PURPOSE: To obtain a screen printable insulating film by using In2O3-Al2O3 or a mixture of an org. indium compound with an org. aluminum compound convertible into In2O3-Al2O3 by calcination as a principal component.

CONSTITUTION: By using In2O3-Al2O3 as a composition for forming a transparent insulating film, a defect caused by separately using In2O3 and Al2O3 as components is made up. A mixture of an org. indium compound with an org. aluminum compound is dissolved in an org. solvent, a thickener is added to the soln. to prepare paste, and the paste is applied to a substrate by screen printing and calcined to obtain an In2O3-Al2O3 film. Indium alkoxide, indium acetylacetonate or the like is used as the org. indium compound, and aluminum alkoxide, aluminum acetylacetonate or the like as the org. aluminum compound.