EP0506876A1 - Super-high contrast silver halide material - Google Patents

Abstract

A silver halide photographic material and a method of processing the photographic material to form a highly contrasted negative image are subject of the invention. Photographic material includes a silver halide grain sensitive to radiation capable of forming a latent surface image, a binder, an amount improving the spot quality of a hydrazine or hydrazide compound and an amount effective to decrease the gray effects of a compound of formula (II), where R'1 is selected from the group consisting of benzothiazole, quinoline, indolenine, nitrobenzothiazole, benzotriazole and rhodanine, each of these compounds being able to be substituted or unsubstituted, and m is an integer between 0 and 6 inclusive.

Description

SUPER-HIGH CONTRAST SILVER HALIDE MATERIAL

FIELD OF THE INVENTION

This invention relates to high-contrast silver halide photographic materials for use in the field of graphic arts and to a process for reducing black spots ("pepper") in exposed photographic materials of the foregoing type.

BACKGROUND OF THE INVENTION

In the field of graphic arts, an image-forming system providing a super-high contrast photographic characteristic, especially one having a sensitivity ("gamma") of 10 or more, is required for satisfactory reproduction of continuous tone images or line images by dot images. For this purpose, a specific developer called a lith-type developer is generally used. The lith developer contains, as a developing agent, hydroquinone and, as a preservative, a sulfite usually in the form of an adduct with formaldehyde at a concentration of not more than 0.1 mol/l, thereby preventing deterioration of the infectious development ability of the developing agent. The lith developer has a serious disadvantage in that it is very susceptible to air oxidation and cannot withstand use for a period of time exceeding 3 days. Increasing the sulfite content of the developer improves its useful life but deteriorates its high-contrast development characteristics.

Known ways to obtain equivalent or substantially equivalent high-contrast photographic characteristics with a stable developer include the use of hydrazine or hydrazide derivatives as described for example in U.S. Patent Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,211,857 and 4,243,739 all incorporated by reference in their entirety. Use of hydrazine or hydrazide compounds in image formation systems provides super-high contrast and high sensitivity, and also ensures greatly improved stability of the developer against air oxidation as compared to the conventional lith developer because hydrazine (and/or derivative) presence in the film or in the developer permits use of a higher sulfite ion concentration in the developer.

However, it has been found that use of hydrazine or hydrazide compounds in high-contrast image formation systems tends to cause black silver spots (also called "black pepper" or simply "pepper") on non-image area (i.e. in areas of no exposure), for example between dots. This phenomenon becomes particularly conspicuous when the sulfite ion content in a developer is decreased or the pH of a developer increases, e.g., due to fatigue of the developer, and causes significant impairment of photographic quality.

Various attempts have hitherto been made to eliminate the problem of black spots, but whatever ad hoc improvement was achieved was frequently accompanied by reduction in sensitivity and gamma. For example, use of several hydrazides disclosed in U.S. Patent No. 4,686,167 (incorporated by reference in its entirety) describes several hydrazides which, when used in photographic emulsions, produce very good results including favorable pepper ratings. However, no general applicability means has been proposed for solving the problem of black spots without substantially hindering the ability of the above- described hydrazine or hydrazide compounds to increase sensitivity and contrast, especially as measured by dot quality. Moreover, although the hydrazides of U.S. Patent No. 4,686,167 produce low pepper when processed in fresh developer, the pepper increases upon processing in exhausted oxidized or inhibitor-contaminated developer. It is therefore desirable to provide a method for enhancing the performance of photographic materials by substantially reducing or eliminating pepper over a wide processing latitude (i.e. processing solution quality and age) essentially without affecting the contrast and sensitivity properties of the processed photographic material.

U.S. Patent No. 4,851,321 issued 7/25/889 to Takagi discloses hydrazide-containing, low-sensitivity, high-contrast photographic materials in which sensitivity (and pepper) has been lowered by use of a development restrainer. Such restrainers are said to ordinarily also lower contrast. According to this patent, contrast is not lowered because the photographic material also contains a contrast-enhancing compound. The hydrazides specifically contemplated are formyl phenyl hydrazides with various substituents and other function- alities appended to the phenyl ring. The restrainers con- templated ("organic desensitizers") are compounds having a positive polarographic half-wave potential (Col. 24:57-65) and are represented by formulas disclosed at Col. 25-26. Specific restrainer examples are disclosed at Col. 27-31 and include

XI-1 2-[4,6 dinitrophenylthioether]-3-[benzene carboxylic acid]-imidazole,

XI-3 2-[4,6 dinitrophenylthioether]-3-[benzene sulfonic acid]-benzeimidazole,

XII-1 5-[p nitrobenzelidine]-3-[carboxymethyl] rhodanine, and

XIII-6 3-[m-nitrobenzelidene] rhodanine.

The amounts of restrainer range between 10^-8 and 10^{- 4} mol/m² (using 3.8 g Ag/m²) (Col. 31:59-62).

All of the Takagi photographic materials must contain a contrast-enhancing compound and are intended to have low sensitivity. Thus, Takagi does not provide a solution to the pepper problem of a high-sensitivity, high-contrast photographic material.

U.S. Patent No. 4,737,442 issued 4/12/88 to Yogihara discloses photographic materials containing a formyl phenyl hydrazide (or certain derivatives) as well as a restrainer of the type C_A-B wherein C_A is a blocking group capable of releasing during the development process a development restrainer or a precursor thereof regardless of the degree of exposure of the photographic material, and D is a restrainer or a precursor of a restrainer. Examples of restrainers include:

1-(2,4-dihydroxyphenyl)-5-mercaptotetrazole,

4-phenyl-5-methyl-3-mercaptotetrazole,

5-nitro-2-mercaptobenzimidazole,

2-mercaptobenzoxazole,

benzimidazole, and

6-nitroindazole.

The purpose of adding the restrainer is to avoid pepper. The amount of restrainer ranges between about 5.4x10^-4 to 1x10^-1 mole/mole Ag. The restrainers disclosed in the '442 patent are of the so-called "stabilizer" type which form strong silver salts and not of the "antifoggant" type. Stabilizer- type restrainers would decrease speed markedly more than antifoggant-type compounds when used with hydrazides, notably the hydrazides of the Formula I, below.

U.S. Patent No. 4,839,259 issued 6/13/89 to Sasaoka discloses hydrazide-containing photographic materials that are said to have simultaneously high sensitivity (gamma) and are free (or substantially free) of black spots or pepper. The pepper-free quality according to the patent is imparted by the use of dual developing agents in combination with a sulfite preservative and a pH in the range of 10.5-12.3. Optional ingredients include sensitizing dyes to improve emulsion sensitivity and/or various conventional antifoggant/stabilizers such as benzothiazoles, nitrobenzothiazoles, benzotriazoles, etc. (Col. 10:26-46). The antifoggants can be added to the developer.

U.S. Patent No. 4,789,618 issued 12/06/88 to Inoue et al discloses "black-spot" prone hydrazide-containing photographic materials in which black spots are said to be reduced or prevented by incorporation of an oxidizing agent (at 10^-5 - 1 mole/mole Ag) such as N-bromosuccinimide, hydrogen peroxide and its addition products, peroxy acid salts, peroxy complexes , ozone, etc. Conventional antifoggant stabilizers such as azoles, mercaptobenzothiazoles, nitrobenzotriazoles, etc. are listed as optional ingredients (Col. 11:4-24) for their conventional antifoggant/stabilizer purpose, as in Sasaoka.

U.S. Patent No. 4,785,587 issued to Kuwabara on 11/22/88 discloses hydrazine-containing photographic materials of high-sensitivity, and "very high" contrast in which pepper is said to be reduced by using two different silver halide emulsions which differ in mean grain size (within specified limits). Thiazoles and rhodanines are disclosed as (optional) sensitizers. Antifoggants/stabilizers such as thiazoles, etc. are also disclosed as optional ingredients (Col. 13:37-60).

European Application No. A2 306,833 of Fuji Photo Film published on 3/15/89 discloses photographic materials of high contrast and sensitivity containing a hydrazine derivative and two additional compounds;

a photographic restrainer bearing a late-absorbing group PWR (Time)_t - LA(1) and a tetrazole derivative. Antifog- gants/stabilizers are also added. Pepper reduction is attributable to the electron-withdrawal properties of the nitro group.

European Application No. A₁ 286,840 discloses allegedly reduced-pepper photographic materials comprising a hydrazine compound of the Formula:

R₁-SO₂-NH-Y-N—N-G-R₂

wherein G is CO, sulfonyl, sulfoxy, phosphoryl or N-substituted or unsubstituted iminomethylene. The pepper-reducing properties are attributable to the hydrazide.

None of the above-cited documents (the disclosure of which is incorporated by reference) disclose use of a small amount of antifoggant/stabilizer of Formula II to reduce pepper, nor a combination of the hydrazide of U.S. Patent No. 4,686,167 with a pepper-reducing effective amount of a stabilizer/antifoggant in high-contrast, high-sensitivity photographic materials.

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide a highly sensitive high-contrast silver halide photographic material which can be developed with a stable developer in the presence (in the photographic material or in the developer) of a hydrazine or hydrazide contrast-enhancing compound to obtain a super-high contrast image with substantial reduction or elimination of black spots.

Another object of this invention is to provide a method for reducing or eliminating black spots upon development of a silver halide photographic material which contains, or which is developed in a developer containing, a hydrazine or hydrazide compound and which yields a super-high contrast negative image.

The above objects can be accomplished by the incorporation in a photographic material or in its developer of a compound within Formula II below in an amount effective to reduce or eliminate black spot formation but not capable of substantially affecting sensitivity or contrast (i.e. not reduce sensitivity more than about 10% or speed more than about a quarterstop or decrease the value of gamma below 10). Preferably, use of this compound is made in a negative-working surface-latent image system (but the present invention is not limited to such systems). The Formula II compound is preferably incorporated in the photographic material, in at least one of the emulsion layer or in another (e.g. a hydrophilic colloid) layer coated on the photographic material support. Most preferably, the photographic material comprises the following: a support having provided thereon at least one silver halide emulsion layer, wherein said emulsion layer or another layer of the silver halide photographic material provided on the support contains at least one compound represented by the Formula I and also contains at least one compound of the Formula II. It is again emphasized, however, that the present invention is not limited to hydrazide derivatives of Formula I not to hydrazines or hydrazides present in the film. Formyl phenyl hydrazide could, for example, be used in the developer with a compound of Formula II in the film in accordance with the present invention.

A super-high contrast negative image is formed by a process comprising imagewise exposing a hydrazine- or hydrazide- containing photographic material (preferably a material containing a Formula I compound) to light and developing the exposed material with a developer containing a dihydroxybenzene derivative (as a developing agent), a benzotriazole antifoggant, a sulfite preservative and an effective amount of an amine compound.

Compounds of Formula I include: (Formula I) wherein:

X=-NR₅R₆, or -OR₇;

R₁ and R₂ are independently hydrogen and substituted or unsubstituted (i) alkyl, having up to 18 carbons; (ii) cycloalkyl; (iii) phenyl or naphthyl or (iv) aryl sulfonyl.

R₃ is hydrogen, phenyl or benzyl, the latter two substituted or unsubstituted, but if neither R₁ nor R₂ is hydrogen then R₃ is hydrogen.

R₄ is a substituted or unsubstituted divalent aromatic group.

R₅, R₆, and R₇ are independently hydrogen, substituted or unsubstituted (i) alkyl having up to 12 carbons; (ii) cycloalkyl; (iii) phenyl or naphthyl.

R₁ and R₃ or R₁ and R₂ can be linked to form a heterocyclic ring system with the ring containing three to ten atoms.

R₅ and R₆ can be linked to form a heterocyclic ring system with the ring containing 3-10 atoms.

Y is an oxygen or sulfur atom; n=0,1, but if Y is sulfur then n=1.

Suitable substituents include without limitation halogen, hydroxy, alkoxy, amino, alkylamino, aryl, arylamino, cyano, acylamino. The substituents themselves may be further substituted.

Compounds of Formula II, include compounds containing one moiety selected from the group consisting of benzothiazoles, quinolines, indolenine benzotriazoles, and rhodanines having one or more nitro groups attached to a benzene nucleus, which is either a part of the heterocyclic compound or is attached to it through a doubly-bonded carbon- to-carbon chain. The quaternary salts (such as ammonium, triethylamine, piperidine and alkali metal salts, preferably methanol-soluble) of the benzothiazoles, quinolines and indolenines are also suitable. Compounds of Formula II are defined as follows:

wherein m is an integer between 0 and 6 inclusive; R₁ is selected from the group consisting of benzothiazole, quinoline, indolenine, nitrobenzothiazole, benzotriazole and rhodanine, each of which may be unsubstituted or substituted by, e.g. halogen, hydroxy, alkoxy, aryl, amino, arylamine, sulfuric acid, carboxylic acid, phenyl, etc., or fused to the nitrobenzene nucleus.

Preferably, R₁ is substituted by hydrogen or carboxy and m is 1. Furthermore, the substituents in R₁ are preferably in the 3-position if the ring S is 1 and numbering is clockwise.

DETAILED DESCRIPTION OF THE INVENTION

Several of the compounds represented by Formula II according to the present invention were previously known and used as photographic stabilizers/antifoggants (in amounts generally ranging between about 10^-2 and about 1 moles/mole Ag) to improve the speed constancy of photographic emulsions. Unexpectedly, in experiments testing the ability of such compounds to improve speed stability of silver halide emulsions containing hydrazide derivatives, especially hydrazide derivatives of the Formula I type, it was discovered that such compounds also reduced and/or eliminated "pepper" in a con- centration-dependent manner but at very small concentrations. Most unexpectedly, at such small concentration, such compounds remarkably reduce or eliminate black spots without inhibiting the ability of the compound represented by the Formula I to increase sensitivity and contrast. The range of substantial pepper reduction effectiveness of such compounds is generally between about 5x10^-8 and about 1x10^-3 moles/mole Ag and preferably about 10^-5 to about 10^-4 moles/mole Ag. (The present emulsion is preferably used at 3.6 g Ag/m².)

The compound of the Formula I or another contrast- enhancing hydrazide and the compound of the Formula II are preferably incorporated into the same layer, but may also be incorporated into different layers or the compound of Formula I can be used in the developing solution.

In the general Formula I described above, R₁ preferably represents a hydrogen atom, an unsubstituted or substitute alkyl group (suitable preferred substituents include without limitation alkyl, cyano, halo, or alkoxy), a substituted or unsubstituted cycloalkyl group or a substituted or unsubstituted arylsulfonyl group. The total number of carbon atoms in R₁ can be up to 18 but preferably, should be less than 12. Most preferably, R₁ is unsubstituted alkyl or cycloalkyl containing 1-6 carbon atoms.

R₂ is independently chosen from the group representing R₁; preferably, however, the total number of carbon atoms between R₁ and R₂ should not exceed 12.

R₃ preferably represents a hydrogen atom, an unsubstituted or substituted benzyl group (suitable preferred substituents include without limitation alkoxy, halo or alkyl).

If neither R₁ nor R₂ is hydrogen, then R₃ must be hydrogen. Most preferably, R₃ is hydrogen.

In the preferred case, Y is a sulfur atom. If Y is a sulfur atom then n=1. In the most preferred case n=1.

R₄ preferably represents either an unsubstituted or substituted divalent aromatic group. Suitable substituents include without limitation alkyl, alkoxy, halo, or acylamino functionalities. In the most preferred case R₄ is phenylene with the thioamide or amido group in the ortho- or para-posi tion relative to the hydrazido group. Furthermore, it is preferred that any suitable substituent as described herein be attached at a remaining, unoccupied ortho- or para-position relative to the hydrazine group.

R₅ preferably represents either a hydrogen atom, an unsubstituted or substituted alkyl group (suitable preferred substituents include hydroxy, halo, alkoxy, alkylamino, acylamino, amino and aryl such as phenyl), a cycloalkyl group, an unsubstituted or substituted aryl group (suitable preferred substituents include alkyl, cyano, halo or alkoxy) or an unsubstituted or substituted amine. The total number of carbon atoms in R₅ should be up to 12. Preferably, R₅ is alkyl, cycloalkyl, dialkylaminoalkyl or acylaminoalkyl each containing 1-6 carbon atoms.

R₆ and R₇ are independently chosen from the group representing R₅; preferably, however, the total number of carbon atoms between R₅ and R₆ should not exceed 12. In addition, R₅ and R₆ preferably do not contain amino functionalities that are directly linked to the nitrogen atom of X.

Furthermore, R₅ and R₆ can be linked to form a heterocyclic ring system with the ring containing 3-10 atoms.

Additionally, either R₁ and R₃ or R₁ and R₂ can be linked to form a heterocyclic ring system with the ring containing 3-10 atoms.

The preferred compounds represented by the general Formula I are those represented by the general Formula (IA). (Formula IA)

In this formula, Y = S or 0; Z = 0 or HN; R₈ and R₉ have the same meaning as R₁ and R₅ respectively for the above described general Formula I. Most preferably R₈ is ethyl, n-butyl or cyclohexyl, R₉ is hydrogen, methyl, ethyl, dimethylaminoethyl or acetylaminoethyl, Z = HN, and Y = S.

Specific examples of the compounds represented by the general Formula I are given below in Table I, but the present invention is not limited to these examples. In fact, the present invention broadly involves the use or incorporation of a Formula II compound, in an amount sufficient to reduce or eliminate pepper, in any high-contrast image forming system (photographic material and/or developer) containing a contrast- enhancing amount of a hydrazine or hydrazide compound.

The amount of the compound of Formula I added to the silver halide emulsion layer or to one or more hydrophilic colloidal layer(s) is such that the compound enhances contrast but does not appreciably function as a developer. Typically, amounts from about 10^-8 to about 5x10^-3 moles/mole Ag and preferably from about 10^-5 to about 5x10^-4 mole/mole Ag are used.

In the above described Formula II the electron-accepting compounds are compounds having one or more nitro groups attached to a benzene nucleus which is either a part of the heterocyclic compound or is attached to it through a doubly bonded carbon-to-carbon chain as described in US Patent 2,541,472 (incorporated by reference). Specific but non-limiting examples of Formula II according to our present invention are shown below. Generally suitable amounts of the Formula II compound are within the range of about 10^-8 to about 10^-3 moles/mole Ag, with about 1x10^-5 to about 4x10^-4 being preferred. This is different from the stabilizer effective amounts, which as stated above, are much higher in the system employing Formula I hydrazides. In other systems (e.g. using different hydrazides or different silver halide emulsions, etc.) the conventional stabilizing/antifoggant amounts may be different but the anti-pepper effective amounts are also anticipated to be much smaller. The anti-pepper effect will persist at higher amounts but as the amount of Formula II compounds approaches or reaches the antifoggant/stabilizer effective range, sensitivity will (begin to) be affected, which is undesirable in the present invention. Table I below lists compounds within Formula II as an illustration. It should be understood that any combination of the Table II groups R and left and right moiety substituents are fully within the scope of Formula II and the present invention, not only individually but also generally (e.g. "methyl" shall be an illustration of alkyl, etc.).

II-1

II-2

II-3

II-4

II-5

II-6

II-7 II-8

II-9

II-10

II-11

II-12

II-13

II-14 II-15

II-16

II-17

II-18

II-19 II-20

II-21

II-22

II-23

II-24 II-25

As stated above, the pepper-reducing amounts of the Formula II compounds should not be higher than about 10^-3 moles/mole Ag in order to avoid desensitization and loss of contrast, the latter due to interference with the contrast- enhancing function of the (e.g. Formula I) hydrazide.

The compounds of Formula I and II can be incorporated in the photographic element by well-known techniques used for the incorporation of additives to photographic emulsions or elements. The compounds are typically dissolved in a solvent selected from organic solvents compatible with water, such as alcohols, glycols, ketones, esters, amides, and the like which exert no adverse influences on photographic characteristics, and the solution is added to the photographic element. Preferred solvents include dimethylformamide (DMF), dimethylsulfoxide (DMSO) and N-methyl-2-pyrrolidinone (NMP).

Alternatively, the compound of Formula I and II can be added to an emulsion in a dispersion by known methods used when water-insoluble (so-called "oil soluble") couplers are added to emulsions. Preferred oils include N-butyl acetanilide, N-methyl formanilide and N,N-diethyl-m-toluamide. These oils are commercially available. Ultrasound can be employed to dissolve (more precisely finely disperse) marginally soluble ethanedioic acid hydrazides. These solutions or dispersions can be added to the photographic emulsion at any stage subsequent to the emulsion precipitation and washing steps. Preferably these agents should be added during chemical ripening or just prior to coating.

Gelatin is advantageously used as a binder or protective colloid in the photographic emulsion, but other hydrophilic colloids can also be used. For example, gelatin derivatives, graft polymers of gelatin with other high molecular weight materials, proteins such as albumin or casein; cellulose derivatives such as hydroxyethyl cellulose, carboxymethyl cellulose or cellulose sulfate, saccharide derivatives such as sodium alginate or starch derivatives, polyglycoside dextrans and various synthetic hydrophilic high molecular weight materials such as homopolymers or copolymers of e.g., polyvinyl alcohol, polyvinyl alcohol (partial acetal), poly-N-vinyl pyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinyl imidazole, polyvinyl pyrazole, etc., can also be used. Gelatin is preferred. All these materials are well-known and commercially available.

Lime-processed gelatin and acid-processed gelatin can alternatively be used as the gelatin. Hydrolyzed or enzymedecomposed gelatin can also be used. Suitable gelatin derivatives are prepared by reacting gelatin with various compounds such as acid halides, acid anhydrides, isocyanates, bromoacetic acid, alkanesulfones, vinylsulfonamides, maleinimide compounds, polyalkylene oxides or epoxy compounds and, preferably, with phthalic anhydride or succinic anhydride. Specific examples of these gelatin derivatives are described in e.g., U.S. Patent Nos. 2,614,928, 3,132,945, 3,186,846 and 1,005,784, all incorporated by reference.

Examples of suitable gelatin graft polymers include those prepared by grafting a homopolymer or a copolymer of a vinylic monomer such as acrylic acid, methacrylic acid, the derivatives thereof (such as the esters or the amides thereof), acrylonitrile or styrene to gelatin. In particular, graft polymers prepared from polymers which are compatible with gelatin to some degree, such as those of acrylic acid, methacrylamide or a hydroxyalkyl methacrylate which are preferred. Examples of those polymers are described in, e.g., U.S. Patent Nos. 2,763,625, 2,831,767 and 2,956,884. Typical synthetic hydrophilic high molecular weight materials are described in, e.g., German Patent Application (OLS) 2,312,708, U.S. Patent Nos. 3,620,751 and 3,879,205, all incorporated by reference.

The photographic emulsion used in this invention can be prepared using the well-known methods described in, e.g., P.

Glafkides, Chimie et Physique Photographique, Paul Montel, Paris

(1967), G. F. Duffin, Photographic Emulsion Chemistry, The Focal Press, London (1966), V. L. Zelikman et al., Making and Coating Photographic Emulsions, the Focal Press, London (1964), all incorporated by reference. These methods include the acid method, the neutral method, the ammonia method and others. Moreover, a soluble silver salt can be reacted with a soluble halogen salt using any of the single jet method, the double jet method and a combination thereof. The well-known method of forming grains in the presence of an excess of silver ions (the so-called "reverse mixing method") can also be used. The "controlled double jet method" (also called "controlled diffusion method") is preferred. According to this method, the pAg of the liquid phase (in which the silver halide is to be produced) is kept constant. This method can provide silver halide emulsions having a regular crystal form and an almost uniform grain size.

The silver halide grains in the photographic emulsion used in this invention can have a relatively wide grain size distribution, but a narrow grain size distribution is preferred. In particular, the size of the silver halide grains amounting to 90% of the total, based on the weight or number of the grains, is preferably within + 40% of the average grain size (such an emulsion is usually called a monodispersed emulsion). Grain size can be controlled by known techniques such as are disclosed in, e.g. U.S. Patents No. 3,271,157; No. 3,704,130; No. 3,574,628; No. 4,276,374 and No. 4,297,439 and in Research Disclosures RD No. 17643, December 1978 and 18716, November 1979, all incorporated by reference.

The individual reactants can be added to the reaction vessel through surface or sub-surface delivery tubes by gravity feed or .by delivery apparatus for maintaining control of the pH and/or pAg of the reaction vessel contents, as illustrated by Culhane et al U.S. Patent No. 3,821,002, Oliver U.S. Patent No. 3,031,304 all incorporated by reference. In order to obtain rapid distribution of the reactants within the reaction vessel, specially constructed mixing devices can be employed, as illustrated by Audran U.S. Patent No. 2,996,287, McCrossen et al U.S. Patent No. 3,342,605, Frame et al U.S. Patent No. 3,415,650, Porter et al U.S. Patent No. 3,785,777, Saito et al German OLS No. 2,556,885 and Sato et al German OLS No. 2,555,364 all incorporated by reference. An enclosed reaction vessel can be employed to receive and mix reactants upstream of the main reaction vessel, as illustrated by Forster et al U.S. Patent No. 3,897,935 and Posse et al U.S. Patent No. 3,790,386, all incorporated by reference.

The grain size distribution of the silver halide emulsions can be controlled by silver halide grain separation techniques or by blending silver halide emulsions of differing grain sizes. The emulsions can include ammoniacal emulsions, as illustrated by Glafkides, Photographic Chemistry, Vol. 1, Fountain Press, London, 1958, pp. 365-368 and pp. 301-304; thiocyanate ripened emulsions, as illustrated by Illingsworth U.S. Patent No. 3,320,069; thioether ripened emulsions, as illustrated by McBride U.S. Patent No. 3,271,157, Jones U.S. Patent No. 3,574,628 and Rosecrants et al U.S. Patent No. 3,737,313 or emulsions containing weak silver halide solvents, such as ammonium salts, as illustrated by Perignon U.S. Patent No. 3,784,381 and Research Disclosure, Vol. 134, June 1975, Item 13452 all incorporated by reference. The method using ammonium salts is preferred.

The crystal form of the silver halide grains in the photographic emulsion may be regular (such as cubic or octahedral) or irregular (such as spherical or plate-like) or it may be a composite of these forms. The grains may comprise mixed grains having various crystal forms.

The interior and the surface layer of the silver halide grain may be different or the grains may be uniform throughout. During the process of the formation or physical ripening of the grains, cadmium salts, zinc salts, lead salts, thallium salts, rhodium salts or complex salts thereof, iron salts or iron complex salts, and the like can be present, as can mixtures thereof. Preferred as such dopants, are rhodium or iridium salts or mixtures thereof.

Two or more of silver halide emulsions which are separately prepared can be mixed and then used, if desired.

After the formation of the precipitates or after physical ripening, the soluble salts are usually removed from the emulsion. For this purpose, the well known noodle washing method may be used. Alternatively, the flocculation method may be used. This method employs an inorganic salt having a polyvalent anion such as sodium sulfate, an anionic surface active agent, an anionic polymer (such as polystyrene sulfonic acid) or a gelatin derivative (such as an aliphatic acylated gelatin, an aromatic acylated gelatin or an aromatic carbamoylated gelatin). The removal of the soluble salts may be omitted, if desired.

Although the silver halide emulsions used in the present invention do not need to be chemically sensitized, chemically sensitized silver halide emulsions are preferred. Processes for chemical sensitization of the silver halide emulsions which can be used include known sulfur sensitization, reduction sensitization and noble metal sensitization processes. In addition to sulfur sensitization, selenium, tellurium, rhenium or phosphorus sensitizers or combinations of these sensitizers can be used. Chemical ripening can be performed at pAg levels of from 5 to 10, pH levels of from 5 to 8 and at temperatures from 30° to 80ºC.

These processes are described in references such as P. Glafkides, Chimie et Physique Photographique, Paul Montel, Paris (1967) or Zelikmann, Making and Coating Photographic Emulsions, The Focal Press, London (1964) or H. Frieser, Die Gundlagen der Photographischen Prozesse mit Silberhalogeniden, Akademische Verlagsgesellschaft (1968). The disclosure of these references is incorporated by reference. In the noble metal sensitization processes, a gold sensitization process is a typical process where gold compounds or gold complexes are used.

Complexes of noble group VIII metals other than gold, such as those of platinum, palladium, osmium, rhodium or iridium, etc. can also be used as chemical sensitizers. A reduction sensitization process may be used if the process does not generate fog to a degree which causes practical difficulties (with or without the use of known antifoggents). A particularly preferred chemical sensitization process for the present invention is the use of a sulfur sensitization process. Examples of sulfur sensitizing agents which can be used include not only sulfur compounds present in the gelatin per se, but also various sulfur compounds such as thiosulfates, thioureas, thiazoles or rhodanines, etc. Examples of suitable sulfur compounds are described in U.S. Patent Nos. 1,574,994, 2,410,689, 2,278,947, 2,728,668 and 3,656,955, all incorporated by reference. Typical examples of reduction-sensitizing agents include stannous salts, amines, formamidine sulfinic acid and silane compounds, methyldichlorosilane, hydrazine derivatives, boranes such as aminoboranes, thiourea dioxide, hydrogen, and other boron hydrides such as cyanoborohydrides. Reduction sensitization can also be obtained by low pAg (less than 5) or high pH (greater than 8) treatment, as is well-known in the art.

Specifically contemplated is the combined use of several of the aforementioned chemical ripening techniques; in particular gold-sulfur sensitization combinations are highly preferred.

A photographic material used in this invention may contain an antifoggant. Examples of antifoggants which can be advantageously used for the photographic material used in this invention are 1,2,4-triazole compounds substituted with a mercapto group at the 3-position, benzotriazole compounds, 2-mercaptobenzimidazole compounds (which do not contain a nitro group), 2-mercaptopyrimidines, 2-mercaptothiazoles, 2-mercaptobenzothiazoles, benzothiazolium compounds (such as N-alkylbenzothiazolium halides, nitrobenzindazole, substituted triazaindolizines (tetraazaindenes) or N-allylbenzothiazolium halides), and 2-mercapto-1,3,4-thiazoles. Antifoggants which are not effective when used alone, such a 6-nitrobenzimidazole, however, can be used in combination with advantageous antifoggants.

It has been observed that both fog reduction and an increase in contrast are obtainable by employing benzotriazole antifoggants. When the benzotriazole is located in the photographic element concentrations of 10^-4 to 10^-1, preferably 10^-3 to 3x10^-2, mole per mole of silver are employed.

Useful benzotriazoles can be chosen from among conventional benzotriazole antifoggants, such as those disclosed by Land U.S. Patent No. 2,704,721 and Rogers et al U.S. Patent No. 3,265,498, both incorporated by reference. The preferred benzotriazoles for use in this invention are benzotriazole (that is, the unsubstituted benzotriazole compound), halo-substituted benzotriazoles (e.g., 5-chlorobenzotriazole, 4-bromobenzotriazole and 4-chlorobenzotriazole) and alkyl-substituted benzotriazoles wherein the alkyl moiety contains from about 1 to 12 carbon atoms (e.g., 5-methylbenzotriazole). 5-methylbenzotriazole is most preferred. The use of 5-methylbenzotriazole as an antifoggant is illustrated by Baldassari et al U.S. Patent No. 3,925,086, incorporated by reference.

The effect of this invention is enhanced even more by adding a small amount of an iodide salt (such as potassium iodide) to the emulsion after the formation of the grains, before chemical ripening, after chemical ripening or before coating. A suitable amount of iodide added ranges from about 10 -4 to about

10^-2 mol/mol Ag. Larger amounts are not harmful but are unnecessary. Smaller amounts may still be effective in isolated cases but as a general rule amounts within the aforementioned range should be used.

The photographic emulsions used in this invention can be used for camera exposure. To insure good safelight protection UV absorbing compounds are used, such as those in U.S. Patents Nos. 3,533,794; 3,314,794 and 3,352,681, all incorporated by reference. Safelight dyes such as oxonols, hemioxonols, styryl dyes, merocyanine dyes and aso dyes can also be used, as long as such dyes are easily removed or decolorized during processing (see US Patents Nos. 2,274,782; 2,956,879; 3,423,207; 3,976,661 and 3,384,487, all incorporated by reference). Desensitizing dyes (see, e.g. U.S. Patent No. 3,501,307, incorporated by reference) can also be used.

The present emulsion can be spectrally sensitized (e.g. to long blue, green, red or infrared) with at least one methinetype and/or other spectrally-sensitizing dye. Suitable sensitizing dyes include cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, hemicyanine dyes, styryl dyes and hemioxonol dyes. Particularly useful dyes are cyanine dyes, merocyanine dyes and complex merocyanine dyes. These dyes can contain, as a basic heterocyclic nucleus, any of the nuclei which are usually employed in cyanine dyes: a pyrroline nucleus, an oxazoline nucleus, a thiazoline nucleus, a pyrrole nucleus, an oxazole nucleus, a thiazole nucleus, a selenazole nucleus, an imidazole nucleus, a tetrazole nucleus, a pyridine nucleus and the like; one of the above-described nuclei condensed with an alicyclic hydrocarbon ring; and one of the above-described nuclei condensed with an aromatic hydrocarbon ring, such as an indolenine nucleus, a benzindolenine nucleus, an indole nucleus, a benzoxazole nucleus, a naphthoxazole nucleus, a benzothiazole nucleus, a naphthothiazole nucleus, a benzoselenazole nucleus, a benzimidazole nucleus and a quinoline nucleus. The carbon atoms of the above-described nuclei may be mono- di- or poly-substituted with such diverse substituents as alkyl, aryl, carboxy, sulfo, phenyl, alkoxy and halo, without limitation, and, optionally themselves further substituted.

The merocyanine dyes or complex merocyanine dyes can contain, as nucleus having a ketomethylene structure, a 5- to 6-membered heterocyclic nucleus such as a pyrazolin-5-one nucleus, a thiohydantoin nucleus, a 2-thiooxazolidin-2,4-dione nucleus, a thiazolidin-2,4-dione nucleus, a rhodanine nucleus or a thiobarbituric acid nucleus.

Useful sensitizing dyes include those described in, e.g., German Patent No. 929,080, U.S. Patent Nos. 2,231,658, 2,493,748, 2,503,776, 2,519,001, 2,912,329, 3,656,959, 3,672,897 and 3,694,217, and British Patent No. 1,242,588, all incorporated by reference. Preferred sensitizing dyes include dicarbocyanine derivatives and tricarbocyanine derivatives (most preferably symmetric) sensitizing within the range of about 680 to about 850 nm.

These sensitizing dyes may be used individually or as a combination. A combination of sensitizing dyes is often employed particularly for the purpose of supersensitization. Typical examples of such combinations are described in, e.g., U.S. Patent

Nos. 2,688,545, 2,977,229, 3,397,060, 3,522,052, 3,527,641, 3,617,293, 3,628,964, 3,666,480, 3,679,428, 3,703,377, 3,769,301, 3,814,609 and 3,837,862, and British Patent No. 1,344,281, all incorporated by reference. Preferred sensitizing dye combinations are mixtures of cyanine and merocyanine dyes that orthochromatically sensitive at wavelengths between 400 and 580 nm.

The sensitizing dyes may be present in the emulsion together with dyes which themselves do not have any spectral sensitizing effects but exhibit a supersensitizing effect when used in combination with sensitizing dyes, or with other materials which do not substantially absorb visible light but exhibit a supersensitizing effect when used in combination with sensitizing dyes. Examples of such materials are dyes, heterocyclic mercaptans, styryl bases, "Q" salts (e.g. quaternary ammonium salts) and high-molecular weight sulfonic acids such as stilbenes. More specifically, examples include stilbene such as aminostilbene compounds preferably substituted with a nitrogen-containing heterocyclic ring group (e.g., those described in U.S. Patent Nos. 2,933,390 and 3,635,721), aromatic organic acid formaldehyde condensates (e.g., those described in U.S. Patent No. 3,743,510), azaindene compounds, and the like, can be present. The combinations described in U.S. Patent Nos. 3,615,613, 3,615,641, 3,617,295 and 3,635,721 are particularly useful. (The disclosure of all patents mentioned in this paragraph is incorporated by reference.)

A water-soluble dye may be present in any of the hydrophilic colloid layers in the photographic light-sensitive materials used in this invention, for example, as a filter dye or for prevention of light scattering, or for antihalation. Examples of these dyes include oxonol dyes, hemioxonol dyes, styryl dyes, merocyanine dyes, cyanine dyes and azo dyes. Of these dyes, oxonol dyes, hemioxonol dyes and merocyanine dyes are particularly useful. Specific examples of dyes which can be used are those described in British Patent Nos. 584,609 and 1,177,429, and U.S. Patent Nos. 2,274,782, 2,533,472, 2,956,879, 3,148,187, 3,177,078, 3,247,127, 3,540,887, 3,575,704, 3,653,905 and 3,718,472, all incorporated by reference.

An inorganic or organic hardener may be present in any of the hydrophilic colloid layers in the light-sensitive material used in this invention. These hardeners include, for example, chromium salts (such as chrome alum or chromium acetate), aldehydes (such as formaldehyde, glyoxal or glutaraldehyde), N-methylol compounds (such as dimethylolurea or methyloldimethyl- hydantoin), dioxane derivatives (such as 2,3-dihydroxydioxane), active vinyl compounds (such as 1,3,5-triacryloyl-hexahydro-s-triazine or bis (vinylsulfonyl)methyl ether), active halogen compounds (such as 2,4-dichloro- 6-hydroxy-s-triazine), mucohalic acids (such as mucochloric acid or mucophenoxychloric acid), isooxazoles, dialdehyde starch, 2-chloro-6-hydroxytriazinylated gelatin and the like can be used individually or in combination. Specific examples- of these compounds are described, e.g., U.S. Patent Nos. 1,870,354, 2,080,019, 2,726,162, 3,870,013, 2,983,611, 2,992,109, 3,047,394, 3,057,723, 3,103,437, 3,321,313, 3,325,287, 3,362,827, 3,539,664 and 3,543,292, British Patent Nos. 676,628, 825,544 and 1,270,578, German Patent Nos. 872,153 and 1,090,427, all incorporated by reference. A preferred hardener is one that will not cause reduction-sensitization (formaldehyde, for example, should be avoided). An example of a preferred hardener is dichlorohydroxytriazine.

The light-sensitive material of this invention may contain various known surface active agents for various purposes, e.g., as a coating aid, for preventing the generation of static charges, improving slip characteristics, improving emulsion dispersion, preventing adhesion, improving photographic characteristics (e.g., accelerating development, increasing contrast, sensitization), etc.

Examples of suitable surfactants are: nonionic surface active agents such as saponin (steroids), alkylene oxide deriva- tives (such as polyethylene glycol, polyethylene glycol/polypropylene glycol condensates, polyethylene glycol alkyl or alkylaryl ethers, polyethylene glycol esters, polyethylene glycol sorbitan esters, polyalkylene glycol alkylamines or amides or silicone/polyethylene oxide adducts), glycidol derivatives (such as alkenylsuccinic acid polyglycerides or alkylphenol polyglycerides), aliphatic esters of polyhydric alcohols, alkyl esters of sucrose, urethanes or ethers; anionic surface active agents containing an acidic group such as a carboxy group, a sulfo group, a phospho group, a sulfuric acid ester group or a phosphoric acid ester group, such as triterpenoid type saponin, alkylcarboxylates, alkylsulfonates, alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkyl sulfuric acid esters, alkyl phosphoric acid esters, N-acyl-N-alkyltaurines, sulfosuccinates, sulfoalkylpolyoxyethylene alkylphenyl ethers or polyoxyethylene alkylphosphates; amphoteric surface active agents such as amino acids, aminoalkylsulfonic acids, aminoalkylsulfuric acid esters, aminoalkylphosphoric acid esters, alkylbetaines, amineimides or amine oxides; and cationic surface active agents such as alkylamine salts, aliphatic or aromatic quaternary ammonium salts, (such as pyridinium or imidazolium salts) or phosphonium or sulfonium salts containing an aliphatic or heterocyclic ring.

Specific examples of these surface active agents are those described in, e.g., U.S. Patent Nos. 2,240,472, 2,831,766, 3,158,484, 3,210,191, 3,294,540 and 3,507,660, British Patent Nos. 1,012,495, 1,022,878, 1,179,290 and 1,198,450, U.S. Patent Nos. 2,739,891, 2,823,123, 3,068,101, 3,415,649, 3,666,478 and 3,756,828, British Patent No. 1,397,218, U.S. Patent Nos. 3,133,816, 3,441,413, 3,475,174, 3,545,974, 3,726,683 and 3,843,368. Belgium Patent No. 731,126, British Patent Nos. 1,138,514, 1,159,825 and 1,374,780, U.S. Patent Nos. 2,271,623, 2,288,226, 2,944,900, 3,253,919, 3,671,247, 3,772,021, 3,589,906 and 3,754,924, all incorporated by reference. Specifically preferred is a mixture of saponin, nonionic surfactants such as aliphatic esters of polyhydric alcohols, and an anionic surfactant containing a sulfuric acid ester group.

The photographic emulsion used in this invention can contain a dispersion of a synthetic polymer which is insoluble or slightly soluble in water for the purpose of improving the dimensional stability, the development and the fixing and drying rates. Examples of polymers which can be used include polymers composed of one or more alkyl acrylates or methacrylates, alkoxyalkyl acrylates or methacrylates, glycidyl acrylates or methacrylates, acyl or methacrylamide, vinyl esters (for example, vinyl acetate), acrylonitrile, olefins and styrene, etc., and polymers comprising a combination of the above described monomers and acrylic acid, methacrylic acid, unsaturated dicarboxylic acids, hydroxyalkyl acrylates or methacrylates or styrenesulfonic acid, etc. For example, those compounds described in U.S. Patent

Nos. 2,376,005, 2,739,137, 2,853,457, 3,062,674, 3,411,911,

3,488,708, 3,525,620, 3,607,290, 3,635,715 and 3,645,740, and British Patent Nos. 1,186,699 and 1,307,373, all incorporated by reference, can be used. A suitable amount of the polymer ranges from about 20 to 80% by weight based on the total weight of the binders. Since high-contrast emulsions such as that used in this invention are suitable for the reproduction of line drawings and the dimensional stability is of importance for such a purpose, it is preferred to use the above-described polymer dispersion to be employed.

In addition to the components of the photographic emulsions and other hydrophilic colloid layers described above, it is appreciated that other conventional agents compatible with obtaining relatively high contrast images can be present. For example, the photographic elements can contain developing agents (described below in connection with the processing steps), development modifiers, plasticizers and lubricants, coating aids, antistatic materials, matting agents, brighteners and color materials, these conventional materials being illustrated in Paragraphs V, VIII, XI, XII and XVI of Research Disclosure, December 1978 Item 17643, all incorporated by reference. Preferably, the photographic emulsion also contains anti-ageing agents, useful to prolong the shelf life of the emulsion. Suitable anti-ageing agents (especially for rhodium-doped emulsions) include polyhydroxyspiro-bis-indane as disclosed in U.S. Patent No. 4,346,167 of E. Imatomi and preferably phenidone (up to 2 g/kg of emulsion) as disclosed in U.S. Patent No. 2,751,297 of G. Hood.

In forming photographic elements, the layers can be applied on photographic supports by various procedures, including immersion or dip coating, roller coating, reverse roll coating, air knife coating, doctor blade coating, gravure coating, spray coating, extrusion coating, bead coating, stretch-flow coating and curtain coating. High speed coating using a pressure differential is illustrated by Beguin U.S. Patent No. 2,681,294. Controlled variation in the pressure differential to facilitate coating starts is illustrated by Johnson U.S. Patent No. 3,220,877 and to minimize splicing disruptions is illustrated by Fowble U.S. Patent No. 3,916,043. Coating at reduced pressures to accelerate drying is illustrated by Beck U.S. Patent No. 2,815,307. Very high speed curtain coating is illustrated by Greiller U.S. Patent No. 3,632,374. Two or more layers can be coated simultaneously, as illustrated by Russell U.S. Patent No. 2,761,791, Wynn U.S. Patent No. 2,941,898, Miller et al U.S. Patent No. 3,206,323, Bacon et al U.S. Patent No. 3,425,857, Hughes U.S. Patent No. 3,508,947, Herzhoff et al U.K. Patent No. 1,208,809, Herzhoff et al U.S. Patent No. 3,645,773 and Dittman et al U.S. Patent No. 4,001,024. In simultaneous multilayer coating varied coating hoppers can be used, as illustrated by Russell et al U.S. Patent No. 2,761,417, Russell U.S. Patent Nos. 2,761,418 and 3,474,758, Mercier et al U.S. Patent No. 2,761,419, Wright U.S. Patent No. 2,975,754, Padday U.S. Patent No. 3,005,440, Mercier U.S. Patent No. 3,627,564, Timson U.S. Patent Nos. 3,749,053 and 3,958,532, Jackson U.S. Patent No. 3,933,019 and Jackson et al U.S. Patent No. 3,996,885. Silver halide layers can also be coated by vacuum evaporation, as illustrated by Lu Valle et al U.S. Patent Nos. 3,219,444 and 3,219,451.

The photographic emulsions are coated on conventional supports which do not undergo serious dimensional changes during processing. Typical suitable supports which can be used are a cellulose acetate film, a polystyrene film, a polyethylene terephthalate film, a polycarbonate film, a laminate thereof, paper, baryta paper, paper coated on laminated with a hydrophobic polymer such as polyethylene, polypropylene, etc. as are commonly used for photographic light-sensitive materials. Transparent supports can be employed for certain end uses of the light-sensitive material. Also, transparent supports may be colored by adding a dye or a pigment thereto as described in J.

SMPTE, 67, 296 (1958), or Cleare, U.S. Patent No. 3,822,131

(1984), incorporated by reference. Where the adhesion between the support and the photographic emulsion layer(s) is insufficient, a subbing layer (an adhesive layer) that adheres to both the support and the photographic emulsion layer(s) can be employed. Also, in order to improve the adhesion, surface of the support may be subjected to a preliminary processing such as corona discharge, irradiation with ultraviolet light, flame treatment, etc. A suitable coating amount of silver is about 0.5 g/m² to about 10 g/m² of the support.

The photographic elements can be imagewise exposed with various forms of energy, which encompass the ultraviolet and visible (e.g., actinic) and infrared regions of the electromagnetic spectrum as well as electron beam and beta radiation, gamma ray. X-ray, alpha particle, neutron radiation and other forms of corpuscular and wavelike radiant energy in either noncoherent (random phase) forms or coherent (in phase) forms, as produced by lasers ("flash exposure"). Exposures can be monochromatic, orthochromatic or panchromatic. Imagewise exposures at ambient, elevated or reduced temperatures and/or pressures, including high or low intensity exposures, continuous or intermittent exposures, exposure times ranging from minutes to relatively short durations in the millisecond to microsecond range and solarizing exposures, can be employed within the useful response ranges determined by conventional sensitometric techniques, as illustrated by T. H. James, The Theory of the Photographic Process, 4th Ed., Macmillan, 1977, Chapters 4, 6, 17, 18 and 23, incorporated by reference.

The photographic light-sensitive material of this invention can be photographically processed using known methods and known processing solutions. The processing temperature usually ranges from about 18° to about 50ºC., but temperatures lower than about 18ºC. or higher than about 50ºC. may be used. This invention is particularly useful for the formation of an image by development in which a silver image is formed (a black-and-white photographic processing). The developers used for black-and-white photographic processing preferably contain, as a developing agent, aminophenols (such as N-methyl-p-aminophenol), 3-pyrazolidones (such as 1-phenyl-3-pyrazolidone), 1-phenyl-3-pyrazolines, dihydroxybenzenes (such as hydroquinone) and other of the aforementioned developing agents. Specific examples of the useful developing agents include hydroquinone alone, hydroquinone plus N-methyl-p-aminophenol, hydroquinone plus 1-pheny1-3-pyrazolidone, and hydroquinone plus N-methyl-p-aminophenol plus 1-phenyl-3-pyrazolidone. Moreover, the developers usually contain a known antioxidant, an alkali agent, a pH buffer or the like and, if desired, a dissolving aid, a color toning agent, a development accelerator, a surface active agent, an anti-foaming agent, a water softener, a hardener, a tackifier, etc., may be present. An anti-fogging agent (such as an alkali metal halide or benzotriazole) may be present in the developer.

According to this invention, even when development is carried out using a developer containing more than about 0.15 mol/l of sulfite ions, a gamma of more than 8 can be obtained. The pH of the developer is preferably about 11 to about 12.3. If the pH exceeds about 12.3, the developer is unstable even when a high concentration of sulfite ions is present, and it is difficult to maintain stable photographic characteristics for more than 3 days under usual use conditions.

Fixing solutions having a composition generally employed in the art can be used in the present invention. Not only thiosulfates and thiocyanates but also organic sulfur compounds known as fixing agents can be used as fixing agents in the present invention.

Preferred examples of fixing agents which can be used in the fixing solution include water-soluble thiosulfates such as sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate, etc., water-soluble thiocyanates such as sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate, etc., water-soluble organic diol fixing agents containing an oxygen atom or a sulfur atom such as 3-thia-1,5-pentanediol, 3,6-dithio-1,8-octaneddol, 9-oxo-3,6,12,15-tetrathio-1,17-heptadecanediol, etc., water soluble sulfur-containing organic dibasic acids and water-soluble salts thereof such as ethylenebisthioglycollic acid and the sodium salt thereof, etc., imidazolidimethiones such as methylimidazolidimethione, etc. These agents described in L. F. A.Mason, Photographic Processing Chemistry, pages 187 to 188, Focal Press (1966).

A particularly preferred developing system in accordance with the present invention contains a hydroquinone developing agent, a benzotriazole antifogging agent (development restrainer), diethylamino-propanediol, sodium sulfite, and a pH modifier (preferably NaOH and/or Na₂CO₃) to adjust the pH to 11.6 ± 0.5. The most preferred developing system is set forth in the Examples below.

The preferred ethanedioic acid hydrazides of the present invention are listed in Table I. Among them, the semioxamazides I-1, I-2, I-3 and I-15 are particularly preferred.

The compounds of the present invention, "I", are synthesized as described in U.S. Patent No. 4,686,167. The compounds of Formula II are synthesized as follows":

+ H₂O

Briefly, the reaction is carried out at 60º-90ºC in a appropriate solvent such as dimethyl formamide or pyridin without any catalyst being necessary. All compounds of Formul

II can be synthesized using the foregoing scheme. Startin materials such as

2,4-dinitrobenzaldehyde;

2,6-dinitrobenzaldehyde;

2-nitrobenzaldehyde;

3-nitrobenzaldehyde;

4-nitrobenzaldehyde;

rhodanine;

rhodanine-3-acetic acid; and 5-nitroquinoline

are commercially available from Eastman Kodak, Rochester, N.Y. and/or Aldrich Chemical, Milwaukee, Wise, and compounds II-3 and

11-25 are commercially available from Anitec, Binghamtom, N.Y.

The following examples are given to illustrate the present invention in more detail. However, the scope of the present invention is not limited to these examples.

EXAMPLE 1 (Synthesis)

Compound II-2: 5 meta-nitrobenzylidene rhodanine

To 507cc of dimethyl formamide (DMF) add 72 g of mnitrobenzaldehyde followed by the addition of 60 g of rhodanine.

Warm to dissolve solids 60-70ºC. Add slowly 50cc of pyridine.

Heat to 80-70ºC with stirring for one hour. Cool to 20ºC, filter and wash with cool DMF. Dissolve cake in 507cc DMF (80-90ºC), filter. Cool to 20ºC, filter solids, wash with DMF at 40ºC.

Stir solids in 900cc of methanol at room temperature for one hour. Filter, wash on funnel with an additional 450cc of methanol, dry.

Analysis

% C % H % N % S

Theory 45.11 2.27 10.52 24.06 Found 45.39 2.37 10.21 23.73

Compound II-3: 5 meta-nitrobenzylidone rhodanine-3-acetic

acid

To 1000 cc of pyridine 166 g of m-nitrobenzaldehyde are added followed by 193 g of 3-carboxymethyl rhodanine. Heat is applied for 5 hours at 90-95ºC. The mixture is then cooled and 4000 ml of methanol are added, is then washed with methanol followed by acetone and ethyl ester and left to dry. The yield is 880 g. M.P. > 300, maximum nm. methanol.

Compound II-4: 5 para-nitrobenzylidene rhodanine

To 500 cc of dimethyl formamide (DMF) 72 g of p- nitrobenzaldehyde are added followed by addition of 60 g of rhodanine. The mixture is warmed to dissolve solids to 60-70ºC. Slowly 50 cc of pyridine are added and heated to 80-90ºC for 1 hour while stirring. It is then cooled to 20ºC, filtered and washed with cool DMF. The cake is dissolved in 500 cc of solids, and washed with DMF at 40ºC. The solids are stirred for 1 hour in 900 cc of methanol at room temperature, filtered and washed on funnel with the addition of 450 cc of methanol and left to dry. Maximum 371 nm in methanol.

Compound II-6: 5 meta-nitrobenzylidene-3-hydroxy rhodanine

To 500 cc of dimethyl formamide (DMF) 72 g of metanitrobenzaldehyde are added followed by addition of 60 g of 3- hydroxyrhodanine (Aldrich). The mixture is warmed to dissolve solids to 60-70ºC. Slowly 50 cc of pyridine are added and heated to 80-90ºC for 1 hour while stirring. It is then cooled to 20°C, filtered and washed with cool DMF. The cake is dissolved in 500 cc of DMF (80-90ºC), filtered hot, cooled to 20'C. The solids are filtered, washed with DMF at 40'C and stirred in 900 cc of methanol for 1 hour in 900 cc of methanol at room temperature. Filtered and washed on funnel with the addition of 450 cc of methanol and left to dry. Maximum 373 nm in methanol.

Compound II-9: 5[7-nitro-2-naphthylidene]-rhodanine

To 500 cc of dimethyl formamide (DMF) 96 g of 7 nitro- 2-naphthaldehyde (Aldrich) are added followed by addition of 60 g of rhodanine. The mixture is warmed to dissolve solids to 60-

70ºC. Slowly 50 cc of pyridine are added and heated to 80-90ºC for 1 hour while stirring. It is then cooled to 20ºC, filtered and washed with cool DMF. The cake is dissolved in 500 cc of DMF (80-90ºC) filtered hot, and then cooled to 20ºC. The solids are washed with DMF at 40ºC, and stirred for 1 hour under addition of

900 cc of methanol at room temperature, filtered and washed on funnel with the addition of 450 cc of methanol and then left to dry. Maximum 369 nm in methanol.

EXAMPLE 2

A gelatino(silver chlorobromoiodide) emulsion containing approximately 90 percent chloride, 9 percent bromide and 1 percent iodide was prepared at 68ºC for 10 minutes by a standard double jet addition technique producing silver halide grains having an average size of 0.30 micron. After removal of soluble salts by a conventional method, the emulsion was chemically ripened using labile sulfur compounds at 61ºC for 70 minutes. This emulsion contained gelatin in the amount of 71.3 g per mole silver halide.

EXAMPLE 3

A gelatino(silver bromide) emulsion was prepared at 65ºC for 37 minutes by a controlled double jet addition technique while the pAg was maintained an 8.3. The average grain size of the silver bromide crystals was 0.27 micron with a size distribution of 16%. After removal of the soluble salts by conventional methods, the emulsion was chemically ripened using both labile sulfur and gold agents at 65ºC for 65 minutes. This surface sensitized emulsion contained gelatin in the amount of 81.9 g per mole silver bromide.

In the examples that follow, a comparison is made between the preferred compounds from Group I and II. Significant parameters for comparison include:

a) relative mid speed

b) gamma

c) pepper level = arbitrary scale from 1 (best) to 5 (worst). (Any level below 4 is acceptable.) A decrease in pepper from any unacceptable level to any acceptable level (e.g. from 4 to 3) is considered substantial.

EXAMPLE 4

The emulsion described in Example 3 was split into 250 g portions. Each portion was identically prepared for coating by the addition of an infrared sensitizing dye (substituted dicar- bocyanine) and surfactant coating aids (ethoxylated phenol).

Various levels of compounds of Formulas I and II were added as in

Table A below. The finaled emulsions were coated at 3.7 g silver/m² on a subbed polyester film support along with a gelatin protective layer which contained formaldehyde, ethoxylated phenol surfactant and a silica matting agent.

The exposed element was processed in an "exhausted" development chemistry (run through a table top processor for 8 hours at 90ºF) having the following composition (EDTA is ethylene-diaminetetraacetate) H₂O 850 ml

Na₂SO₃ 70 g

Hydroquinone 33 g

NaBr 3 . 2 g

5-methylbenzotriazole 0 .225 g

EDTA 1. 0 g

Diethylaminopropanediol 15 ml

50% NaOH 23 ml

Na₂CO₃ 45 g

Water to 1 . 0 liter

pH 11 . 6 ± 0 . 5

Development conditions 90 ° , 30 sec . in a machine

As illustrated in the above test results, if Compounds I are added alone, gamma goes up but pepper also goes up. Pepper is substantially decreased with incorporation of about 1x10^-4 mole Compound II/mole Ag. By contrast, neither sensitivity nor gamma were substantially affected.

The remaining Type I compounds can be anticipated to yield comparable results when tested with the above and other Type II compounds.

The amount of compound II that could be used in the developing solution would be about 500-1000 times larger (per liter of solution) than in the photographic material.

Claims

What is claimed is:

1. A silver halide photographic material comprising radiation-sensitive silver halide grains capable of forming a surface-latent image, a binder, a dot quality-promoting amount of at least one compound of the Formula I, and a pepper-reducing effective amount of at least one compound of the Formula II:

(I)

wherein:

X=-NR₅R₆, or -OR₇

R₁ and R₂ are independently selected from the group consisting of hydrogen, substituted and unsubstituted alkyl having up to 18 carbon atoms; substituted and unsubstituted cycloalkyl, phenyl and naphthyl;

R₃ is selected from the group consisting of hydrogen, substituted and unsubstituted benzyl provided that R₃ is hydrogen when neither R₁ and R₂ are hydrogen; wherein R₁ and R₂ or R₁ and R₃ can be linked together for form a heterocyclic ring system with the ring having 3-10 carbon atoms;

R₄ is a divalent aromatic group with the two valences being ortho- or para- to each other said group being substituted or unsubstituted;

R₅, R₆ and R₇ are independently selected from the group consisting of hydrogen, substituted or unsubstituted alkyl having up to 12 carbon atoms; substituted or unsubstituted cycloalkyl, phenyl and naphthyl; wherein R₅ and R₆ can be linked to form a hetercyclic ring system with the ring containing 3-10 atoms;

Y is selected from the group consisting of sulfur and oxygen atoms;

n is zero or one; provided that n = 1 when Y is sulfur;

(II) R'₁ is selected from the group consisting of benzothiazole, quinoline, indolenine, nitrobenzothiazole, benzotriazole and rhodanine nuclei, each of which may be substituted or unsubstituted, and m is an integer between 0 and 6 inclusive; and

wherein said amount of said Formula II compound is insufficient to substantially decrease sensitivity of said emulsion.

2. A silver halide photographic material as in claim 1, wherein said at least one compound represented by the Formula I is present in an amount of 1x10^-6 to 1x10^-1 mol per mol of silver halide and said at least one compound represented by the Formula II is present in an amount of 5x10^-6 to 1.0 mol per mol of silver halide.

3. A silver halide photographic material as in claim 1, wherein said at least one compound represented by the Formula I is present m an amount of 1x10^-5 to 4x10^-1 mol per mol of silver halide and said at least one compound represented by the Formula II is present in an amount of from 1x10^-5 to 5x10^-4 mol per mol of silver halide.

4. The material of claim 1 wherein both said compounds are incorporated in said emulsion.

5. The material of claim 1 wherein at least one of said compounds is incorporated in another hydrophilic layer of said material.

6. A silver halide photographic material as in claim 1, wherein said at least one compound represented by the Formula I and said at least one compound represented by the Formula II, are independently incorporated in at least one of a silver halide emulsion layer, a protective layer, an intermediate layer, a filter layer, and an antihalation layer.

7. A process for forming a super-high contrast negative image, comprising imagewise exposing and developing a silver halide photographic material comprising a support having provided thereon at least one silver halide emulsion layer, said emulsion layer or another layer or the developer solution used to develop said image said material containing a dot-quality promot ing amount of at least one compound represented by the Formula I and a pepper-reducing effective amount of a compound of the Formula II: (I)

wherein:

X=-NR₅R₆, or -OR₇

R₁ and R₂ are independently selected from the group consisting of hydrogen, substituted and unsubstituted alkyl having up to 18 carbon atoms; substituted and unsubstituted cycloalkyl, phenyl and naphthyl;

R₃ is selected from the group consisting of hydrogen, substituted and unsubstituted benzyl provided that R₃ is hydrogen when neither R₁ and R₂ are hydrogen; wherein R₁ and R₂ or R₁ and R₃ can be linked together for form a heterocyclic ring system with the ring having 3-10 carbon atoms;

R₄ is a divalent aromatic group with the two valences being ortho- or para- to each other said group being substituted or unsubstituted;

R₅, R₆ and R₇ are independently selected from the group consisting of hydrogen, substituted or unsubstituted alkyl having up to 12 carbon atoms; substituted or unsubstituted cycloalkyl, phenyl and naphthyl; wherein R₅ and R₆ can be linked to form a hetercyclic ring system with the ring containing 3-10 atoms;

Y is selected from the group consisting of sulfur and oxygen atoms;

n is zero or one; provided that n = 1 when Y is sulfur;

(II)

wherein R' ₁ is selected from the group consisting of benzothiazole, quinoline indolenine, nitrobenzothiazole, benzotriazole and rhodanine, each of which may be substituted or unsubstituted, and m is an integer between 0 and 6 inclusive; and wherein said amount of said Formula II compound is insufficient to substantially decrease sensitivity of said emulsion.

8. A process for forming a super-high contrast negative image according to claim 7, wherein said developing is carried out with a developer containing a sulfite ion in an amount of from 0.4 mol/l to 2.5 mol/l and having a pH of 10.5 to 12.3.

9. The process of claim 7 wherein said Formula I compound is present in the developing solution.

10. The proσess of claim 7 wherein said Formula II compound is present in the developing solution.

11. The process of claim 7 wherein both said Formula I and said Formula II compounds are both present in the photographic material.

12. A process for forming a super high-contrast image comprising imagewise exposing and developing a silver halide containing photographic material comprising a support having provided thereon at least one silver halide emulsion layer, at least one of said emulsion layer, another layer and the developer used to develop said image, said material containing a dotquality promoting amount of a hydrazine or hydrazide compound and a pepper-reducing effective amount of a compound of the Formula II (II)

wherein R'₁ is selected from the group consisting of benzothiazole, quinoline, indolenine, nitrobenzothiazole, benzotriazole and rhodanine, each of which may be substituted or unsubstituted, and m is an integer between 0 and 6 inclusive; and wherein said amount of said Formula II compound is insufficient to substantially decrease sensitivity of said emulsion.

13. The process of claim 12 wherein said image is a negative image.

14. The process of claim 13 wherein said emulsion is of the surface latent image negative-working type.

15. The process of claim 14 wherein said Formula II compound is incorporated in the photographic material.

16. The process of claim 14 wherein said Formula II compound is incorporated in the developer.

17. The process of claim 15 wherein said Formula II compound is 5-metanitrobenzylidene rhodanine.

18. The process of claim 16 wherein said hydrazide compound is 1-[4,-(3"-ethylthioureido)-phenyl]-5-methyl- semioxamazide, and is also incorporated in the photographic material.

19. The process of claim 18 wherein the amount of said Formula II compound is within the range of about 1x10^-5 to about 5x10^-4 mol per mol of silver halide.

20. The process of claim 19 wherein the amount of said semioxamazide is within the range of about 1x10^-5 to about 4x10^-1 mol per mol of silver halide.

21. The material of claim 1 wherein said Formula I compound is Compound I-2 and said Formula II compound is 5-meta nitrobenzylidene rhodanine.

22. The material of claim 21 wherein said Formula I and said Formula II compounds are incorporated in said emulsion in amounts within the range of 1x10^-5 to 4x10^-1 for the compound of Formula I and the range of 1x10^-5 to 5x10^-4 for the compound of Formula II.