JPH08171164A - Radiation-sensitive emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the function of an emulsion of photographic plate type grains. SOLUTION: This emulsion contains a dispersion medium, silver halide grains containing the specified lithography type grains, and a spectral sensitization pigment adsorbed to the surface of the grains. Furthermore, the plate type grains contain less than 10mol% of iodide. Also, a surface chemical sensitization part includes the projected parts of silver halide having the epitaxially deposited structure of rock salt type face centered cubic lattice to form an epitaxial joint with the plate type grains. In this case, the projected parts are positioned nearest the edge of the grains and limited to an area occupying less than 50% of a principal plane [111] of the grains. In addition, the projected parts have larger silver chloride concentration than the grains by 10mol% or more, and contains 1mol% or more of iodide relative to a silver quantity required for the formation of the projections.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to silver halide photography. More particularly, this invention relates to improved spectrally sensitized silver halide emulsions and multilayer photographic elements containing one or more of these emulsions.

[0002]

2. Description of the Prior Art U.S. Pat. No. 4,439,520 (Kofron et al.) Ushered in the current high performance silver halide photographic era. Kofron et al. Show chemical sensitization in which tabular grains having a diameter of at least 0.6 μm and a thickness of less than 0.3 μm exhibit an average aspect ratio higher than 8 and account for more than 50% of the total grain projected area; Disclosed and demonstrated remarkable photographic advantages for spectrally sensitized tabular grain emulsions. Of the numerous emulsions shown, one or more of these numerical parameters often far exceeded the above requirements. Kofron et al.
It has been recognized that the chemically and spectrally sensitized emulsions disclosed in one or more of the various embodiments will be useful in color photography and black and white photography (including indirect radiography). Not only orthochromatic and panchromatic spectral sensitizations for black and white imaging applications were attempted, but also spectral sensitizations in all parts of the visible spectrum and at longer wavelengths. Kofron
Et al. Used a combination of one or more spectral sensitizing dyes with middle chalcogen (eg, sulfur) and / or noble metal (eg, gold) chemical sensitization. However, Kof
Ron et al. teach yet another conventional sensitization method, such as reduction sensitization.

An early cross-reference modification to the teachings of Kofron et al. Was described in US Pat. No. 4,435,501 (Maskasky) (hereinafter "Maskasky-
I "). Maskasky-
I is a site director such as iodide ion, aminoazaindene, or a selected spectral sensitizing dye adsorbed on the surface of host tabular grains,
It has been recognized that silver salt epitaxy can be directed to selected sites on the host grain, typically edges and / or corners. A marked increase in speed was observed depending on the composition and site of silver salt epitaxy. M
The highest photographic speed and highest controlled site attachment (eg, corner-specific epitaxy configuration) reported by askasky-I was obtained by epitaxially depositing silver chloride on silver iodobromide tabular grains. Was given. Mas
Kasky-I discloses the epitaxial deposition of silver iodobromide on the surface of tabular silver bromide grains (col. 24, pp. 37-38), while Maskasky-I.
I teaches that it is preferable to epitaxially deposit a silver salt that has a higher solubility than the host tabular grains, which reduces the tendency of the tabular grains to dissolve during the deposition of the silver salt. (The 24th column, the 10th column)
14). Maskasky-I transfers a small portion of the halide contained in the host tabular grains to silver chloride epitaxy even when silver chloride is the only halide that is flowed into the tabular grain emulsion during epitaxial deposition. I am aware of the possibilities. Maskasky-I
Proposes, by way of example, to include a small amount of bromide ion when silver and chloride ions flow into the tabular grain emulsion during epitaxial deposition. Mas
From the concentration of iodide contained in the tabular grain emulsion of kasky-I, and from the discussion of the present invention reported in the Examples below, the moles of iodide transferred from the host tabular grains involved in the epitaxial deposition of Maskaky-I. It is clear that the% is only a small amount.

Maskasky US Pat. No. 4,47
No. 1,050 (hereinafter Maskasky-II) describes that non-isomorphic silver salts can be selectively attached to the edges of silver halide host grains without resorting to an auxiliary site director. There is. This non-isomorphic silver salt includes silver thiocyanate, β-phase silver iodide (having a hexagonal wurtzite type crystal structure), γ-phase silver iodide (having a zinc blend type crystal structure), silver phosphate (metaphosphoric acid and (Including pyrophosphate) as well as silver carbonate. None of these non-isomorphic silver salts exhibit a face centered cubic structure of the type found in photographic silver halide, ie a rock salt type isomorphic face centered cubic structure.
In fact, the speed improvement obtained by non-isomorphic silver salt epitaxy was much smaller than that obtained by comparable isomorphic silver salt epitaxial sensitization.

[0005]

Despite the many advantages of common tabular grain emulsions and the particular improvements in color photographic elements in which they are used, tabular tabulations not available in the art. There remains an unmet need for improved performance in grain emulsions. Specifically, there is a need for tabular grain emulsions that have an improved speed-granularity relationship, that is, increased speed, decreased granularity, or a combination of both. Another problem is that increased speed is often obtained at the expense of contrast. It is necessary to maintain the contrast, or increase it in some cases to improve the speed.

[0006]

According to one aspect, the present invention provides (1) a dispersion medium, (2) (a) a {111} major surface, and (b) silver. It contains more than 70 mol% of bromide and 0.25 mol% or more of iodide, (c) accounts for more than 90% of the total grain projected area, and (d) has an average equivalent circular diameter of 0.7 μm or more. (E) an average thickness of 0.07 μm or more and less than 0.3 μm, and (f) a silver halide grain containing a tabular grain having a latent image-forming chemically sensitized site on its surface, ) An improved radiation-sensitive emulsion comprising a spectral sensitizing dye adsorbed on the surface of said tabular grains, said tabular grains containing less than 10 mol% iodide, said surface chemically sensitized The site is an epitaxy of a rock-salt type face-centered cubic crystal lattice structure that forms an epitaxial junction with the tabular grains. Include silver halide protrusions that interstitial attached, the protrusion, (a) the tabular grains of the nearest located and tabular grains of the peripheral portion {11
1} Limited to the area that occupies less than 50% of the main surface, (b)
A radiation-sensitive emulsion characterized by having a silver chloride concentration higher than that of the tabular grains by 10 mol% or more, and (c) containing 1 mol% or more of iodide with respect to the amount of silver forming the protrusions. Regarding

[0007]

DETAILED DESCRIPTION OF THE INVENTION It has been surprisingly found that intentionally increasing the iodide concentration of silver halide epitaxy containing silver chloride results in increased speed and contrast and reduced granularity. It was This is contrary to common knowledge in the art to maintain iodide concentrations in tabular grains higher than their associated silver halide epitaxy. With increasing iodide in silver halide epitaxy, unexpected improvements in speed, granularity and contrast can be realized. Further, the amount of iodide in the epitaxy can be higher than that of the tabular grain host. Thus, the amount of iodide is reduced overall, allowing for faster processing.

The present invention relates to improvements in spectrally sensitized photographic emulsions. This emulsion is specifically intended for incorporation into camera speed color photographic film. In the emulsion of the present invention, the tabular grains have (a) {111} major faces and contain (b) more than 70 mol% of bromide and 0.25 mol% or more of iodide, based on silver. , (C) account for more than 90% of the total grain projected area, (d) have an average equivalent circular diameter (ECD) of 0.7 μm or greater, and (e) have an average thickness of 0.0.
It can also be realized by chemically and spectrally sensitizing any conventional tabular grain emulsion having a size of 7 μm or more and less than 0.3 μm.

Tabular grain emulsions satisfying the above criteria (a) to (e) are conventional, apart from their sensitization which is the subject of the present invention. Representative teachings of tabular grain emulsions meeting these criteria are provided below. Wilgus et al., U.S. Pat. No. 4,434,226; Kofron.
U.S. Pat. No. 4,439,520; Daub et al.
US Pat. No. 4,414,310 to endiek et al .; US Pat. No. 4,433,048 to Solberg et al.
U.S. Pat. No. 4,672,0 to Yamada et al.
No. 27; Sugimoto et al., US Pat. No. 4,6.
65,012; Yamada et al U.S. Pat. No. 4,679,745; Maskasky U.S. Pat. No. 4,713,320; Nottorf U.S. Pat. No. 4,722,886; Sugimo
to U.S. Pat. No. 4,755,456; God
U.S. Pat. No. 4,755,617; Elli.
U.S. Pat. No. 4,801,522; Iked
U.S. Pat. No. 4,806,461 to A .; Oha.
Shi et al., U.S. Pat. No. 4,835,095; M
akino et al., U.S. Pat. No. 4,835,322; Daubendiek et al., U.S. Pat.
014; Aida et al., U.S. Pat. No. 4,962,
015; Ikeda et al., U.S. Pat. No. 4,98.
5,350; US Pat.
No. 061,609; US Pat. No. 5,061,616 to Piggin et al .; US Pat. No. 5,147,771 to Tsaur et al .; US Pat. No. 5,147,772 to Tsaur et al. U.S. Pat. No. 5,147,773 to Tsaur et al .; U.S. Pat. No. 5,171,659 to Tsaur et al .; U.S. Pat. No. 5,300,413 to Sutton et al .; Delto.
n US Pat. No. 5,310,644; Chan
g., et al., US Pat. No. 5,314,793; Bla.
ck et al., US Pat. No. 5,334,495; Ch.
US Pat. No. 5,358,840 to Affee et al. and US Pat. No. 5,372,927 to Delton.

In describing grains and emulsions containing multiple halides, the halides are listed in order of increasing concentration. For camera speed films, tabular grains should contain at least 0.25 mol% iodide, based on silver, preferably at least 1.0 mol%.
It is generally preferred to include. In each case, the tabular grains in the emulsion of the present invention contain 10 mol% of iodide.
Less than, preferably less than 6 mol% and optimally 4
It is contained in less than mol%. It is possible to include small amounts of chloride ion in the tabular grains. For example, US Pat.
372,927 (Delton) describes 0.4 to 20 mol% chloride and 10 mol% iodide, based on total silver.
A tabular grain emulsion is described which contains the following and the balance of the halide is bromide.

Tabular grains accounting for at least 90 percent of total grain projected area contain at least 70 mole percent bromide and at least 0.25 mole percent iodide, based on silver. These tabular grains include silver iodobromide, silver iodochlorobromide and silver chloroiodobromide grains. All references to tabular grain compositions exclude silver halide epitaxy.

The iodide in the tabular grains may be uniformly or non-uniformly distributed by any conventional method. For example, Wilgus et al., U.S. Pat. No. 4,434,226 and Kofron et al., U.S. Pat. No. 4,439,520, cited above, disclose conventional iodide-uniform silver iodobromide tabular forms. It describes a grain emulsion. Solberg et al., U.S. Pat. No. 4,4, cited above.
33,048 and Chang et al., U.S. Pat. No. 5,314,793, show that non-uniform placement of iodide in silver iodobromide tabular grains results in increased graininess without increasing granularity. It is said to be particularly preferable for increasing the speed. In the tabular grains of the emulsion of the present invention,
Forming an epitaxial junction of tabular grains with at least silver halide deposited as a chemical sensitizer {11
1) It is particularly preferable that the portion extending between the principal planes has a lower iodide concentration than silver halide epitaxy. Most preferably, the tabular grains have a lower overall iodide concentration than silver halide epitaxy and, optimally, the tabular grains contain less total iodide than silver halide epitaxy.

The tabular grains in the emulsion of the present invention all have {111} major faces. Such tabular grains typically have a triangular main surface or a hexagonal main surface. The tabular structure of these grains is due to the inclusion of parallel twin planes.

The tabular grains of the emulsion of the present invention account for more than 90% of the total grain projected area. Tabular grain emulsions are preferred in which the tabular grains account for greater than 97 percent of total grain projected area. Most preferably, the tabular grains account for greater than 99 percent (substantially all) of the total grain projected area. Emulsions of this type are described, for example, in Tsau, cited above.
r et al. and Delton. Providing emulsions in which the tabular grains account for a high percentage of the total grain projected area is important to achieve the maximum achievable image sharpness level, especially in multilayer color photographic films. It is also important to utilize silver efficiently and achieve the most desirable speed-granularity relationship.

Tabular grains accounting for greater than 90% of total grain projected area have an average ECD of at least 0.7 μm.
Indicates. The benefits realized by maintaining an average ECD of at least 0.7 μm are shown in Tables III and IV of Antoniades et al. US Pat. No. 5,250,403. Emulsions with very large average grain ECD's are sometimes prepared for scientific grain studies, but for photographic applications, ECD's are typically less than 10 μm, and most often less than 5 μm. The optimum ECD range for medium to high image structure quality is in the range of 1-4 μm.

In the tabular grain emulsion of the present invention, tabular grains accounting for more than 90% of the total grain projected area have an average thickness of 0.07 μm or more and less than 0.3 μm. Kofron et al., Cited above, teaches that emulsions with larger tabular grain thicknesses are useful for recording blue exposures, but they do so in the spectral minus blue (ie, green and / or red). ) Is absolutely inferior to record in the part. Efficient imaging levels due to lower silver requirements can be achieved by keeping the average tabular grain thickness below 0.3 μm and using spectral sensitizing dyes. When the minimum average thickness of tabular grains is 0.07 μm or more, a far wider range of emulsion preparation methods and preparation conditions than those required for producing tabular grain emulsions having an average grain thickness of less than 0.07 μm. Can be used.

Preferred tabular grain emulsions are those in which the intergrain variability is kept at a low level. It is preferable that more than 90% of the tabular grains have a hexagonal main surface. Preferred tabular grain emulsions exhibit a coefficient of variation (COV) for ECD of less than 25%, most preferably less than 20%. The term “COV” in the present specification is a value obtained by dividing the standard deviation (σ) of ECD by the average ECD and multiplying by 100.

Both the photographic sensitivity and the granularity are the average grain E.
It is recognized that it increases with increasing CD. From a comparison of sensitivity and granularity of optimally sensitized emulsions with different grain ECDs, speed in the art is doubled (ie 0.3 log E increase in speed, where E is exposure dose (lux-sec). It has been demonstrated that with each increase, the granularity of emulsions exhibiting the same speed-granularity relationship increases by 7 granularity units. It has been observed that the presence of even smaller proportions of the larger ECD grains in the tabular grain emulsions of this invention can significantly increase the granularity of the emulsion. The usual solution is to use a low COV emulsion, as limiting the COV will always bring the ECD of the tabular grains present close to the mean.

According to the present invention, COV is not the best technique for determining emulsion granularity. The need for low emulsion COV values limits both grain populations larger and smaller than the average grain ECD, whereas only the former grain population provides high levels of granularity. Total C
The OV measurements depend on the assumption that the particle size-frequency distribution is a normal error function distribution that is intrinsic to the precipitation method and is not easily controllable, regardless of whether the variance is wide or narrow. That is.

It is specifically contemplated to modify the conventional tabular grain precipitation method to selectively reduce the grain size-frequency distribution of tabular grains exhibiting an ECD greater than the average ECD of the emulsion. Since the size-frequency distribution of particles with ECD less than the mean value does not decrease correspondingly, the total COV value does not appreciably decrease. However, the benefits of reducing emulsion granularity are clearly demonstrated.

The reduction of the disproportionated size range in the particle size-frequency distribution of tabular grains larger than the average ECD (hereinafter referred to as "> average ECD grains") can be measured by the following method for precipitation of tabular grain emulsions. It has been found that this can be achieved by modification: nucleation of tabular grains is carried out with a gelatino-peptizer which has not been treated to reduce the natural methionine content, while the gelatino-peptizer present and Grain growth is carried out after substantially removing the methionine component of the gelatino-peptizer introduced in (1). A convenient way to achieve this is to suspend the precipitation sufficiently after the nucleation and before the growth proceeds to introduce the methionine oxidant.

Any of the conventional techniques for oxidizing the gelatinous peptizer methionine can be used.
U.S. Pat. No. 4,713,320 (Maskasky)
(Hereinafter, referred to as “Masksky-III”)
The amount of methionine obtained by oxidation is 3 per gram of gelatin.
It teaches to reduce to less than 0 μmol, preferably to less than 12 μmol by using strong oxidizing agents. In fact, the oxidant treatment used by Maskasky-III reduces methionine below the detection limit.
Agents used to oxidize methionine in gelatinous peptizers include, for example, NaOCl, chloramine, potassium monopersulfate, hydrogen peroxide and peroxide releasing compounds, and ozone. U.S. Pat. No. 4,94
2,120 (King et al.) Teaches the oxidation of the methionine component of gelatinous peptizers with alkylating agents. European Patent Application No. 0434012 (Takada et al.) Discloses the precipitation in the presence of a thiosulfonate represented by one of the following _{formulas: (I) R-SO 2} S-M ( II) in ^{_{R-SO 2 S-R 1}} (III) R-SO 2 S-Lm-SSO 2 -R 2 ( wherein, R, R ¹ and R ² are identical or different, aliphatic group, aromatic group or A heterocyclic group, M is a cation, L is a divalent linking group, and m is 0 or 1, provided that R, R ¹ , R ² and L are joined to form a ring. To). Gelatinous peptizers include gelatin,
For example, alkali-treated gelatin (livestock, bone or hide gelatin) or acid-treated gelatin (pigskin gelatin) and gelatin derivatives such as acetylated or phthalated gelatin.

Although not essential to the practice of the invention, improved photographic performance, consistent with the advantages described herein, can be realized by incorporating dopants in the tabular grains. As used herein, the term "dopant" means a substance other than silver or halide ions contained within the face centered cubic lattice structure of silver halide forming tabular grains.

Any of the conventional dopants known to be useful in silver halide face centered cubic lattice structures can be used. Photographically useful dopants selected from a wide range of periods and groups within the Periodic Table of the Elements have been reported. As used herein, the periods and families refer to the American Chemical Society.
Adopted by ty, Chemical and En
Gineering News, February 4, 1985,
It is based on the Periodic Table of the Elements published on page 26. Typical dopants are Fe, Co, Ni, Ru,
Rh, Pd, Re, Os, Ir, Pt, Mg, Al, C
a, Sc, Ti, V, Cr, Mn, Cu, Zn, Ga,
Ge, As, Se, Sr, Y, Mo, Zr, Nb, C
d, In, Sn, Sb, Ba, La, W, Au, Hg,
The third of the periodic table of elements such as Tl, Pb, Bi, Ce and U
Ions from ~ 7 cycles (most commonly the 4th to 6th cycles) are included. Dopants are (a) increased sensitivity, (b)
High or low illumination reciprocity law decrease, (c) increase or decrease in contrast fluctuation, (d) decrease in pressure sensitivity, (e) decrease in dye desensitization, (f) stability (of thermal instability) Increase (including decrease), (g) decrease minimum concentration and / or (h) increase maximum concentration. For certain applications, any polyvalent metal ion is effective. The following are examples of common dopants that can produce one or more of the above effects when incorporated into silver halide epitaxy: B. H. Carroll, "I
Ridium Sensitization: A Li
“Terature Review”, Photogra
phic Science and Engineer
ing, Vol. 24, No. 6, November / December 1980,
265-267; U.S. Pat. No. 1,951,933 (Hochsetter); U.S. Pat.
28,167 (De Witt); U.S. Pat. No. 3,687,676 (Spence et al.) And U.S. Pat. No. 3,761,267 (Gilman).
Etc.); US Pat. No. 3,890,154 (Ohk
Ubo et al.); U.S. Pat. No. 3,901,711 (Iwaosa et al.); U.S. Pat. No. 3,901,713 (Yamasue et al.); U.S. Pat. No. 4,173.
483 (Habu et al.); U.S. Pat. No. 4,26.
No. 9,927 (Atwell); U.S. Pat.
413,055 (Weyde); US Pat. No. 4,477,561 (Menjo et al.); US Pat. No. 4,581,327 (Habu et al.); US Pat. No. 4,643,965. Specification (Kobuta
Etc.); US Pat. No. 4,806,462 (Yam)
Ashita et al.); U.S. Pat. No. 4,828,962 (Grzeskowiak et al.); U.S. Pat. No. 4,8.
35,093 (Janusonsis); U.S. Pat. No. 4,902,611 (Leubner).
Etc.); US Pat. No. 4,981,780 (Inoue et al.); US Pat. No. 4,997,751 (Ki
m); US Pat. No. 5,057,402 (Shi
ba, etc.); US Pat. No. 5,134,060 (M
aekawa et al.); US Pat. No. 5,153,110 (Kawai et al.); US Pat. No. 5,164,292.
(Johnson et al.); US Pat. No. 5,16
6,044 and 5,204,234 (Asami); US Pat. No. 5,166,045 (Wu); US Pat. No. 5,229,263 (Yoshida et al.). U.S. Pat. No. 5,252,451
And 5,252,530 (Bel
l); EPO No. 0244184 (Komori)
ta et al.); EPO No. 0488737 and No. 04.
88601 (Miyoshi et al.); EPO No. 0
368304 (Ihama et al.); EPO No. 04
05938 (Tashiro); EPO No. 05
09674 and 0563946 (Mu
Rakami et al.) and Japanese Patent Application No. 2-249588 and WO 93/02390 (Budz).

When the dopant metal is present during the precipitation in the form of coordination complexes, especially tetra- and hexa-coordination complexes,
Both metal ions and coordinating ligands can be occluded in the particles. U.S. Pat. No. 4,847,191 (Grze
Skowiak), U.S. Pat. Nos. 4,933,272, 4,981,781 and 5,03.
7,732 (McDugle et al.), U.S. Pat. No. 4,937,180 (Marchetti).
Et al., U.S. Pat. No. 4,945,035 (Kee).
Vert et al.), US Pat. No. 5,112,732 (Hayashi), EPO No. 0509674 (Murakami et al.), EPO No. 0513738 (Ohya et al.), WO 91/10166. Janusonis), WO 92/16876 (Beavers), Germany DD 298,32.
No. 0 (Pietsch et al.), Halo, aquo, cyano, cyanate, fluminate, thiocyanate, selenocyanate, tellurocyanate, nitrosyl, thionitrosyl, azide, oxo,
Carbonyl and ethylenediaminetetraacetic acid (EDTA) ligands have been disclosed, and in some cases improvements in emulsion properties have been observed with the ligands. US Pat. No. 5,360,71
No. 2 (Olm et al.) Discloses hexacoordination complexes containing organic ligands, while US Pat. No. 4,092,171.
Bigelow discloses organic ligands in Pt and Pd tetracoordination complexes.

It is specifically contemplated to incorporate a dopant into the tabular grains to reduce reciprocity law failure. Iridium is the preferred dopant for reducing reciprocity failure. Carroll, Iwaosa et al., Habu et al., G
rzeskowiak, etc., Kim, Maekawa, etc.,
Johnson et al., Asami, Yoshida et al., B
Ell, Miyashi et al., Tashiro's teachings and EPO 0509674 (Murakami).
Etc.) can be applied to the emulsions of the invention simply by incorporating the dopant in the silver halide precipitation.

In another particularly preferred embodiment of the present invention, it is envisioned that the face-centered cubic lattice of tabular grains incorporate a dopant that can increase photographic speed by forming shallow electron traps. Shallow electron capture (SET)
Research on criteria for selecting dopants
Disclosure (Vol. 367, Nov. 1994)
Month, Item 36736).

In certain preferred embodiments, it is contemplated to use as the dopant a hexacoordination complex satisfying the formula: (IV) [ML ₆ ] ⁿ , where M is a full frontier orbital polyvalent metal ion. , Preferably Fe ⁺² , Ru ⁺² , Os ⁺² , Co ⁺³ , Rh ⁺³ , I
r ⁺³ , Pd ⁺⁴ or Pt ⁺⁴ ; L ₆ represents _six independently selectable coordination complex ligands,
Provided that at least 4 of the ligands are anionic ligands and at least 1 (preferably at least 3 and optimally at least 4) of the ligands are more electronegative than either halide ligand; and n is-
It is 2, -3 or -4.

Specific examples of dopants capable of providing shallow electron traps are: SET-1 [Fe (CN) ₆ ] ^-4 SET-2 [Ru (CN) ₆ ] ^-4 SET-3 [Os (CN) _6] ^-4 SET-4 [Rh (CN) _6] ^-3 SET-5 [Ir (CN) _6] ^-3 SET-6 [Fe (pyrazine) (CN) _5] ^-4 SET-7 [ RuCl (CN) _5] ^-4 SET-8 [OsBr (CN) _5] ^-4 SET-9 [RhF (CN) _5] ^-3 SET-10 [IrBr (CN) _5] ^-3 SET-11 [FeCO ( CN) _5] ^-3 SET-12 [RuF ₂ (CN) _4] ^-4 SET-13 [OsCl ₂ (CN) _4] ^-4 SET-14 [RhI ₂ (CN) _4] ^-3 SET-15 [IrBr ₂ (CN) _4] ^-3 SET-16 [Ru (CN) ₅ (OCN)] ^-4 SET- 7 _{[Ru (CN) 5 (N 3} ) ] ^-4 SET-18 [Os (CN) ₅ (SCN)] ^-4 SET-19 [Rh (CN) ₅ (SeCN)] ^-3 SET-20 [Ir ( CN) ₅ (HOH)] ^-2 SET-21 [Fe (CN) ₃ Cl _3] ^-3 SET-22 _{[Ru (CO) 2 (CN)} 4 ] ^-1 SET-23 [Os (CN) Cl _5] ^-4 SET-24 [Co (CN) ₆ ] ^-3 SET-25 [Ir (CN) ₄ (oxalate)] ^-3 SET-26 [In (NCS) ₆ ] ^-3 SET-27 [Ga (NCS) ₆ ] ^-3

Further, US Pat. No. 5,024,931
As taught in the specification (Evans et al.)
It may be possible to increase the speed by using a gomer coordination complex.
Be done. Dopants are added at their normal concentrations (where the concentration is
Including both silver in tabular grains and silver in protrusions
The concentration is based on total silver). general
1 mol of a shallow electron trap forming dopant was applied to
At least 1 × 10 ^-6Molar to solubility limit (typically silver
About 5 x 10 per mole^-FourUp to a molar concentration)
Is intended. A preferred concentration is about 1 mole of silver
10^-Five-10^-FourIt is in the molar range. Of course, a part is a flat plate
In the shape of grains and the rest in the silver halide protrusions
The dopant can be distributed in any desired manner.

The chemical sensitization and the spectral sensitization of the present invention are performed by Mas
It improves the best chemical sensitization and spectral sensitization described in kasky-I. That is, in the practice of the present invention, the tabular grains, during chemical sensitization, receive the epitaxially deposited silver halide to form protrusions at specific sites on the tabular grain surface. Maskasky-I is
It was observed that double jet injection of silver ion and chloride ion gave the highest photographic sensitivity when epitaxially adhering to a specific site of a silver iodobromide tabular grain. In the practice of the present invention, in any case, the silver halide protrusions are 10% or more, preferably 15% or more, of the host tabular grains.
Optimally, it is considered to precipitate so as to show a chloride concentration higher than 20%. More precisely, it should be the chloride ion concentration in the silver halide protrusions relative to the chloride ion concentration in the portion forming the epitaxial junction of the tabular grains, but the chloride ion concentration in the tabular grains is substantially Is uniform (ie at the average level)
Or, it is not always necessary because it is considered to be slightly lowered due to the replacement of iodide in the epitaxial junction region.

In contrast to the Maskasky-I teachings, it has been found that photographic performance can be improved by the addition of iodide ions along with silver and chloride ions to the tabular grain emulsion while performing epitaxial deposition. Was given. Specifically, 1 in the silver chloride-containing epitaxy
It is conceivable to contain iodide in an amount of mol% or more.
The silver chloride-containing epitaxy exhibits an iodide concentration that is 1 mol% or more higher than the concentration present in at least the {111} major faces of the tabular grains and forming the epitaxial junction with the protrusion. Is preferred. When the tabular grains contain a uniformly distributed iodide,
The protrusions epitaxially attached are higher than the average iodide concentration of the tabular grains (preferably higher than 1 mol%).
The iodide concentration is shown. In addition, the total amount of iodide in the emulsion can be reduced to obtain superior performance, which also leads to higher development rates.

Since iodide ion is much larger than chloride ion, there is a limit to the extent of iodide ion that can be introduced into the face centered cubic lattice structure formed by silver chloride and / or silver bromide. That is the recognition in the art. In this regard, for example, Maskask
US Pat. Nos. 5,238,804 and 5,28 to Y.
No. 8,603 (hereinafter referred to as Maskasky
-IV and Maskasky-V). Precipitation at atmospheric pressure, which is commonly practiced in the art, limits the amount of iodide introduced into the silver chloride crystal lattice to less than 13 mol%. For example, when silver is introduced with a chloride: iodide molar ratio of 84:16 during the silver halide epitaxial deposition, the iodide concentration in the obtained epitaxial protrusions is higher than that of silver contained in the protrusions. Was less than 2 mol%. By replacing some of the chloride with bromide, much higher concentrations of iodide can be introduced into the protrusions. For example, when silver halide is epitaxially deposited, the molar ratio is 42: 42: 1.
When silver was introduced together with chloride: bromide: iodide of 6, the iodide concentration in the obtained epitaxial protrusions was 7.1 mol% based on the silver contained in the protrusions. A preferable iodide ion concentration in the protrusion is in the range of 1 to 15 mol% (most preferably 2 to 10 mol%) based on silver in the protrusion.

Surprisingly, it was discovered that the introduction of chloride, bromide and iodide ions with silver during epitaxial deposition further improves the speed-granularity relationship. Was done.
Since the epitaxy of silver bromide or silver iodobromide on the silver iodobromide host tabular grains has a lower sensitization level than that when silver, chloride and iodide ions are simultaneously introduced during epitaxy, It was not expected that replacing some of the chloride with bromide would further improve photographic performance. Analysis shows that the introduction of chloride and bromide ions during the deposition of epitaxial protrusions increases the amount of iodide introduced. This can be explained in terms of an increase in crystal cell lattice size imparted by an increase in bromide ion concentration.
No explanation is given as to why the photographic performance increases without even closer to that provided by the silver iodobromide epitaxial protrusions.

The silver halide epitaxy includes (1) a large difference in chloride concentration between the tabular grains of the host and the epitaxially deposited protrusions, and (2) in the face centered cubic lattice structure of the protrusions. It is believed that the highest levels of photographic performance are achieved at high iodide loadings.

One of the preferred techniques related to (1) above is a method of introducing different halide ions in the order of decreasing solubility of silver halide formed by them in the step of depositing protrusions. For example, when chloride, bromide and iodide ions are all introduced when depositing protrusions, it is preferable to introduce chloride ions first, then bromide ions, and finally iodide ions. Since the solubility of silver iodide is lower than that of silver bromide, and the solubility of silver bromide is lower than that of silver chloride, when halide ions are added in the preferred order, chloride ions adhere to the vicinity of the junction. Have the highest chance of doing
In some cases, the protrusion forms a clear layer, and a region having a high chloride ion concentration and a region having a low chloride ion concentration can be detected. However, when the halide is added in the preferred order, it may not be detected. This is because both the bromide ion and the iodide ion have the ability to partially replace the chloride of the previously deposited silver chloride.

The technique of increasing the iodide concentration in the protrusions should minimize iodide in the epitaxially deposited protrusions to avoid morphological instability of the host tabular grains. It is the exact opposite of the traditional thinking in the field. However, the increase in iodide concentration in the above epitaxially deposited protrusions is
It was found to be compatible with maintaining the tabular shape of the host grains.

In practicing the present invention, the high iodide concentration at the protrusions results in a rock-salt type face centered cubic lattice structure, ie, isomorphic crystals formed by one or both of chloride and bromide and silver. This is the concentration that can be accommodated in the lattice structure type. Of course, a limited amount (generally 10 mol% or less) of bromide and / or chloride ions is not isomorphic to β or γ.
Although non-isomorphic silver halide epitaxy can be incorporated into the phase silver iodide crystal structure, it does not form part of the invention. These structures are too diverse to be attributed to equivalent photographic properties. Further, Maskasky-II shows that the non-isomorphic epitaxial protrusions have a much lower sensitization level than the silver halide epitaxial protrusions having the isomorphic crystal structure.

By subjecting the composition modifications specifically described above, the preferred techniques of chemical and spectral sensitization may be the same as those described above in Maskasky-I. Maskasky-I reports an improvement in sensitization by epitaxially depositing silver halide at specific sites on the surface of host tabular grains. Maskasky-I attributed the observed speed increase to limiting epitaxy deposition of silver halide to a region of small host tabular grain surface area. The silver halide epitaxy is closest to the periphery of the host tabular grains and less than 50% of the {111} major faces of the tabular grains, preferably a much smaller proportion of the {111} major faces of the tabular grains, preferably Is less than 25%, most preferably 1
It is possible to limit it to a portion occupying less than 0%, optimally less than 5%. When the tabular grains contain a central region of low iodide concentration and regions located on the sides of high iodide concentration, silver halide epitaxy is typically employed, with tabular grain edges and corners It is preferable to limit to the portion of the tabular grains formed by the region arranged on the side including the.

As in Maskasky-I, the practice of the invention is to use a nominal amount of silver halide epitaxy [total silver (including silver in host and epitaxy) of 0.
About 05 mol%] is effective. It is preferred to limit silver halide epitaxy to less than 50% of total silver. Generally, a silver halide epitaxy concentration of 0.3 to 25 mol% is preferred, and a concentration of about 0.5 to 15 mol% for sensitization.
Is generally best.

Maskasky-I teaches various techniques applicable to the formation of emulsions of this invention to limit the surface coverage of host tabular grains by silver halide epitaxy. Maskasky-I teaches the use of spectral sensitizing dyes in aggregated form adsorbed onto tabular grain surfaces which can direct silver halide epitaxy towards the edges or corners of the tabular grains. J
Cyanine dyes that are adsorbed to the surface of host tabular grains in agglomerated form constitute a particularly preferred type of site director. Maskasky-I also teaches using non-dye adsorption site directors such as aminoazaindenes (eg, adenine) to direct epitaxy to the edges or corners of tabular grains. In yet another embodiment, Maskasky-I directs epitaxy to the edges or corners of the tabular grains with a total iodide content in the host tabular grains of at least 8 mole percent. In yet another aspect, Maskasky-I adsorbs small amounts of iodide to the surface of host tabular grains to direct epitaxy to the edges and / or corners of the grains. The site-directed techniques described above are mutually compatible and are used in combination in a particularly preferred embodiment of the invention. For example, iodide in the host grains, even if alone does not reach the level of 8 mol% that can direct the epitaxy to the edges or corners of the host tabular grains, in adsorbed surface site director (in the position of epitaxy ( It can work effectively with one or more (eg, spectral sensitizing dyes and / or adsorbed iodides).

Selective site attachment of silver halide epitaxy to host tabular grains can reduce sensitized site competition for conduction band electrons released by photon absorption in imagewise exposure, thus improving sensitivity. Generally accepted. That is, epitaxy to a limited portion of the major surface of the tabular grain is more efficient than epitaxy covering all or most of the major surface, and more preferably,
Epitaxy that is substantially limited to the edges of the host tabular grains and has a limited amount of coverage on the major surface, more efficient at or near the corners of the tabular grains or separately It is epitaxy restricted to the site. The distance between the corners of the main surface of the host tabular grain itself is
Reduce optoelectronic competition sufficiently to achieve near maximum sensitivity. Maskasky-I can reduce the number of epitaxial attachment sites on host tabular grains by slowing the epitaxial attachment rate. US Pat. No. 5,011,767 (Yamashita et al.)
Suggests the conditions for advancing this further and forming one epitaxy junction per host particle with a specific spectral sensitizing dye. As taught by Solberg et al., Cited above, when the host tabular grains contain a higher concentration of iodide in the laterally disposed regions, the silver halide protrusions are An improvement in photographic performance is observed by confining it to the areas located on the higher sides.

The dopants described above in connection with the tabular grains can, alternatively, be located wholly or partially in the silver halide epitaxy.

Silver halide epitaxy itself is
Photographic speed can be increased to levels comparable to those obtained by substantially optimal chemical sensitization with sulfur and / or gold. Further chemical sensitization of tabular grains on which silver halide has been epitaxially deposited with a normal middle chalcogen (that is, sulfur, selenium or tellurium) sensitizer or a noble metal (for example, gold) sensitizer further increases the photographic speed. To do. These conventional chemical sensitization methods applicable to silver halide epitaxial sensitization are described in Research Disclosure, No. 36.
Volume 5, September 1994, Item 36544, Section IV, Chemical Sensitization. Kofron et al. Describe applying these sensitizations to tabular grain emulsions.

In a particularly preferred approach to silver halide epitaxial sensitization, sulfur-containing ripening agents are used in combination with middle chalcogen (typically sulfur) and noble metal (typically gold) chemical sensitizers. Intended sulfur-containing ripening agents include U.S. Pat. No. 3,271,157 (M
cBride), U.S. Pat. No. 3,574,628 (Jones) and U.S. Pat. No. 3,737,313 (Rosenrants et al.), including thioethers. A preferred sulfur-containing ripening agent is US Pat. No. 2,222,2
64 (Nietz), U.S. Pat. No. 2,448,
534 (Lowe et al.) And US Pat. No. 3,32.
Thiocyanates described in No. 0,069 (Illingsworth). A preferred class of middle chalcogen sensitizers is described in US Pat. No. 4,749,6
46 and 4,810,626 (He
rz et al.) and tetra-substituted middle chalcogen ureas. Preferred compounds include those of the formula:

[0046]

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(Wherein X is sulfur, selenium or tellurium; each of R ₁ , R ₂ , R ₃ and R ₄ independently represents an alkylene, cycloalkylene, alkarylene, aralkylene or heterocyclic arylene group. Or, together with the nitrogen atom to which it is attached, R ₁ and R ₂ or R ₃ and R ₄ can complete a 5 to 7 membered heterocycle; and A ₁ , A ₂ , A ₃ and A ₄ Each independently represents a group containing hydrogen or an acid group, provided that A ₁ R _{1 to} A _1
At least one of ₄ R ₄ contains an acid group bonded to the nitrogen of urea through a carbon chain having 1 to 6 carbon atoms).

X is preferably sulfur and A ₁ R ₁
~ A ₄ R ₄ is preferably methyl or carboxymethyl (provided that the carboxy group may be in an acid form or a salt form). Particularly preferred tetra-substituted thiourea sensitizers are 1,
It is 3-dicarboxymethyl-1,3-dimethylthiourea. A preferred gold sensitizer is US Pat. No. 5,049,4.
No. 85 (Deaton) is a gold (I) compound. These compounds include those represented by the formula: (VI) AuL ₂ ⁺ X ⁻ or AuL (L
¹ ) ⁺ X ⁻ , where L is a mesoionic compound; X is an anion; and L ¹ is a Lewis acid donor.

Kofron et al. Introduces a spectral sensitizing dye into the emulsion prior to the heating step (finishing) which results in chemical sensitization.
The advantages of "dye in finish sensitization" are disclosed. Dyes in finish sensitization are particularly advantageous in the practice of this invention in which the spectral sensitizing dyes adsorb to the tabular grain surfaces and act as site directors for silver halide epitaxial deposition. Maskasky-I teaches the use of J-aggregating spectral sensitizing dyes, especially green and red absorbing cyanine dyes as site directors. These dyes are present in the emulsion before the chemical sensitizing finishing step. A much wider range of spectral sensitizing dyes is available if the spectral sensitizing dye present in the finish is not utilized as the site director for silver halide epitaxy. Kofron
Spectral sensitizing dyes disclosed by et al., Especially blue spectral sensitizing dyes represented by structures showing absorption maximums in the green and red parts of the spectrum and longer methine chain analogues,
It is particularly preferable to incorporate it in the tabular grain emulsion of the present invention. It is particularly conceivable to select a J-aggregating blue absorption spectral sensitizing dye for the site director. Useful spectral sensitizing dyes include Research Disclosure,
Item 36544, section V.6. Spectral sensitization and desensitization, A. Spectral sensitizing dyes, are generally summarized.

In a particularly preferred embodiment of the invention, the spectral sensitizing dye can also act as a site director and / or be present in the finish, although it must be fulfilled by the emulsion of the invention. Its only function is to increase the sensitivity of the emulsion to at least one region of the spectrum. Thus, if desired, the spectral sensitizing dye can be added to the tabular grains according to the invention after chemical sensitization is complete.

In addition to the characteristics of the spectrally sensitized silver halide epitaxially sensitized tabular grain emulsions described above, the emulsions and emulsions of this invention can be in any convenient conventional form. For example, although not required, a novel emulsion satisfying the requirements of the invention can be prepared and then this emulsion can be blended with one or more other novel emulsions according to the invention or any other conventional emulsion. The usual emulsion formulation is Res
search Disclosure, item 3654
4, Section I, E.I. Blends, layers and performance categories.

The emulsion, once formed, can be further made available for photographic use by any convenient conventional method. Further usual features are the Research Disclosure, item 3 above.
6544, Section II, vehicle, vehicle extenders, vehicle-like additives and vehicle-related additives; Section III, emulsion wash; Section V, spectral sensitization and desensitization; Section VI, UV dyes / optical brighteners / luminescent dyes Section VII, antifoggants and stabilizers; Section VIII, absorbers and scatterers; Section I
X, coating physical property modifiers; Section X, dye image-forming agents and modifiers. VI, VII
The I, IX and X features can optionally be provided in other photographic element layers. Other features relating to the construction of photographic elements are Section XI, layers and layer arrangements; XII, features only applicable to color negatives; XIII, features only applicable to color reversal; XIV, scan facilitating features and X.
V, described on the support.

The novel silver halide epitaxially sensitized tabular grain emulsions of this invention can be used in any other conventional photographic element. The emulsion can be included in, for example, a photographic element having one or more silver halide emulsion layers. In one embodiment, the novel emulsions of this invention can be in a single emulsion layer of a photographic element intended to produce a silver or dye photographic image for viewing or scanning.

In one simple embodiment, the photographic element can be a black and white (eg silver image forming) photographic element in which the underlying (first) emulsion layer is orthochromatic or panchromatic sensitized. In another embodiment, the photographic element is a multicolor photographic element containing blue recording (yellow dye image forming), green recording (magenta dye image forming) and red (cyan dye image forming) layer units in either coating order. Can be. A wide variety of coating arrangements can be found in the above Kofron
Et al., Columns 56-58, the disclosure of which is hereby incorporated by reference.

[0055]

EXAMPLES By reference to the following examples of emulsion preparations, emulsions and photographic elements satisfying the requirements of the invention,
The invention can be better understood. For the photographic sensitivity, the speed difference of 30 log units is 0.3 log E (however, E
Represents a relative log speed equal to the unit: exposure in lux second). Contrast is measured as midscale contrast. The halide ion concentration is represented by mol% (M%) with respect to silver.

Emulsion A This emulsion was precipitated in a two part process. The first part formed 9 moles of an Ag (Br, I) emulsion having an average diameter of about 1.9 μm and an average thickness of about 0.047 μm. A portion of this emulsion was then used as the seed emulsion for further growth in Part 2. In this second part, silver bromide was deposited and deposited predominantly on the {111} major faces of the tabular grains, that is, in the second part of the precipitation, the thickness was increased rather than the side growth.

Part 1 Lime-treated bone gelatin 3.75 in a container equipped with a stirrer
g, 4.12 g NaBr, antifoam, and pH at 39 ° C
Was charged with 6 liters of water containing sufficient sulfuric acid to adjust to 1.8. AgNO ₃ solution and halide (NaBr and KI are 98.5M% and 1.5M, respectively)
%) Solution and silver iodobromide 0.0133
During the nucleation achieved by adding in balance enough to produce 5 moles and simultaneously adding pBr and p
H was kept approximately at the value initially set for the solution in the reactor. Following nucleation, Oxone ™ (2KHS
O ₅ · KHSO ₄ · K ₂ SO ₄ Aldrich) 12
The gelatin in the reactor was rapidly oxidized by adding a solution of 8 mg dissolved in 50 mL of water, and the temperature was adjusted to 5 in 9 minutes.
Raised to 4 ° C. The reactor and its contents were held at this temperature for 9 minutes and then a solution of 100 g of methionine oxidised lime bone gelatin in 1.5 liter of water was added.
Add to reactor at ° C. The pH was then raised to 5.90 and 43.75 mL of 2.8M NaBr was added to the reactor. Twenty-five minutes after nucleation, the growth phase started, during which 2.5M AgNO ₃ , 2.8M NaBr and Ag
0.108M suspension of I (Lippmann)
(A) keeping the iodide concentration in the growing silver halide crystals uniform at 4.125 M%; and (b)
Until 0.813 mol of silver iodobromide was produced,
Br was added proportionately to maintain the value obtained by the addition of NaBr described above before the onset of nucleation and growth, at which time 37.5 mL of 2.8 M NaBr was added to add excess Br ⁻ concentration. Was maintained; the in-reactor pBr was maintained at the value obtained to balance growth. next,
The flow of the reactants was restarted and the flow rate was accelerated to bring the final flow rate at the end of growth (total 127 minutes) to about 13 times that at the start; 9 moles total silver iodobromide (4. 125M
% I) produced.

Six moles of the emulsion formed in the first step of the second part were withdrawn, and the remaining three moles in the reactor were used as seed crystals for further thickness growth for further growth. Before starting this additional growth, methionine oxide-lime treated bone gelatin 34
p in the reactor by adding a solution of g dissolved in 500 mL of water at 54 ° C. and gradually adding AgNO _3.
The r was adjusted to about 2.05. Then, 3.0 M AgNO ₃ and 5.0 M NaBr were added by the double jet method at a relative rate to further adjust the pBr in the reactor to 3.3 over 10 minutes to start the growth. This high pB
While maintaining the r-value and the temperature of 54 ° C., the above AgNO ₃ and NaBr solution was added to continue the growth until 9.0 mol of silver bromide was attached to the surface of the host grain. The flow rate was accelerated 1.85 times during the 162 minute growth of Part 2.

The total composition of the finally obtained silver iodobromide tabular grain emulsion was about 98.97 M% Br and about 1.03 I.
It was M%. After the growth is completed, the pBr is lowered to about 2,
The emulsion was coagulated and washed. After washing, the pH and pBr were adjusted to 6.0 and 3.1, respectively, and stored.

The obtained emulsion was subjected to scanning electron microscopy (SE
M) and connected to an IBM personal computer, Summagraphics SummaS
The average particle area was determined from the particle photographs obtained with a Ketch Plus sizing tablet. More than 98% of the total grain projected area was occupied by tabular crystals. The average ECD of the emulsion grains was 1.37 μm (coefficient of variation = 43). In Part 2, the average ECD of the tabular grain emulsions actually fell below the values at the end of Part 1. This indicates that, assuming a constant number of grains, negative side growth occurred, ripening occurred at the edges of the tabular grains and silver halide deposition was predominantly on the tabular grains. This suggests that it has occurred on the {111} main surface. Grain thickness was measured using the dye adsorption method because the grain population of the final emulsion consisted almost exclusively of tabular grains: 1,1 'required for saturation coverage.
-The level of the diethyl-2,2'-cyanine dye was measured and the solution absorption coefficient of this dye was 77,300 liters /
Mol-cm, and the site area per mol is 0.56
The equation for surface area was solved, assuming 6 nm ² . This technique gave a mean grain thickness value of 0.175 μm.

Epitaxial Sensitization Next, emulsion samples were sensitized in the presence of silver salt epitaxy. The nominal epitaxy composition is silver chloride, silver iodochloride or silver iodobromochloride. A 0.5 mole sample of Control Emulsion A was melted at 40 ° C and
_The pBr was adjusted to about 4 by the simultaneous addition of ₃ and KI solutions. At this time, the AgNO ₃ solution and the KI solution contained 12% I of silver halide precipitated during the preparation.
Was added in such a ratio that Then, after addition of 2M% NaCl (based on the initial amount of silver iodobromide host),
Spectral sensitizing dye 1 [anhydro-9-ethyl-5 ', 6'
-Dimethyoxy-5-phenyl-3 '-(3-sulfopropyl) -3- (3-sulfobutyl) oxathia-carbocyanine hydroxide] and dye 2 [anhydro-5.
5'-di-chloro-9-ethyl-3,3'-bis (3-
Sulfopropyl) thiacarbocyanine hydroxide, sodium salt] and then CaCl ₂ and AgNO ₃
6M% AgCl epitaxy was formed by sequential addition of the solution. This operation caused epitaxial growth to occur mainly at the corners and edges of the host tabular grains. Epitaxy was 6 M% of silver in the starting tabular grain emulsion. The nominal composition of the tabular grain host, i.e. the halide added to form the host grain, and the actual composition of the host grain is set forth in Table 1. The nominal composition of epitaxy and the actual composition of epitaxy are listed in Table 2.

Example 1 The epitaxial sensitization procedure employed for the epitaxial control was repeated, except that CaCl ₂ , AgI (Lippmann) and AgNO ₃ were added in that order. The total silver loading was maintained at 6 M% relative to the tabular grain silver. The tabular grain host nominal composition and the actual host grain composition are listed in Table 1. Table 2 lists the chloride to iodide ratios in the epitaxy as nominal (added amount) and actual (measured) AgCl and AgI compositions.

Example 2 The epitaxial sensitization procedure of Example 1 was repeated, except that CaCl ₂ , NaBr, AgI (Lippmann) and A were used.
The Gno ₃ were added in this order. Thus, chloride,
Bromide and iodide were added sequentially. The total silver loading was maintained at 6 M% relative to the tabular grain silver. The tabular grain host nominal composition and the actual host grain composition are listed in Table 1. Table 2 lists the chloride, bromide and iodide ratios in the epitaxy as nominal and actual AgCl, AgBr and AgI compositions.

The electron microscopy (AEM) method was used to measure the actual composition of the silver halide epitaxy protrusions rather than the nominal (input) composition. The general operation of AEM is
J. I. Goldstein and D.M. B. William
ms, "X-ray Analysis in the
TEM / STEM ", Scanning Elect
ron Microscopy / 1977; Volume 1, I
IT Research Institute, 1977
March 1989, page 651. The composition of individual epitaxy protrusions was measured by focusing the electron beam small enough to illuminate only the protrusions to be tested. By selectively arranging the epitaxy protrusions at the corners and edges of the host tabular grains, addressing only the epitaxy protrusions was facilitated. Each corner epitaxy protrusion for each of the 25 grains was examined for each sensitization. The results are summarized in Table 1 and Table 2.

Table 1: Halide detection in tabular grains Halide (standard deviation) Sample added Halide Cl Br I Control Br 99% 4.7% 93.9% 1.3% I 1% (0.3) (0.4) (0.2) Implementation Example 1 Br 99% 4.7% 93.7% 1.6% I 1% (0.4) (0.6) (0.1) Example 2 Br 99% 4.6% 93.9% 1.5% I 1% (0.4) (0.6) (0.2)

Table 2: Halide Detection Halides in Epitaxy (Standard Deviation) Sample Addition Halide Cl Br I Control Cl 100% 65.6% 34.4% 0% (5.4) (5.4) Example 1 I 16% 81.2% 17.7 % 1.1% Cl 84% (4.4) (4.1) (0.7) Example 2 Cl 42% Br 42% 39.8% 54.6% 5.6% I 16% (9.9) (9.1) (1.6)

The minimum AEM detection limit was 0.5 M% at halide concentration. Looking at the control in Table 2, when chloride is the only halide added to the silver iodobromide tabular grain emulsion upon precipitation of the epitaxial protrusions, the iodide ion transferred from the host tabular grains is Essentially absent (below detection limit). When 16 M% iodide and 84 M% chloride were added to form epitaxy, the iodide concentration in the epitaxy increased to just over 1 mol% based on the silver forming the epitaxial protrusions. .
When chloride and bromide were co-deposited with a nominal 16 M% iodide, the iodide content in the epitaxial protrusions increased by more than 5 mol%.

The prepared epitaxially sensitized emulsion after epitaxy was divided into small pieces to determine the optimum level of the subsequently added sensitizing component and to test the effect of level fluctuations. Into these split portions, a further portion of Dyes 1 and 2, 60 mg NaSCN / mol A
g, sulfur sensitizer 1, gold sensitizer 2 and 11.44 mg of 1
-(3-Acetamidophenyl) -5-mercaptotetrazole (APMT) / mol Ag was added. After all the ingredients were added, the mixture was heated to 50 ° C. to complete the sensitization, and after cooling another 114.4 mg APMT was added.

[0069]

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Based on the construction and sensitometric evaluation of photographic elements as reported below using a portion of the emulsion, the optimum densities of Dye 1 and Dye 2 in each of the control, Example 1 and Example 2 emulsions were: , 87.7 and 358.7 m respectively
It was determined to be g / mol Ag. The optimum concentrations of sensitizer 1 and sensitizer 2 are 3.1 and 0.9 mg / mol Ag (control), 1.5 and 0.9 mg / mol Ag (Example 1) and 2.7 and 0, respectively. It was determined to be 0.8 mg / mol Ag (Example 2).

The optimum sensitized emulsion obtained was coated on a gray silver antihalation layer on a cellulose acetate film support, and a surfactant and a bis (vinylsulfonyl) methane hardener (gelatin) were added to this emulsion layer. 1.7 for total weight
5% by weight) and was overcoated with a 4.3 g / m ² gelatin layer. The emulsion coating amount is 0.646 g-Ag /
m ² and in this layer coupler 1 and coupler 2 were 0.323 g / m ² and 0.019 g / m ² , respectively.
4-hydroxy-6-methyl-1,3,3a, 7, -tetraazaindene (Na ⁺ salt) at 10.5 mg / m ^{2 and} 2- (2-octadecyl) -5-sulfohydroquinone (Na ⁺ salt) Of 14.4 mg / m ² , a surfactant and a total gelatin amount of 1.08 g / m ² .

[0072]

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Sensitometry The emulsion thus coated was subjected to a Wratten 23A ™ filtration (wavelength> 560 nm transmission) daylight balance light exposure for 0.01 sec through a calibrated neutral step tablet, and a color negative Kodak Flexicolo.
Developed using the r (TM) C41 process. Speed was measured at a density of 0.15 above the lowest density.

SPSE Handbook of Ph
otographic Science and En
Gineering (W. Thomas, ed., 934-)
Granularity was measured according to the procedure described on page 939). The granularity reading at each step was divided by the gamma at each step [ΔD ÷ ΔlogE, D = density, E = exposure dose (lux-sec)] and plotted against logE. There is typically a minimum in these plots. This minimum value of gamma-normalized granularity allows comparison of coatings with different contrasts. The smaller the value, the lower the granularity. The reported granularity reading was the average of the observations taken from four adjacent exposure steps from near the speed point to higher exposure. These four readings were typically near the minimum granularity.

The contrast-normalized granularity obtained as described above is reported in Table 3 below as a particle unit (gu). In this, each g. u. Represents the amount of change of 5%,
A positive change corresponds to high image graininess, and a negative change corresponds to low image graininess. In other words, a negative difference in granularity indicates that the granularity has decreased. The results are summarized in Table 3.

Table 3 Epitaxy Relative Intermediate Δ Normalization Halide log Scale Granularity Sample Addition D _min Speed Contrast (gu) Control Cl 100% 0.18 100 0.48 Reference Example 1 Cl 84% 0.19 127 0.62 -5.5 I 16 % Example 2 Cl 42% 0.15 115 0.66 -11.9 Br 42% I 16%

It is clear from Table 3 that increasing the iodide concentration during epitaxy increases speed and midscale contrast and decreases granularity while keeping the minimum concentration perfectly acceptable. . Example 1
Comparing Example 2 with Example 2, the emulsion of Example 2 having a higher iodide concentration in the epitaxial protrusion was superior to the emulsion of Example 1. Granularity is 7 g. u. Applying the general criterion that the speed is reduced by 30 units for each decrease, the emulsion of Example 2 is 6.4 gm less than the emulsion of Example 1. u. It is excellent, but it can be seen that with respect to the decrease in speed, it shows only a decrease of 12 speed units as compared with the decrease of 27 speed units due to the equivalent speed-granularity relationship.

Emulsion B The above evaluation was repeated as follows, but the host tabular grain emulsion was 4.125 M% iodide, average EC
The silver iodobromide emulsion had a D of 1.76 μm (COV = 44) and an average grain thickness of 0.130 μm. For forming the epitaxial protrusion, NaCl is used instead of CaCl _2.
It was used. Two emulsions (Control 2 and Example 3) were prepared by epitaxial deposition as described above for Control and Example 2, respectively. Optimal concentrations of Dye 1 and Dye 2 are 13 for Control 2
2.4 and 542.8 mg / mol Ag, and for Example 3 145.6 and 597 mg / mol Ag, respectively. The optimum concentrations of sensitizer 1 and sensitizer 2 were 2.4 and 0.97 mg / mol Ag respectively for Control 2 and 2.7 and 1.08 mg / mol Ag respectively for Example 3. These performance results are summarized in Table 4 below.

Table 4 Epitaxy Relative Intermediate Δ Normalization Halide log Scale Granularity Sample Addition D _min Speed Contrast (gu) Control 2 Cl 100% 0.19 100 0.69 Reference Example 3 Cl 42% 0.18 99 0.77 -7.6 Br 42% I 16%

What is clear from Table 4 is again that
The higher the iodide concentration in the epitaxial protrusions, the better the performance.

The preferred embodiments of the present invention will be described below item by item. [1] (1) Dispersion medium, (2) (a) {111} major surface, and (b) over 70 mol% of bromide and 0.25 mol% or more of iodide with respect to silver. Contained, (c) accounting for more than 90% of the total grain projected area, (d) having an average equivalent circular diameter of 0.7 μm or more, and (e) having an average thickness of 0.07 μm or more, 0.3
a silver halide grain containing a tabular grain having a latent image-forming chemical sensitization site on the surface, and (3) a spectral sensitizing dye adsorbed on the surface of the tabular grain. And a tabular grain containing less than 10 mole percent iodide, wherein the surface chemically sensitized sites form an epitaxial junction with the tabular grain. Comprising a salt-type face-centered cubic lattice structure epitaxially attached silver halide protrusions, said protrusions comprising:
(A) limited to a portion located closest to the peripheral edge portion of the tabular grain and occupying less than 50% of the {111} main surface of the tabular grain, and (b) 10 mol% more than the tabular grain. A radiation-sensitive emulsion characterized by exhibiting a high silver chloride concentration as described above, and (c) containing 1 mol% or more of iodide with respect to the amount of silver forming the protrusion.

[2] It is further characterized in that the protrusion has a higher iodide concentration than a portion of the tabular grain where the protrusion forms an epitaxial junction.
The emulsion according to the item. [3] The emulsion according to item [2], further characterized in that the tabular grains contain less than 4 mol% of iodide. [4] The emulsion according to any one of [1] to [3], further characterized in that the protrusions contain 1 to 15 mol% of iodide.

[5] The emulsion according to the item [4], wherein the protrusions further contain 2 to 10 mol% of iodide. [6] The emulsion according to any one of [1] to [5], wherein the protrusions have a chloride ion concentration higher than that of the tabular grains by 15 mol% or more. [7] The emulsion according to any one of [1] to [6], further characterized in that the protrusions account for 0.3 to 25% of the total silver amount. [8] The emulsion according to any one of [1] to [7], further characterized in that the epitaxially deposited silver halide protrusions are arranged in less than 25% of the surface of the tabular grains.

[0084]

[9] The emulsion according to the item [8], wherein the epitaxially deposited silver halide protrusions are arranged mainly in the vicinity of at least one of an edge portion and a corner portion of the tabular grain. [10] Further characterized in that the tabular grains account for more than 97% of the total grain projected area [1]-

The emulsion according to any one of [9].

 ─────────────────────────────────────────────────── --Continued front page (31) Priority claim number 359251 (32) Priority date December 19, 1994 (33) Priority claim country United States (US) (31) Priority claim number 441491 (32) Priority date May 15, 1995 (33) Priority claim United States (US) (72) Inventor Joseph Charles Deaton United States, New York 14617, Rochester, Nob Hill 37 (72) Inventor Timothy Richard Jersey United States, New York 14609, Rochester, Alford Street 53 (72) Inventor Joseph George Lighthouse USA, New York 14626, Rochester, Countryshire Drive 133 (72) Inventor Miratoforon Orm United States, New York York 14580, Webster, Wycliffe Drive 181 (72) Inventor Shin Wen United States, New York 14618, Rochester, Tillstone Place 70 (72) Inventor Robert Don Wilson United States, New York 14612, Rochester, Seafarers Lane 133

Claims (2)

[Claims] 1. A dispersion medium comprising: (1) a dispersion medium; (2) a {111} major surface of (a); and (b) more than 70 mol% bromide and 0.25 mol% or more iodine based on silver. And (c) occupy more than 90% of the total grain projected area, (d) the average equivalent circular diameter is 0.7 μm or more, and (e) the average thickness is 0.07 μm or more, 0. Three
a silver halide grain containing a tabular grain having a latent image-forming chemical sensitization site on the surface, and (3) a spectral sensitizing dye adsorbed on the surface of the tabular grain. And a tabular grain containing less than 10 mol% of iodide, wherein the surface chemically sensitized site forms an epitaxial junction with the tabular grain. An epitaxially attached silver halide protrusion having a rock salt type face centered cubic lattice structure, wherein the protrusion is (a) located closest to the peripheral edge of the tabular grain and {111} of the tabular grain. Confined to less than 50% of the major surface, (b) exhibiting a silver chloride concentration of at least 10 mol% higher than the tabular grains, and (c)
A radiation-sensitive emulsion containing 1 mol% or more of iodide with respect to the amount of silver forming the protrusions. 2. The tabular grains account for 97% of the total grain projected area.
The emulsion according to claim 1, further characterized in that it accounts for more than%.