GB1336044A - Direct-positive silver halide photographic emulsion - Google Patents

Abstract

1336044 Supersensitizing direct positive silver halide emulsions FUJI PHOTO FILM CO Ltd 2 June 1971 [2 June 1970] 18670/71 Heading G2C A direct positive fogged silver halide emulsion contains a supersensitizing combination of a cyanine dye of formula I: in which Z and Z<SP>1</SP> each represent the atoms necessary to complete a 5- or 6- membered heterocyclic nucleus, which may carry further substituents except at the N-position, R and R<SP>1</SP> each represent alkyl or aryl, which groups may be substituted, cycloalkyl or allyl, L<SP>1</SP>, L<SP>2</SP> and L<SP>3</SP> each represent methine or a substituted methine in which the substituents of two substituted methine groups may link to form a ring of the following formula:- in which R<SP>6</SP> is H or CH 3 and R<SP>7</SP> is H, alkyl, substituted alkyl, aralkyl, phenyl, substituted phenyl or furyl, p and q are each 1 or 2, n is 1, 2 or 3, m is 1 or 2, X is an anion but is absent when m is 1, the dye forming a betaine structure, together with a compound of formula II:- wherein each Y, which may be the same or different, is =CH- or =N-, R<SP>2</SP>, R<SP>3</SP>, R<SP>4</SP> and R<SP>5</SP> each represent H, OH, alkoxy, aryloxy, halogen, heterocyclic nucleus, alkylthis, arylthio, amino substituted or unsubstituted arylamino or alky lamino, heterocyclylamino, aryl or mercapto, and -A- is -A 1 - or -A 2 - where -A 1 - represents:- in which M is H or a cation giving water-solubility to the group, and -A 2 - is:- with the limitation that when -A- is -A 2 - at least one of R<SP>2</SP>, R<SP>3</SP>, R<SP>4</SP> and R<SP>5</SP> is a substituent having a -SO 3 M group wherein M is as defined above. The emulsion may also contain as a sensitizer the salt of a Group VIII metal e.g. an iridium or thodium salt.