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Home > Products > Thermal Printhead Products > Technology > Glaze Types Background On Kyocera printheads, glaze refers to a pattern of glass deposited on the surface of the ceramic substrate, underneath the thin film heaters. The outermost layer is the overcoat, not the glaze. Glaze is necessary for efficient performance of thermal printheads because it retards the escape of heat through the ceramic substrate, leaving more heat to flow into the thermal media. In the glaze sketches that follow, imagine that the substrate is below the glaze mound and the platen roller is above the overcoat. The sketches are exaggerated to show all layers. Otherwise the heater and electrode layers would not be visible. For partial glaze, as an example, the actual glaze thickness is about eight times the combined thickness of the other layers. Glaze Heater Layer Electrodes Overcoat Partial Glaze (code P) Classic partial glaze is a mound of glass underneath the heater line. Partial glaze printheads dominate the bar code and label printer applications. Most of the standard Kyocera printheads are built on partial glaze. The glaze mound elevates the heater indentation for good contact with the media. The size of the glaze mound is a good compromise between efficient utilization of heat and efficient dissipation of heat. Thin Glaze (code T) Thin glaze has only one third the volume of partial glaze, so it more efficiently dissipates heat to the substrate and carries less heat over to the next print line. Thin glaze raises the print speed limit beyond which history control is required.  Thin glaze printheads are being used to increase the speed of bar code and label printers. Refer to Printing Speed for a discussion of the improved Thermal Response of thin glaze. The photos below show a print quality comparison between thin glaze and partial glaze at about 4 inches/sec. Partial Glaze Thin Glaze Printing Conditions Printhead: KPA-80-8MP/TA1;    Media: SH-13B (Oji Paper Co.) Platen Diameter: 20 mm;    Pressure: 0.048 kgf/mm    Power=0.752 w/dot;     Tcy=1.25 ms;     Ton=0.5 ms The lump at the bottom of the vertical stem of the partial glaze example is called tailing, where retained heat images an area which should remain white. The ragged leading edge occurs because there is not quite enough energy to fully heat the glaze from a cold state. Flat Glaze (code G) Flat glaze is a layer rather than a mound. It is very wide relative to the heater size, although it does not cover the whole ceramic wafer. Flat glaze printheads are preferred in fax applications because the alignment of the platen roller to the heater line is not as critical. Fine Glaze (code F) Fine glaze consists of narrow bead on top of a much wider base. The bead has a short radius of curvature, so that the bumps of the electrodes do not touch the media and the platen force is entirely carried by the heater surfaces. This results in higher pressure against the media, better heat flow into the media and a sharper printed dot. The bead is extremely straight, assuring that all heaters are centered on the top of the bead, with their centers at exactly the same height across the printhead. Fine glaze is also relatively high to retard the escape of heat through the ceramic substrate. Fine glaze is used for printing digital photos or other gray scale graphics.

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