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Direct positive type silver halide photosensitive material
| Details |
Inventors: Matsuda, Terumi; Ishiguro, Shoji; Moriuchi, Shigenori; Suzuki, Yoshiaki;
Assignee: Fuji Photo Film Co., Ltd. (Kanagawa, JP)
Primary Examiner: Louie, Jr.; Won H.
Assistant Examiner:
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak and Seas
A high contrast, chemically fogged direct positive type silver halide photosensitive material is described containing at least one ammine complex salt selected from those including cobalt, nickel, ruthenium or chromium, by which the contrast in the lower optical density region is improved while retaining superior Dmax and sensitivity. |
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DETAILED DESCRIPTION OF THE INVENTION The cobalt, nickel, ruthenium and chromium metal ammine complex salts used in the present invention are inert metal complex salts which are relatively stable (slow) with respect to the ligand exchange reaction.
From the viewpoint of stability of the metal complexes, valence states of Co.
sup.
3+, Cr.
sup.
3+, N.
sup.
2+, and Ru.
sup.
3+ are preferred.
The ligands of said metal complex salts necessarily incorporate the ammine (NH.
sub.
3) ligand (1 to 6 ammine ligands), but in addition to the ammine ligand, chloride, nitrate, water and carbonate ligands can also be employed.
Especially useful among such metal complex salts are those having from 4 to 6 ammine groups; some particularly preferred complex salts are illustrated by the following formulae: [Co(NH.
sub.
3).
sub.
5 H.
sub.
2 O]X; [Co(NH.
sub.
3).
sub.
5 CO.
sub.
3 ]X; [Co(NH.
sub.
3).
sub.
5 Cl]X; [Co(NH.
sub.
3).
sub.
4 (OCOO)]X; [Co(NH.
sub.
3).
sub.
5 (NO.
sub.
2)]X; [Co(NH.
sub.
3).
sub.
6 ]X; [Ni(NH.
sub.
3).
sub.
6 ]X; [Cr(NH.
sub.
3).
sub.
5 (H.
sub.
2 O)]X; [Cr(NH.
sub.
3).
sub.
5 Cl]X; and [Ru(NH.
sub.
3).
sub.
6 ]X wherein X represents one or more anions.
The number of said anions are determined by the charge neutralization rule.
Among the above metal complex salts, cobalt ammine complex salts, especially the pentaammine and hexaammine complex salts thereof, have a remarkable effect on the toe gradient of the characteristic curve.
The direct positive type silver halide photosensitive material used in accordance with the present invention is that which does not form a color dye image, but rather forms a silver image.
That is, the direct positive type photosensitive material according to this invention is different from the type of material disclosed in U.
S.
Pat.
No.
3,862,842 issued to Bissonette, wherein the substitution metal complexes, such as Co complexes, are employed as oxidants in the course of a redox reaction in which silver images are converted into dye images.
Rather, this invention is directed to direct positive type materials for forming silver images having high contrast (i
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Manufacturing Materials 
