Curable composition and use of same

A curable composition comprising:

• (A) a first siloxane oligomer being free from a siloxane unit represented by the following formula (I) and containing an alkoxy-group-containing siloxane unit,
• (B) a second siloxane oligomer containing a siloxane unit represented by the above formula (I) and an alkoxy-group-containing siloxane unit,
• (C) a silicone oil having a kinetic viscosity at 25° C. of not less than 100 mm2/s,
• (D) at least one curing catalyst selected from the group consisting of a metal alkoxide, a metal chelate compound, and a metal carboxylate, and
• (E) a solvent containing an organic solvent having a vapor pressure at 20° C. of not less than 1 kPa,
• wherein a total proportion of the first siloxane oligomer (A) and the second siloxane oligomer (B) in the composition is 20 to 50% by mass,
• a mass ratio of the second siloxane oligomer (B) relative to the first siloxane oligomer (A) is 0.15 to 10,
• a mass ratio of the solvent (E) is 40 to 300 parts by mass relative to 100 parts by mass of a total of the first siloxane oligomer (A), the second siloxane oligomer (B), and the silicone oil (C), and
• when the composition is applied and is allowed to stand at 23° C. for 24 hours to give a cured layer, the composition has a pencil hardness measured in accordance with JIS K5600-5-4(1999) of not less than 2H as the cured layer:
• wherein R1 and R2 are the same or different and each represent an alkyl group.