Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-03-27
2001-10-23
Chea, Thorl (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S577000, C430S580000, C430S584000, C430S588000, C430S593000, C430S594000, C430S599000, C430S600000, C430S607000, C430S610000, C430S613000
Reexamination Certificate
active
06306570
ABSTRACT:
These application are related to the following commonly assigned copending U.S. Patent applications:
Ser. No. 08/740,536 filed Oct. 30, 1996, which is a continuation-in-part of Ser. No. 08/592,106 filed Jan. 26, 1996;
Ser. No. 08/739,911 filed Oct. 30, 1996, which is a continuation-in-part of Ser. No. 08/592,166 filed Jan. 26, 1996;
Ser. No. 08/39,921 filed Oct. 30, 1996, which is a continuation-in-part of Ser. No. 08/592,826 filed Jan. 26, 1996;
Ser. No. 08/900,694 filed Jul. 25, 1997, and Ser. No. 08/900,956 filed Jul. 25, 1997
The entire disclosures of these applications are incorporated herein by reference.
FIELD OF THE INVENTION
This invention relates to a photographic element comprising at least one light sensitive silver halide emulsion layer which has enhanced photographic sensitivity.
BACKGROUND OF THE INVENTION
A variety of techniques have been used to improve the light-sensitivity of photographic silver halide materials.
Chemical sensitizing agents have been used to enhance the intrinsic sensitivity of silver halide. Conventional chemical sensitizing agents include various sulfur, gold, and group VIII metal compounds.
Spectral sensitizing agents, such as cyanine and other polymethine dyes, have been used alone, or in combination, to impart spectral sensitivity to emulsions in specific wavelength regions. These sensitizing dyes function by absorbing long wavelength light that is essentially unabsorbed by the silver halide emulsion and using the energy of that light to cause latent image formation in the silver halide.
Many attempts have been made to further increase the spectral sensitivity of silver halide materials. One method is to increase the amount of light captured by the spectral sensitizing agent by increasing the amount of spectral sensitizing agent added to the emulsion. However, a pronounced decrease in photographic sensitivity is obtained if more than an optimum amount of dye is added to the emulsion. This phenomenon is known as dye desensitization and involves sensitivity loss in both the spectral region wherein the sensitizing dye absorbs light, and in the light sensitive region intrinsic to silver halide. Dye desensitization has been described in The Theory of the Photographic Process, Fourth Edition, T. H. James, Editor, pages 265-266, (Macmillan, 1977).
It is also known that the spectral sensitivity found for certain sensitizing dyes can be dramatically enhanced by the combination with a second, usually colorless organic compound that itself displays no spectral sensitization effect. This is known as the supersensitizing effect.
Examples of compounds which are conventionally known to enhance spectral sensitivity include sulfonic acid derivatives described in U.S. Pat. Nos. 2,937,089 and 3,706,567, triazine compounds described in U.S. Pat. Nos. 2,875,058 and 3,695,888, mercapto compounds described in U.S. Pat. No. 3,457,078, thiourea compounds described in U.S. Pat. No. 3,458,318, pyrimidine derivatives described in U.S. Pat. No. 3,615,632, dihydropyridine compounds described in U.S. Pat. No. 5,192,654, aminothiatriazoles as described in U.S. Pat. No. 5,306,612 and hydrazines as described in U.S. Pat. Nos. 2,419,975, 5,459,052 and 4,971,890 and European Patent Application No. 554,856 A1. The sensitivity increases obtained with these compounds generally are small, and many of these compounds have the disadvantage that they have the undesirable effect of deteriorating the stability of the emulsion or increasing fog.
Various electron donating compounds have also been used to improve spectral sensitivity of silver halide materials. U.S. Pat. No. 3,695,588 discloses that the electron donor ascorbic acid can be used in combination with a specific tricarbocyanine dye to enhance sensitivity in the infrared region. The use of ascorbic acid to give spectral sensitivity improvements when used in combination with specific cyanine and merocyanine dyes is also described in U.S. Pat. No. 3,809,561, British Patent No. 1,255,084, and British Patent No. 1,064,193. U.S. Pat. No. 4,897,343 discloses an improvement that decreases dye desensitization by the use of the combination of ascorbic acid, a metal sulfite compound, and a spectral sensitizing dye.
Electron-donating compounds that are convalently attached to a sensitizing dye or a silver-halide adsorptive group have also been used as supersensitizing agents. U.S. Pat. Nos. 5,436,121 and 5,478,719 disclose sensitivity improvements with the use of compounds containing electron-donating styryl bases attached to monomethine dyes. Spectral sensitivity improvements are also described in U.S. Pat. No. 4,607,006 for compounds containing an electron-donative group derived from a phenothiazine, phenoxazine, carbazole, dibenzophenothiazine, ferrocene, tris(2,2′-bipyridyl)ruthenium, or a triarylamine skeleton which are connected to a silver halide adsorptive group. However, most of these latter compounds have no silver halide sensitizing effect of their own and provide only minus-blue sensitivity improvements when used in combination with a sensitizing dye.
PROBLEM TO BE SOLVED BY THE INVENTION
There is a continuing need for materials which, when added to photographic emulsions, increase their sensitivity. Ideally such materials should be useable with a wide range of emulsion types, their activity should be controllable and they should not increase fog beyond acceptable limits. This invention provides such materials.
SUMMARY OF THE INVENTION
Commonly assigned, co-pending application Ser. No. 08/740,536, filed Oct. 30, 1996, the entire disclosure of which is incorporated herein by reference, discloses a new class of organic electron donating compounds that, when incorporated into a silver halide emulsion, provide a sensitizing effect alone or in combination with dyes. These compounds donate at least one electron and are fragmentable, i.e., they undergo a bond cleavage reaction other than deprotonation. Commonly assigned, co-pending applications Ser. No. 08/739,911 and Ser. No. 08/739,921 both filed Oct. 30, 1996, the entire disclosures of both these applications are incorporated herein by reference, disclose the attachment of such fragmentable electron donors to sensitizing dyes and other silver halide adsorptive groups. The attachment of the fragmentable electron donors to the sensitizing dyes and other silver halide adsorptive groups is accomplished by a covalent bond comprising an organic linking group that contains at least one C, N, S, or O atom.
We have now discovered that fragmentable electron donors that contain a silver halide adsorptive group or a sensitizing dye moiety directly attached to the fragmentable electron donor moiety improve the sensitivity of photographic emulsions with the added advantage of increased emulsion efficiency at relatively low concentrations.
In accordance with this invention, a silver halide emulsion layer of a photographic element is sensitized with a fragmentable electron donor moiety that upon donating an electron, undergoes a bond cleavage reaction other than deprotonation. The term “sensitization” is used in this patent application to mean an increase in the photographic response of the silver halide emulsion layer of a photographic element. The term “sensitizer” is used to mean a compound that provides sensitization when present in a silver halide emulsion layer.
One aspect of this invention comprises a photographic element comprising at least one silver halide emulsion layer in which the silver halide is sensitized with a compound of the formula:
wherein A is a silver halide adsorptive group that contains at least one atom of N, S, P, Se, or Te that promotes adsorption to silver halide, and Z is a light absorbing group including for example cyanine dyes, complex cyanine dyes, merocyanine dyes, complex merocyanine dyes, homopolar cyanine dyes, styryl dyes, oxonol dyes, hemioxonol dyes, and hemicyanine dyes, k is 1 or 2, and XY is a fragmentable electron donor moiety in which X is an electron donor group and Y is a leaving group other than hydrogen, and wherein:
1) XY has an oxid
Adin Anthony
Farid Samir Y.
Godleski Stephen A.
Gould Ian R.
Lenhard Jerome R.
Chea Thorl
Eastman Kodak Company
Rice Edith A.
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