Abstract: The invention relates to cyanine dyes, which have alkyl substituents in the meso position of the methine chain, sulphoaryl groups as well as at least one reactive group which permits the binding to a target substance.

Abstract: The invention relates to cyanine dyes, which have alkyl substituents in the meso position of the methine chain, sulphoaryl groups as well as at least one reactive group which permits the binding to a target substance.

Abstract: This invention relates to a radiation-sensitive, silver-free recording material for direct optical recording with high sensitivity, characterized by its exceptional resistance to light and heat and large solubility. This is achieved by the fact that the recording material contains as coloring substances, azo dyestuffs of the general formula ##STR1## R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 are the same or different and are halogen, alkoxy, alkyl, acetyl, amino; R.sub.8 hydroxy, alkoxy or acetylamino. The material distinguishes itself by the different processing variations that are possible so that with a same basic type, it is possible to obtain pictures operating according to a positive principle as well as according to a negative principle.