| 摘要 |
PURPOSE:To allow no heat of a heating element to be diffused horizontally when it is diffused into a protective film by protecting a heating element using a protective film having a horizontal thermal conductivity higher than a vertical thermal conductivity. CONSTITUTION:An anti-oxidation protective film 7 to protect a heating element 5 against oxidation is applied on the surface of the heating element 5. Further, on the applied film, an anti-abrasion protective film 9 is applied considering the abrasion of the heating element 5. The anti-abrasion protective film 9 has approx. 10<10> pieces pier square centimeter of hole 9a having a diameter of approx. 300 to 500Angstrom provided vertically with the surface of the heating element 5. The thermal conductivity of air is approx. 1/10<3> of that of alumna. On account of the air existing in the holes 9a opened vertically with the surface of the heating element 5, the anti-abrasion protective film 9 having vertical thermal conductivity higher than a horizontal thermal conductivity can be obtained. Consequently, the heat obtained in the heating element 5 does not run out horizontally, so that a vertical heat conduction alone is achieved, thus eliminating bleeding in the printing dot and improving printing quality. |
