| 摘要 |
A method has been described for preparing a gelatinous emulsion having grains rich in silver choride, wherein at least 70%, and more preferred 90%, of the total projected area of all grains is provided by {111} tabular grains having an average aspect ratio of more than 2:1, an average equivalent circular diameter of at least 0.3 mu m and an average thickness of from 0.05 to 0.25 mu m , wherein a percent variation on average equivalent circular diameter of said tabular grains is 30% or less and wherein a percent variation on average thickness of said tabular grains is 20% or less and wherein said tabular grains are present in percent numerical amounts of at least 90%, said method comprising following steps: preparing in a reaction vessel a dispersion medium comprising an initial amount of a crystal habit modifying agent; precipitating therein silver halide crystal nuclei by double-jet precipitation of an aqueous silver nitrate and an aqueous solution comprising halide ions, wherein less than 10% by weight of a total amount of silver nitrate used is consumed; growing said silver halide crystal nuclei by further precipitation of silver halide by means of double-jet precipitation of an aqueous silver nitrate solution and an aqueous solution comprising halide ions, wherein more than 90% by weight of a total amount of silver nitrate is consumed, characterized in that during at least one of the said steps at least one compound is added to the said reaction vessel, said compound being a hydrophilic amphoteric block copolymer containing (i) a non-ionic acrylic block comprising a sequence of units having pendant nitrile groups according to formula I given in the claims and (ii) a acrylamid(in)ic block comprising a sequence of units according to formula II given in the claims, said hydrophilic amphoteric block copolymer further comprising within said acrylamid(in)ic block(s) units having pendant acidic groups or salts thereof as well as units having pendant basic groups or salts thereof. Emulsions having tabular grains prepared according to the method of the present invention and light-sensitive silver halide photographic materials wherein said emulsions have been coated in light-sensitive layers have also been disclosed.
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