Patent ID: 6300051
Filing Date: 2001-10-09
Classification: G03C

Abstract:
Method for preparing a tabular silver halide emulsion wherein tabular silver halide grains having an average aspect ratio of at least 2:1, an average crystal diameter from 0.3 .mu.m to 3.0 .mu.m and an average thickness of less than 0.50 .mu.m accounting for at least 50% of the total projective surface area of said grains, said method having the consecutive steps of precipitating, spectrally sensitizing and chemically ripening said grains, characterized by spectrally sensitizing the said grains by adding before chemically ripening one cyanine dye of formula (I) having a maximum J-band absorption in a wavelength range from 540 nm to 555 nm and one merocyanine dye of formula (II) and absorbing irradiation having a wavelength between 380 and 500 nm in an addition sequence such that said merocyanine dye is added after said cyanine dye, wherein the formula (I) and the formula (II) correspond to ##STR7##whereinZ represents a nitrogen or an oxygen atom and is substituted with R"" if Z is a nitrogen atom,R, R' and R"" each independently represent alkyl,R'"" represents hydrogen, alkyl or aryl,T and T' each independently represent 5-phenyl, 5-Cl, 5-OCH.sub.3 and 5-CH.sub.3,(X.sup.-).sub.p represents a negatively charged atom or group of atoms to compensate for the positive charge(s) present on the dye, and(M.sup.+).sub.q represents a positively charged atom or group of atoms to compensate for the negative charge(s) present on the dye,wherein p and q each represent an integer in order to get an electronically neutral compound; and ##STR8##whereinY represents the atoms, necessary to form a heterocyclic5- or 6-membered ring;Q represents S, NR.sup.3, O, or --(C.dbd.O)--N(R.sup.4)--;M.sup.+ represents a cation;n' equals 0, 1, or 2;b equals 0 or 1;R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each independently represents a C.sub.1 -C.sub.5 alkyl chain,with the proviso that at least one of R.sup.2, R.sup.3 and R.sup.4 has a solubilizing group or a latent alkali solubilizing group.