Ultraviolet-curable composition for light-transmission layer and optical disk

An ultraviolet-curable composition, which is used for a light transmission layer of an optical disk in which at least a light reflection layer and the light transmission layer are formed, and reproduction of information is performed by entering a blue laser from a side of the light transmission layer,

• the composition comprising epoxy(meth)acrylate, urethane(meth)acrylate, and a silicone compound represented by formula (1):
• (CH3)3Si—O—X—O—Si(CH3)3 (1)
• wherein X represents a group having a structure in which n structural units represented by formula (2):
• wherein R1 represents an alkylene group of 1 to 18 carbon atoms, and a divalent group connected with one, or two or more groups selected from divalent groups having a structure in which plural alkylene groups of 2 to 18 carbon atoms are connected through an ether bond, R1 may be bonded directly to Si or bonded through an oxygen atom to Si, and R2 represents a hydrogen atom or a methyl group, and
• m structural unit represented by formula (3):
• are connected in a random or blocked shape, provided that n is an integer within a range from 1 to 15 and n/m is within a range from 1/5 to 1/20, and the structural units represented by the formula (2) and the formula (3) are neither connected with each other nor connected with the other structural moiety through an oxygen-oxygen bond, wherein
• a B-type viscosity at 25° C. is within a range from 800 to 3.000 mPa·s. and
• an elastic modulus at 25° C. of a cured film obtained alter irradiation with ultraviolet light is within a ranee from 100 to 2.000 MPa.