摘要 |
Concerning the compound of the formula (I) R<SUP>1</SUP>, R<SUP>3 </SUP>are each independently, for example, H R<SUP>2</SUP>, R<SUP>4 </SUP>are each independently, for example, H X<SUP>1</SUP>, X<SUP>2 </SUP>are each independently H or F M<SUP>1 </SUP>is -CO-O-, -O-CO-, -CH<SUB>2</SUB>-O-, -O-CH<SUB>2</SUB>-, -CF<SUB>2</SUB>-O-, -O-CF<SUB>2</SUB>-, -CH-CH-, -CF-CF-, -C≡C-, -CH<SUB>2</SUB>-CH<SUB>2</SUB>-CO-O-, -O-CO-CH<SUB>2</SUB>-CH<SUB>2</SUB>-, -CH<SUB>2</SUB>-CH<SUB>2</SUB>-, -CF<SUB>2</SUB>-CF<SUB>2</SUB>-, -(CH<SUB>2</SUB>)<SUB>4</SUB>-, -OC(-O)CF-CF- or a single bond A<SUP>1 </SUP>is, for example, 1,4-phenylene, and R<SUP>5 </SUP>has the same possible definitions as specified for R<SUP>2 </SUP>and R<SUP>4</SUP>, with the exception of -M<SUP>1</SUP>-A<SUP>1</SUP>-R<SUP>5</SUP>, but independently of the particular definitions of R<SUP>2 </SUP>and R<SUP>4 </SUP> with the following provisos: 1) at least one of X<SUP>1</SUP>, X<SUP>2 </SUP>has to be F 2) R<SUP>1</SUP>, R<SUP>2</SUP>, R<SUP>3 </SUP>and R<SUP>4 </SUP>must not at the same time be H 3) at most two of R<SUP>1</SUP>, R<SUP>2</SUP>, R<SUP>3 </SUP>and R<SUP>4 </SUP>may be c).
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