| 摘要 |
A spark plug comprising an insulator, on at least a part of a surface of the insulator being formed a marking layer and a glaze layer, wherein the marking layer is exposed on the surface of the insulator and contains: a Pb component of not more ton 5% by mole in terms of PbO; an Si component of from 36% by mole to 72% by mole in tens of SiO2; an Al component of from 0.1% by mole to 18% by mole in terms of Al2O3; an alkali metal component containing at least one of an Li component, an Na component and a K component of from 0.1% by mole to 9% by mole in terms of Li2O, Na2O and K2O, respectively; a B component of from 3% by mole to 30% by mole in terms of B2O3; and a color developing component containing at least one of a V component, a Cr component, an Mn component, an Fe component, a Co component, an Ni component, a Cu component, a Pr component, an Nd component, an Au component, a Cd component, an Sn component, an Sb component, an Se component, an S component and an La component of more than 0% by mole but not more than 50% by mole in terms of V2O5, Cr2O3, MnO2, Fe2O3, CoO, NiO, CuO, Pr2O3, Nd2O3, Au2O3, Cd2O3, SnO2, Sb2O5, SeO2, SO3 and La2O3, respectively.
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