepped portion being limited such that said thermosensitive medium is prevented from sticking to said thermal head.