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US 3,971,808 AGranted
Spirodipyrans and chromogenic materials for copying processes
AssigneeBASF SE
InventorsHans Baumann, Andreas Oberlinner
Life of this patent
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Abstract
Spirodipyrans based on condensed pyrylium salts and 4-dialkylamino-2-hydroxybenzaldehydes, their manufacture and their use as chromogenic materials in pressure-sensitive recording materials, particularly copying papers.
Claims6
A spirodipyran of the formula ##SPC16##
- in which
- A is an unsubstituted benzene or (2,1-b)-naphthalene nucleus, or a benzene or a (2,1-b)-naphthalene nucleus substituted by one chloro, bromo, methoxy, ethoxy or carbalkoxy containing a C.sub.1 to C.sub.4 alkoxy,
- R.sup.1 is phenyl, phenyl substituted by chloro, bromo or alkyl of from 1 to 4 carbon atoms,
- R.sup.2 is hydrogen, alkyl of from 1 to 8 carbon atoms or phenyl, and
- R.sup.3 and R.sup.4 are methyl, ethyl or propyl.
2 more elements
Dependencies are inferred from the claim text.