TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Solvent: The solvent is a solvent capable of reacting with the siloxane prepolymer, such as water, aliphatic alcohol, aliphatic ether and/or aromatic alcohol. The solvent is propylene glycol monomethyl ether, propylene glycol propyl ether, 2-propanol, water, ethanol, methanol and/or ethyl lactate. Preferred Compounds: The photo-reactive compound is a photo-acid generator or photoinitiator. The photo-reactive compound is capable of cross-linking the siloxane composition by ultraviolet light or thermally. The composition further contains a thermo-acid generator as an additive, and solid nanoparticles (5-50 wt.%). The nanoparticles are light scattering pigment and inorganic phosphor.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: Alternately, the siloxane composition comprises a siloxane prepolymer having a siloxane backbone formed by repeating siloxane unit (5-70 mol%) and epoxy group (1-15 mol%) and having molecular weight of 4000-10000 g/mol, in a solvent phase, and cationic photo-reactive compound (0.1-3 wt.%). Preferred Unit: The organosiloxane polymer contains unit (1-5 mole%) derived from monomer comprising group (a1). Preferred Properties: The content of photo-reactive compound is 0.1-10 mass%, preferably 0.5-5 mass%. The aqueous base developer solution has pH of 7 or more, preferably 9 or more and most preferably 12-13. The siloxane prepolymer has average molecular weight of 2000-20000 g/mol, preferably 3000-10000 g/mol. The composition has solid concentration of 1-70 wt.%. The film has dielectric constant of 4 or less at frequency of 100 kHz, refractive index of 1.2-1.9 at wavelength of 633 nm, resolution of 3 mu m or less, preferably l mu m or less, aspect ratio of 1:1 or more, preferably 1:1.5 or more, and cross-linking degree of 70% or more at UV dose of 100 mJ/cm2 or less at I-line wavelength of mercury UV source. Preferred Process: The siloxane prepolymer is cross-linked using an active group present on the siloxane polymer or by hydrosilylation. EXAMPLE - Phenyltrimethoxysilane (in g) (10.2), methyl triethoxysilane (168.67), 3-glycidoxypropyl trimethoxysilane (24.32), acetone (290.68) and water (112.3) were stirred for 5 minutes, and refluxed for 5 hours. Propylene glycol methyl ether acetate (260) was added to the reaction mixture, and refluxed at 120 degrees C for 1 hour to form film having thickness of 0.1 mu m.