Black-and-white developing compositions and methods of use

Details Black-and-white developing compositions and methods of use Black-and-white developing compositions and methods of use

2002-04-18

2003-08-05

Le, Hoa Van (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Nonradiation sensitive image processing compositions or...

Developer

C430S489000

Reexamination Certificate

active

06602655

ABSTRACT:

FIELD OF THE INVENTION
This invention relates in general to photography and in particular to improved black-and-white developing compositions. More particularly, it relates to improved and black-and-white developing compositions and to methods for their use in processing silver halide materials, and particularly radiographic materials.
BACKGROUND OF THE INVENTION
Photographic black-and-white developing compositions containing a silver halide black-and-white developing agent are well known in the photographic art for reducing silver halide grains containing a latent image to yield a developed photographic image. Many useful developing agents are known in the art, with hydroquinone and similar dihydroxybenzene compounds and ascorbic acid (and derivatives) being some of the most common. Such compositions generally contain other components such as sulfites, buffers, antifoggants, halides and hardeners.
Dihydroxybenzenes (such as hydroquinone) are the most common black-and-white developing agents and are quite active to provide development in various black-and-white photographic elements with or without booster and nucleating compounds. Another class of black-and-white developing agents are known in many publications as ascorbic acid and its various derivatives, for example as described in U.S. Pat. No. 5,236,816 (Purol et al).
Efforts have been made to provide an environmentally suited developing composition that would be useful for a wide variety of radiographic films. Such compositions would also increase contrast in black-and-white photographic images and promote a blue or “cold” tone in the processed films. It is also desired to provide such compositions in concentrated form. However, to accomplish all of these results, the composition must be carefully formulated to have all of the desired components in the right proportion, and may have to be supplied in multiple “parts” or formulations that are mixed together for use. In particular, the antifoggant(s) must be chosen carefully so contrast is maximized and are soluble in concentrated solutions.
Some black-and-white developing compositions include a combination of an indazole and benzimidazole antifoggants. Indazoles are described for example, in U.S. Pat. No. 4,323,642 (Levinson). Indazoles are generally dissolved in low pH solutions or in solutions containing glutaraldehyde.
However, it has been difficult to find a combination of antifoggants that are suitably soluble in concentrated solutions and provide the desired sensitometric properties. Thus, there is a need, however, for environmentally suitable black-and-white developing compositions that provide such properties and that can be provided in concentrated form.
SUMMARY OF THE INVENTION
This invention provides an improved concentrated black-and-white photographic developing composition having a pH of at least 9 and comprising:
a) at least 0.6 mol/l of a black-and-white developing agent,
b) at least 0.5 mmol/l of a mercapto-substituted tetrazole antifoggant, and
c) at least 0.5 mmol/l of a benzimidazole antifoggant having one or more electron withdrawing groups.
This invention also provides a two-component (or two “part”) black-and-white developing composition kit comprising:
I) as a first component (or first “part”), the concentrated black-and-white photographic developing composition noted above, and
II) a second component (or second “part”) comprising a concentrated composition having a pH of at least 3 and comprising at least 0.01 mol/l of a gelatin hardening agent.
Further, this invention provides a working strength black-and-white developing composition provided by mixing the two components I and II noted above, the first component being diluted from about 1 to about 10 times with water, and the second component being diluted from about 10 to about 25 times with water, and the ratio of the diluted first component to the diluted second component being from about 2:1 to about 10:1.
Still again, the present invention provides a working strength black-and-white photographic developing composition having a pH of at least 9 and comprising:
a) at least 0.16 mol/l of a black-and-white developing agent,
b) at least 0.1 mmol/l of a mercapto-substituted tetrazole antifoggant,
c) at least 0.1 mmol/l of a benzimidazole antifoggant substituted with one or more electron withdrawing groups, and
d) if present, at least 0.01 mol/l of a gelatin hardening agent.
A method of providing an image comprises contacting an imagewise exposed silver halide photographic material with a working strength black-and-white photographic developing composition as described above for at least 10 seconds.
We have found that the two-part concentrated developing composition kit can be used to provide a working strength composition that can be used to provide black-and-white images with desired sensitometric properties. The individual concentrated “parts” are stable under typical storage conditions and can be appropriately diluted and mixed to provide this composition. In the “first” part containing the developing agent, we have found that two specific types of antifoggants can be solubilized and mixed to provide desired D
min
, contrast and tone when used in processing. These antifoggants are specific mercapto-substituted tetrazoles and nitro-substituted benzimidazoles. The use of each type of antifoggant presents a unique set of problems that are not evident with the combination of antifoggants.
In addition, the concentrated black-and-white photographic developing composition described above can be used directly for providing an image with or without dilution. Thus, the first “part” described above can be used alone if desired for black-and-white image formation in photographic materials.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
The term “contrast” as herein employed indicates the average contrast (also referred to as &ggr;) derived from a characteristic curve of a radiographic element using as a first reference point (1) a density (D
1
) of 0.25 above minimum density and as a second reference point (2) a density (D
2
) of 2.0 above minimum density, where contrast is &Dgr;D (i.e. 1.75)÷&Dgr;log
10
E(log
10
E
2
−log
10
E
1
), E
1
and E
2
being the exposure levels at the reference points (1) and (2).
The term “dual-coated” is employed to indicate radiographic elements having image forming layer units disposed on opposite sides of a support.
The terms “front” and “back” refer to features or elements nearer to and farther from, respectively, the X-radiation source than the support of the radiographic element.
The term “fully forehardened” is employed to indicate the forehardening of hydrophilic colloid layers to a level that limits the weight gain of a radiographic material to less than 120 percent of its original (dry) weight in the course of wet processing. The weight gain is almost entirely attributable to the ingestion of water during such processing.
The term “rapid access processing” is employed to indicate dry-to-dry processing of a radiographic element in 45 seconds or less. That is, 45 seconds or less elapse from the time a dry imagewise exposed radiographic element enters a wet processor until it emerges as a dry fully processed element.
In all references to silver halide grains and emulsions containing two or more halides, the halides are named in order of ascending concentrations.
The “aspect ratio” of a silver halide grain is the ratio of its equivalent circular diameter (ECD) to its thickness. The ECD of a grain is the diameter of a circle having an area equal to the projected area of the grain.
The “coefficient of variation” (COV) of silver halide grain size (ECD) is defined as 100 times the standard deviation of grain ECD divided by mean grain ECD.
The term “tabular grain” refers to a silver halide grain having two parallel crystal faces that are clearly larger than any remaining crystal faces and an aspect ratio of at least 2.
The term “tabular grain emulsion” refers to an emulsion in which tabular grains account for greater than 50% of total grain projected area.
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