JPS5851252B2 - silver halide photographic emulsion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel silver halide emulsion.

It is known that photographic sensitivity can be increased by increasing the size of silver halide crystals.

However, in the conventionally known method of using ammonia as a silver halide solvent, large crystals of silver halide can only be produced in a high pH range.

This resulted in a high fog level, making it difficult to obtain high photographic sensitivity.

Furthermore, the emulsion obtained by this method is relatively sensitive to pressure, which is not preferable.

Therefore, a silver halide solvent that can increase the size of silver halide grains even in a low pH region is desirable.

It is also desired to produce silver halide grains that are less sensitive to pressure.

Regarding a silver halide solvent that can increase the size of silver halide grains even in a low pH range, organic onythyl is known from Japanese Patent Publication No. 11386/1986.

However, organic thioethers tend to cause fog in photographic emulsions, and the synthesis of the compound requires a relatively large number of purification cycles, making it difficult to achieve industrial profitability.

Therefore, a better silver halide solvent is desired.

One of the objects of the present invention is to provide a silver halide emulsion with excellent photographic sensitivity.

Another object of the present invention is to provide a new coarse grain silver halide emulsion.

Yet another object is to provide a direct positive silver halide emulsion with high photographic sensitivity.

A further object is to provide a silver halide emulsion that is less sensitive to pressure.

Yet another object is to provide a novel method for producing silver halide photographic emulsions.

In accordance with the present invention, it has been found that the above objects of the invention can be achieved by producing silver halide crystals in the presence of a tetrasubstituted thiourea silver halide solvent.

Preferably, the emulsions of this invention are made by a process consisting of reacting a water-soluble silver salt and a water-soluble halide in an aqueous hydrophilic colloid solution containing a tetrasubstituted thiourea solvent.

The tetrasubstituted thiourea silver halide solvent is added at any step of the manufacturing process until the silver halide grains reach their final size and shape.

The abovementioned solvents are added, for example, to the colloidal material in which the silver halide is precipitated.

Also, water-soluble silver salts (such as silver nitrate) or water-soluble halides (
It is added in combination with any of the water-soluble salts used to make silver halides, such as alkali metal halides such as potassium bromide, sodium chloride, etc.

Alternatively, it may be added before or during the physical ripening of the silver halide, or during one or more steps of manufacturing such an emulsion.

In the present invention, it is preferable to add tetrasubstituted thiourea before physical ripening of silver halide.

The method for preparing the emulsion of the present invention includes P, Glafk-id
es author “Shimmy・Technology・Fujiiku Photographic J”
(Chimie et Physique Photo
ograp-hique) (Paul Monte1
Publishing, 1967), by G, F-Duf in ``
Photographic Emulsion Chemistry J
(Photographic Em-ulsion C
hemistry,] (The Focal Pre
ss, 1966), V, L, Zelikman
“Making End Coating Photographic Emulsion J” by et al.
and C-oating Photography
c Emulsin) (The Focal Pres.
For example, the method described in J.S., 1964) can be used.

As a method for reacting the water-soluble silver salt and the water-soluble halide, any one of a one-sided mixing method, a simultaneous mixing method, a combination thereof, etc. may be used.

It is also possible to use a method in which particles are formed in an excess of silver ions (so-called back-mixing method).

As one type of simultaneous mixing method, a method in which the pAg in the liquid phase in which silver halide is produced can be kept constant, that is, a so-called Chondrald double jet method can also be used.

The manufacturing process of the emulsion of the present invention is generally performed at a temperature of about 30 to 90°C.
, the pH is up to about 9, preferably 8 or less, and the pAg is up to about io.

In the process of silver halide grain formation or physical ripening,
A cadmium salt, a zinc salt, a lead salt, a thallium salt, an iridium salt or a complex salt thereof, a rhodium salt or a complex salt thereof, an iron salt or an iron complex salt, etc. may be present.

As the silver halide for the silver halide emulsion of the present invention, for example, silver bromide, silver iodide, silver chloride, silver chlorobromide, silver bromoiodide, silver chlorobromoiodide, etc. can be used.

Preferred silver halide emulsions comprise at least 50 mole percent silver bromide, and the most preferred emulsions are silver bromoiodide emulsions, especially those containing up to about 10 mole percent silver iodide.

Average particle diameter of about 0.2 to 4 microns, preferably about 0
．． Silver halide grains of 25 to 2 microns give particularly good results.

The particle size distribution may be narrow or wide.

The average particle diameter can be determined using conventional methods, e.g. The Photographic Journal.
Journal) Vol. 79, pp. 330-338 (193
9 years) Can be measured using the method described.

The silver halide grains in the photographic emulsion may have a regular crystal structure such as a cube or an octahedron, or an irregular crystal structure such as a spherical or plate-like structure.
It may have an egular crystal form or a composite form of these crystal forms.

It may also consist of a mixture of particles of different crystalline forms.

The silver halide grains may have different phases inside and on the surface, or may consist of a uniform phase.

Further, the particles may be particles in which a latent image is mainly formed on the surface, or may be particles in which a latent image is mainly formed inside the particles.

The silver halide emulsion is coated at a silver content of about 50 to 600'Ir1fI per square foot of support.

The aqueous solution of the tetrasubstituted thiourea silver halide solvent used in the present invention is more soluble in silver chloride than in water.

More specifically, such tetrasubstituted thiourea silver halide solvents, when used in aqueous solution at a 0.01 molar concentration (at 60'C), have a higher concentration than silver chloride dissolved in water at 60°C.
．． Dissolve and dissolve more than 5 times (by weight) silver chloride.

The tetrasubstituted thiourea silver halide solvent used in the present invention is a thiourea derivative that does not have hydrogen atoms at the 1 and 3 positions.
This cannot have a thiol structure, so silver ions are present, and silver sulfide is not substantially produced even under alkaline conditions.

A preferred tetrasubstituted thiourea silver halide solvent used in the present invention is represented by the following general formula.

In the formula, R1, R2, R3 and R4 represent a substituted or unsubstituted alkyl group, an alkenyl group (such as an allyl group), or a substituted or unsubstituted aryl group, and these may be the same or different from each other, and R1 The total number of carbon atoms in -R4 is preferably 30 or less.

Also, a 5- to 6-membered heterocyclic imidazolidinethione bonded by R1 and R2, R2 and R3, or R3 and R4,
Piperidine, morpholine, etc. can also be made.

Both straight chain and branched alkyl groups are used as the alkyl group.

As a substituent for an alkyl group, for example, a hydroxy group (-
OH), carboxy group, sulfonic acid group, amino group, alkoxy group in which the alkyl residue has 1 to 5 carbon atoms (
0-alkyl), phenyl group, or 5- to 6-membered heterocycle (such as furan).

The substituent for the aryl group is a hydroxy group, a carboxy group or a sulfonic acid group.

Here, it is particularly preferable that R1 to R4 have three or more alkyl groups, each alkyl group has 1 to 5 carbon atoms, the aryl group is a phenyl group, and the total number of carbon atoms in R1 to R4 is 20 or less. be.

Examples of compounds that can be used in the present invention include the following.

For example, methods for producing the compounds exemplified herein are described in J. Brau
n.
Richte der Deutschen chem
ischenGesellschaft)632846
(1930) ], V., Mozolis and S.
Jokubaityte's [Lietbos Te Nis・
Earl Moksul Akademyos Darbai Series・
Bi・（Lietuvos TS RMokslu Ak
ademi jos Darbai, 5er0B)
1969 (3), l 25-31), H,W
ei-dinger and H, Ei lings f
e ld German Patent No. 1.119,843, RoA
, Donia et al. [Journal of Organic Chemistry]
nic Chemistry) 14,946-951 (
1949)), F. B. Zienty [Journal]
of American Chemical Society (Jou
rnal of American Chemic-a
l 5ociety)68.1388-1389(19
46),], G.S., Brooker
Journal of American Chemical Society
Chemical 5ociety) 73, 532
9-5332 (1951), 1, etc.

The amount of the tetrasubstituted thiourea silver halide solvent used in the present invention can vary widely depending on the desired effect, the nature of the tetrasubstituted thiourea employed, etc.

Generally about 1X1O-5 to 5 moles per mole of silver halide
XlO = moles of tetrasubstituted thiourea may be used, but about I
Particularly preferred is IO-'mol-2,5XlO-2 mol.

Generally, soluble salts are removed from the emulsion of the present invention after precipitation or physical ripening, but methods for this purpose may include the long-known Nudel water washing method in which gelatin is gelatinized; Inorganic salts that are better than anions, such as sodium sulfate, anionic surfactants,
A flocculation method using an anionic polymer (eg, polystyrene sulfonic acid) or a gelatin derivative (eg, aliphatic acylated gelatin, aromatic acylated gelatin, aromatic carbamoylated gelatin, etc.) may also be used.

A preferred sedimentation method is U.S. Pat. No. 2,614,928;
No. 18,556, No. 2,565,418, No. 2,48
9.341 etc.

The process of removing soluble salts may be omitted.

The silver halide emulsion of the present invention does not undergo chemical sensitization,
Although so-called Primit 1ve emulsions can be used, they are usually chemically sensitized.

For chemical sensitization, the Glafkides or Z
e-1ilanan et al.'s book or H, Fr1ese
s edition
Die Grundlagen der Photog
raphisc-hen Prozesse mit
Silberhalogeniden) (Akadem)
i 5che Verlagsgesel l 5ch
a f t.

(1968) can be used.

That is, sulfur sensitization method using active gelatin or a sulfur-containing compound that can react with silver ions.1. A reduction sensitization method using a reducing substance, a noble metal sensitization method using gold or other noble metal compounds, etc. can be used alone or in combination.

As the sulfur sensitizer, thiosulfates, thioureas, thiazoles, rhodanines, and other compounds can be used, and specific examples thereof are described in U.S. Pat. No. 1,574,944.
No. 2.410,689, No. 2,278,947, 2
, No. 728,668 and No. 3,656,955.

As the reduction sensitizer, stannous salts, amines, hydrazine derivatives, formamidine sulfinic acid, silane compounds, etc. can be used, and specific examples thereof are described in U.S. Pat.
No. 487,850, No. 2,419,974, 2.518
, No. 698, No. 2,983,609, No. 2,983,61
No. 0, No. 2,694,637.

For noble metal sensitization, in addition to total complex salts, complex salts of metals in group I of the periodic table, such as platinum, iridium, and palladium, can be used. Specific examples thereof include U.S. Pat. , No. 060, British Patent No. 618.061, etc.

The photographic emulsions of this invention may be spectrally sensitized with methine dyes and others.

The dyes used include dianine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, hemicyanine dyes, styryl dyes,
and hemioxonol dyes.

Particularly useful dyes are those belonging to the cyanine dyes, merocyanine dyes and complex merocyanine dyes.

Any of the basic five-segmented ring nuclei commonly used for cyanine dyes can be applied to these dyes.

That is, pyrroline nucleus, oxazoline nucleus, thiazoline nucleus, pyrrole nucleus, oxazole nucleus, thiazole nucleus, selenazole nucleus, imidazole nucleus, tetrazole nucleus, pyridine nucleus, etc.; a nucleus in which an alicyclic hydrocarbon ring is fused to these nuclei;
and a nucleus in which an aromatic hydrocarbon ring is fused to these nuclei, that is, an indolenine nucleus, a benzindolenine nucleus, an indole nucleus, a benzoxazole nucleus, a naphthoxazole nucleus, a benzothiazole nucleus, a naphthothiazole nucleus, a benzoselenazole nucleus, Benzimidazole nuclei, quinoline nuclei, etc. are applicable.

These nuclei may be substituted on carbon atoms.

Merocyanine dyes or composite merocyanine dyes include a pyrazolin-5-one nucleus, a thiohydantoin nucleus, and a 2-thioxazolidine-2 nucleus having a ketomethylene structure.
, 4-dione nucleus, thiazolidine-2,4-dione nucleus, rhodanine nucleus, thiobarbic acid nucleus, and the like can be applied.

Useful sensitizing dyes include, for example, German Patent No. 929,080;
U.S. Patent Nos. 2,231,658 and 2,493,748
No. 2.503.776, No. 2,519,001, No. 2,912,329, No. 3,655,394,
This invention is described in No. 3,656,959, No. 3,672,897, No. 3,694,217, British Patent No. 1,242,588, and Japanese Patent Publication No. 44-14030.

These sensitizing dyes may be used alone or in combination, and combinations of sensitizing dyes are often used particularly for the purpose of supersensitization.

Representative examples are U.S. Patent Nos. 2,688,545, 2, 9
No. 77.229, No. 3,397,060, No. 3.52
No. 2,052, No. 3,527,641, No. 3.617
, No. 293, No. 3,628,964, No. 3.666.
No. 480, No. 3,679,428, No. 3.703, 3
No. 77, No. 3,769,301, No. 3.814,60
No. 9, No. 3,837,862, British Patent No. 1,344,
No. 281, Japanese Patent Publication No. 43-4936, etc.

Along with the sensitizing dye, it is a dye that itself does not have a spectral sensitizing effect or a substance that does not substantially absorb visible light,
A substance exhibiting supersensitization may also be included in the emulsion.

For example, aminostilbene compounds substituted with nitrogen-containing heterocyclic groups (for example, those described in U.S. Pat. ,743,5
10), cadmium salts, azaindene compounds, etc.

U.S. Patent No. 3,615,613, U.S. Patent No. 3,615,641
The combinations described in US Pat. No. 3,617,295 and No. 3,635,721 are particularly useful.

Silver halide grains made according to the present invention can be fogged directly into a positive emulsion.

Alternatively, silver halide grains prepared in the presence of tetrasubstituted thiourea can be doped with metal ions such as iridium salts, rhodium salts, lead salts, etc. to produce direct positive emulsions with high photographic sensitivity.

It is also applicable to direct positive emulsions that are not doped with metal ions.

Fogging is achieved by chemically and physically treating the silver halide by known methods.

Fog nuclei in the present invention can be produced by chemically fogging the silver halide emulsion in advance, that is, by adding an inorganic reducing compound such as stannous chloride or boron hydride, or by adding an organic reducing compound such as hydrazine. It is advantageously provided by the addition of formalin, thiourea dioxide, polyamino compounds, aminoborane or methyldichlorosilane.

For example, a reducing agent may be used in combination with a metal ion more noble than silver ion, or a combination with a halide ion (for example,
U.S. Patent Nos. 2,497,875 and 2,588,982
No. 3,023,102, No. 3,367.778, No. 3,501,307; British Patent No. 707.704, No. 723,019, No. 821, . No. 251, same 1,
No. 097,999; French Patent No. 1.513,840, French Patent No. 739,755, French Patent No. 1.498,213, French Patent No. 1.5
20,822, Belgian Patent No. 1.520,824, Belgian Patent No. 708,563, Belgian Patent No. 720,660;
-13488, 46-40900, etc.).

In the present invention, the silver halide grains can be fogged before being coated on the support, or can be fogged after being coated.

When the emulsion of the present invention is used as a direct positive light-sensitive material, not only the above-mentioned sensitizing dye but also a desensitizer or a desensitizing dye, so-called electron acceptor, may be contained in the emulsion.

Many of the useful electron acceptors are described, for example, in U.S. Pat.
No. 3,102, No. 3,314.796, No. 2,901
, No. 351, No. 3,367.779, No. 3,501,
No. 307, No. 3,505,070, British Patent No. 723
, No. 019, No. 698,575, No. 667, No. 206, No. 748,681, No. 698,576, No. 834
, No. 839, No. 796,873, No. 875.887, No. 905,237, No. 907, No. 367, No. 940
, No. 152, No. 1.155,404, No. 1,237,
No. 925, Special Publication No. 43-13167, No. 43-145
00, No. 46-23515, etc.

For the purpose of increasing sensitivity, increasing contrast, or accelerating development, the photographic emulsion of the present invention contains, for example, polyalkylene oxide or its derivatives such as ethers, esters, and amines, thioether compounds, thiomorpholines, quaternary ammonium salt compounds, and urethane. It may also include derivatives, urea derivatives, imidazole derivatives, 3-pyrazolidones, and the like.

For example, U.S. Patent Nos. 2,400,532 and 2,423,
No. 549, No. 2,716,062, No. 3,617,2
No. 80, No. 3.772,021, No. 3,808,00
Those described in No. 3 etc. can be used.

The silver halide emulsion of the present invention contains an antifoggant (An t
if oggant) and stabilizers (stabil
1zer) t=gold-bearing vine.

As a compound, “Antifoggant” in Product Licensing Index, Volume 92, P107
Those described in the section s and 5 tabilizers J can be used.

Silver halide emulsions contain a developing agent.

As a developing agent, the mouth-velop of Product Licensing Index, Vol. 92, P107-108
ing agents described in section J7) are used.

Silver halide can be hardened with various organic or inorganic hardeners and dispersed in a vine colloid.

As the hardening agent, those described in "Hardener sJ" section of Product Licensing Index, Vol. 92, p. 108 may be used.

Silver halide emulsions may contain coating aids.

As a coating aid, "coating aids" in Product Licensing Index, Vol. 92, P108.
Those described in Section J may be used.

The silver halide emulsions of the invention can contain so-called color couplers.

As a color coupler, "Co1or m" of Product Licensing Index, Volume 92 PIIO
Those described in the section of ateria-1sj are used.

The photographic material produced according to the present invention may contain a dye in the photographic emulsion layer or other hydrophilic colloid layer as a filter dye or for the purpose of preventing irradiation and other various purposes.

As such dyes, product licensing,
“Absorbin” in Index, Volume 92, P109
The one described in the section ``g and filter dies'' is used.

Silver halide photographic emulsions also contain antistatic agents, plasticizers, matting agents, lubricants, ultraviolet absorbers, fluorescent whitening agents, air antifoggants, toning agents, and the like.

The silver halide emulsion used in the present invention has a vehicle as described in Product Licensing Index, Vol. 92 PI.
08 “Vehicles section J (December 1971)
Use the vehicle listed in .

The silver halide emulsion is coated on a support along with other photographic layers if necessary.

The coating method is described in Product Licensing Index, Vol. 92, P109, JCoating procedure.
The method described in Section ures J may be used.

Further, as the support, those described in "5upports J" of Product Licensing Index, Volume 92, P108 can be used.

The silver halide photographic emulsion of the present invention is used for various purposes.

For example, it is used for the following purposes. Color positive emulsion,
Emulsions for color paper, emulsions for color negatives, emulsions for color reversal (sometimes containing couplers, sometimes not), holes Thl for photosensitive materials for plate making (for example, lithium film, etc.).

Emulsion X used in photosensitive materials for cathode ray tube displays
Emulsions used in line recording light-sensitive materials (particularly materials for direct and indirect photography using screens), colloid transfer process
r process) (e.g. U.S. Pat. No. 2.716,
059) used in the silver salt diffusion transfer process (Si 1ver Sal tdiff
transfer process) (
For example, ψ U.S. Patent No. 2,352,014, U.S. Patent 2,
No. 543,181, No. 3,020,155, No. 2,8
61,885)),
Color Diffusion Transfer Process (U.S. Pat. No. 3,087,817)
No. 3.185,567, No. 2,983,606, No. 3.253,915, No. 3.227.550,
3, 227.551, 3,227,552,
3.415,644, 3,415,645, 3,415.646, Research Disclosure No. 15
Volume 1 A: 15162P75 87 (November 1976)
Emulsions used in dye transfer processes (described in
er process) (U.S. Patent 2,882,15
Emulsions used in silver dye bleaching methods (described in Friedman's "History of Co., Ltd."),
1orPho tography” Amer 1c
an pho tographi cPublish
rs Col 944, especially Chapter 24) and “Br1
tissue Journal of Photography
hy″Vol Ill, P-308~309Apr
-7.

Emulsions used in direct positive photosensitive materials (for example, U.S. Pat. No. 2,497,875, U.S. Pat. No. 2,588,982, U.S. Pat.
．． No. 367,778, No. 3,501,306, No. 3,
No. 501.305, No. 3,672,900, No. 3.4
No. 77.852, No. 2,717,833, No. 3.02
No. 3,102, No. 3,050,395, No. 3.501
, 307, etc.), photosensitive materials for heat development (for example, U.S. Pat. No. 3,152,904,
No. 3,312,550, No. 3,148,122, British Patent No. 1,110,046), emulsions used in physical development photosensitive materials (for example, British Patent No. 9
20.277, 1.131, 238, etc.).

The emulsion of the present invention is particularly suitable for use in internal color of multilayer structure, especially for reversal color and negative color, emulsion for black and white high-sensitivity negative, emulsion for color diffusion transfer process, and emulsion for use in direct positive light-sensitive materials. It is advantageously used as

Exposure to obtain a photographic image may be carried out using a conventional method.

That is, any of the various known light sources can be used, such as natural light (sunlight), a tungsten electric lamp, a fluorescent lamp, a mercury lamp, a xenon arc lamp, a carbon arc lamp, a xenon flash lamp, and a cathode ray tube flying spot.

Fluorescence times range from 171,000 seconds to 1 second, which is normally used in cameras, as well as exposure times shorter than 1/1,000 seconds, such as 1/1,000 seconds using xenon flash lamps and cathode ray tubes.
Exposures of 104 to 1/l 06 seconds can be used, or exposures longer than 1 second can be used.

If necessary, the spectral composition of the light used for exposure can be adjusted using a color filter.

Laser light can also be used for exposure.

Alternatively, exposure may be performed using light emitted from a phosphor excited by electron beams, X-rays, γ-rays, α-rays, or the like.

Any known method can be used for photographic processing of the light-sensitive material produced using the present invention.

For example, the photo processing described in 1-Processing j of Product Licensing Index, Volume 92, PIIO may be used.

The silver halide photographic emulsion prepared in the presence of the above-mentioned tetrasubstituted thiourea has less fog and higher photographic sensitivity.

This emulsion has low pressure sensitivity. Tetrasubstituted thiourea has a pH of
Even in the low range of , it acts as a silver halide solvent and provides coarse grain silver halide emulsions.

In addition, the average particle diameter of silver halide crystals produced in the presence of tetrasubstituted thiourea is the average particle diameter of silver halide crystals produced in the presence of tetrasubstituted thiourea and an equimolar number of organic thioethers under the same conditions. It can be larger than the particle size.

One embodiment of the present invention relates to a method of making such grains in a relatively coarse grained silver halide emulsion in the presence of a tetrasubstituted thiourea silver halide solvent.

Preferably, the silver halide grains of the emulsion have an average grain diameter greater than about 0.25 microns.

Another embodiment relates to novel direct positive photographic emulsions having prefogged silver halide grains with average grain diameters greater than 0.25 microns.

Another embodiment relates to novel photographic emulsions having metal ion-doped silver halide grains having an average grain diameter greater than 0.25 microns.

Other embodiments relate to photographic emulsions with low pressure sensitivity having average grain diameters greater than 0.25 microns.

The embodiments of the present invention are listed below.

(1) A photographic emulsion according to the claims, wherein the silver halide emulsion is used for reversal color, negative color, and black and white high-sensitivity negatives.

(2) A photographic emulsion according to the claims, wherein the silver halide grains are prefogged grains.

(3) The photographic emulsion according to the claims, wherein the silver halide grains are core/shell type internal latent image type grains.

(4) A method for producing a silver halide photographic emulsion comprising mixing a water-soluble silver salt and a water-soluble halide in a liquid reaction medium, the method comprising: about 105 moles to 5 X l O per mole of silver;
A method for producing a silver halide photographic emulsion, characterized in that it is carried out in the presence of -2 moles of a tetrasubstituted thiourea silver halide solvent.

(5) The above tetrasubstituted thiourea silver halide solvent, provided that
R1, R2, R3 and R4 each represent a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and these may be the same or different from each other, and R1-R
The total number of carbon atoms in 4 is 30 or less.

Furthermore, R1 and R2, R2 and R3, or R3 and R4 can be combined to form a 5- or 6-membered heterocycle.

(6) The method of (4), wherein the tetrasubstituted thiourea silver halide solvent is tetramethylthiourea.

(7) The method of (4), wherein the pH during mixing of the solution is adjusted to below about 8, and the pAg is adjusted to below about 10.

(8) A process for preparing a photographic emulsion consisting of mixing an aqueous solution of silver nitrate with an aqueous alkali halide solution in an aqueous gelatin solution, the pH being adjusted to below 8 during mixing and p
Ag is adjusted to below 10, approximately 10-5 per mole of silver.
1. A method for producing a photographic emulsion, characterized in that -5X 1 O-2 moles of tetramethylthiourea is contained before physical ripening of silver halide.

(9) A silver halide photographic emulsion produced by the method described in (4) above.

00) A silver halide photographic emulsion produced by the method (8) above.

The present invention will be explained in more detail with reference to Examples below.

Example 1 An aqueous solution of potassium bromide and an aqueous solution of silver nitrate were simultaneously added to an aqueous gelatin solution with vigorous stirring at 75°C over a period of about 90 minutes to produce a monodispersed silver bromide photograph with an average particle size of about 0.2 microns. An emulsion (emulsion A) was prepared.

The pH was kept at about 4 throughout the precipitation process and the pAg was kept at about 8.9.

This emulsion was washed with water according to a conventional method.

A monodispersion of approximately 1.3μ was prepared in the same manner as Emulsion A, except that 2.6g of tetramethylthiourea (compound l), a tetrasubstituted thiourea silver halide solvent, was added to the aqueous gelatin solution before silver halide precipitation. A silver bromide photographic emulsion (emulsion B) was produced.

Microscopic examination of the emulsions showed that the presence of tetrasubstituted thioureas in the emulsion precipitate increased grain size.

Each emulsion was sulfur and gold sensitized as described in US Pat. No. 2,399,083.

Each emulsion sample was transferred to a cellulose acetate film support with 400 ml/ft of silver and 656 ml/ft of gelatin.
It was applied at a ratio of 2.

Each coated sample was exposed to 400 lux tungsten light for 1710 seconds through an optical wedge, and then developed for 10 minutes at 20° C. with surface developer X described below.

The same method was used for each coating to measure photographic speed at a constant density above fog density (0,1 optical density) and maximum density.

The results are shown in Table 1 and show that the speed is much slower for emulsion coatings precipitated in the presence of tetrasubstituted thioureas.

Similar results were obtained when aqueous solutions of potassium bromide and potassium iodide were used instead of an aqueous solution of potassium bromide.

Composition of surface developer
35.0g potassium bromide
i, adding og water 11 In the same manner as emulsion B, but using ammonia as the silver halide solvent instead of tetramethylthiourea (however, p
A monodispersed silver bromide photographic emulsion (emulsion C) with a diameter of about 9.5) and a diameter of about 1.3 .mu.m was prepared.

This emulsion was sulfur and gold sensitized, coated and tested in the manner described above, and the following results were obtained.

The results of the second column show that the emulsion coating precipitated in the presence of tetrasubstituted thiourea has a much higher sensitivity than the emulsion coating precipitated in the presence of ammonia;
It can be seen that n is very small.

Example 2 Example 1 was carried out in the same manner as in Example 1, except that tetraethylthiourea was used as the silver halide solvent instead of tetramethylthiourea. Similar results were obtained.

Example 3 An aqueous solution of potassium bromide and an aqueous solution of silver nitrate were simultaneously added to an aqueous gelatin solution with vigorous stirring at 75°C over a period of about 90 minutes to obtain a silver bromide emulsion with an average particle size of about 1.2 microns. Ta.

2.5 g of tetramethylthiourea was added to the aqueous gelatin solution before precipitation, the pH was kept at about 6 throughout the precipitation process, and the pA9 was kept at about 8.2.

The silver bromide grains were then chemically sensitized by adding 1.71 rIg of sodium lithiosulfate per mole of silver and 1.71 rI9 of potassium chloroaurate per mole of silver.

One mole of chemically sensitized particles was further grown by further treatment for 25 minutes in the same precipitation environment as the first time, and the final average particle size was about 1.4 μm.

This emulsion was then added to 0.0% sodium lithiosulfate per mole of silver.
26■ and potassium chloroaurate 0.35■ per mole of silver
The particle surfaces were chemically sensitized by adding and finishing by heating at 60°C.

This emulsion (core/shell type internal latent image type) was prepared in Example 1.
After coating and exposing in the same manner as above, apply the following fogging developer Y.
When processed with , a good inverted image was obtained.

Fogging developer Y N-Methyl-p-aminophenol sulfate Hydroquinone Sodium sulfite Sodium metaborate hydroxide Potassium p-tolylhydrazine hydrochloride 5-Methylbenzotriazole Emulsion obtained in Example 4 by adding water Thiourea dioxide (additive 1) was added to emulsion A and emulsion B in the amounts shown in the table below, respectively.
Heated at 65°C for 60 minutes, then added potassium chloroaurate (additive 2) in the amount shown in the table below and heated at 65°C for 60 minutes to perform reduction and gold-bridging. ,
The electron acceptor Pinacryptol Yellow (Dye I) was added in the amount shown in the table below.

Each emulsion sample was prepared in Example 1. Coat and expose in the same manner as
The surface was treated with developer X.

The photographic sensitivity at a density of 1/2 of the sum of the maximum and minimum densities and the maximum density were determined using the same method for each coating.

The third coating shows the results of the reduction and flashing under the optimum conditions for each emulsion, and the results of dye 1 under the optimum conditions for each emulsion.

It can be seen that photographic speed is very poor for emulsion coatings precipitated in the presence of tetrasubstituted thioureas.

5g 10g 10g 0g pH11.5 0,1,9 0,029 A

Claims (1)

[Claims] 1 A photographic emulsion having silver halide grains formed in the presence of a tetrasubstituted thiourea silver halide solvent, wherein the substituted thiourea is dissolved in a 0.01 molar aqueous solution (60°C
) to 1 weight of silver chloride that can be dissolved in pure water at the same temperature.
．． A photographic emulsion characterized in that it can be dissolved five times or more.