摘要:
The present invention is directed to a process of precipitating for use in photography a thin tabular grain silver bromide or bromoiodide emulsion within a novel range of low bromide ion concentrations (high pBr levels) at the nucleation stage. A variety of advantages can be realized, including thinner and/or larger diameter tabular grains and novel tabular grain forms.
摘要:
A chemically and spectrally sensitized ultrathin tabular grain emulsion is disclosed including tabular grains (a) having {111} major faces, (b) containing greater than 70 mole percent bromide, based on silver, (c) accounting for greater than 90 percent of total grain projected area, (d) exhibiting an average equivalent circular diameter of at least 0.7 .mu.m, and (e) exhibiting an average thickness of less than 0.07 .mu.m.It has been observed that increased speed and contrast as well as improvements in speed-granularity relationships can be realized when the surface chemical sensitization sites include epitaxially deposited silver halide protrusions forming epitaxial junctions with the tabular grains, the protrusions (a) being located on up to 50 percent of the surface area of the tabular grains, (b) having a higher overall solubility than at least that portion of the tabular grains forming epitaxial junctions with the protrusions, and (c) forming a face centered cubic crystal lattice.In further improving photographic performance by incorporating a photographically useful dopant, it has been observed that thinner tabular grains can be realized by locating the dopant in the protrusions. Still further improvements in photographic sensitivity can be realized by selecting the dopant to act as a shallow trap for photoelectrons.
摘要:
A chemically and spectrally sensitized ultrathin tabular grain emulsion is disclosed including tabular grains (a) having {111} major faces, (b) containing greater than 70 mole percent bromide and at least 0.25 mole percent iodide, based on silver, (c) accounting for greater than 90 percent of total grain projected area, (d) exhibiting an average equivalent circular diameter of at least 0.7 .mu.m, and (e) exhibiting an average thickness of less than 0.07 .mu.m.It has been observed that faster rates of development, relatively thinner tabular grains under comparable conditions of preparation, increased contrast and improvements in speed-granularity relationships can be realized when (1) the tabular grains contain less than 10 mole percent iodide and (2) the surface chemical sensitization sites include epitaxially deposited silver halide protrusions of a face centered cubic crystal lattice structure of the rock salt type forming epitaxial junctions with the tabular grains, the protrusions (a) being restricted to those portions of the tabular grains located nearest peripheral edges of and accounting for less than 50 percent of the {111} major faces of the tabular grains, (b) containing a silver chloride concentration at least 10 mole percent higher than that of the tabular grains, and (c) including a higher iodide concentration than those portions of the tabular grains extending between the {111} major faces and forming epitaxial junctions with the protrusions.A photographic element is disclosed in which an ultrathin tabular grain emulsion as described above is coated over an emulsion layer intended to record visible light.
摘要:
A chemically and spectrally sensitized tabular grain emulsion is disclosed including tabular grains (a) having {111} major faces, (b) containing greater than 70 mole percent bromide and at least 0.25 mole percent iodide, based on silver, (c) accounting for greater than 90 percent of total grain projected area, (d) exhibiting an average equivalent circular diameter of at least 0.7 .mu.m, and (f) exhibiting an average thickness in the range of from less than 0.3 .mu.m to at least 0.07 .mu.m.It has been observed that photographic performance is enhanced when surface chemical sensitization sites include epitaxially deposited silver halide protrusions forming epitaxial junctions with the tabular grains, the protrusions (a) being located on up to 50 percent of the surface area of the tabular grains, (b) having a higher overall solubility than at least that portion of the tabular grains forming epitaxial junction with the protrusions, (c) forming a face centered cubic crystal lattice, and (d) containing a speed enhancing dopant selected to provide shallow electron trapping sites.
摘要:
A chemically and spectrally sensitized ultrathin tabular grain emulsion is disclosed including tabular grains (a) having {111} major faces, (b) containing greater than 70 mole percent bromide and at least 0.25 mole percent iodide, based on silver, (c) accounting for greater than 90 percent of total grain projected area, (d) exhibiting an average equivalent circular diameter of at least 0.7 .mu.m, and (e) exhibiting an average thickness of less than 0.07 .mu.m.It has been observed that increased speed and contrast as well as improvements in speed-granularity relationships can be realized when during the chemical sensitization silver and halide ions including iodide and chloride ions are added to the ultrathin tabular grain host emulsion to deposit epitaxially on up to 50 percent of the surface area of the tabular grains silver halide protrusions (a) having an isomorphic face centered cubic crystal lattice structure, (b) containing at least a 10 mole percent higher chloride ion concentration than the tabular grains, and (c) containing an iodide concentration that is increased by the iodide ion addition.
摘要:
A chemically and spectrally sensitized tabular grain emulsion is disclosed including tabular grains (a) having major faces, (b) containing greater than 70 mole percent bromide and at least 0.25 mole percent iodide, based on silver, (c) accounting for greater than 90 percent of total grain projected area, (d) exhibiting an average equivalent circular diameter of at least 0.7 .mu.m, and (f) exhibiting an average thickness in the range of from less than 0.3 .mu.m to at least 0.07 .mu.m.It has been observed that increased speed, lower granularity, increased contrast and faster rates of development can be realized when (1) the tabular grains contain less than 10 mole percent iodide and (2) the surface chemical sensitization sites include epitaxially deposited silver halide protrusions of a face centered cubic crystal lattice structure of the rock salt type forming epitaxial junctions with the tabular grains, the protrusions (a) being restricted to those portions of the tabular grains located nearest peripheral edges of and accounting for less than 50 percent of the major faces of the tabular grains, (b) containing a silver chloride concentration at least 10 mole percent higher than that of the tabular grains, and (c) including at least 1 mole percent iodide.
摘要:
Moderate camera speed photographic elements for producing subtractive primary dye images are disclosed, including one emulsion layer comprised of silver bromide or bromoiodide grains having a mean diameter in the range of from 0.2 to 0.55 .mu.m including tabular grains having an aspect ratio of greater than 8:1 accounting for at least 50 percent of the total projected area of the grains in the emulsion layer and being positioned to receive imaging radiation prior to one or more blue recording emulsion layers. Enhancement of speed-granularity relationships, blue to minus blue speed separation, silver utilization, and image sharpness can all be realized.
摘要:
A process of preparing a high bromide tabular grain emulsion comprising a dispersion medium and silver halide grains including tabular grains having {111} major faces and an aspect ratio of at least 2, which contain greater than 50 mole percent bromide, based on silver, and which account for greater than 50 percent of total grain projected area, where such tabular grains have an average aspect ratio of at least 5, the process comprising (i) in a grain nucleation step creating in a dispersing medium tabular silver halide grain nuclei containing parallel twin planes and (ii) in a grain growth step subsequently growing the tabular grain nuclei into tabular grains in a silver halide reaction vessel by adding a silver ion source and a halide ion source to the reaction vessel and precipitating silver halide onto the tabular grain nuclei, wherein thiocyanate ion is introduced into the silver halide reaction vessel prior to the addition of at least the final 10 mole percent of the total silver added to the reaction vessel, and further wherein the introduced thiocyanate ion concentration is at most 0.4 mole %, based on the total silver added to the reaction vessel. Use of thiocyanate during grain precipitation result in increased aspect ratio without degrading morphological purity.
摘要:
The invention provides a radiation-sensitive silver halide emulsion comprisingsilver halide grains including tabular grains(a) having {111} major faces(b) containing greater than 70 mole percent bromide, based on silver,(c) accounting for greater than 90 percent of total grain projected area,(d) exhibiting an average equivalent circular diameter of at least 0.7 .mu.m,(e) exhibiting an average thickness of less than 0.07 .mu.m, and(f) having latent image forming chemical sensitization sites on the surfaces of the tabular rains, anda spectral sensitizing dye adsorbed to the surfaces of the tabular grains,wherein the surface chemical sensitization sites include at least one silver salt epitaxially located on said tabular rains and wherein said grains further comprise a mercapto compound represented by Formula III ##STR1## where R.sup.1 is an aliphatic or aromatic radical containing up to 20 carbon atoms.
摘要:
An improved spectrally sensitized ultrathin tabular grain emulsion is disclosed in which tabular grains (a) having {111} major faces, (b) containing greater than 70 mole percent bromide and at least 0.25 mole percent iodide, based on silver, (c) accounting for greater than 90 percent of total grain projected area, (d) exhibiting an average equivalent circular diameter of at least 0.7 .mu.m, (e) exhibiting an average thickness of less than 0.07 .mu.m, and (f) having latent image forming chemical sensitization sites on the surfaces of the tabular grains, are spectrally sensitized. The speed-granularity relationship of the emulsion is improved by employing in forming the surface chemical sensitization sites at least one silver salt epitaxially located on tabular grain surface sites that contain increased iodide concentrations.A photographic element is disclosed comprised of a support, a first silver halide emulsion layer coated on the support and sensitized to produce a photographic record when exposed to specular light within the minus blue visible wavelength region of from 500 to 700 nm, a second silver halide emulsion layer capable of producing a second photographic record coated over the first silver halide emulsion layer to receive specular minus blue light intended for the exposure of the first silver halide emulsion layer, the second silver halide emulsion layer being capable of acting as a transmission medium for the delivery of at least a portion of the minus blue light intended for the exposure of the first silver halide emulsion layer in the form of specular light, wherein the second silver halide emulsion layer is comprised of the improved spectrally sensitized ultrathin tabular grain emulsion of the invention.The ultrathin tabular grain emulsions with silver salt epitaxy chemical sensitization have been observed to produce larger than expected speed increases, to produce higher than expected contrasts, to be unexpectedly specularly transmissive and therefore compatible with forming sharp photographic images in underlying emulsion layers, to exhibit a higher percentage of total light absorption in the wavelength region of maximum absorption by the spectral sensitizing dye or dyes employed, and to exhibit a surprising tolerance of inadvertent manufacturing variances.