JPH0443569B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to the field of silver halide emulsion production, and in particular to silver halide produced by the so-called "splash" process. Furthermore, the present invention relates to a method for producing a silver halide emulsion prepared by a splash method in which the grain size distribution of silver halide crystals is uniform. Splash method refers to precipitation by rapid addition of silver nitrate solution in one or more doses. PRIOR ART The preparation of light-sensitive silver halides for photographic emulsions is a complex process. Basically, silver halide crystals or grains can be prepared by two well known methods: the single jet or "splash" method or the double jet or balanced double jet (hereinafter referred to as "BDJ") method. In the splash method, the alkali halide solution is initially placed in a mixing vessel together with a protective colloid (eg, gelatin) and then the silver nitrate solution is added to this mixture. The silver nitrate can be added all at once, gradually over time, or can be added quickly in several portions. In the BDJ method, a halide solution and a silver nitrate solution are added simultaneously to a gelatin solution in a mixing vessel. Typically, splash precipitation increases so-called "crystal lattice defects" in which a large number of ions are not properly positioned in the silver ion-halide ion network. Emulsions formed from these crystals have lower lattice defects compared to films formed from silver halide emulsions having crystals with little or no lattice defects or disorientation.
It can be used for improved sensitometry, particularly for producing films that exhibit improved sensitivity. Despite this advantage, it is difficult to prepare emulsions with uniform grain size distribution using the splash method. In some photographic fields, it is important for the emulsion to have this uniform distribution, for example to adjust the gradient. Thus, in the field of graphic arts, high gradients are required and broad particle size distributions are unacceptable. On the other hand, the production of silver halide crystals by the BDJ method yields grains with good grain size uniformity, but these grains generally lack disorientation or lattice defects and are different from emulsions prepared by the splash method. They do not have the same degree of sensitivity. It is also known to use a seed emulsion with a known grain size and to add this seed emulsion or crystals during the preparation of the BDJ emulsion. Silver halide forms on top of these seeds and forms uniform final grains. This method has not been used for particle splash preparation. This is because it was believed that uniform particles with a high degree of internal defects could not be formed. SUMMARY OF THE INVENTION The present invention involves adding silver nitrate by a splash method to an aqueous solution containing (a) one or more alkali halides in a protective colloid and (b) monodisperse silver halide seeds. relates to a method for preparing silver halide emulsions with a narrow particle size distribution. The addition of monodisperse seed crystals (themselves produced by the BDJ method) to the gelatin-alkali metal halide solution prior to the addition of silver nitrate by the splash method gives the best results for both methods.
Although the resulting crystal size distribution is much more monodisperse than that normally obtained with splash methods, the crystals still have a high degree, ie a large number of crystal lattice defects. Particle size and distribution is uniform, predictable, and controlled by the size, number, and distribution of seed crystals in the gel salt and by the total amount of silver added during the splash process. Thus, it is possible to predictably vary the grain size distribution in splash-prepared emulsions simply by preparing seed crystals by the BDJ method, which itself yields a narrow range of grain sizes. can. A combination of these two precipitation procedures is possible according to the teachings of the present invention. DETAILED DESCRIPTION OF THE INVENTION The method of the present invention can be applied to the production of any conventionally produced silver halide, such as silver bromide, silver chloride, silver iodide, or mixtures thereof. Any conventional colloidal binder system can be used, such as gelatin, as well as water-permeable or water-soluble polyvinyl alcohol and its derivatives, partially hydrolyzed polyvinyl acetate, polyvinyl ether, etc. Other useful colloidal binders include partially hydrolyzed gelatin, poly-N-vinyl lactam, and the like, among others. Gelatin is preferred as it is well known to be an especially good protective colloid during the precipitation of silver halide and the formation of its crystals. Conventionally, the desired alkali metal halide (salt) is added to an aqueous dispersion of gelatin. next,
Add the desired amount of silver halide seed crystals of desired size previously prepared by the BDJ method and start stirring.
Add aqueous silver nitrate by splash method at desired time and temperature. This may be done by two rapid splashes of about 30 seconds each, one long initial splash followed by a rapid splash, or a single long splash. These processing procedures are well known to those skilled in the art. moreover,
In another embodiment, some of the alkali metal halide can be added to the gelatin in the reaction vessel and the remainder can be added after some of the silver nitrate has been added. As mentioned above, seed crystals are formed by the BDJ method according to such well-known processing procedures. By modifying these processing procedures, it is possible within the scope of the present invention to prepare particles with any average particle size distribution and select the desired ones to be used. The seed crystal is, for example, silver bromide,
It can be formed from any common halides such as silver iodobromide, silver bromochloride and silver iodide. Additionally, these seed crystals may be doped with other metals, such as rhodium and lead, as is well known. After the silver halide has precipitated, the emulsion is typically further ripened to achieve the desired crystal size. After this, the emulsion can be further "bulked" with a colloidal binder and subjected to chemical and spectral sensitization as is well known. After the sensitization step, hardeners, surfactants, antifoggants, stabilizers, coating aids, etc. may be added. The emulsion can then be coated on any of the well-known photographic supports, such as polyethylene terephthalate film, suitably coated with a subbing layer to receive the silver halide emulsion coating. The coated emulsion may be overcoated with a protective abrasion resistant layer such as hardened gelatin. These films may be used in any conventional manner, for example as X-ray or graphic arts films, or as direct positive surfaces. It all depends on how the product structure is manufactured. The present invention will be explained with reference to the following examples.
We believe that Example 6 represents the best mode. Example 1 Four types of silver halide seed crystal samples were used as standard
Manufactured according to the BDJ procedure. Halide composition and silver halide grain size electrolytic analyzer [see AB Holland and JRSawers, Photogr.Sci.Eng. 17 , 1295 (1973)] The average particle size measured by: Sample halide particle size (μ ³ ) 1 Bromide 0.02 2 Bromide 0.06 3 Iodobromide (1%) 0.03 4 Iodobromide (1%) 0.06 Silver bromide and Ag () each containing a small amount of bone gelatin from the precipitation process The Br seed crystals were redispersed in the gelatin and water by stirring for about 3 hours and the PH was adjusted to about 6.3-6.7. Approximately per 0.51 mole of silver nitrate (18%) added to these seed crystals
A 0.09 molar ratio was used to seed an emulsion prepared by splash technique using the solution and processing procedure described below. A Solution: 7g Gelatin 120c.c. Deionized water 52g NH ₄ Br 20c.c. 0.5M KI 0.06 units Various crystals listed above (1 unit = 1.5 moles of silver,
0.06 units = 0.09 moles of silver) B Solution: 140c.c. Deionized water 45c.c. 3.0M AgNO ₃ 30c.c. 12.0M NH ₄ OH C Solution: 70c.c. Deionized water 125c.c. 3.0 M AgNO ₃ D Solution: 23 c.c. Glacial Acetic Acid E Solution: 10 c.c. Coagulant (see Polyanion US Pat. No. 2,772,165) G Solution: 120 c.c. 3M H ₂ SO ₄ Place Solution A in a mixing container. 105 while stirring
heated to. Solution B was then added to A over 30 seconds (first "splash" of silver nitrate). This mixture
Aged for 5 minutes at 105° and then solution C was added to this over 30 seconds (second "splash" of silver nitrate). After aging this mixture for 8 minutes, solution D was added to stop the aging process. A coagulant is then added to coagulate the gelatin-silver halide as a "curdled material", then deionized water is added,
These curds were washed to remove excess soluble salts by decanting to remove water and salts. Solution G was available to adjust the PH to 3.0. For comparison purposes, an identical splash precipitation step was also carried out (Sample 5) except that no seeds were present. Each sample of the emulsion was then analyzed using a particle size analyzer. Furthermore, electron micrographs were taken for each emulsion. These results show that the final emulsions in each case had approximately the same volume of crystals as the comparative examples, and more importantly, these emulsions were more uniform than the comparative examples. The comparative emulsions were non-uniform and had a broader distribution of grain sizes. Sample volume (μ ³ ) σg* 1 0.291 1.86 2 1.456 1.50 3 0.258 1.56 4 0.505 1.37 5 0.373 2.11 *Polydispersity index (σg) - The smaller σg, the more uniform the particle size range. V84 = Volume at the 84th percentile of the cumulative distribution curve, V16 = Volume at the 16th percentile of the cumulative distribution curve Example 2 Four additional splash prepared silver iodobromide emulsions were prepared. In three of these emulsions, varying proportions of silver iodobromide (2% iodide) seed crystals of 0.068 μ ³ , σg = 1.34 were used. The subsequent procedure consists of applying the first silver splash amount (Example 1)
(27% vs. 30%) and the amount of seed crystals (described below) were exactly the same as in Example 1.

[Table] After completing the emulsion formation process using the splash technique, the grain size was examined and an electron micrograph was taken. The inventive samples, Samples 2 and 3, exhibited improved uniformity and grain size similar to the comparative emulsion. This example shows that up to 0.2 moles of species per mole of AgNO ₃ are acceptable. Example 3 To demonstrate the photographic utility of emulsions prepared in accordance with the teachings of the present invention, four additional splash-prepared emulsions were prepared as described in Example 1. The seeds used in three of these emulsions were exactly the same as in Example 2. The addition of silver nitrate solution to the emulsion was varied as follows. Sample mixing type 1 Two quick splashes, 30 seconds (same as Example 1) 2 Two long splashes (4.8 minutes and 4.9 minutes) 3 One long splash (7.5 minutes) 4 - Comparative example Two Rapid splash (Example 1)
) - unseeded These emulsions were then brought to their optimum sensitivity by gold and sulfur sensitization as is well known to those skilled in the art. After addition of conventional surfactants, antifoggants, hardeners, etc., each emulsion was coated onto a polyethylene terephthalate film substrate suitably coated with a subbing layer and a thin fixing underlayer of gelatin. Each sample was overcoated with a hardened gelatin abrasion resistant layer. Coating weight is approximately AgBr
It was 47mg/ ^dm2 . Sample pieces from each coating were sandwiched between two Cronex® HiPlus screens and placed in an X-ray ^source operated for 40 ms at 60 Kvp. 100 ma at 40 in. Exposure was through a √2 aluminum step optical wedge. These were then processed with a standard hydroquinone/phenidone mixed developer, fixed in the usual manner, and washed with water. The obtained sensitometry was as follows.

[Table] Electron micrographs show that the emulsions of the comparative example had standard splash preparation grains with variations in grain size, whereas those of the present invention were more uniform and had a grain size close to that of the grains of the comparative example. It shows that it was. It can be seen that the emulsion of the present invention provided a better gradient in the tow portion than the comparative example. Example 4 Four splash prepared emulsions were prepared for this example as taught in Example 1. Three types of emulsions representative of the present invention used exactly the same seed particles as those in Example 2, and added AgNO ₃ 1
Added 0.2 moles per mole. The changes to the manufacturing process were as follows. Silver halide composition AgIBr (4% iodide). Add ammonia only to solution A. Addition of iodide - 1/2 to solution A, 1/2 added after the initial silver nitrate splash. The percentage of silver in the initial splash was varied as follows. A comparative example (without seeds) was also used. The emulsion was redispersed, sensitized, coated, overcoated, dried, exposed and processed as described in Example 3. The following results were obtained.

[Table] Other experiments were also performed with changes in the processing procedure, such as shortening the aging time and lowering the aging temperature. In all cases, the emulsions prepared according to the invention had high gradients, but the sensitivity was somewhat reduced. And in all cases, the electron micrographs show that the grains from the emulsions representative of the invention have grain sizes close to that of the comparative examples and that the grain sizes are more uniform than each of the comparative examples. These experiments demonstrate the widespread utility of the inventive procedure. Example 5 To further demonstrate the utility of the process of the invention, two splash-prepared emulsions were made as described in Example 1, but with seeds added to one and the other (comparative). was prepared without seeds. Seed type and amount were as described in Example 2. During the precipitation process, samples were taken at regular intervals for particle size analysis and electron microscopy. These results indicate that the emulsions of the present invention (seeded) matured faster than the comparative examples and the grains quickly reached their optimum size and grain size distribution.

EXAMPLE 6 In a similar manner, two additional splash-prepared emulsions were made according to the procedure described above. In this case, we followed the same procedure as Sample 1 in Example 4, but added 1/2 I ^- to "A" and added 1/2 I ^- to the mixing vessel over a period of 7 minutes starting from the first silver splash. Ta. One emulsion had seeds while the other was a comparative example. After ripening and redispersion of the emulsion, the emulsion was sensitized. During these processing procedures, different samples of the emulsion were sensitized with different levels of sulfur sensitizer and with different ripening times. Sensitometric results indicate that emulsions prepared according to the teachings of the present invention have broader sensitization latitude than the comparative examples. The results were as follows. Crystal parameter Vol. (μ ³ ) σg Comparative example 0.32 2.16 Example 0.30 1.56 Sensitization conditions: 1.3 mg of AuCl ₃ per Ag mole in both;
1.7 mg Na ₂ S ₂ O ₃ / Ag mole vs. 0.1 g NaSCN comparative example.
5H ₂ O 2.7 mg Na ₂ S ₂ O ₃ per Ag mole for the experimental example.
5H ₂ O typical stabilizer was added to coat the sample. Exposure and development conditions: Kodak Model 101 Process and Control Sensitometer, 1/5 second exposure through ² √2 step optical wedge; 90 second development in 84〓 HSD. result:

[Table] This product exhibits better aging latitude as well as higher gradients with equivalent sensitivity. Example 7 A direct-grade emulsion was prepared from silver iodobromide precipitated by a splash processing procedure in the presence of Ag(I)Br seed crystals as described below. Three types of emulsions were made. The first, comparative example, did not use seeds. The second one uses ^0.0086μ3 Ag(I)Br species, and the third one uses
^0.0378μ3 of Ag(I)Br species was used. These emulsions,
It was redispersed in gelatin, covered with tetraazaundecane, and the usual surfactants, antifoggants and coating aids were added thereto. Each emulsion was coated on a support as described above and a strip from the coating was exposed to a tungsten flash for 10 ^-2 seconds in an EG and G sensitometer.
These strips were then developed in DP-2 for 90 seconds, followed by fixing, washing, and drying. The sensitometric results show that a higher gradient was obtained with a photospeed equal to the comparative example. Example 8 An emulsion was prepared by splash technique. First, a seed emulsion was formed in situ using the BDJ technique. This process was as follows. Monodisperse AgIBrCl (approximately 0.5% I, 18.8% Br and
Preparation of 8.07% Cl) The first 50% of the volume is a monodisperse BDJ mixture at 120㎓, pAg 6.17. of all silver
50% was added using the following procedure. a 1.7% of the total silver nitrate (3.4% seed silver nitrate) is added by single-jet method; b 37.5% of the total silver nitrate (75% seed silver nitrate) is added to 1.3% iodide; In halide composition of 52% bromide and 46.7% chloride
Each unit (1.5 mol) of silver nitrate by BDJ precipitation
Continue seed precipitation with an amount of rhodium chloride to give 0.2 micromoles of rhodium for c. Seed crystal precipitation by BDJ precipitation using 100% chloride (adding 50% of all silver nitrate) ). At this point, the analysis by the particle size analyzer is
It showed crystals with V= ^0.0056μ3 and σg=1.40. The temperature was then lowered to 110° and KCl was rapidly added (1.4 times the amount of remaining _AgNO3 to be added). The temperature dropped to 100㎓ and the pAg was 9.96. After 1 minute AgNO ₃ (remaining 50% by volume) was added and the resulting emulsion was stirred for 5 minutes. After the addition of AgNO ₃ the temperature was 108〓 and after 5 minutes it dropped to 104〓.
pAg was 7.56. This final emulsion was analyzed with a grain size analyzer and was found to contain crystals with V= ^0.0150μ3 and σg=1.55. Example 9 A sample of the seeds prepared by the BDJ method (AgIBr, 2.5% I ^- particle size approximately 0.0378μ ³ ) was placed in a mixing vessel and sufficient potassium iodide was added to convert all of the sample to AgI. A scrub precipitation process (see Example 1) was carried out on these species. Films made from this emulsion were sensitized and coated as described above and then processed to obtain equivalent sensitometry. Analysis of the particles showed that they were uniform in size and shape.

[Table] Example 10 Seeds prepared by BDJ method (Ag1.5%, I ^- 98.5%,
A sample of Br ⁻ , particle size 0.04 μ ³ ) was prepared.
A solution for preparing a scrub of AgIBr (2% I ⁻ ) was prepared as follows. A Solution (“Heel”, prepared in a preparation vessel) Distilled water 955 c.c. NH ₄ Br solid 310 g 0.5N KI 120 g Gelatin 40 g Seed (0.2 mol per mol of AgNO ₃ ) Maintained at 40.6°C B Solution (first silver): Distilled water 1020 c.c. Thallium nitrate solution (8 g/water) 5.4 cc 3N AgO ₃ 320 c.c. Maintained at 29.8°C C Solution (second silver): Distilled water 373 c. c. 3N AgNO ₃ 680c.c. Thallium nitrate (see above) 4.4cc Maintain at 120℃ Processing procedure - 5 minutes before first silver, add seed to A solution - 1 minute before first silver, B solution 12M _NH4OH191
Add cc, time = 0, add B to A over 30 seconds, time = 3 minutes, add C to A over 15 minutes, time = 9 minutes, ripen with 124 c.c. of glacial acetic acid. Stopping - Coagulation and washing treatment as described in Example 1. The emulsion thus prepared is then redispersed in gelatin as described above, sensitized with gold and sulfur, wetting agent and antifogging agent. agent, etc. were added, coated, and overcoated. For comparison, one element was prepared, sensitized, and coated under the same conditions but without the addition of silver halide seeds. Samples from this coating were exposed, developed, fixed, washed and dried as described above and the following sensitometry was obtained.

Films prepared from emulsions made in accordance with the teachings of the present invention had excellent gradients and top densities, but were somewhat less sensitive than the comparative examples. The particles were uniform in size and shape when examined by electron microscopy. Example 11 Two additional splash preparation emulsions were prepared following the procedure of Example 1, varying the seed emulsion or particle size used. In one case,
Seeds prepared by the BDJ method have approximately 0.06 μ ³ (approximately 2.5% I ^- ).
AgIBr species, in the second case approximately 0.39μ ³
(approximately 2.5% I ^- ) of AgIBr species. The emulsion was analyzed by grain size analyzer and electron micrograph and was found to contain uniform grain size. This indicates that fairly large seed particles can be used within the scope of the present invention. Seed volume (μ ³ ) Final crystal volume (μ ³ ) σg 0.039 0.24 1.48 0.06 0.44 1.27 Examples 12 and 13 In a similar manner, AgIBr (approximately 2.5
% ^I- ) seeds and even a small amount of rhodium (Example 12)
Alternatively, a splash preparation emulsion was produced using one containing lead (Example 13). Methods for preparing these seed particles are well known and described in detail in US Pat. No. 4,221,863. These splash prepared emulsions were redispersed and then fogged to yield excellent quality direct positive elements with good grain uniformity. Example 14 Two mixtures, a normal splash mixture (comparative example) and a mixture using seed crystals (experimental example), were prepared in the same manner as Sample 1 of Experimental Example 4, but with 1/2 of the I ^- In addition to solution A, 1/2 I ^- was added over a period of 7 minutes starting from the addition of the first silver solution. Sensitization treatment: 1.37 mg AuCl ₃ per mole of Ag for both,
0.11 g of NaSCN per mole of Ag vs. 1.66 mg of NaSCN per mole of Ag.
Na ₂ S ₂ O ₃・5H ₂ O For the experimental example, 2.66 mg per mole of Ag.
Na ₂ S ₂ O ₃・5H ₂ O Aging of comparative example: 50 minutes Experimental example: 70 minutes Results after exposure and development as in Example 6:

TABLE The results show that the emulsion made according to the teachings of the present invention has a higher gradient and slightly faster sensitivity compared to the comparative emulsion.

Claims (1)

[Claims] 1. Silver nitrate is added by a splash method to an aqueous solution containing (a) one or more alkali halides in a protective colloid and (b) monodisperse silver halide seed crystals. A method for producing a silver halide emulsion with a narrow grain size distribution. 2. Claim 1 in which the monodisperse seed crystal (b) is prepared by the equilibrium double jet method.
The method described in section. 3. The method of claim 1, wherein a portion of the alkali metal halide is added first and the remainder is added after adding a portion of the silver nitrate.