JPH11295833A - Production of silver chloride-rich tabular grain with reduced thickness growth and improved uniformity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain silver chloride-rich tabular grains with high shape homogeneity by adding a specified compd. to a reactor in one of specified steps in the case of including the steps for specified grains. SOLUTION: A dispersive medium is prepd. in a reactor, an aq. soln. contg. halide ions and an aq. soln. of silver nitrate are subjected to double jet precipitation to precipitate silver halide crystal nuclei and the nuclei are grown. In this step, a hydrophilic amphoteric block copolymer contg. nonionic acrylic blocks contg. a pendant nitrile group represented by formula I and acrylamide blocks represented by formula II is added to the reactor to obtain the objective silver chloride-rich flat platy grains. 111} Flat platy grains having an average aspect ratio of >=2:1, 0.3 μm average equivalent circular diameter, <=30% variation in equivalent circular diameter, 0.05-0.25 μm average thickness and <=20% variation in thickness account for 70% of the total projection area of all the grains and the 111} tabular grains exist in 90% by number. In formula I, R<1> is H, alkyl or the like. In formula II, R<2> and R<3> are each H, alkyl or the like and X is O or NH.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a process for preparing silver chloride-rich {111} tabular emulsion grains exhibiting reduced thickness growth and improved diameter and thickness homogeneity, and a silver halide photograph containing said emulsion. About the material.

[0002]

2. Description of the Related Art Tabular silver halide grains are grains having two parallel crystal faces having an aspect ratio of 2 or more. The aspect ratio is defined as the ratio of the diameter of a circle having a surface area equivalent to one of these crystal planes to the thickness, which is the distance between the two principal planes.

[0003] Tabular grains have been known in the photographic industry for quite some time. Early in 1961, Berry et al.
otographic Science and Engineering, Vol 5, No. 6
Reported the production and growth of tabular silver bromoiodide grains. For a discussion of tabular grains, see Duffin, Photographic Emulsio
n Chemistry, Focal Press, 1966, pp. 66-72.

[0004] Early patent documents include Bogg's US-A.
4063951, Lewis US-A 4067739
And Maternaghan, US-A 4,150,994; 418.
4877 and 4184878. However, the tabular grains described therein cannot be regarded as exhibiting a high diameter to thickness ratio commonly referred to as the aspect ratio. In many US patent applications filed in 1981 and issued in 1984, tabular grains with high aspect ratios and their advantages in photographic applications are described in US Pat.
-A 4434226; 4439520; 442542
5; 4425426 and Research Disclosure, Volume
225, January 1983, Item 22534.

The main photographic advantage of tabular grains compared to conventional spherical grains for radiographic applications is US-A 44143, especially in double-side coated spectral sensitized materials.
High covering power at high pre-cure levels, high developability and high sharpness as described in US Pat. No. 4,425,425 and 4,425,426
Reduces crossover as described in

The references cited above for {111} tabular grains disclose silver bromide or silver iodobromide emulsions having particularly high sensitivity. However, high speed is EP-
It has been shown that tabular silver halide grains rich in silver chloride, such as A0687872, can be achieved.

[0007] It is known that the anisotropic growth characteristics of the tabular grains are due to the formation of parallel twin planes in the nucleation step of precipitation. However, for the {111} tabular silver halide grains rich in silver chloride, US-A 4,713,323; 4,804,621;
6692; 5183732; 5185239; 5252
452; 5286621; 5298385 and 5298.
As described at 388, the use of relatively high amounts of crystal habit modifier is required. Treatment of tabular grain emulsions with {111} crystals rich in silver chloride with iodide for enhanced morphological stability and enhanced photographic performance is described in EP-A.
0678772 and Research Disclosure 38804
6 (issued August 1, 1996).

However, the spherical result results in a rather heterogeneous emulsion crystal distribution: 0.30 to 0.30 μm, due in part to the presence of a large number of nontabular grains having a sphere equivalent diameter of less than 0.3 μm. A general variation coefficient of 0.60 (common
A variability coefficient (defined as the ratio between the average standard deviation for the equivalent circular diameter and the average equivalent circular diameter) is calculated. Further differences in thickness growth were observed,
The differences lead to non-uniformities as a result of the observed differences in image tones.

Heterogeneous dispersion of the grain morphology leads, for example, to uncontrolled chemical and spectral sensitization, low contrast and low covering power, thereby losing the typical advantages of said grains as described above.

Efforts to obtain a monodisperse tabular silver halide crystal distribution in emulsion production have been described in, for example, US-A
4797354; 5147771; 5147772; 5
147773; 5171659; 5248587; 52
04235; 5210013; 5215879; 525
0403; 525442; 525453; 5254
453; 5318888; 5439787; 54728
37; 5482826 and 5484697 and Research
Disclosure No. 391, 713-723 (199
It has been directed to silver bromide- rich silver halide crystals as described in 6).

EP-A 0866636 for controlling the thickness growth for tabular {111} grains rich in silver chloride.
A solution as disclosed in No. 2 has been proposed: a process in which the dispersing medium during nucleation is maintained at a constant starting pH value of 6.0 to 9.0, further comprising the core. At least 3 between the end of the forming step and the end of the growing step.
A process is provided which comprises resetting the pH to the starting pH value after setting the pH to a value less than 6.0 for 0 seconds.

Nevertheless, the problem of too low covering power remains due to the still large number of particles exhibiting a thickness greater than the average thickness observed .

As a result, many attempts have been made to improve the homogeneity of the size and shape of the crystals, the majority of which are associated with tabular grains rich in silver bromide grains. Radiographic materials containing emulsions having monodisperse tabular silver bromo (iodide) iodide crystals are described, for example, in US-A 5,252,442 and 5,508.
158. However, the same manufacturing process as for the tabular grains rich in silver bromide produces tabular grains rich in silver chloride, especially due to the presence of a habit modifier (usually adenine), which leads to the aforementioned disadvantages. Sometimes this is not the case.

[0014]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for producing silver chloride-rich tabular {111} grains having a high degree of morphological homogeneity with a considerable reduction in thickness growth. To provide. As much homogenous as possible for other particle shapes leading to the presence of large amounts of silver that do not contribute effectively to the desired photographic properties, such as low coverage silver , which exhibits high covering power after processing. Consider a hexagonal tabular {111} crystal having a crystal diameter.

[0015] Other objects will be apparent from the following description.
Preferred embodiments of the invention are disclosed and summarized in the dependent claims.

[0016]

SUMMARY OF THE INVENTION A method for producing a gelatin emulsion having silver chloride-rich grains, wherein at least 70%, more preferably at least 90%, of the total projected area of all grains is greater than 2: 1. Average aspect ratio, average equivalent circular diameter of at least 0.3 μm and 0.05 to 0.2.
Provided by {111} tabular grains having an average thickness of 5 μm, the variation in the average equivalent circular diameter of the tabular grains is less than 30%, and the variation in the average thickness of the tabular grains is less than 30%. Fluctuation (procentual va
riation) is not more than 20%, the tabular grains are present in at least 90% (procentual numerical amounts), and the method comprises the following steps:-a dispersion medium comprising an initial amount of a habit modifier; In a reaction vessel; precipitate silver halide crystal nuclei in the vessel by double jet precipitation of an aqueous solution containing halide ions and an aqueous silver nitrate solution (1% of the total amount of silver nitrate used).
0% by weight is consumed);-The silver halide crystal nuclei grow by further precipitation of silver halide by double jet precipitation of an aqueous solution containing halide ions and an aqueous solution of silver nitrate (90% by weight or more of the total amount of silver nitrate). Wherein at least one compound is added to the reaction vessel during at least one of the steps, wherein the compound (i) has a pendant nitrile group according to formula I given in claim 1 A non-ionic acrylic block comprising a series of units having: and (ii) an acrylamide (acrylamidine) comprising a series of units according to formula II as claimed
A hydrophilic amphoteric block copolymer containing an (acrylamid (in) ic) block, wherein the hydrophilic amphoteric block copolymer has a unit having a pendant acidic group or a salt thereof and a pendant basic group in the acrylamide (acrylamidine) block. A method is described which further comprises a unit or a salt thereof. Also disclosed are emulsions having tabular grains prepared according to the method of the present invention and light-sensitive silver halide photographic materials wherein the emulsions are coated in light-sensitive layers.

Formulas I and II are further disclosed in the following detailed description and claims.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The hydrophilic amphoteric block copolymer added to the reaction vessel according to the present invention is an acrylic polymer having the three essential characteristics described below.

As used herein, "acrylic"
Means the basic structure CH irrespective of the nature of the substituent R
₂ = means any derivative of acrylic acid with CR-COOH. Preferred acrylic monomers are derivatives of acrylic acid (R = H) and methacrylic acid (R = CH _3).

The acrylic polymer derivatives used according to the invention are so-called amphoteric polymers having both anionic and cationic groups in the same polymer chain. Such ionic groups can have interactions that impart certain special properties (pH dependent swelling, pH dependent crosslinking, etc.) to the polymer. Amphoteric polymers form internal salts at some well-defined pH value called the isoelectric point, and the polymer in this state has minimal solubility and swelling in water. In this regard, amphoteric (meth) acrylates are similar to other natural fibers such as proteins and gelatin.

The first essential feature of the hydrophilic amphoteric block copolymer used according to the invention is the presence of a nonionic block comprising a succession of units having pendant nitrile groups according to formula I:

Embedded image In Formula I, R ¹ is hydrogen, alkyl or substituted alkyl.

The nonionic block is a homopolymer,
Preferably, the blocks may be a continuous sequence of the same monomers to form polyacrylonitrile or polymethacrylonitrile, but the blocks may be, for example, random polymers of acrylonitrile and methacrylonitrile units. The number of units contained in the nonionic block is 2
As mentioned above, preferably at least about 10. According to the invention, the units of the formula I may be separated from one another by other nonionic acrylic comonomers without pendant nitrile groups. The ratio of such non-CN comonomer to monomer according to formula I may be as high as 50%, but preferably the amount of non-CN comonomer is kept below 15 mol% for optimal results.

A second essential feature of the hydrophilic amphoteric block copolymer used according to the invention is the presence of a so-called acrylamide (acrylamidine) block comprising a succession of acrylamide or acrylamidine according to formula II:

Embedded image In formula II, R ² is hydrogen, alkyl or substituted alkyl, preferably hydrogen or methyl, R ³ is hydrogen, alkyl or substituted alkyl, aryl or substituted aryl, and X is O or NH It is. This series of acrylamide or acrylamidine may be a homopolymer or a random polymer. Acrylamide (acrylamidine) units may be N-substituted. N-substituted R ³ can be a carrier of various functional groups, including the acidic and basic groups mentioned below. Hydrophobic moieties can also be present in the acrylamide (acrylamidine) block, and alkyl-containing aryl groups having 4 to 24 carbon atoms, oxygen-containing substituents such as hydroxyls, esters, saccharides or epoxides, alkylsiloxane- (Si (R) ₂ -O) _n -Si (R)
_{3 (wherein,} n is 0 to about 100, R is alkyl as having carbon atoms of 4 to 24) can be obtained by N-substituted with R ³ is a non-polar substituents such as. When R ³ is an alkyl or aryl group, it may be substituted, for example, with one or more halogen atoms, lactones, lactams, nitriles, nitro or nitroso groups.

A third essential feature of the hydrophilic amphoteric block copolymer used according to the present invention is the presence of acrylic units having pendant acidic groups and acrylic units having pendant basic groups in acrylamide (acrylamidine) blocks. is there. The acidic and basic groups may be randomly distributed over some or all of the acrylamide (acrylamidine) blocks of the polymer.
Each of the acrylamide (acrylamidine) blocks may contain either only acidic groups, only basic groups, or a mixture of acidic and basic groups. The polymers used in accordance with the present invention can have a molar excess of any of the groups, and thus the molar ratio between basic and acidic groups, which may vary from about 1:20 to about 20: 1. Has an isoelectric point at either an alkaline or acidic pH, depending on the pH. Due to their strong interaction, acidic and basic groups already affect the properties of the polymer at very low concentrations (about 1 mol%), but preferably the concentration of ionic groups is 5 mol%.
Greater than%.

In a preferred embodiment, the unit having a pendant acidic group is of the general formula III or IV or a salt thereof.
If present as a salt, preferred counterions are metal ions or nitrogenous bases.

Embedded image

In formula III, R ⁴ represents hydrogen, alkyl or substituted alkyl. Preferably R ⁴ is hydrogen or methyl.

Embedded image

In formula IV, R ⁵ represents hydrogen, alkyl or substituted alkyl, preferably hydrogen or methyl;
Is O or NH, R ⁶ is an organic linking group having at least one carbon atom, preferably ethylene or substituted ethylene, and Y is —COOH, —OPO ₃ H
₂ , —SO ₃ H or —OSO ₃ H. The unit having a pendant basic group is preferably represented by the general formula V or VI or a salt thereof. If present as a salt, the counterion is, for example, a carboxylate, sulfate, sulfonate, phosphate, nitrate, nitrile, carbonate or halide.

Embedded image

In formula V, R ⁷ represents hydrogen, alkyl or substituted alkyl, preferably hydrogen or methyl;
⁸ represents hydrogen, alkyl or substituted alkyl, aryl or substituted aryl. Formula V is not limited to amidines. This is because amides are not generally considered basic.

Embedded image

In formula VI, R ⁹ represents hydrogen, alkyl or substituted alkyl, preferably hydrogen or methyl, X is O or NH, and R ¹⁰ is an organic linking group having at least one carbon atom, preferably Is ethylene or substituted ethylene, and Z is a nitrogen-containing base. Such nitrogenous bases include primary, secondary and tertiary amines, quaternary bases,
Pyridine or naphthyridine derivatives, guanidine, amidine, imine and imidine.

When X = NH in formula IV, the unit also corresponds to formula V, thereby indicating that such a unit contains an acidic group (Y) and a basic group (amidine function). Results as pendant groups ^-CNH-NH-R 6 -Y
The units with are themselves amphoteric.

Therefore, a block copolymer having a polyacrylonitrile block of the formula I and an acrylamide (acrylamidine) block of the formula II (with the pendant group -CNH-NH- as a single ionic unit within said acrylamide (acrylamidine) block) R ⁶ -Y) are also hydrophilic amphoteric block copolymers within the scope of the present invention.

Highly preferred examples of special hydrophilic amphoteric block copolymers used according to the present invention are N- (2-
HYMEDICS comprising sulfo-ethyl) -acrylamide and N- (2-sulfo-ethyl) -acrylamide
Is a polymer referred to herein as HYPAN TC240®. HYPAN TC240
(Registered trademark) may be represented by Formula VII.

Embedded image

It is generally known in the art that it is not possible to characterize a particular polymer with a single, clear formula. Therefore, the above formula should not be interpreted literally. Brackets are used to indicate that acrylonitrile units are composed of blocks other than those containing acrylamide and acrylamidine units. Furthermore, the five different units present in the acrylamide (acrylamidine) block of Formula VII are not organized into blocks in the exact order given above, but are randomly distributed across the acrylamide (acrylamidine) block. HYPAN TC240
The frequency distribution of (registered trademark) units is approximately as follows:

[Table 1]

The hydrophilic amphoteric polymers used in the process according to the invention are described in US-A 5,252,692 and 494,361.
8 (they are incorporated herein by reference). A preferred method is the hydrolysis of the CN groups of polyacrylonitrile dissolved in a mixture of a solvent, a primary amine, water and optionally a basic catalyst. If the reaction conditions are chosen appropriately, CN
Hydrolysis of the group is called the “zipper mechanism (zipper
mechanism), which may lead to a structure as shown in Formula VII with the various substituents being comprised within the block rather than being randomly distributed along the polymer chain. The resulting block The copolymer may be optionally conjugated or physically crosslinked and may form a hydrogel, which is swellable rather than soluble in water, having an average molecular weight of typically 150,000, Block copolymers having much higher or lower molecular weights can also be used according to the invention.

The very remarkable effect of the properties of the polymers used in the process according to the invention and of the photographic materials containing such polymers and containing the emulsions produced by the process according to the invention will be shown by way of example.

According to the method of the present invention, the polymer is initially added to a reaction vessel containing a habit modifier to produce a suitable dispersion medium. In that case, nucleation takes place in the nucleation step and also in one or more parts of a different step (for example after nucleation, before or during one of the subsequent growth steps). Furthermore, addition during physical ripening after growth is not excluded,
The addition of the polymer before or during redispersion and the addition to the coating solution before coating are not excluded. In a preferred embodiment, the copolymer is added before silver nitrate precipitation, preferably in a minimum amount of about 10% of the total amount of hydrophilic protective colloid present in the nucleation step in order to give good control and reproducibility of the production process.

According to the method of the present invention, silver chloride-rich # 11
1. An emulsion having tabular grains, wherein the grains are composed of silver chloride, silver chlorobromide, silver chloroiodide or silver chlorobromoiodide,
At least 50 mol% silver chloride, more preferably 90 mol%
%. Emulsions having more than% silver chloride are produced. $ 11 above
1% tabular emulsion grains are characterized by at least 70%, more preferably 90%, of the total projected area of all grains;
Average aspect ratio of 2: 1 or more, 0.3 μm to 5 μm,
More preferably, having an average equivalent circular diameter of 0.4 μm to 2.0 μm and an average thickness of 0.05 to 0.25 μm,
The variation in the average equivalent circular diameter (also referred to as "ECD") of the tabular grains is 30% or less, usually 20% to
The range is 30%. Considering all the grains present in the emulsion, the variance can be found to be quite large, reaching 30% to about 60% variability. The average "ECD" is defined as the average calculated from the surface areas of all {111} tabular grains, and the equivalent circular diameter is the diameter of a circle having the same (equivalent) surface area as the corresponding tabular grains. Represents

Further in accordance with the present invention, the presence in the emulsion preparation of a hydrophilic amphoteric block copolymer as previously disclosed reduces variations in the average grain thickness of tabular grains present to levels of 20% or less. Yes: preferably the variation in thickness is in the range of 10-20%.

According to the present invention, in the above {111} tabular grains having a silver chloroiodide or silver chlorobromoiodide composition, iodide contains 3
It is present in amounts up to mol%. The iodide ion is RD 3
9433, issued Jan. 1997, by using an aqueous solution of an inorganic salt such as, for example, potassium iodide, sodium iodide or ammonium iodide, but as an alternative, for example EP-A 05614
15,0563701,0563708,064905
2 and 0651284, WO 96/13759 and R
Iodide ions provided by organic compounds which release iodide ions as described in D 39423, published January 1997 are very useful. In order to obtain a homogeneous iodide distribution, especially over the entire crystal population and in the crystal lattice of the individual crystals, iodide ions provided by organic agents which release iodide ions are more preferred. Examples of such iodide ion releasing agents are monoiodoacetic acid,
A hydrogel containing iodide ions capable of generating monoiodopropionic acid, monoiodoethanol and iodide ions. The generation of iodide ions is initiated in the manufacturing process by changing the pH value in the reaction vessel during or preferably after the addition of the organic agent releasing iodide ions, which pH change is required by the method of the present invention. This is done in such a way. Said organic compounds, which release iodide ions as opposed to the addition of potassium iodide as a source of iodide ions, lead to a homogeneous distribution of iodide ions over different tabular crystals, thus resulting in unclear heterogeneous parts and non-reproduction Avoid parts.

In another example according to the method of the present invention, said tabular grains are enriched in iodide by adding silver iodide microcrystals having an average crystal size of at most 0.05 μm or less. Generation of iodide ions is initiated by differences in solubility between large {111} tabular silver chloro (iodide) or silver chlorobromo (iodide) crystals and such fine silver iodide microcrystals (see Ostwald). Aging). However, well-known inorganic iodide salts (preferably alkaline earth metal salts such as potassium or sodium iodide)
A simple conversion technique utilizing the can be applied.

Combinations of inorganic and organic ions that provide iodide ions may be useful. Thereby, the presence of iodide ions stabilizes the {111} crystal planes: for example, the concentration of the habit modifier present on the surface of tabular grains rich in silver chloride is such that the iodide ions provided on the surface of said grains are stable. It has been established that it can be reduced to a considerable extent because it leads to protection of the crystal habit. Iodide ions can thus replace conventional crystal habit modifiers such as adenine. Other compounds such as spectral sensitizers or stabilizers can also be used as suitable compounds to replace said habit modifier due to their habit stabilizing action. Furthermore, the presence of iodide ions on the crystal surface of the tabular crystals rich in silver chloride is preferred for adsorption of the spectral sensitizer on the large {111} tabular crystal surfaces by improved J-aggregation. As a result, improved light absorption in the wavelength range where the crystals are sensitized is observed.

According to the method for producing silver chloride-rich {111} tabular silver halide grains, a dispersion medium containing an initial amount of a crystal habit modifier is added to a reaction vessel. Compounds useful as habit modifiers for silver chloride-rich crystals include EP-A 043
0196,0481133 and 0532801 and US
-A 5176991; 5176992; 517899
7; 5178998; 518732; 518523
9; 5217858; 5221602; 525245
2: 5264337; 5272052; 529838
5; 5298387; 5298388; 539947
8; 5405738; 5411182 and 541812
5 are disclosed.

According to the method of the present invention, the habit growth modifier is adenine, 2-hydro-amino-azine or 4-amino-azine.
Pyrazolo [3,4, d] pyrimidine. Further hydrophilic protective colloids can be present, for example, gelatin, colloidal silica, potato starch, dextran, acrylamide or a combination thereof. Such protective colloids or binders are described in Research Disclosure No. 38
957, in a general review issued September 1, 1996. Since a gelatin emulsion is formed according to the method of the present invention, it is clear that gelatin remains an essentially hydrophilic protective colloid during the preparation of said emulsion. In a preferred embodiment, the gelatin is present in a reaction vessel in which the dispersion medium is produced before nucleation. In a more preferred example, a small portion of gelatin is added before nucleation (1 of said gelatin).
(with a methionine content of less than 30 μmol / g), a large amount of gelatin is added during subsequent steps, preferably during the physical ripening step between nucleation and growth or between continuous growth steps (optionally 30 μm / g of said gelatin)
(with a methionine content of less than ol). A considerable amount of gelatin can be added even after the end of growth, but it is preferred to add said amount after flocculation or ultrafiltration in order to give good redispersibility to the emulsion thus produced. Gelatin for use in the production of photographic emulsions is described, for example, in Research Disclosure No. 38957, Chapter 2,
It is listed on September 1, 1996.

During the nucleation step and / or the physical ripening step between the nucleation step and the first growth step, when gelatin is present as a hydrophilic dispersion medium in the reaction vessel, less than 10 (about 4).
The ratio of gelatin to silver (expressed as silver nitrate equivalents) of ７7) was calculated, which is quite high. “Ge
Said ratio, also referred to as si ", is about 0.
It falls to a value of 30 to 0.25. However, gelatin may be added during or during the nucleation step and the first growth step and / or during or between different growth steps, as well as the hydrophilic amphoteric block copolymer used in the method of the present invention. Good.

The process for producing tabular grains having {111} tabular habits is preferably carried out at a temperature of 35 ° C., preferably up to 10%, more preferably up to 5%, of the total amount of silver salt in the diluted medium.
It is usually characterized by the presence of a nucleation step which is consumed at a constant temperature of 55 ° C. (other temperature ranges are not excluded). Precipitation of silver halide crystal nuclei in the reaction vessel is performed by double jet precipitation of an aqueous solution containing halide ions and an aqueous silver nitrate solution, and consumes less than 10% by weight of the total amount of silver nitrate used. If iodide is present, concentrations of 0.5% or less are preferred in the nucleation step to prevent excessive nucleation. If silver chlorobromoiodide crystals are produced, the bromide may be present in the nucleation step, but the absence of bromide is preferred and the chloride present therein is generally in an amount of at least 99.5%. . One or more growth steps, with at least one physical ripening step in between, usually follows the nucleation step. Therefore, the growth of silver chloride-rich silver halide crystal nuclei due to further precipitation of silver nitrate is 90% by weight or more, more preferably 95% by weight, of the total amount of silver nitrate.
It is carried out by double jet precipitation of an aqueous solution containing halide ions and an aqueous silver nitrate solution, which consumes not less than% by weight.

To provide sufficient silver and halide ions proportional to the growth rate of the growing crystal surface, it is advantageous to accelerate the rate of silver and halide salt addition as a function of time. Also, from an economic point of view, this measure is an advantageous way to save time. In combination, the growth volume in the reaction vessel, which leads to increased dilution of the emulsion crystals in the reaction vessel, is kept constant by removing excess water and soluble alkali nitrate by dialysis and / or ultrafiltration. Is also good.

According to the method of the invention, the growth of said nuclei is carried out by double jet precipitation and the iodide salt solution is optionally present in said halide salt solution consisting essentially of chloride salts and optionally bromide salts. Further, the chloride salt in the reaction vessel is maintained at a constant concentration of 0.15M. During the growth step, the nuclei are further grown by double jet precipitation, the remainder of the silver is consumed, and the iodide salts are essentially chloride salts and, if desired, bromide salts (if silver chlorobromoiodide crystals are produced). (If the chloride salt is present in excess relative to the iodide salt, usually as an alkali iodide solution in an alkali chloride solution).

During physical ripening, increasing the temperature of the reaction vessel to about 70 ° C. may be performed during tabular grain growth to maintain the same temperature. Preferably the pH is eg E
After setting the pH to a value of less than 6.0 for at least 30 seconds as described in P-A 0866362, the pH is reset to the starting pH and the particle thickness and grain size distribution are determined. Unless the homogeneity is further controlled, about 6.0
To keep the same value. The application of the method of the invention leads to homogeneity, expressed mathematically as a coefficient of variation for an average thickness of less than 0.30, for example 0.10 to 0.30 and for an average equivalent circular diameter.

In thin tabular silver chlorobromoiodide or silver chloroiodide emulsions containing iodide in an amount of from 0.1 mol% to 3 mol% and the corresponding emulsions without iodide, the halide distribution in the tabular grains is all crystal Homogeneous or heterogeneous over volume. When different phases of silver halide composition are present over the crystal volume, the crystals have a "core-shell" structure. One or more shells can be present and it is recommended that the phases be enriched in silver bromide and / or silver iodide by applying so-called conversion techniques during the preparation between the different phases.

In a preferred embodiment, according to the method of the present invention,
At least one conversion step is performed during and / or after the growth of the nuclei, and the conversion of the emulsion grains comprises releasing a compound that releases an inorganic bromide and / or iodide salt and / or an organic bromide and / or iodide into a reaction vessel. It is done by adding.

In yet another example, the growth of the nucleus and / or
Alternatively, at least one subsequent conversion step is performed, wherein the conversion of the emulsion grains is performed by adding silver iodide or silver bromide microcrystals having an average crystal size of at most 0.05 μm.

According to the method of the present invention, in one embodiment, the silver chlorobromide emulsion is such that the emulsion comprises {111} tabular grains having a variable bromide distribution such that the emulsion is rich in bromide at the crystal surface. Produced by transforming grains, said distribution characterized by the presence of bromide ions in a smaller amount of crystal volume than the crystal surface of said tabular grains, and in a more preferred embodiment a total amount of bromide ions of 50%.
An amount of １００100 mol% is located on the surface of the tabular grains.

In another embodiment, according to the method of the present invention, a silver chlorobromoiodide or silver chloroiodide emulsion comprises tabular grains having a variable iodide distribution such that said emulsion is rich in iodide at the crystal surface. Produced by converting the emulsion grains to include, wherein the distribution is characterized by the presence of iodide ions (and optionally bromide ions) in a smaller amount of crystal volume than the crystal surface of the tabular grains. 50-100 of the total amount of bromide ions (and, if desired, bromide ions)
An amount of mol% is located on the surface of the tabular grains.

When different phases of silver halide composition are present over the crystal volume, the crystals are said to have a core-shell structure. One or more shells can be present depending on the number of growth steps, and a phase enriched in silver iodide and / or silver bromide can be applied between the different phases.

Although the presence of iodide is preferred in terms of internal sensitivity and spectral sensitivity, the average iodide concentration is 0.05 mol
Limiting the amount to 1 mol% to 3 mol% silver based, more preferably the concentration is 0.05 mol based on total silver
% To 1.3 mol%. Higher densities slow development and lead to unsatisfactory sensitivity. Furthermore, the fixing speed is then disturbed, so that residual coloration may be unavoidable. EP-A 067877
In 2, for example, an excess of iodide is provided by the transformation at the end of the precipitation (ie at the end of the last growth step) and thus has a total iodide concentration of 1.3 mol% in the silver chloroiodide emulsion thus obtained. .

A bromide ion concentration of 25 mol% or less based on total silver is contemplated, but was prepared according to the method of the present invention to strongly suppress processing and to avoid increased replenishment of the developer and / or fixer. {111} tabular silver chlorobromoiodide or silver chlorobromide emulsion crystals are 10 mol% based on silver
It preferably has the following amount of silver bromide.

It is more preferred to reduce the amount of bromide ions to less than 5 mol% in order to reduce the amount of replenisher in the processing of an exposed silver halide material containing a photosensitive emulsion as described above. Bromide ions may be provided from at least one inorganic and / or organic agent that provides bromide ions.

According to the present invention there is provided a photographic material comprising a support and on one or both sides thereof one or more silver halide emulsion layers coated from a gelatin emulsion prepared as described above, more preferably A photographic material is provided which is a single or double coated radiographic material.

The above hydrophilic amphoteric block copolymers are present in light-sensitive emulsion layers coated from emulsions having {111} tabular grains rich in silver chloride, but their presence in another hydrophilic layer, such as The presence in the undercoat layer between the body and the emulsion layer, in the interlayer between the two emulsion layers or between the emulsion layer farthest from the support and the protective stress-resistant layer or in the stress-resistant layer is not excluded. The amount of such a hydrophilic amphoteric block copolymer is from 0.05 to 250 mg / m ² , more preferably from 0.
5-100 mg / m ² , still more preferably 0.5-
10 mg / ^{m 2,} most preferably be in the range of 1 to 5 mg / ^{m 2.}

The hydrophilic amphoteric block copolymer can also be present in one or more processing solutions applied on the imaging element. Examples of such processing solutions include those applied after image-wise exposure of the silver halide photographic material according to the present invention. Examples of processing solutions are alkaline processing solutions, such as developing or activating solutions, neutralizing solutions (also called stabilizing solutions), rinsing solutions and finishing solutions.

The gelatin emulsion according to the present invention has silver chloride, silver chlorobromide, silver chloroiodide or silver chlorobromoiodide grains, wherein at least 70% of the total projected area of all grains is 2: 1 or more. # 11 with aspect ratio, average equivalent circular diameter of at least 0.3 μm and average thickness of 0.05-0.25 μm
Provided by 1｝ tabular grains, the variation in the average equivalent circular diameter of the tabular grains is 30% or less, the variation in the average thickness of the tabular grains is 20% or less, and (i) At least one compound which is a hydrophilic amphoteric block copolymer comprising a nonionic acrylic block comprising a series of units having pendant nitrile groups according to formula I and (ii) an acrylamide (acrylamidine) block comprising a series of units according to formula II Wherein the hydrophilic amphoteric block copolymer further comprises a unit having a pendant acidic group or a salt thereof in the acrylamide (acrylamidine) and a unit having a pendant basic group or a salt thereof.

The silver halide emulsion is described, for example, in "Chimie et Ph.
ysique Photographique ”, by P. Glafkides,“ Photog
raphic Emulsion Chemistry ”, GF Duffin,“ Ma
kingand Coating Photographic Emulsion ”, VL Zeli
kman et al. and “Die Grundlagen der Photographisch
en Prozesse mit Silberhalogeniden ", edited by H. Frieser and published by Akademische Verlagsgesellschaft (1968). As described in the literature, chemical sensitization involves the addition of small amounts of sulfur, Performed by performing ripening in the presence of a compound containing selenium or tellurium, such as thiosulfate, thiocyanate, thiourea, selenosulfate, selenocyanate, selenourea, tellurosulfate, tellurocyanate, sulfite, mercapto compound, and rhodamine. In a preferred example, these compounds are applied in combination with a noble metal salt, preferably a gold complex salt, but with platinum, palladium and iridium as described in U.S. Patent No. 2,448,060 and British Patent No. 6,180,61. Salts may be used, sulfur And / or selenium and / or tellurium and gold may be added sequentially or simultaneously, in the latter case gold thiosulphate, gold selenosulphate or gold tellurosulphate compounds are recommended. A preferred chemical ripening system for 111 ° tabular grains is, for example, E
P-A 0443453, 0476345,05060
09,0563708,0638840 and 08620
88 and EP Application No. 97202395 (August 1997
On March 1). If desired, Rh, R
Small amounts of compounds of u, Ir and other elements of group VIII of the Periodic Table of the Elements can be added. Also, for example, a British patent
Reductors such as tin compounds, amines, hydrazine derivatives, formamidine-sulfinic acids and silane compounds as described in No. 789823 may be added as chemical sensitizers. Chemical sensitization may include phenidone and / or a derivative thereof, hydroquinone, resorcinol, dihydroxybenzene and / or a derivative thereof such as catechol, one or more stabilizers or antifoggants, one or more spectral sensitizers or a combination of the above components. Can also be performed in the presence of Chemical sensitization may be carried out at elevated temperatures as described in US-A 5,494,788, for example at a temperature of 60 ° C. or higher, more preferably 70 ° C. to 80 ° C., as opposed to EP Application No. 97202169 (1997). (Filed on July 11, 2011) in the absence of bromide.

Silver halide emulsions can be spectrally sensitized according to the spectral emission of the exposure source for which the silver halide photographic material is designed. Sensitizing dyes suitable for the visible spectral region include John Wiley & Sons, 1964, FM Hamer, "The Cyanine Dyes and Related.
Dyes that can be used for this purpose include cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, isopolar cyanine dyes, hemicyanine dyes, and the like.
Styryl dyes and hemioxonol dyes are included.
Particularly valuable dyes are those belonging to the cyanine dyes, merocyanine dyes and complex merocyanine dyes. In the case of an ordinary light source, for example, tungsten light, a green dye is required. In the case of exposure with an argon ion laser, a blue-sensitive dye is mixed. In the case of red light emitting sources, for example LEDs or He / Ne lasers, red dyes are used.
In the case of exposure with a semiconductor laser, a special spectral sensitizing dye suitable for near infrared is required. Suitable infrared sensitizing dyes are described in US-A 20 958 854, 209 585
6,295,939,3482978,355297
4,357,921,3582,344,3623881
And 3695888. Preferred blue, green, red and infrared sensitizing dyes in connection with the present invention are described, for example, in EP-A 0554585.

In order to enhance the sensitivity in the red or near infrared region, a so-called supersensitizing dye can be used in combination with a so-called red or infrared sensitizing dye. Suitable supersensitizing dyes are
Research Disclosure Vol.289, May 1988, it
em 28952. The spectral sensitizer can be added to the photographic emulsion in the form of an aqueous solution, a solution in an organic solvent or in the form of a dispersion. Suitable blue dyes are, for example, W
O 93/1522, US-A 4520098 and E
P Application No. 97202169 (filed on Jul. 11, 1997). Suitable green sensitizers are, for example, EP-A
0678772, EP-A 0862088 and Rese
arch Disclosure No. 37312, published May 1, 1995.

The silver halide emulsion may contain a conventional emulsion stabilizer. Preferred emulsion stabilizers are azaindene,
Preferred are tetra- or penta-azaindenes, especially those substituted with hydroxy or amino groups. Compounds of this type are described by BIRR in Z. Wiss. Photogr. Photophys. Phot.
ochem. 47, 2-27 (1952). Other suitable emulsion stabilizers are (heterocyclic) mercapto compounds such as those described in US Pat. No. 5,290,674 and mercaptotriazole, mercaptoimidazole, mercaptothiadiazole or EP-A0.
454149 is a mercaptooxadiazole compound.

The silver halide emulsion may contain a pH controlling component. Preferably, the emulsion layer is coated at a pH value near the isoelectric point of gelatin to improve the stability of the coated layer. Other ingredients such as fog inhibitors, development accelerators, wetting agents, and hardeners for gelatin may be present.
The silver halide emulsion layers may contain light-blocking dyes that absorb scattered light and thus promote image sharpness. Suitable light absorbing dyes are for example US-A 4,092,168; 431.
1787; 5344449; 5380634 and DE-
A 2453217. The method for producing the dispersion is described in EP-A 0554834 and 0756201.
Is disclosed.

Further details on the composition, preparation and coating of silver halide emulsions can be found, for example, in the Product Licensing Index.
x, Vol. 92, December 1971, publication 923
2, pages 107-109 and Research Disclosure No. 3
8957, issued September 1, 1996.

The base layer, which preferably contains an antihalation substance such as a light absorbing dye which absorbs light used for image-wise exposure of the imaging element between the support and the silver halide emulsion layer. It is preferably provided. As an alternative, finely divided carbon black can be used as an antihalation material. On the other hand, to obtain sensitivity, a light reflecting pigment, for example titanium dioxide, can be present in the base layer. This layer may further contain hardening agents, matting agents such as silica particles, and wetting agents. Suitable matting agents preferably have an average diameter of 2-10 μm, more preferably 2-5 μm. 0.1 for matting agent
It is generally used in a total amount of the imaging element in ^{g / m 2 ~2.5g / m 2} . These matting agents and / or light reflecting pigments may be present in the silver halide emulsion layer and / or the cover layer. As a further alternative, the light reflecting pigment may be present in a separate layer provided between the antihalation layer and the photosensitive silver halide emulsion layer. The base layer, like the emulsion layer, is preferably coated at a pH value near the isoelectric point of the gelatin in the base layer.

In a further example, the backing layer is preferably provided on the non-photosensitive side of the support in the case of a one-sided coating material. This layer, which can act as an anti-curl layer, comprises common ingredients such as, for example, matting agents (eg, silica particles), lubricants, antistatic agents, light absorbing dyes, opacifiers (eg, titanium oxide) and hardeners and wetting agents. Can be contained. The backing layer can consist of a single or double layer pack.

The hydrophilic layer usually contains gelatin as a hydrophilic colloid binder. Mixtures of different gelatins with different viscosities can be used to adjust the rheological properties of the layers. Other hydrophilic layers, such as emulsion layers, are preferably coated at a pH value near the isoelectric point of gelatin.
However, instead of or together with gelatin, one or more other natural and / or synthetic hydrophilic colloids, such as albumin, casein, zein, polyvinyl alcohol,
Alginic acid or a salt thereof, a cellulose derivative such as carboxymethyl cellulose, denatured gelatin, for example, phthaloyl gelatin and the like can be used.

Particularly when the binder used is gelatin, the hydrophilic layer of the imaging element may comprise a suitable hardener, for example of the vinylsulfone type (for example methylenebis (sulfonylethylene)), an aldehyde (for example formaldehyde,
Glyoxal and glutaraldehyde), N-methylol compounds (such as dimethylolurea and methyloldimethylhydantoin), active halogen compounds (such as 2,4-dichloro-6-hydroxy-s-triazine), and mucohalic acids (such as mucochlorine) Acid and mucophenoxychloric acid). These curing agents can be used alone or in combination. The binder can also be hardened with a fast-reacting hardener such as a carbamoylpyridinium salt of the type disclosed in U.S. Pat. No. 4,063,952. Preferably used curing agents are of the aldehyde type. The curing agent can be used in a wide concentration range, but preferably the hydrophilic colloid 4
% To 7%. Different amounts of curing agent can be used for different layers of the imaging material, or the curing of one layer may be adjusted by diffusion of the curing agent from another layer.

The photographic material according to the present invention may further comprise various types of surfactants in the silver halide emulsion layer or in at least one other hydrophilic colloid layer. Examples of suitable surfactants are described, for example, in EP-A 0 545 452. Preferably, a perfluorinated alkyl group-containing compound is used. The photographic material of the present invention may further comprise various other additives such as Research Disclosure No. 38957,1.
Compounds which improve the dimensional stability of the imaging element as described in Chapters VI and IX, published September 1, 996,
It may contain UV absorbers, spacing agents and plasticizers.

Additives suitable for improving the dimensional stability of the imaging element are, for example, water-soluble or poorly water-soluble synthetic polymers such as alkyl (meth) acrylates, alkoxy (meth) acrylates, glycidyl (meth) acrylates, Polymers of (meth) acrylamide, vinyl ester, acrylonitrile, olefin, and styrene, or the above and acrylic acid, methacrylic acid, α-β-
Dispersions of unsaturated dicarboxylic acids, hydroxyalkyl (meth) acrylates, sulfoalkyl (meth) acrylates, and styrene sulfonic acids).

While the invention will be described in connection with preferred embodiments thereof, it will be understood that it is not intended to limit the invention to those embodiments.

[0075]

EXAMPLES Example 1 Emulsion A (Silver chloroiodide tabular grains: Comparative Example ) The following solutions were prepared:-5.91 l of dispersion medium containing 0.47 mol of sodium chloride and 100 g of oxidized gelatin ( C) to 5
Prepared at a temperature of 5 ° C. -A solution (N) containing 36 ml of a 1% adenine solution. A 2.94 mol silver nitrate solution (A1). -2.93 mol of sodium chloride, 0.015mo
Solution containing 1 l potassium iodide and 42 ml 1% adenine solution (1 l) (B1). -A solution (1 ml) containing 14.7 mmol of potassium iodide (B2). -A solution (250 ml) containing 25 g of inert gelatin at 60 ° C (N2).

Solution N was added to solution C before the start of precipitation.
Solution C was then stirred for 15 minutes and the pH was set to a value of 6.0.

The solution A1 and the solution B1 were simultaneously dispersed in the dispersion medium C
The nucleation step was carried out by introducing the mixture at a flow rate of 70 ml / min for 30 seconds.

During the physical ripening time of 20 minutes, the temperature was raised to 70 ° C. and solution N2 was added.

The solution A1 was then applied at a flow rate of 10 ml / min, which increased linearly to 27.4 ml / min, to maintain a constant mV value measured by a +115 mV silver electrode vs. Ag / AgCl ingold reference electrode. Solution B1 at flow rate
Was introduced by a double jet for 1730 seconds.

Next, a silver electrode pair of Ag / A of +135 mV was applied.
Solution A1 at a constant flow rate of 10 ml / min to obtain the desired mV value measured by the gCl ingold reference electrode
The pAg adjustment step was performed for 9 minutes by introducing

After this pAg adjustment step, the flow rate of solution A1 was increased temporarily to 19.80 ml / min over 22.5 minutes, while the flow rate of solution B1 was increased to maintain a constant potential value of +135 mV.

Another physical ripening step of 4 minutes was performed.

The last precipitation step was performed by introducing solution B2 by a single jet at a constant flow rate of 20 ml / min for 120 seconds.

After precipitation, 56 ml of polystyrene sulfonic acid was added to the emulsion and the emulsion was stirred for 5 minutes. pH 3.5
And the emulsion was desalted by three successive washing steps, each using 4 l of deionized water.

A silver chloroiodide tabular grain emulsion having 1 mol% iodide ion based on silver is obtained, the emulsion comprising a high percentage (at least 80%) of tabular grains and corresponding electron microscopy. As calculated from the photograph, it had an aspect ratio of 7 or more, an average ECD (equivalent circular diameter) of 0.96 μm, and an average thickness of 120 nm.

The coefficient of variation was 0.33, calculated from the data obtained for the ECD, while the number of tabular grains of approximately 14% was calculated from photographs made by electron microscopy.

Emulsion B (Silver chloroiodide tabular grains: Inventive Example ) The following solutions were prepared: 5 containing 0.47 mol of sodium chloride, 100 g of oxidized gelatin and xg of block copolymer Y (see table) .84 l of dispersion medium (C) were prepared at a temperature of 55 ° C. -A solution (N) containing 36 ml of a 1% adenine solution. A 2.94 mol silver nitrate solution (A1). -2.93 mol of sodium chloride, 0.0147 m
ol of potassium iodide and 42 ml of a solution containing 1% by weight of adenine (1 l) (B1). -A solution (1 ml) containing 14.7 mmol of potassium iodide (B2). -A solution (250 ml) containing 25 g of inert gelatin at 60 ° C (N2).

Solution N was added to solution C before the start of precipitation.
Solution C was then stirred for 15 minutes and the pH was set to a value of 6.0.

The solution A1 and the solution B1 were simultaneously dispersed in the dispersion medium C
The nucleation step was carried out by introducing the mixture at a flow rate of 70 ml / min for 30 seconds.

During the physical ripening time of 20 minutes, the temperature was raised to 70 ° C. and solution N2 was added.

The solution A1 was then applied at a flow rate of 10 ml / min, which increased linearly to 27.4 ml / min, to maintain a constant mV value measured by a +115 mV silver electrode vs. Ag / AgCl ingold reference electrode. Solution B1 at flow rate
Was introduced by a double jet for 1730 seconds.

Next, a silver electrode pair of Ag / A of +135 mV was applied.
Solution A1 at a constant flow rate of 10 ml / min to obtain the desired mV value measured by the gCl ingold reference electrode
The pAg was adjusted over 9 minutes by introducing

After this pAg adjustment step, the flow rate of solution A1 was increased primarily to 19.80 ml / min over 22.5 minutes, while the flow rate of solution B1 was increased to maintain the same constant potential of +135 mV. .

A separate physical ripening step of 4 minutes was introduced.

The last precipitation step was performed by introducing solution B2 by a single jet at a constant flow rate of 20 ml / min for 120 seconds.

After precipitation, 56 ml of polystyrene sulfonic acid was added to the emulsion and the emulsion was stirred for 5 minutes. pH 3.5
And the emulsion was desalted by three successive washing steps, each using 4 l of deionized water.

The dimensions obtained by electron microscopy of the thus obtained silver chloroiodide tabular grain emulsions having 1 mol% iodide ion based on silver are summarized in Table 1 below.

[0098]

[Table 2] Compound I.1 = PLURONICS® 31R
1 (Comparative) Compound II.1 = HYPAN® MS16002
(Invention) Compound 1.2 = PLURONICS (registered trademark) 17R
4 (Comparative) Compound II.2 = TETRONIC® 1508
(Invention) Compound II.3 = HYPAN® MS16105
(Invention) var ^* : Calculated for the average equivalent circular diameter (ECD) of individual particles as measured by electrolysis.

As can be seen from Table 1, PLURONIC
Adding S.RTM.31R1 provides an improvement in variability when it is used in large quantities,
There is no significant reduction in spherical and thick tabular grains (termed "tabs").

The addition of HYPAN® MS 16002 results in a considerable improvement (decrease) in the variation in the average volume of the grains, with a noticeable and favorable decrease in the amount of spherical and thick tabular grains.

PLURONICS (registered trademark) 17R4
Does not produce any noticeable improvement when used at the highest concentration. In contrast, noticeable thickness growth is observed.

The addition of TETRONIC® 1508 has no positive effect on variations in the average volume of the grains, but has a positive effect in that a reduction is seen in the amount of spherical and thick tabular grains present.

The addition of HYPAN® MS16105 has about the same effect on the variation in average volume of the grains and the amount of spherical and thick tabular grains present as was seen for HYPAN® MS16002 above. . As a result, the addition of polymer is PLURO
No increase in tabular grain thickness occurs except for the addition of NICS®.

Example 2 Emulsion B (silver chloroiodide tabular grains) as described in Example 1 was prepared using gelatin, adenine and HYPAN.
The same procedure was repeated except for the amount of (registered trademark) MS16002 added in the production method. The amounts are summarized in Table 2 according to the variation in the average thickness of the tabular grains obtained in the emulsion crystal distribution (indicated as "% var.t _{TA B} ") and all that is present in the emulsion crystal distribution. Further obtained are the results obtained for the variation in the thickness of the particles (shown as “% var.t _ALL ”).

[0105]

[Table 3]

Table 2 shows that HYPAN® MS16
It can be seen that the addition of 002 during the preparation of the tabular grain emulsion reduces the variation in average thickness of the tabular grains present in the emulsion. If the coating No. 11 and 12, 13 and 1
Comparing 4, 15 and 16, respectively, shows that when a high amount of HYPAN® MS 16002 is used as a preferred hydrophilic amphoteric block copolymer, it indicates the presence of high (ie, high percentage) tabular grains. ) It can be seen that the variation in the average thickness of all particles is reduced.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ann Vervik, Septograt 27, Mortzel, Belgium Inside Agfa Geverth Namloze Bennacht Chap (72) Inventor Nadia Verman, Septograt 27, Motzer, Belgium (72) Inventor Frank Rue Septograt, Mortzeel, Belgium 27 Inside Agfa Gewert Namloze Bennachtapp

Claims (8)

[Claims] 1. A method for producing a gelatin emulsion having silver chloride-rich grains, wherein at least 70% of the total projected area of all grains has an average aspect ratio of at least 2: 1 and an average of at least 0.3 μm. Equivalent circular diameter and 0.05 ~
Provided by {111} tabular grains having an average thickness of 0.25 μm, wherein the variation in the average equivalent circular diameter of the tabular grains is 30% or less, and the variation in the average thickness of the tabular grains is 20% or less, wherein said tabular grains are present in a quantity of at least 90%, said method comprising the steps of:-preparing a dispersion medium containing a starting amount of crystal habit modifier in a reaction vessel; Silver halide crystal nuclei are precipitated in the vessel by double jet precipitation of an aqueous solution containing silver nitrate and an aqueous solution containing silver nitrate (1% of the total amount of silver nitrate used).
0% by weight is consumed);-The silver halide crystal nuclei grow by further precipitation of silver halide by double jet precipitation of an aqueous solution containing halide ions and an aqueous solution of silver nitrate (90% by weight or more of the total amount of silver nitrate). Wherein at least one compound is added to the reaction vessel during at least one of the steps, wherein the compound comprises (i) a series of units having a pendant nitrile group according to Formula I A hydrophilic amphoteric block copolymer comprising a nonionic acrylic block and (ii) an acrylamide (acrylamidine) block comprising a sequence of units according to formula II, wherein said hydrophilic amphoteric block copolymer is pendant within said acrylamide (acrylamidine) block. Units having acidic groups or salts and pendants thereof Further comprising a unit or a salt thereof having a group group, wherein the formula I and II is characterized in that corresponding to the following structural formula: ## STR1 ## In formula I, R ¹ represents hydrogen, alkyl or substituted alkyl. In Formula II, R ² represents hydrogen, alkyl or substituted alkyl, R ³ represents hydrogen, alkyl, substituted alkyl, aryl or substituted aryl, and X represents O
Or NH. 2. The unit having a pendant acidic group has the formula
The method according to claim 1, which corresponds to III or IV: In formula III, R ⁴ represents hydrogen, alkyl or substituted alkyl. In Formula IV, R ⁵ represents hydrogen, alkyl or substituted alkyl, X represents O or NH, R ⁶ represents an organic linking group having at least one carbon atom, and -Y represents-
_{COOH, -OPO 3 H, -SO 3} H or -OSO ₃ H
Represents 3. A process according to claim 1, wherein said unit having a pendant basic group corresponds to formula V or VI: In formula V, R ⁷ represents hydrogen, alkyl or substituted alkyl, and R ⁸ represents hydrogen, alkyl, substituted alkyl, aryl or substituted aryl. In formula VI, R ⁹ represents hydrogen, alkyl or substituted alkyl, X represents O or NH, R ¹⁰ represents an organic linking group having at least one carbon atom, and Z represents a nitrogen-containing base. 4. The method according to claim 1, wherein the hydrophilic amphoteric block copolymer is N-
(2-sulfo-ethyl) -acrylamide and N- (2
-Sulfo-ethyl) -acrylamidine units. 5. The method according to claim 1, wherein said tabular {111} grains rich in silver chloride are composed of silver chloride, silver chlorobromide, silver chloroiodide or silver chlorobromoiodide. . 6. A gelatin emulsion having silver chloride, silver chlorobromide, silver chloroiodide or silver chlorobromoiodide grains, wherein at least 70% of the total projected area of all grains is 2: 1 or more. Ratio, average equivalent circular diameter of at least 0.3 μm and 0.1.
Provided by {111} tabular grains having an average thickness of from 0.5 to 0.25 μm, wherein the variation about the average equivalent circular diameter of the tabular grains is 30% or less, and the average thickness of the tabular grains is about (I) a nonionic acrylic block comprising a succession of units having pendant nitrile groups according to formula I, and (ii) a formula II
Further characterized by the presence of at least one compound which is a hydrophilic amphoteric block copolymer containing an acrylamide (acrylamidine) block comprising a series of units according to claim 1, wherein said hydrophilic amphoteric block copolymer is pendant within said acrylamide (acrylamidine) block A gelatin emulsion further comprising a unit having an acidic group or a salt thereof and a unit having a pendant basic group or a salt thereof, wherein the above-mentioned formulas I and II correspond to the following structural formulas: In formula I, R ¹ represents hydrogen, alkyl or substituted alkyl. In Formula II, R ² represents hydrogen, alkyl or substituted alkyl, R ³ represents hydrogen, alkyl, substituted alkyl, aryl or substituted aryl, and X represents O
Or NH. 7. A photographic material comprising a support and on one or both sides thereof one or more silver halide emulsion layers coated from a gelatin emulsion according to claim 6. 8. The photographic material according to claim 7, wherein said photographic material is a single-sided or double-sided radiographic material.