JPH02222940A - High aspect ratio flat particle emulsion - Google Patents

Abstract

PURPOSE: To establish superior relation between the dispersibility of particles and the high aspect ratio of flat platy particles by regulating the quotient given by dividing the average aspect ratio of flat platy silver iodobromide particles by the coefft. of variation of all silver iodobromide particles to >=0.7. CONSTITUTION: This emulsion is an emulsion in which flat platy particles each having <0.3μm thickness have an average aspect ratio of >=12 and account for >=50% of the total projection area of all particles and the quotient given by dividing the average aspect ratio of flat platy silver iodobromide particles by the coefft. of variation of all silver iodobromide particles is regulated to >=0.7. Superior relation between the dispersibility of particles and the high aspect ratio of flat platy particles is established.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to photography. More particularly, this invention relates to improvements in radiation-sensitive silver halide emulsions.

[Conventional technology]

Representative examples of the earliest publications teaching high aspect ratio (greater than 8:1) silver iodobromide emulsions include:
U.S. Patent No. 4.43 by WHgus et al.
No. 4.226, U.S. Pat. No. 4.439.520 to Kofron et al., Solbe
U.S. Pat. No. 4.433.048 to Daabendiek et al., U.S. Pat.
No. 4,478.929 by Evans et al.
U.S. Pat. No. 4,504,570 by Evans et al. and U.S. Pat. No. 4,435.501 by Maskasky et al. More recently,
U.S. Pat. Nos. 4,693,964 and 4.672 to Daubend 1ek et al.
, No. 027 reports on the preparation of high aspect ratio silver iodobromide emulsions with much smaller average grain sizes, called small and thin grained silver iodobromide emulsions.

Also, U.S. Pat. No. 4,713,320 to Maskasky et al. describes the effect of methionine reduction of gelatin on the production of silver iodobromide high aspect ratio tabular grain emulsions.

Advantages of silver iodobromide high aspect ratio tabular grain emulsions include an improved relationship between speed and granularity, improved image sharpness (for both single layer and multilayer photographic elements), increased development speed,
Improved insensitivity to temperature changes during development, faster fixing speed, more favorable toning, improved coverage color, negative blue (green or red) and blue speed when spectrally sensitized to the negative blue portion of the spectrum. as well as various other advantages found in certain photographic applications.

Although almost all silver iodobromide high aspect ratio tabular grain emulsions are produced by double jet precipitation,
Difficulties are initially encountered in reducing the dispersibility of the emulsion.

That is, while regular grain emulsions containing only the desired grain group (e.g., cubic or octahedral grain emulsions) are easily produced by double-jet precipitation, tabular grain emulsions containing only tabular grains cannot be produced. It is rarely done. Therefore, the mixing of tabular grains and non-tabular grains is one factor that determines the dispersibility of tabular grain emulsions. The second factor that determines dispersibility is the difference in the dispersibility of the tabular grain groups themselves, which is correlated with twinning, and twinning is the difference between the tabular grain emulsion and the twinning. There is a correlation with the edge precipitation growth pattern that distinguishes it from normal grain emulsions in which crystals are absent or rare and precipitation is not biased toward a particular group of crystal planes. Furthermore, the dispersibility of tabular grain emulsions increases with increasing average aspect ratio of the tabular grains. Thus, the levels of dispersion readily achieved with low aspect ratio tabular grain emulsions were not achievable with high aspect ratios.

U.S. Pat. No. 4,477.565 to Htmmelwright and Sug.
U.S. Patent No. 4,609,621 by imo to) et al.
No. 4.656.120 and No. 4.665.012
No. 6, No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, No. 2003, No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, 2006, and No. 1, No. 3, No. 1, No. 1, No. 1, No. 1, No. 1, No. 1, No. 2, No. 2, No. 2, No. 1, 2003, 1997, and describes various methods of preparing high aspect ratio tabular grain silver iodobromide emulsions.

From the beginning of research into high aspect ratio tabular grain emulsions, silver bromide tabular grain emulsions were much easier to prepare than their silver iodobromide counterparts, offering both high aspect ratios and low levels of dispersibility. was known to show. Research Disclosure
ure), Volume 232, August 10, 1983, Item 23212 [corresponding to French Patent No. 2,534.036 by Mignot et al.], the aging method results in coefficients of variation of 15, 16 and 28.
Tabular grain silver bromide emulsions with average aspect ratios of 10, 12, and 25.6 have been prepared. Research Disclosure and Previously Published Products
Licensing Index (Product Li
cen-sing Index) is owned by Kenneth Masson Publications Limited, Emsworth, Hampshire PO 107DD, UK.
h Mason Publications, LL+
j,) is a publication published by. Sai-tou
) et al., West German Patent Application Publication No. 3.707. i,
No. 3541 uses a double-jet precipitation method and a single-jet precipitation method to obtain an aspect ratio comparable to Mignot and a higher coefficient of variation (Saito only reports a coefficient of variation based on tabular grain groups only). We manufacture silver bromide emulsions that exhibit

[Problem to be solved by the invention]

The object of the present invention is to contain a dispersion medium and silver iodobromide particles,
Tabular silver iodobromide grains having a thickness of less than 0.3 ta account for more than 50% of the total projected area of the total silver iodobromide grain group, and high aspect ratio tabular grains having an average aspect ratio of more than 12. It is an object of the present invention to provide a high aspect ratio tabular grain emulsion that exhibits both the advantages of high aspect ratio tabular grain silver iodobromide emulsions and the art recognized advantages of monodispersity.

[Means to solve the problem]

The emulsion of the present invention has an average silver iodobromide tabular grain aspect ratio divided by a coefficient of variation of the total silver iodobromide grain group of 0.7.
It is characterized by exceeding.

Prior to this invention, either the average tabular grain aspect ratio or the monodispersity of silver iodobromide emulsions had to be compromised. In the case of the present invention, an excellent relationship between grain dispersibility and high tabular grain aspect ratio can be realized.

The present invention is based on U.S. Pat. No. 4,434,226 to Wilgus et al.
U.S. Patent No. 4,439,520 to Sorberg et al., U.S. Patent No. 4,433,0 to Sorberg et al.
No. 48, U.S. Pat. Nos. 4.414.310 and 4.693 to Daubendiek et al.
．． No. 964 and 4,672,027, U.S. Pat. No. 4,504,5 by Evans et al.
No. 70 and Maskasky U.S. Pat. Nos. 4.435.501 and 4,713,3
This issue concerns improvements to the teachings in No. 20. Unless otherwise specified, all characteristics, preparation and photographic applications of the emulsions of this invention are as described in these publications.

The present invention relates to a silver iodobromide tabular grain emulsion having an improved relationship between grain tabularity and dispersibility. Definitions of terms necessary for a detailed explanation of the invention will be given below.

As used herein, "high aspect ratio tabular grain emulsion" refers to an emulsion in which tabular grains less than 0.3 tm in thickness have an average aspect ratio greater than 12 and greater than 50% of the total grain projected area. It means the emulsion that accounts for the proportion. The average aspect ratio of tabular grains can be determined by measuring the aspect ratio of each grain and averaging the aspect ratios of all tabular grains, or by calculating the average diameter of all tabular grains by the average thickness of all tabular grains. It can be found by dividing.

"Coefficient of variation", as used in the art, means one hundred times the standard deviation of all silver iodobromide grain sizes divided by the average silver iodobromide grain size.

The coefficient of variation obtained by counting and averaging all grains, including tabular grains and non-tabular grains, is as follows:
This value is higher than that based only on tabular grain groups.

Dividing the average aspect ratio of the tabular silver iodobromide grains of the emulsions of this invention by the coefficient of variation of all the silver iodobromide grains present yields a quotient greater than 0.7. This quotient is greater than that exhibited by any silver iodobromide tabular grain emulsion hitherto known in the art, as shown in the Examples below, by 0.7°0.8 and 1.0. Exceeding quotients can be obtained without rigorous optimization of emulsion manufacturing operations. By routine optimization of the example emulsion preparation process in view of the general teachings herein, quotients of 1.1.1.5.2.0 and higher can be achieved. The reason for defining the present invention by the quotient obtained by dividing the average aspect ratio by the coefficient of variation, rather than simply defining it by the minimum coefficient of variation, is that when a suitable emulsion manufacturing process is used, the coefficient of variation is This is because it increases linearly as the average aspect ratio of . For silver iodobromide emulsions with average aspect ratios ranging from 5:1 to 0:1, acceptable monodispersity with respect to the photographic performance requirements of this invention is easily achieved. However, for average aspect ratios exceeding 12:1, monodispersity is insufficient, and higher monodispersity is desired. In the present invention, the balance between tabular grain average aspect ratio and monodispersity is improved at aspect ratios for which a satisfactory desired monodispersity has not previously been achieved.

Preferred emulsions of the invention have tabular grain silver iodobromide grains having a thickness of less than 0.3 nm (optimally less than 0.2 nm) and an average aspect ratio of greater than 12 (optimally at least 20).
It is something. Very high aspect ratios of 100 or less are preferred. In a preferred embodiment of the invention, the tabular silver iodobromide grains satisfying the thickness criteria described above account for more than 70% (optimally more than 90%) of the total projected area of the silver iodobromide grains. . It goes without saying that the emulsion of the present invention ideally consists essentially of tabular silver iodobromide grains that satisfy the above-mentioned thickness criteria.

In order to meet the usual photographic image clarity requirements, the average grain size (diameter) of the emulsions of the present invention is less than 100%.
U.S. Pat. Nos. 4,672,027 and 4 by K) et al.
Preparation of tabular grain emulsions of very small diameter (average diameter 0.2 to 0.6 pm) as well as emulsions having an average tabular grain diameter greater than 0.6 ta as disclosed in No. 693.964. While the present invention can be used for particles with an average particle diameter of 1.5 to 3.5 tra, especially 1.
It is particularly well suited to emulsions having average grain diameters in the range 5 to 2.5.

The unique population of silver iodobromide grains required in the tabular grain emulsions of the present invention is made by monodisperse silver iodobromide tabular grain precipitation in place of the experimental methods of emulsion preparation disclosed in the prior art. This was achieved by specifically devising particle nucleation and growth to maintain the properties.

This approach begins by dividing the emulsion precipitation process into three separate steps:

(1) A nucleation step in which all the grains constituting the emulsion exist as separate entities. In this process, especially
Minimize nuclear variation.

(2) A holding step to reduce particles that remain irregular in the particle core.

(3) A growth process that can further reduce particles that remain irregular, especially at the beginning of the growth process. It goes without saying that this growth process can be controlled so that particle nuclei do not continue to form.

Although various specific techniques exist for carrying out the precipitation process, not all techniques are equally important nor are all necessary. In the present invention, it is most important to eliminate particle variations as early as possible. The reason for this is that if the grains vary at an early stage, this will continue to affect the subsequent steps of emulsion production.

The most important single process variation for achieving emulsions satisfying the requirements of the present invention is to carry out an approach in which all grain nuclei are produced as nearly simultaneously as possible.

In a solution of 7 that is supersaturated with silver and bromide ions,
Precipitation occurs and particle nuclei are formed. This nucleus immediately begins to grow. Unless all the mullets are generated at the same time, the nuclei that are generated earlier are larger than the nuclei that are generated later. The precipitation process illustrated in the examples for producing emulsions meeting the requirements of the invention involves increasing the concentration of the aqueous silver and bromide salt solutions added to the reaction vessel and reducing the addition time to less than 10 seconds. Preferably, addition of both silver and bromide salts is completed within 5 seconds, ideally less than 1 second. To achieve this, it is preferred that the salt solution concentration exceeds 1 molar. In this way, the bulk of the substance to be introduced is reduced.

Since the objective is to get the silver and bromide salts out of solution as quickly as possible, temperature can be controlled to limit solubility. Although the precipitate concentration is known to be up to 90°C, it is preferable to limit the nucleation temperature to 60°C or less. In summary, reducing the time required for initial silver and bromide salt addition is the most important change in a single process. Increased salt concentration and limited temperature are preferred components in nucleation. Finally, omit iodine ions from the nucleation step to avoid unnecessarily complicating nucleation.

Once the emulsion grains are formed by nucleation, the next step in the precipitation process immediately reverses the initial direction of net ion transfer from solution to the nuclei. However, at this time, control is performed so that most of the nuclei remain. This is accomplished by rapidly changing the supersaturated solution to one in which the silver and bromide ions are below the saturation limit. The second process is
This is a ripening process in which small silver halide nuclei disappear while the remaining nuclei remain. This step can be achieved by using any one or a combination of known aging methods. The simplest of these methods is to adjust the temperature of the core emulsion upwards to increase the solubility level of silver and bromide ions. It is also possible to increase the pBr of the solution while maintaining the growth range taught in the art for silver iodobromide tabular grain production. As a result, the bromide ion concentration in the solution decreases, and the bromide ions move into the solution and return. A net loss of silver and bromide ions occurs for small grains, and a net gain for the remaining grains, which is a characteristic of ripening as understood in boat fishing. Ripening removes small grain nuclei, which has the overall effect of narrowing the grain size frequency distribution.

In the extreme case of nucleation at room temperature in the absence of a peptizer, ripening can be carried out by increasing the temperature up to 90°C.
A temperature difference is created between nucleation and ripening at 70°C.

In practice, significant improvements in emulsion properties are obtained when the temperature difference between nucleation and ripening is in the range of about 10-40°C, optimally about 15-30"C.

The time required for ripening in the second step is preferably 5 to 30 minutes in the absence of a ripening agent other than dissolved bromide ions. Addition of known ripening agents such as thioethers, thiocyanates, ammonia, etc. accelerates ripening. If ammonia is used as a ripening agent, it is preferably deactivated at the end of the ripening interval by suitably adjusting the pH. Notloff (N
Particularly preferred is the nuclear ripening procedure described in U.S. Pat. However, this operation alone does not produce the emulsion of the present invention.

At the end of the ripening process, there is a population of grain nuclei with smaller particle-to-particle variations than at the end of the nucleation process. At this stage, emulsions satisfying the requirements of the invention can be grown using conventional silver iodobromide tabular grain growth conditions, such as those described in the publications cited above.

Iodine ions are introduced during the growth process. Solbelb (So
U.S. Pat. No. 1,433,048 to
In this issue, the reason why the addition of iodine ions is preferable is disclosed.

During both the ripening and growth steps, the par in the reaction vessel is preferably sufficiently higher than the pBr in the reaction vessel during nucleation. Generally, at the beginning of the ripening step, it is preferred to adjust the pBr in the reaction vessel to greater than 1.6 and below the growth process pBr limit taught in the above-mentioned publications. Further increasing pBr causes tabular grains to precipitate on the major faces, reducing the average aspect ratio of the emulsion.

Modifying compounds can be present in the silver iodobromide precipitation. Such compounds can be initially introduced into the reaction vessel or added together with one or more salts according to conventional methods. That is, Arnold
) et al., U.S. Patent No. 1,195,432; Hochstetter et al., U.S. Patent No. 1
．． No. 951.933, U.S. Patent No. 2.448.060 to TrLvelli et al., U.S. Patent No. 2.628.16 to Overman.
No. 7, U.S. Patent Tube 2 by Mul!er et al.
．． 950.972, Stde-both
U.S. Pat. No. 3,488.709 to Rosecrants et al., U.S. Pat.
4,269.927 and Research Disclosure, Volume 134, June 1975, Item 13452, ≦
Similarly, modifying compounds such as thallium, lead, bismuth, cadmium, zinc, medium chalcogens (ie sulfur, selenium and tellurium), gold and Group I noble metals can be present in the precipitation. Tabular grain emulsions are Moisar
) and others in the Journal of Photographic Science.
c 5science), Volume 25, 1977, No. 1
Internal reduction sensitization can be performed during precipitation as described on pages 9-27.

Once silver iodobromide high aspect ratio tabular grain emulsions are produced by the method of the present invention, they can be shelled to form core-shell emulsions by methods well known in the art. Photographically effective silver salts can be used to form shells in the high aspect ratio tabular grain emulsions produced by the method of this invention. A method for producing a silver halide shell is described by Eva
ms) et al., US Pat. No. 4,504,570.

In forming tabular grain emulsions, peptizers can be used at concentrations of 0.2 to about 10 percent by weight, based on the total weight of emulsion components in the reaction vessel. Generally, by maintaining the concentration of peptizer in the reaction vessel in the range of less than about 6% by total weight before and during particle formation and adding the vehicle in slow additions, It is common to adjust the emulsion vehicle concentration upwards to obtain optimal coating properties. The initially formed emulsion contains approximately 5 to 5
Preferably it contains 0g, preferably about 10-30g of peptizer. Additional vehicle can be added later to achieve higher concentrations up to 1000 g per mole of silver halide. The vehicle concentration in the final emulsion is preferably greater than 50 g per mole of silver halide, and when coated and dried to form the photographic element.
Preferably, the vehicle accounts for about 30-70% by weight of the emulsion layer.

The vehicle (including both binder and peptizer) is
It can be selected from those conventionally used in silver halide emulsions. Preferred peptizers include hydrophilic colloids, which may be used alone or in combination with hydrophobic substances; suitable hydrophilic substances include:
Proteins, protein derivatives, cellulose derivatives such as cellulose esters, gelatin such as alkali-treated gelatin (cow bone or skin gelatin) or acid-treated gelatin (pork skin gelatin), gelatin derivatives such as acetylated gelatin, phthalated gelatin Examples include substances such as polysaccharides such as dextran, gum arabic, zein, casein, pectin, collagen derivatives, agar, arrowroot, albumin, and the like. Regarding these hydrophilic substances, U.S. Pat. No. 2,614.9213 and 2.61.4.
No. 929, US Patent No. 2, by Lowe et al.
No. 691,582, No. 2,614,930, No. 2.6
No. 14.931, No. 2.327,808 and No. 2.4
No. 48,534; U.S. Pat. Nos. 2,787.545 and 2,958.880 to Gates et al.; U.S. Pat.
U.S. Patent No. 2.816,027 by Rel, 1) et al., U.S. Patent No. 3.132,9 by Ryen.
No. 45, No. 3.138,461 and No. 3.186.84
No. 6, British patent cylinder 1 by Dersch et al.
, 167, 1.59 and U.S. Pat. No. 2,960.
No. 405 and No. 3,436,220, Geary (Ge.
U.S. Patent No. 3.486.896 by ary), British Patent No. 793.54 by Gazzard.
No. 9, U.S. Patent No. 2,9 by Gates et al.
92,213, No. 3. ．． No. 157,506, 3.18
4.312 and 3,539,353, Miller (formerly 1
U.S. Pat.
No. 502, U.S. Patent No. 3 by Malan,
No. 551,151, U.S. Pat. No. 4,018,609 to Lohmar et al.
-anj) et al., British Patent No. 1,186,790,
British patent cylinder 1.489,0 by Poly(llori) etc.
No. 80, Belgian Patent No. 856.631, British Patent No. 1.490,644, British Patent No. 1.483,551
British Patent Tube 1.45 by Arase et al.
No. 9,906, U.S. Patent No. 2 by Salo,
110,491 and 2,311,086, U.S. Patent No. 2.34 by Fal 1esen et al.
No. 3.650, U.S. Patent No. 2,322.085 to Yutzy, U.S. Patent No. 2.563.791 to Lowe, Talb.
U.S. Pat. No. 2,725.293 to Hifborn, U.S. Pat.
No. 022, U.S. Pat. No. 2,956,883 to PePautm et al., Ritchie
British Patent No. 2.095 by Desipner (DeS)
U.S. patent tube 1.752.069 by
No. 2,127,573 by Sheppard et al., U.S. Patent No. 2,256,720 by Lierg et al.
U.S. Patent No. 2,361.936 by Spar; British Patent No. 15,72 by Farmer.
No. 7, British Patent No. 1,062,116 by Stephens and Yaw
US patent cylinder 3.923.51 by +amo to) et al.
It is stated in No. 7.

The average tabular grain thickness is less than about 0.074, especially 0.05
When preparing silver iodobromide high aspect ratio tabular grain emulsions according to the invention of less than -, it is preferred to use gelatin and gelatin-derived peptizers containing 30 micromoles of methionine per gram.

The methionine content can be reduced by treating the demulcent with an oxidizing agent such as hydrogen peroxide. In this regard, Daubendiek et al., U.S. Pat.
, No. 964 is particularly applicable. Although not required, reducing or removing methionine from the peptizer can result in a very thin particle structure.

Other materials commonly used in combination with hydrophilic colloids as vehicles (materials containing vehicle fillers, e.g. in the form of latex) include poly(vinyl lactams), acrylamide polymers, polyvinyl alcohol and/or their derivatives, polyvinyl acetals,
Polymers of alkyl and sulfoalkyl acrylates and metharylates, hydrolyzed polyvinyl acetates, polyamides, polyvinylpyridine, acrylic acid polymers, maleic anhydride copolymers, polyalkylene oxides,
Methacrylamide copolymers, polyvinyloxazolidinones, maleic acid copolymers, vinylamine copolymers, methacrylic acid copolymers, acryloyloxyalkyl sulfuric acid copolymers, sulfoalkyl acrylamide copolymers, polyalkyleneimine copolymers, polyamines Class, N, N-
Synthetic polymer peptizers such as dialkylaminoalkyl acrylates, vinyl imidazole copolymers, vinyl sulfide copolymers, halogenated styrene polymers, aminoacrylamide polymers, polypeptides, carriers and/or
Alternatively, a binder may be mentioned. These synthetic polymeric peptizers, carriers and binders are described in the following publications: Hollister et al., U.S. Patent No. 3.679.425, 3.7'86
, No. 564 and No. 3,813,251, Lo.
No. 2,253,078, 2.
No. 276.322, No. 2,276.323, No. 2.2
No. 81.703, No. 2.311.058 and No. 2.4
No. 14.207, US Pat. No. 2,484.456, US Pat. No. 2.541.474 and US Pat. No. 836, Swit
U.S. Patent Nos. 3.415.653 and 3.
, 615.624, U.S. Patent No. 3,488,708 by Smith (Sn+1th) et al., Whiteley (Wh
U.S. Patent No. 3,392,025 by iteley et al.
No. 47 and No. 3,511,818, F.
U.S. patent cylinder 3.681,0 by itzgerald
No. 79, No. 3,721.565, No. 3.852.07
No. 3, No. 3.861.918 and No. 3,925,08
No. 3, U.S. Patent No. 3.879.205 by Fitzgerald et al., Nottorf (N.
U.S. Patent No. 3.142.568 by ottorf, U.S. Patent No. 3.062 by Houck et al.
．． No. 674 and No. 3,220,844, Dan
U.S. Pat. No. 2.882.161 by n) et al.
U.S. Patent Tube 2.579.0 by Schupp
16, U.S. Pat. No. 2.829,053 to Weaver, U.S. Pat. No. 2.698.240 to Alles et al., Pri
U.S. Patent No. 3.003,879 by Merrill et al., U.S. Patent No. 3.419 by Merrill et al.
, 397, U.S. Pat. No. 3,284,207 to Sto-nhaa+, Loha
U.S. Patent No. 3,167.430 by +ar) et al., U.S. Patent No. 2,9 by WHliams
No. 57.767, Dawson et al., U.S. Pat. No. 2,893,867, Smith
U.S. Patent Nos. 2,860,986 and 2,90, et al.
No. 4,539, Pontice I
U.S. Patent No. 3,929.482 and 3.860,428 by Io) et al.
U.S. Pat. No. 3,939.130 by Ello, U.S. Pat.
No. 11,911, Canadian Patent No. 774,054 by Dykstra et al.
) et al., U.S. Patent No. 3, 287, 289; British Patent No. 1,466.600 by Smith
No. 1,062,116 by Stevens, British Patent No. 1,062,116, by Fordyc
U.S. Pat. No. 2.211.323 by e), U.S. Pat.
No. 4,877, U.S. Pat. No. 2,420.455 to Watkins, Jones
U.S. Pat. No. 2.533.166 to Bolton, U.S. Pat. No. 2.495.918 to Bolton.
No. 2, U.S. Patent No. 2 by Graves,
No. 289,775, U.S. Pat. No. 2,565,418 to Yackel, Unruh
) and U.S. Patent No. 2,865.893 and 2,8
No. 75,059, U.S. Pat. No. 3,536.491 to Rees et al., Broadhead
British Patent No. 1,348.815 by Head) et al.
U.S. Patent Tube 3.47 by Tayfor et al.
No. 9.186, U.S. Patent No. 3.520.857 to Merrill et al., Bacon
U.S. Pat. No. 3,690,888 by Bowman et al.
U.S. Patent No. 3.748.143 by Bowman, British Patent No. 808.227 and No. 808.228 by Dickinson et al., British Patent No. 822.192 by Wood and Iguchi. British patent cylinder 1,39 by et al.
No. 8,055. These additional substances do not need to be present in the reaction vessel during precipitation, but rather are conventionally added prior to application.

Vehicle materials, particularly those containing hydrophobic materials that are effective in combination with hydrophilic colloids, may be located not only in the emulsion layer of the photographic element, but also in overcoat layers, interlayers, and under the emulsion layers. It can also be used in other layers, such as layers.

As explained above, ripening may occur during the holding step of emulsion production. However, it is not necessary to limit ripening to just this one step of emulsion production, and
Usually not limited. Well-known halogenation! ! ! Solvents are effective in promoting ripening. For example, when bromine ions are present in the reaction vessel, excess bromine ions are known to accelerate ripening. Therefore, pouring the bromide salt solution into the reaction vessel itself promotes ripening. Other ripening agents may also be used and may be included in the dispersion medium in the reaction vessel prior to addition of the silver and halide salts, or one or more of the halide salts, silver salts, or peptizers. can be introduced into the reaction vessel together with Furthermore, as a variant, it is also possible to introduce the ripening agent separately during the silver halide and silver salt additions.

Among the preferred ripening agents, those containing sulfur are particularly preferred. For example, thiocyanates such as alkali metal (most commonly sodium and potassium) and ammonium thiocyanates can be used. The amount of thiocyanate may be any conventionally used amount, but from about 0.1 to 20 grams of thiocyanate per mole of silver halide is generally preferred. Specific examples of prior art teaching the use of thiocyanates include
U.S. Patent No. 2.222.264 by et al.
U.S. Patent No. 2.448.5 by Lowe et al.
No. 34 and Illingsworth
U.S. Pat. No. 3,320,069 by h). On the other hand, US Pat. No. 3,271,157 by McBride, US Pat.
Conventional thioether ripeners may be used, such as those disclosed in US Pat. No. 3,574,628 by Rosecrant et al. and US Pat.

The silver iodobromide high aspect ratio tabular grain emulsion of the present invention comprises:
Preferably, soluble salts are removed by washing.

Conventional cleaning methods are used for this, such as those disclosed in Research Disclosure, Vol. 176, December 1978, Balagraph H.

The high aspect ratio tabular grain emulsions produced in accordance with the present invention may be blended with each other or with conventional emulsions to meet specific emulsion requirements in accordance with established methods practiced in the art. It is particularly preferable to For example, it is known to incorporate emulsions to tailor the characteristic curves of photographic elements to meet certain objectives. Formulations are used to increase or decrease the maximum density during exposure and processing, increase or decrease the minimum density, and adjust the toe-to-shoulder shape of the characteristic curve. To accomplish this, the emulsions of the present invention can be blended with conventional silver halide emulsions such as those described in Research Disclosure, Item 17643, Balagraph II, cited above. When relatively fine silver chloride emulsions are blended with the silver iodobromide emulsions of the present invention, the sensitivity (ie, the relationship between speed and granularity) of the emulsion can be further increased.

Once silver iodobromide high aspect ratio tabular grain emulsions are prepared by the method of the present invention, they can be subjected to further modification, coating, exposure and processing following operations well known to those skilled in the art. Emulsions prepared by the method of the present invention can be chemically sensitized as described in Research Disclosure, Item 17643, Balagraph II, cited above. The emulsions can also be spectrally sensitized and/or desensitized as described in Balagraph 2. The above Kotron (Kofr)
It is particularly preferred to substantially optimally chemically and spectrally sensitize the emulsions prepared according to the invention using the techniques disclosed in U.S. Pat. No. 4,435,501, et al.

Photographic emulsion is Research Disclosure Item 1
7643, Balagraph V, Vl, ■, X1XI, χ
It may contain fluorescent brighteners, anti-capri agents, stabilizers, scattering or absorbing agents, hardeners, coating aids, plasticizers, lubricants and quenching agents as described in can.

Addition, coating and drying methods such as those described in Balagraph XTV and xV can also be used. Additionally, conventional photographic supports such as those described in Balagraph X■ can be used. The photographic elements produced may be black and white or preferably color photographic elements in which silver and/or dye images are produced by selectively decomposing, forming or physically removing dyes as described in Balagraph. That's fine. Particularly preferred color photographic elements are those that use color developing agents and dye-forming couplers to form dye images.

To use the photographic element, it can be exposed in a conventional manner as described in Balagraph
It can be processed by conventional methods such as those described in X.

〔Example〕

By referring to the following specific examples, the present invention is as follows:
I can understand it better.

In each example, the contents of the reaction vessel were vigorously stirred during the introduction of the silver and halide salts. Moreover, "%" is % by weight unless otherwise specified. Additionally, "M" is molar unless otherwise specified. Furthermore, unless otherwise specified, all solutions are aqueous solutions.

The following are representative examples of silver iodobromide high aspect ratio tabular grain emulsions that are currently used to obtain high photographic performance.

To 1.5f of a 0.25% gelatin solution containing 0.05M sodium bromide (50°C 1 pH 5.8), with vigorous stirring, a 0.12M silver nitrate solution was added over 2.0 minutes (the used Consumes 0.55% of total silver). next,
After increasing the temperature to 70°C over 4 minutes, increase the temperature at 70°C for another 6 minutes.
Hold for minutes. A 1.51% aqueous gelatin solution (4.3% by weight) was added to the reaction vessel. Next, par in the reaction vessel
was adjusted to 1.13 at 70°C. Sodium bromide (1
, 89 M) and potassium iodide (0.06 M) and a 1.50 M silver nitrate solution by double jet addition using accelerated flow rates (7-fold increase in flow rate from start to finish). 40 min pBri, 13
(70°C), 99.45% of total silver used
consumed. Approximately 2.2 moles of silver were used to make this emulsion.

The resulting silver iodobromide high aspect ratio tabular grain emulsion was
The average grain diameter is 2.17-, the average tabular grain thickness is 0.08p, and the average aspect ratio is 27.
The coefficient of variation for the total particle population was 69. Further, tabular grains accounted for 85% of the total grain projected area.

The quotient obtained by dividing the average aspect ratio by the coefficient of variation is 0, 4
Met. This shows that the relationship between granularity (average aspect ratio) and dispersibility (coefficient of variation) is the conventional one. This relationship is significantly inferior (lower quotient) than the relationship achieved by the present invention.

1. To 1.51 (50" C, pi (5,8) of 0.25% gelatin solution containing 0.05 M sodium bromide, add 4 d of 3 M silver nitrate solution with vigorous stirring. Added in 2 seconds (consuming 0.55% of total silver used). Temperature was then increased to 70°C over 4 minutes and held at 70°C for an additional 6 minutes. 1.52 Gelatin An aqueous solution (4.3% by weight) was added to the reaction vessel.Then, the pBr in the reaction vessel was adjusted to 70% by weight.
The temperature was adjusted to 1.78 at °C. Sodium bromide (1,89
A halide solution containing M) and potassium iodide (0.06M) and a 1.5M silver nitrate solution were added by double jet addition using an accelerated flow rate (flow rate increased by 14 times from start to finish) at 42 pBrl for min. 78 (70″
C) consumed 99.45% of the total silver used.

Approximately 2.2 moles of silver were used to make the second emulsion.

The resulting silver iodobromide high aspect ratio tabular grain emulsion was
The average grain diameter is 1.78n, the average tabular grain thickness is 0.08n, and the average aspect ratio is 22.
The coefficient of variation for the total particle population was 29. Further, tabular grains accounted for 85% of the total grain projected area.

The quotient obtained by dividing the average aspect ratio by the coefficient of variation is 0.7
It was 6. This means that the granularity (average aspect ratio)
This shows that the relationship between the dispersibility (coefficient of variation) and the dispersibility (coefficient of variation) has been significantly improved. This relationship is much better (higher quotient) than that obtained using conventional emulsion manufacturing methods for the comparable Control Emulsion 1.

1. of 0.25% gelatin solution containing 1M "Honmata" and 0.05M sodium bromide. ! M! (50° C., pFI 5.8) was added with vigorous stirring 4 d of 3M silver nitrate solution in 2 seconds (consuming 0.55% of the total silver used). The temperature was then increased to 70°C over 4 minutes. Thereafter, 0.17 mmol of 1.10-dithia-4,7,13,16-titraoxacyclooctadecane was added to the reactor. The reaction vessel was held at 70°C for an additional 6 minutes. 1.52
An aqueous solution of gelatin (4.3% by weight) was added to the reaction vessel. Next, the pBr in the reaction vessel was adjusted to 1°78 at 70'C. A halide solution containing sodium bromide (1,89M) and potassium iodide (0,06M) and 1
．． A 5M silver nitrate solution was added by double jet addition using an accelerated flow rate (flow rate increased by 14 times from start to finish) for 4 hours.
Added for 2 minutes at pBr 1.78 (70'C) to consume 99.45% of the total silver used. Approximately 2.2 moles of silver were used to make this emulsion.

The resulting silver iodobromide high aspect ratio tabular grain emulsion was
The average grain diameter is 2.35R and the average tabular grain thickness is 0.121! ra, the average aspect ratio was 20, and the coefficient of variation for the total particle group was 23. or,
Tabular grains accounted for 88% of the total grain projected area.

The quotient obtained by dividing the normal aspect ratio by the coefficient of variation is 0.8
It was 7. This means that the granularity (average aspect ratio)
This shows that the relationship between the dispersibility (coefficient of variation) and the dispersibility (coefficient of variation) has been significantly improved. This relationship is much better (higher quotient) than that obtained using conventional emulsion manufacturing methods for the comparable Control Emulsion 1.

Comparing Emulsions 2 and 3, it is clear that the addition of thioether μ) causes the tabular grains to grow larger in diameter and increase in thickness as they ripen with a larger proportion of small grains; This was manifested in an increase in the proportion of tabular grains occupying the total grain projected area Q.

Although the ripening agent actually reduced the average tabular grain aspect ratio slightly, it caused a relatively much larger reduction in the coefficient of variation, thereby increasing the quotient and thus increasing the granularity and The relationship with dispersibility was comprehensively improved.

This emulsion, which is neither a conventional emulsion nor an emulsion of the present invention, exhibits the granularity and dispersion of the present invention when only a thioether ripening agent is used without the combination of a thioether ripening agent and accelerated nucleation. This emulsion is intermediate between the conventional emulsion and the emulsion of the present invention, which was prepared to clarify the question raised by the comparison of Emulsion 2 and Emulsion 3 as to whether an emulsion is produced that satisfies the requirements in relation to sex.

1. of 0.25% gelatin solution containing 0.05M sodium bromide. ! M! (50"C, p145.8) was added with vigorous stirring a 0.12M silver nitrate solution over 2.0 minutes (consuming 0.55% of the total silver used). The temperature was then increased for 4 minutes. The temperature was then raised to 70°C.
．． 08 mmol of 1,10-dithia-4,7,13,1
6-titraoxacyclooctadecane was added to the reactor. The reaction vessel was held at 70'C for an additional 6 minutes.

A 1.51% aqueous gelatin solution (4.3% by weight) was added to the reaction vessel. Next, the pBr in the reaction vessel was adjusted to 1 at 70°C.
．． Adjusted to 78. A halide solution containing sodium bromide (1,89 M) and potassium iodide (0,06 M) and a 1.5 M silver nitrate solution were prepared using accelerated flow rates (7-fold increase in flow rate from start to finish). Double-jet addition for 40 minutes at pBr 1.78 (70''C) consumed 99.45% of the total silver used. Approximately 2.2 moles of silver were used to make this emulsion. It was done.

The resulting silver iodobromide high aspect ratio tabular grain emulsion was
The average grain diameter was 1.777 m, the average tabular grain thickness was 0.09 Jnn, the average aspect ratio was 20, and the coefficient of variation was 31. Further, tabular grains accounted for 88% of the total grain projected area.

The quotient obtained by dividing the average aspect ratio by the coefficient of variation is 0.6
It was 5. It is clear from this data that slow nucleation rates result in a large dispersion of grain nuclei that cannot be overcome by subsequent ripening. It is also clear that if the ripening agent ripens approximately the same proportion of non-tabular grains, but nucleation is slow, a much greater dispersion occurs within the tabular grain population.

This emulsion is manufactured using a gelatin peptizer treated with an oxidizing agent to remove methionine, and has a high aspect ratio of silver iodobromide with an average grain thickness of 0.05-. It was prepared to illustrate the formation of tabular grain emulsions.

18! 0.125% oxidant treatment (less than 30 micromoles per Ig) containing 0.04 moles of sodium bromide, with vigorous stirring and the pH adjusted to 1.85 using sulfuric acid. The gelatin solution (residual unoxidized methionine) was added at 45°C.

To this solution, add 8.0 ml of 1.67M silver nitrate, 98.5 mol% sodium bromide and 1.5 mol% potassium iodide.
8.0 d of a 1,6M halide solution consisting of
Added at 20ae. Then increase the temperature to 60° for 9 minutes.
After increasing to C, the temperature was held for an additional 9 minutes. Thereafter, 100 g of oxidizing agent-treated gelatin was added, and the pH was adjusted to 5.85 using 2.5M sodium hydroxide. Next, 1
．． The pBr was adjusted to 1.75 using 0M sodium bromide, and at a pBr of 1.75, 12,5
ml and held for 40 minutes. Thereafter, addition of the solution was stopped for 90 seconds and the pBr was adjusted to 1655 using 175M sodium bromide solution. After this, 1.6
M silver nitrate, 0.048 silver iodide Lippmann emulsion suspension and 1.75 M sodium bromide solution were triple-jet added. Then triple-jet addition of the same solution as above was carried out at a flow rate of 12.5 d/min to 120 IdZ. It continued to accelerate linearly in minutes. This yielded a 6 mole silver iodobromide ultrathin tabular grain emulsion, which was
Coagulation cleaning was performed by the method described in U.S. Pat. No. 2,614,929 by Tzy et al.

The resulting silver iodobromide high aspect ratio tabular grain emulsion was
The average grain diameter was 2.9-, the average tabular grain thickness was 0.04-, the average aspect ratio was 72, and the coefficient of variation was 56.

The quotient obtained by dividing the average aspect ratio by the coefficient of variation is 1.3
Met. It is clear from this data that the reduction in tabular grain thickness results in a large increase in projected area that more than offsets the slight increase in the coefficient of variation, which is consistent with the expected increase in the average grain diameter of the emulsion. This was the result.

In Emulsion 5, the relationship between granularity and dispersibility is very favorable, with an average A silver iodobromide high aspect ratio tabular grain emulsion was obtained in which the aspect ratio divided by the coefficient of variation completely exceeded 0.7.

The initial solution before nucleation was prepared in a similar manner to Emulsion 5. In place of the balanced double-jet nucleation used in the preparation of Emulsion 5, single-jet nucleation was used consisting of ejecting 8.0 - of a 1.67 M silver nitrate solution at about 5000 mi per minute. Immediately after this, similar to Emulsion 5, temperature increase, holding, gelatin addition, pH and pBr
adjustment as well as the first constant flow triple jet addition. Instead of adjusting par to 1.55 in Emulsion 5, pBr was adjusted to 1.85 using a 1.6M silver nitrate solution. The final gradient flow rate triple jet addition is pB
Emulsion 5 was prepared in the same manner as in Emulsion 5, except that r was controlled to 1.85.

The resulting silver iodobromide high aspect ratio tabular grain emulsion was
The average grain diameter was 2.3 pm, the average tabular grain thickness was 0.045-, the average aspect ratio was 51, and the coefficient of variation for the total grain population was 43.

The quotient obtained by dividing the average aspect ratio by the coefficient of variation is 1.2
Met.

This emulsion is used to illustrate the production of silver iodobromide high aspect ratio tabular grain emulsions according to the present invention when silver iodide is rapidly added as a Lippmann emulsion during grain growth. Manufactured.

An 18ffi stainless steel reaction vessel was treated with a 0.125% oxidant containing 0.04 moles of sodium bromide (less than 30 micromoles per Ig) with vigorous stirring and the pH was adjusted to 1.85 using sulfuric acid. 6.0 liters of gelatin solution (residual unoxidized methionine) was added at 45°C. Add 8.0 ml of 1.67 M silver nitrate to this solution.
, 98.5 mol% sodium bromide and 1 potassium iodide
．． 1°6M halide solution consisting of 5 mol%8. Od
was added at 120 m per minute by balanced double jet addition. After 60 seconds, 1.0M sodium bromide was added to adjust the pBr to 1.73. The temperature was then increased to 60"C over 9 minutes and held for an additional 9 minutes. 100g of oxidizer-treated gelatin was then added and the pH adjusted to 5.5M using 2.5M sodium hydroxide.
Adjusted to 85. Next, 1.6M silver nitrate, 0.024M
Triple jet addition of silver iodide Lippmann emulsion suspension and 1.75M sodium bromide solution to a pBr of 1.8
3 for 40 minutes at 12.5 d/min. The triple jet addition of the same solution as above was then continued at a linearly accelerated flow rate of 12.5 II 11/min to 120 d/min over 35° 8 min. Thereafter, the addition was stopped and 0.12 mol of silver iodide Lippmann emulsion was added. 1.6M silver nitrate and 1.75M I bromide
- Double jet addition of lithium was carried out at 100 d/min for 3.65 minutes while controlling pBr to 1.83. This resulted in a 6 mole silver iodobromide ultrathin tabular grain emulsion, which was coagulated and washed by the method described in Yutzy et al., US Pat. No. 2,614,929.

The resulting silver iodobromide high aspect ratio tabular grain emulsion was
Tabular grain content greater than 90% and average grain diameter 2.8
54, the average tabular grain thickness is 0.06 feet,
The average aspect ratio was 47.5, and the coefficient of variation for the total particle population was 38.

The quotient obtained by dividing the average aspect ratio by the coefficient of variation is 1.2
It was 5. It is clear from this data that the addition of iodide during the growth process of producing tabular grains in the form of a Lippmann emulsion suspension and the ability to obtain a large average aspect ratio divided by the coefficient of variation. It is compatible with

〔Effect of the invention〕

Overall, the above examples demonstrate a technique for obtaining high aspect ratio tabular grain emulsions exhibiting relatively high levels of monodispersity. From the above discussion, it appears that there is a method for producing high aspect ratio tabular grain emulsions of silver iodobromide with a favorable relationship between granularity and dispersity (a large quotient of the average aspect ratio divided by the coefficient of variation). Once the overall understanding is understood, individual manufacturing parameters can be selected with some degree of freedom to obtain the desired emulsion.

1. Indication of the case 1999 Patent Application No. 257166 2. Name of the invention High aspect ratio tabular grain emulsion 3. Person making the amendment Relationship to the case Patent applicant name Eastman Kodak Company 4, Agent address: 6-8-10 Toranomon-chome, Minato-ku, Tokyo, 105 F105, Specification subject to amendment 7, Engraving of the details of the amendment (no change in content) 8. Engraving details of the list of attached documents 1 copy 5, date of amendment order

Claims (1)

[Claims] 1. Contains a dispersion medium and silver iodobromide particles, and has a thickness of 0.3
Tabular silver iodobromide grains of less than μm account for more than 50% of the total projected area of the total silver iodobromide grain group, and
In a high aspect ratio tabular grain emulsion with an average aspect ratio greater than 12, the quotient of the average silver iodobromide tabular grain aspect ratio divided by the coefficient of variation of the total silver iodobromide grain population exceeds 0.7. A high aspect ratio tabular grain emulsion characterized by: