TECHNOLOGY FOCUS - POLYMERS - Preferred Components: In the inorganic oxide particle-containing silicone resin sheet, as the polysiloxane resin, a condensation-reactive group-containing polysilsesquioxane having a unit (II) comprising substituted trifunctional alkoxysilane of formula (-O-Si(R2)(-O-)-O-) (as a basic structural unit), and a condensation-reactive group-containing polysiloxane having a unit (I) comprising substituted bifunctional alkoxysilane of formula (-O-Si(R1)2-O-) and the unit (II) (as basic structural units) are used.R1, R2 = monovalent, saturated or aromatic hydrocarbyl, preferably CH3.In the primer composition: a proportion of the inorganic oxide particle in the crosslinked structure is 1-30 parts by weight based on 100 parts by weight of the polysiloxane compound; and the polysiloxane compound is an alkoxysilyl group-containing polysiloxane having the unit (I) and the unit (II) as basic structural units, and/or an alkoxysilyl group-containing polysilsesquioxane having the unit (II) as a basic structural unit. EXAMPLE - Solution (15 g) of Snowtex OS (RTM: Colloidal silica) (having an average particle diameter of 8 -11 nm), 2-propanol (15 g) and 2-methoxyethanol (1 g) was added to a vessel equipped with a stirrer, a reflux cooler and a nitrogen introducing tube. A concentrated nitric acid was added to regulate the acidity (pH of 2-4) of the liquid. Then, the liquid was heated to 70 degrees C, and then a liquid in which X-40-9225 (RTM: Silsesquioxane having reactive methoxysilyl groups at the molecular terminals) (25 g) dissolved in 2-propanol (25 g) was dropped over 1 hour using a dropping funnel to cause the silsesquioxane compound to react with the particle surface of the colloidal silica. Then, a liquid in which a polysiloxane compound (35 g) having reactive methoxysilyl groups at the molecular terminals (derived from a trifunctional alkoxysilane and a X-40-9246 (RTM: Bifunctional alkoxysilane)) dissolved in 2-propanol (35 g) was dropped over 1 hour to cause the polysiloxane compound to react with the silsesquioxane compound on the colloidal silica. The resultant was heated and stirred at 100 degrees C for 1 hour, and then the solvent was distilled out by a rotary evaporator, and then toluene (80 g) was added to the resultant, and heated and stirred at 100 degrees C for 1 hour. The resultant was cooled to room temperature, and the solvent was distilled out to regulate the viscosity to thus obtain a resin solution. The resin solution was coated on MRF-38 (RTM: Polyethylene terephthalate) sheet having been subjected to a release treatment with a silicone-based release agent so that the film thickness after drying became 100 mu m, and held in an oven at 100 degrees C for 10 minutes and at 200 degrees C for 30 minutes to obtain the inorganic oxide particle-containing silicone resin sheet.