Photoinitiator mixtures containing acylphosphinoxides and benzophenone derivatives

A photoinitiator mixture comprising

• a) at least one acyl- or diacylphosphine oxide of the formula I
• where
• R1 is C1-C18-alkyl, halogen- or C1-C6-alkoxy-substituted C1-C4-alkyl, C5-C8-cycloalkyl, C7-C9-phenylalkyl, phenyl, naphthyl, biphenylyl, mono- or poly-halogen-, —C1-C12-alkyl- and/or —C1-C12-alkoxy-substituted phenyl, naphthyl or biphenylyl, or a monovalent, N-, O- or S-containing, 5- or 6-membered heterocyclic radical,
• R2 is phenyl, naphthyl, biphenylyl, mono- or poly-halogen-, —C1-C12-alkyl and/or —C1-C12-alkoxy-substituted phenyl, naphthyl or biphenylyl, a monovalent, N-, O- or S-containing, 5- or 6-membered heterocyclic radical, C1-C18-alkoxy, phenoxy, halogen-, C1-C4-alkyl or C1-C4 -alkoxy-substituted phenoxy, benzyloxy, cyclohexyloxy or a group —CO—R4, or R2 and R1 together with the phosphorus form a ring,
• R3 is C1-C18-alkyl, halogen- or C1-C6-alkoxy-substituted C1-C4-alkyl, C5-C8-cycloalkyl, C7-C9-phenylalkyl, phenyl, naphthyl, biphenylyl, mono- or poly-halogen-, —C1-C12-alkyl and/or —C1-C12-alkoxy-substituted phenyl, naphthyl or biphenylyl, a monovalent N-, O- or S-containing, 5- or 6-membered heterocyclic radical or a group
• where X is C2-C8-alkylene, cyclohexylene or unsubstituted or halogen-, C1-C4-alkyl- or C1-C4-alkoxy-substituted phenylene or biphenylene, and
• R4 is C1-C18-alkyl, halogen- or C1-C4-alkoxy-substituted C1-C4-alkyl, C5-C8-cycloalkyl, C7-C9-phenylalkyl, phenyl, naphthyl, biphenylyl, mono- or poly-halogen-, —C1-C12-alkyl- and/or —C1-C12-alkoxy-substituted phenyl, naphthyl or biphenylyl or a monovalent, N-, O- or S-containing, 5- or 6-membered heterocyclic radical, or R4 and R3 together are C2-C12-alkylene, vinylene or o-phenylene,
• and
• b) at least one benzophenone derivative of the formula
• where R5, R6 and R7 independently are C1-C12-alkyl, C1-C4-alkylthio, C1-C4-alkoxy, halogen or C2-C6-alkoxycarbonyl and R8, R9 and R10 are hydrogen, C1-C12-alkyl, C1-C4-alkoxy, halogen or C2-C6-alkoxycarbonyl or C1-C4-alkylthio
• or a mixture of benzophenone derivatives of the formula II with other benzophenone derivatives.