Use of a composition in stereolithography

The use of a compound of formula (A), which comprises a group of sub-formula (I)

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• where R1 is CRa′ where Ra′ is hydrogen or alkyl, and R6 is a bond, or R1 and R6 together form an electron withdrawing group;
• R2 and R3 are independently selected from (CR7R8) , or a group CR9R10, CR7R8CR9R10 or CR9R10CR7R8 where n is 0, 1 or 2, R7 and R8 are independently selected from hydrogen or alkyl, and either one of R9 or R10 is hydrogen and the other is an electron withdrawing group, or R9 and R10 together form an electron withdrawing group, and R4 and R5 are independently selected from CH or CR11 where R11 is an electron withdrawing group;
• the dotted lines indicate the presence or absence of a bond, and X1 is a group CX2X3 where the dotted line bond to which it is attached is absent and a group CX2 where the dotted line bond to which it is attached is present, Y1 is a group CY2Y3 where the dotted line bond to which it is attached is absent and a group CY2 where the dotted line bond to which it is attached is present, and X2, X3, Y2 and Y3 are independently selected from hydrogen and fluorine;
• provided that at least one of (a) R1 and R6 or (b) R2 and R3 or (c) R4 and R5 includes an electron withdrawing group which is able to activate a cyclopolymerization reaction under the influence of radiation used in a stereolithographic process optionally in the presence of a photoinitiator;
• in a stereolithographic composition.