Polysiloxane, composition comprising the same and cured film using the same

A polysiloxane (Pa) comprising:

• a repeating unit represented by the following formula (Ia):
• wherein,
• R1 is hydrogen, a monovalent to trivalent, linear, branched or cyclic, saturated or unsaturated C1-30 aliphatic hydrocarbon group, or a monovalent to trivalent, C6-30 aromatic hydrocarbon group,
• in said aliphatic hydrocarbon group and said aromatic hydrocarbon group, one or more methylene are unsubstituted or substituted with oxy, imide or carbonyl, one or more hydrogens are unsubstituted or substituted with fluorine, hydroxy or alkoxy, and one or more carbons are unsubstituted or substituted with silicon,
• when R1 is divalent or trivalent, R1 connects Si atoms contained in a plurality of repeating units;
• and
• a repeating unit represented by the following formula (Ib):
• wherein,
• R2 is each independently hydrogen, C1-10 alkyl, C6-20 aryl or C2-10 alkenyl, which is unsubstituted or substituted with oxygen or nitrogen, or a linking group represented by the formula (Ib′):
• L is each independently C6-20 arylene, which is unsubstituted or substituted with oxygen or nitrogen,
• m is each independently an integer of 0 to 2,
• n is each independently an integer of 1 to 3,
• q is each independently 0 or 1,
• the total number of n, the number of O0.5, and m, the number of R2, bonding to one Si is 3, and
• the total number of q contained in the repeating unit represented by the above formula (Ib) is 1 or more.