Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-03-13
2004-02-24
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S569000
Reexamination Certificate
active
06696235
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-068796, filed Mar. 13, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a silver halide photographic emulsion and a silver halide photographic lightsensitive material containing the same. More particularly, the present invention relates to a highly sensitive silver halide photographic emulsion ensuring a reduction of pressure mark deterioration and a silver halide photographic lightsensitive material containing the same.
With respect to tabular silver halide grains, for example, U.S. Pat. Nos. 4,434,226, 4,439,520, 4,414,310, 4,433,048, 4,414,306 and 4,459,353 disclose processes for producing the same and techniques for use thereof. These teach advantages such as enhancement of sensitivity/graininess relations, including enhancement of spectral sensitization efficiency, attained by the use of spectral sensitizing dyes.
Various investigations and studies have been made with a view toward further enhancing the performance of tabular grains capable of realizing the above advantages.
Japanese Patent Application KOKAI Publication No. (hereinafter referred to as JP-A-) 63-220238, whose corresponding US application is patented as U.S. Pat. No. 4,806,461, discloses the technique for attaining a sensitivity increase and an improvement of pressure performance by introduction of dislocation lines. However, introducing dislocation lines in thin tabular grains with a large equivalent circle diameter at a high density is difficult. Therefore, it is difficult to realize satisfactory performance with respect to sensitivity increase and pressure characteristics with the use of the technique.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a highly sensitive silver halide photographic emulsion ensuring a reduction of pressure marks, and a silver halide photographic lightsensitive material containing the same.
The object of the present invention is attained by the following silver halide photographic emulsion and silver halide photographic lightsensitive material containing the same.
(I) A silver halide photographic emulsion comprising silver halide grains, wherein 50% in number or more of the total number of all the silver halide grains are occupied by tabular grains, each of which satisfying the following requirements:
(i) composed of silver iodobromide or silver chloroiodobromide having (111) faces as main planes;
(ii) having an equivalent circle diameter of 1.0 &mgr;m or more and a thickness of 0.1 &mgr;m or less;
(iii) having 10 or more dislocation lines per grain at a fringe portion thereof; and
(iv) composed of core portion substantially not containing any dislocation line and a shell portion containing dislocation lines, the shell portion having a thickness of 0.01 &mgr;m or more as measured in a direction perpendicular to the main plane.
(II) The silver halide photographic emulsion according to item (I) above, wherein the thickness of the shell portion is 0.015 &mgr;m or more.
(III) The silver halide photographic emulsion according to item (I) or (II) above, wherein a variation coefficient of the distribution of equivalent circle diameters of all the silver halide grains contained in the silver halide photographic emulsion is 30% or less.
(IV) The silver halide photographic emulsion according to item (III) above, wherein a variation coefficient of the distribution of thicknesses of all the silver halide grains contained in the silver halide photographic emulsion is 20% or less.
(V) A silver halide photographic lightsensitive material comprising at least one lightsensitive silver halide emulsion layer on a support, wherein the lightsensitive silver halide emulsion layer contains the silver halide photographic emulsion according to any of items (I) to (IV) above.
DETAILED DESCRIPTION OF THE INVENTION
Now, the emulsion of the present invention will be described.
The tabular grains for use in the present invention are composed of a silver halide containing silver iodide, more specifically, silver iodobromide or silver chloroiodobromide.
In the present invention, the tabular grains refer to silver halide grains having two mutually opposite and parallel (111) main planes. The tabular grains used in the present invention have one twin plane or two or more mutually parallel twin planes. The twin plane refers to the (111) surface on both sides of which the ions of all the lattice points are in the relationship of reflected images.
The tabular grains, as viewed from a point perpendicular to the main plane of the tabular grains, have the shape of a triangle, a hexagon or an intermediate triangle with angle portions cut off. The tabular grains have mutually parallel external surfaces.
The silver halide grains not comprehended in the tabular grains include regular crystal grains and grains having two or more nonparallel twin planes. The grains having two nonparallel twin planes include those having the shape of a trigonal pyramid or a rod. These are collectively referred to as “nontabular grains”.
In the measurement of the equivalent circle diameter and thickness of the tabular grains, a transmission electron micrograph according to the replica method is taken, from which the diameter of a circle having the same area as the projected area of each individual grain (equivalent circle diameter) and the thickness thereof are determined. The thickness is calculated from the length of the shadow of the replica. With respect to the nontabular grains, the equivalent circle diameter is defined as the diameter of a circle having the same area as the maximized projected area of each individual grain. When there is no plane parallel to a base as encountered in, for example, grains having the shape of a trigonal pyramid among the nontabular grains, the thickness of the grains is defined as the distance between the base and the apex thereof.
The nontabular grains are not favorable because the specific surface area thereof is so small that using them at a high proportion causes it difficult to attain a sensitivity increase.
With respect to the silver halide grains contained in the silver halide photographic emulsion of the present invention, tabular grains having an equivalent circle diameter of 1.0 &mgr;m or more and a thickness of 0.1 &mgr;m or less occupy 50% or more of the total number of all the silver halide grains.
When the equivalent circle diameter is decreased, the grain size is decreased to thereby cause attaining a sensitivity increase to be difficult. When the thickness is increased, the specific surface area is decreased to thereby cause keeping the ratio of sensitivity/graininess high to be difficult. With respect to the silver halide photographic emulsion of the present invention, 50% or more of the total number of all the silver halide grains contained therein have an equivalent circle diameter of 1.0 &mgr;m or more and a thickness of 0.1 &mgr;m or less, preferably an equivalent circle diameter of 1.0 &mgr;m or more and a thickness of 0.07 &mgr;m or less, and more preferably an equivalent circle diameter of 1.5 &mgr;m or more and a thickness of 0.07 &mgr;m or less. Provided that, however, it is preferred that the equivalent circle diameter be 5 &mgr;m or less and the thickness be 0.03 &mgr;m or more.
In the chemical sensitization of silver halide grains, nonuniformity between grains in, for example, the size thereof causes attaining the optimum sensitization of the individual grains to be difficult, thereby inviting a deterioration of photographic sensitivity. From this viewpoint, it is preferred that the equivalent circle diameter and thickness of tabular grains be monodisperse.
With respect to all the silver halide grains of the present invention, the variation coefficient of equivalent circle diameter is preferably 30% or less, more preferably 25% or less The variation coefficient of thickness is preferably 20% or less. The
Baxter Janet
Walke Amanda C.
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