Water-soluble UV-absorbing compounds and uses thereof

A water-soluble, actinically-crosslinkable polyvinyl alcohol prepolymer, comprising:

• repeating units of vinyl alcohol
• repeating crosslinking units of formula (VI);
• and
• repeating UV-absorbing units of formula (VII)
• in which:
• R11 is hydrogen or C1-C6 alkyl;
• R12 is an ethylenically unsaturated group of
• in which q1 and q2 independently of each another are zero or one, and R16 and R17 independently of one another are a C2-C8 alkylene divalent radical, R18 is C2-C8 alkenyl;
• R13 can be hydrogen or a C1-C6 alkyl group;
• R14 is a C1-C6 alkylene divalent radical;
• R15 is a monovalent radical of any one of formula (VIII)-(XII)
• Ro is H or CH3;
• R1, R2 and R2′ independent of one other are H, CH3, CCl3, CF3, Cl, Br, NR′R″ in which
• R′ and R″ independent of each other are H or C1-C4 alkyl, OH, or OCH3;
• R1′ independent of each other are H, CH3, CCl3, CF3, Cl, Br, NR′R″ in which R′ and R″ independent of each other are H or C1-C4 alkyl, OH, OCH3, SO3H, or SO3−Na+;
• R3 and R4 independent of each other are H or a first hydrophilic group which is
• provided that at least one of R3 and R4 is the first hydrophilic group;
• r1 is an integer of 1 to 8;
• n1 is an integer of 2 to 20;
• R5 is H, *—COOH, *—CONH—C2H4—(OC2H4)n1—OCH3, or —CONH—C2H4—(OC2H4)n1—OH;
• R8 is CH3, C2H5,
• R9 is SO3Na,
• R9′ is H, SO3Na,
• R10 is methyl or ethyl;
• L1 is a linkage of
• L2 is a linkage of
• L3 is a linkage of
• X1 is O or NRo;
• one of R19 and R20 is H or a second hydrophilic group which is
• while the other of R19 and R20 is a divalent radical of