Importance

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Abstract

The present invention provides heat-developable, photothermographic elements comprising a support bearing at least one photosensitive, image-forming layer comprising: (a) a photosensitive silver halide; (b) a non-photosensitive, reducible silver source; (c) a reducing agent for silver ions; (d) a binder; and (e) a spectrally sensitizing amount of a compound having the central nucleus: ##STR1## wherein: Z is S, O, Se or N--R.sup.3 ; R.sup.1 and R.sup.2 represent an alkyl group of from 1 to 20 carbon atoms other than carboxy-substituted alkyl, preferably an alkyl group of from 1 to 8 carbon atoms, and most preferably an ethyl group; and R.sup.3 is H or alkyl group; X and Y are thioalkyl groups of from 1 to 20 carbon atoms; n=0 to 4; m=0 to 4; the sum of n plus m equals at least 1; D.sup.1 to D.sup.7 each independently represents a methine group and adjacent methine groups selected from D.sup.2, D.sup.3, D.sup.4, D.sup.5 and D.sup.6 may form cyclic groups; p=0 or 1; and A.sup.- is an anion.

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First Claim