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(11) | EP 0 016 061 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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ORGANIC HALOGEN COMPOUNDS USED IN DIRECT POSITIVE EMULSIONS IN DIREKT-POSITIV-EMULSIONEN VERWENDETE ORGANISCHE HALOGENVERBINDUNGEN COMPOSE ORGANIQUE HALOGENE UTILISE DANS DES EMULSIONS PHOTOGRAPHIQUES DE TYPE POSITIFS |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
Technical field
[0001] This invention relates to the field of photography, and more particularly to direct positive silver halide emulsion technology.
Background art
[0002] The prior art teaches that organic halogen compounds are useful for certain purposes in photoimaging processes and compositions. For example, lllingsworth, U.S. 3,632,340, "Cored Direct Positive Silver Halide Emulsion Developed with Polyhydroxybenzene", teaches mixing 1,1'-diethyl-2,2'-cyanine chloride dye with bromosuccinimide in order to increase the sensitometric response in direct positive emulsions. Other organic halogen compounds, in addition to bromosuccinimide, are disclosed in Moore, U.S. 3,495,987, "Photopolymerizable Products", as useful in photopolymerizable products to provide free radicals when initiated by a radiation-sensitive compound. Japanese Patent No. 919,049, "Direct-Reversal-Type Silver Halide Photographic Emulsions", discloses that organic halogen compounds release halogen on light exposure to increase speed in direct positive emulsions.
[0003] The present invention advances beyond the prior art and is directed to a process requiring the addition of certain organic halogen compounds to direct positive silver halide photographic elements, characterized in that the addition step is followed by a digestion step. The term "digestion" is used here to denote a process in which a direct positive silver halide emulsion containing one of the aforesaid organic halogen compounds is heated for a time and at a temperature sufficient to permit the organic halogen compound to selectively oxidize silver fog centers in the emulsion. The result is an increase in the photosensitivity of the emulsion, with no adverse effect on stability.
Summary of the invention
[0004] A direct positive silver halide photographic emulsion of superior speed and stability is produced by a process which consists of the steps of (1) preparing a silver halide precipitate in a colloid binder, (2) fogging the resulting emulsion, (3) adding an organic halogen compound, and (4) coating the emulsion on a support, characterized in that, the emulsion is digested after step (3) and before step (4) to promote thermal reaction of the organic halogen compound with the fog centers and in that the organic halogen compound is a chlorine- or bromine-containing compound which is a weak oxidizing agent capable of oxidizing fog centers to produce an emulsion of superior speed. During the reaction the organic halogen compound is reduced and the fog centers are partially oxidized.
[0005] According to one feature of the invention, it is possible to achieve increased photosensitivity of the emulsion by treatment with some specific organic halogen compounds without digestion step. A direct positive silver halide photographic emulsion of superior speed and stability is produced in accordance with that feature by a process which comprises the steps of (1) preparing a silver halide precipitate in a colloid binder, (2) fogging the resulting emulsion, (3) adding an organic halogen compound, and (4) coating the emulsion on a support, characterized in that the organic halogen compound is 2 - tribromomethylquinoline, a,a,a',a' - tetrabromoxylene, 2 - tribromomethylquinoxaline, 2,2,3,4 - tetrachloronaphth - 1 - one or 2 - dibromomethylquinoline.
Detailed description of the invention
[0006] In the field of photographic science the search for higher sensitivity has been a continual one. Since direct positive emulsions are newer in the photographic field than more conventional negative working emulsions, sensitization of such emulsions has been less predictable. Also it has been found that discoveries from the negative working field do not necessarily apply to the direct positive field. While elements such as colloid binders, coagulating agents, and grain growth can apply equally well to both fields, there are frequently opposing effects when such items as general sensitizers, spectral sensitizers, e.g., dyes, and antifoggants are considered. The present invention provides the means to increase the sensitometric speed response of direct positive silver halide photosensitive elements without undue sacrifice of gradient, top density, and resolution, and without the need for formulation changes. Speed can be increased by a factor of 5 without affecting Dmax or contrast. The degree of speed increase is surprising in comparison to other means of increasing sensitivity, which include: alteration of silver halide grain growth, metal doping of the grains, and the use of new sensitizing and desensitizing dye structures and dye combinations.
[0007] In the organic halogen compound, the organic molecule to which the bromine or chlorine is attached must serve as a suitable carrier and not allow premature discharge, decomposition, or volatilization since this would negate the desired enhancement of photosensitivity. For example, new control or environmental protection facilities are often necessitated by the use of compounds of high volatility, but the compounds of the present invention have no such disadvantage. Instead, these organic halogen compounds, which are characterized as weak oxidizing agents, derive their utility from being reacted in the emulsion during the thermal treatment, i.e., digestion, whereby the weak oxidant is reduced and therefore no further changes in properties occur upon aging.
[0008] It is as a result of practical limitations imposed by the direct positive photosystem that the activity of particularly effective organic halogen compounds must be determined experimentally. Particularly effective compounds of the instant invention are the following: 2 - chloro - 4 - nitrobenzyl chloride, 2,2,3,4 - tetrachloronaphth - 1 - one, 1,4 - bis(trichloromethyl) - benzene, tribromoacetic acid, tetrachlor - orthobenzoquinone, 1,3 - dibromo - 5,5 - dimethyl hydantoin, 1 - chlorobenzotriazole, a - bromo - p - toluic acid, 2 - trichloromethyl - 4(3H) quinazolinone, p - bromoacetophenone, m - nitrobenzyl chloride, 2 - tribromomethylquinaldine, 2,6 - dichlorobenzonitrile, 2 - tribromomethylquinoline, 2 - dibromomethylquinoline, 2 - tribromomethylquinoxaline, and a,a,a',a' - tetrabromoxylene. By contrast, such compounds as bromosuccinimide, p - nitrobenzyl bromide, 2 - bromo -1 indanol, 3 - bromoquinoline, p - nitrobenzyl chloride, 2 -amino - 5 - bromo pyridine and 2 - bromoethanol have shown no advantage over controls without these compounds.
[0009] The increase in direct positive photosensitivity provided by the present invention results from the simple step of adding and digesting the organic halogen compound in the emulsion. As a result of this straightforward approach it is possible to use this technique to obtain desirable speed increase without the necessity of further modification of an existing direct positive emulsion formulation. By contrast, other techniques for speed increase usually require that other changes and modifications accompany the means for speed increase. For example, to provide a new grain might require alteration of the steps of ripening the emulsion; of washing, sensitizing and stabilizing the emulsion; using auxiliary additives, etc. to allow coating and drying of the emulsion. A new or improved dye may not be compatible with a sensitization technique previously used.
[0010] The present invention is operative with silver halide grains produced by both single jet and double jet precipitation techniques, to yield heterodisperse and monodisperse grain size distribution. Into the grains made by such known techniques metal ions may be introduced to modify the photographic response and/or to act as fogging agents. Nonmetals, and compounds thereof, may also be used to fog or precondition the grains during physical ripening, or, as an alternate fogging mechanism, the grains may be exposed to actinic radiation. In some cases it may be desirable to wash grains which have been chemically modified and then further increase the size of the grains by precipitating a layer of silver halide over the original grains. The term "core-shell" grain has come to apply to such layered grains.
[0011] In the instant invention, as in the prior art, both the type of fogging agent to be used and the degree of fogging are dependent on concentration, pH, pAg, temperature, and duration of the treatment. Both surface and internal fog centers are recognized as functional for direct positive emulsions. Suitable metals for fogging include gold, tin, lead, palladium, and iridium. Suitable nonmetallic compounds include amine borane, hydrazine, thiourea dioxide, formaldehyde, and allyl thiourea.
[0012] Once the fogging reaction is complete the organic halogen compound may be added to the emulsion, and the oxidation-reduction reaction is carried out by holding the system at an elevated temperature to allow it to proceed towards completion.
[0013] The organic halogen compounds of this invention will function in the presence of dyes known to be useful in direct positive emulsions, including those disclosed, for example, in U.S. 3,615,643; U.S. 3,583,870; U.S. 3,867,149; U.S. 3,898,216; and U.S. 3,747,986. These dyes are useful as desensitizers which increase the response of direct positive silver halide emulsions. While useful with these desensitizing dyes, the present invention also functions in their absence. Specially sensitizing dyes that are not electron accepting may also be present in the emulsion such as single and complex cyanines, merocyanines, styryls, and hemicyanines.
[0014] The silver halide constituent of the direct positive silver halide emulsions described herein may consist of pure or mixed silver chloride, bromide, or iodide, and the grains may be regular or irregular in shape, e.g. cubic, octahedral and rhombohedral. The novel emulsions described in GB-A-2,038,792, "Novel Silver Halide Crystals with Two Surface Types", are also useful in the practice of the present invention. As a binding agent and peptizing media for these emulsions it is normal to employ gelatin. However, gelatin may be partially or wholly replaced by other natural or synthetic protective colloids known in the art. Other useful additives include speed-increasing compounds such as polyalkylene glycols; surface active agents which are useful as coating aids; antifoggants; and stabilizers, including indazoles, imidazoles, azaindenes, mercury, and polyhydroxy benzene compounds.
[0015] Other useful ingredients for these direct positive elements include hardeners, antistatics, matting agents, plasticizers, brighteners, and natural and synthetic wetting agents. All these useful ingredients may be combined to yield formulations capable of being coated on suitable supports such as cellulose nitrate film, cellulose ester film, polyvinyl acetal film, polystyrene film, poly(ethylene terephthalate) film, and related films or resinous materials, as well as glass, paper, metal and the like.
Example 1
(feature of the invention without digestion step)
[0017] A rhodium-doped monodisperse cubic Ag(I)Br emulsion containing 1.0% iodide and 0.01% rhodium was prepared by the balanced double jet precipitation technique, maintaining a pAg of 8.2. After completion of physical ripening, the emulsion was coagulated with polyvinyl alcohol o-sulfobenzaldehyde acetal and the excess halide salts removed by decanting. The washed emulsion was redispersed in gelatin; the pH was adjusted to 7.5, and the pAg to 8.0. The emulsion was fogged by adding, per mole of silver halide, 2.4×10-7 mole of cesium thiodecaborane and 3.1×10-6 mole of gold chloride stabilized with hydrochloric acid. After digesting at 72°C for 2 hours the emulsion was cooled to 35°C and cetyl betaine was added as a coating aid.
[0019] The samples were coated on photographic grade polyester base at 35 mg/dm2 silver bromide. The samples with dye were exposed at 10-3 sec. with a 19 line compensator on an EGG sensitiometer through a V2 wedge. The nondyed samples were exposed using a tunsten lamp (750 watts) operated at 35 volts for 15 sec. The samples were developed in a standard metol-hydroquinone developer for one minute, dipped in an acetic acid stop for 30 sec., fixed in a standard thiosulfate fixer for one minute, and dried. The samples showed the sensitometric response reported in Table 2 where the speed was measured at 0.1 optical density over Dmin and the gradient is measured over the straight line curve portion.
[0020] Table 2 shows that similar speed increases can be obtained with and without the presence of the direct positive dye. The results also show that the effects of dye and halogen-donating compound are additive.
Example 2
[0021] An emulsion prepared and fogged in the same manner as that in Example 1 was split into two equal portions. To Part VI, 48.5 mg of 2 - tribromomethylquinoline and 1 g of the cyanine dye reported in Example 1 were added per mole of silver halide. To part VII, 18.7 mg of 2 - tribromomethylquinoline/mole silver halide were added but the emulsion was heated to 54°C for 30 minutes. On cooling, 0.97 g/mole of the direct positive dye were added. The samples were coated at 35 mg AgBr/dm2. Samples of both were aged in the oven at 50°C/50% relative humidity for one week. The samples were exposed at 10-3 seconds with a 19 line compensator on the EGG sensitometer and processed as reported earlier. The following results were obtained.
[0022] The results show that heating the sample after addition of the organic halogen compound allowed the use of smaller quantities and provided increased stability compared to using the compound as a simple afteraddition. The drop in Dmax for sample VI was also accompanied by an increase in speed, yielding poorly reproducible sensitometry.
Example 3
(feature of the invention without digestion step)
[0023] An emulsion prepared as in Example 1 was split into three equal portions. To Part VIII, 1.1 g of 2 - dibromomethylquinoline/mole of silver halide was added. To Part IX 0.12 g of 2 - tribromomethylquinoline/mole silver halide were added. Part X was kept as a control. The direct positive dye was added and samples coated at a coating weight of 40 mg AgBr/dm2. The samples were exposed for one minute through a √2 wedge in a contact mode using a Tungsten source at maximum output with a 0.6 neutral density filter. They were then processed in a standard metol-hydroquinone developer, put in an acid stop for 30 seconds, and fixed in a thiosulfate fixer for one minute. The results are listed in Table 4.
The results show that the dibromo compound will give similar results compared to the tribromo species but -10x more is needed to give the effect.
Example 4
(feature of the invention without digestion step)
[0024] Emulsion samples were prepared as in Example 1 and split into three portions. To sample XI was added 0.122 mg of 2 - tribromomethylquinoxaline/mole of silver halide, to sample XII 0.122 mg of 2 - tribromomethylquinoline/mole silver halide, and sample XIII was the control. The samples were coated without the direct positive dyes and processed as in Example 1. The results are reported in Table 5, and they show that under similar processing conditions the 2 - tribromomethylquinoline and 2 - tribromo- methyl - quinoxaline compounds behave identically.
Example 5
[0025] Five organic halogen compounds were evaluated as oxidants to increase direct positive speed. These were tested in comparision to 2 - tribromomethylquinoline in the emulsion of Example 1. Each experimental stage contained 0.97 g/mole of silver halide of the direct positive dye and was held for 10 min. at 54°C after the addition of the organic halogen compound. The control sample XIV contained only 0.97 g/mole of silver halide of the direct positive dye, but was also digested for 10 min. at 54°C to insure that the superior results of this invention require the presence of the organic halogen compound.
[0026] These results show that by increasing the amount of 2-tribromomethylquinoline relative to Examlpe 1, and using a shorter heat treatment than in Example 2, it was possible to obtain a 5x speed increase relative to a control emulsion. In that particular test, however, only one of the organic halogen compounds, (2,2,2-tribromoethanol) showed any indication of increasing speed. This is illustrative of the unobvious nature of the present invention, since it is necessary to experimentally determine which compounds actually work in this process. Sample XV represents the best mode contemplated for carrying out the invention.
Example 6
(feature of the invention without digestion step)
[0027] An emulsion similar to that of Example but fogged with 2.3×10-7 mole of cesium thiodecaborane and 1.9x10-6 mole of gold chloride/mole of silver halide and without direct positive dye, was used for further comparisons. Saponin was used as a coating aid in place of cetyl betaine. Table 7 gives comparative results.
[0028] Those results show that the quinoline and quinoxaline compounds with a tribrominated group are capable of giving speed increases similar to those in Example 4 while maintaining an advantage over a,a,a',a'-tetrabromxylene as in Example 1.
Example 7
[0029] A monodisperse cubic trihalide emulsion (Br-90/Cl-9.5/1-0.5) was prepared by a balanced double jet precipitation as described in Example 1 of GB-A-2 038 792. Unlike the iodobromide emulsion of Example 1, no rhodium was included during precipitation. The emulsion was washed and redispersed as in Example 1. The emulsion was fogged by adding thereto 7.3x10-8 moles of cesium thiadecaborane and 1.6x10-4 mole of gold chloride, stabilized with HCI, per mole of silver halide, followed by digesting at 72°C for 100 minutes. The emulsion was cooled at 35°C and the direct positive dye and coating aid of Example 1 were added. The emulsion was then split into 5 portions. An organic halogen compound was added to 4 of these portions, with the 5th serving as control. Table 8 gives comparative results obtained with the splits of this emulsion with and without the digestion step of the invention. Samples were coated at 35 mg/dm2 and exposed and processed as in Example 1.
When these same coatings were tested after one month normal aging it was determined that only the control XXV and the two digested emulsions (XXVIII and XXVIX) showed speed values within 10% of those in Table 8. Since a 10% variation is within experimental error, this demonstrates that the digested samples were remarkably storage-stable.
Example 8
[0030] Emulsion splits were prepared and fogged as in Example 7. Table 9 gives comparative results obtained when varied amounts of an organic halogen compound were added with and without the digestion step.
Unlike other organic halogen compounds which show an effect on sensitivity even without digestion, this compound requires a longer digestion period than more active halogen oxidizing agents used in previous examples.
Example 9
[0031] An emulsion was prepared as in Example 1 except that the fogging reaction was carried out with 2.9x10-' mole of cesium thiodecaborane and 4.6x10-6 mole of gold chloride per mole of silver halide. Table 10 gives comparative results obtained when the same amount of an organic halogen compound was digested for different times in comparison to a control containing no addition.
[0032] This illustrates that after 30 minutes, further digestion has produced no speed change, which indicates that the oxidant has been consumed.
[0033] It is a teaching of the instant invention that it is important to digest the emulsion at an elevated temperature after the addition of the organic halogen compound. The emulsion was held at 54°C for 30 minutes in Example 2 and for 10 minutes in Example 5. These should not be considered limiting since they were chosen as a result of experimentation for convenience of operating conditions, and as being suitable without adverse effect on the emulsion used. Due to variations in the organic halogen compound used, the amount added, and the unique characteristics of the emulsion to which the addition is made, it should be obvious to one skilled in the art to vary the time and temperature of the digestion period to obtain optimum results. In this regard, the following information is considered helpful:
[0034] Temperatures of from 40°C to 80°C are useful for the digestion reaction without adversely affecting the emulsion. Times as short as 5 minutes and up to as long as several hours can be used in order to accommodate the reactivity of the particular organic halogen compound being used to react with the fogged centers. Per mole of silver halide emulsion, the effective amount of organic halogen compound may vary from as little as 0.01 g to as much as 1.00 g. It has been found convenient to operate with temperature of from 45°C to 65°C for periods of from 10 to 120 minutes using from 0.015 g to 0.50 g of the organic halogen compounds.
1. A process for the production of a direct positive silver halide photographic emulsion
comprising the steps of (1) preparing a silver halide precipitate in a colloid binder,
(2) fogging the resulting emulsion, (3) adding an organic halogen compound, and (4)
coating the emulsion on a support, characterized in that the emulsion is digested
after step (3) and before step (4) to promote thermal reaction of the organic halogen
compound with the fog centers and in that the organic halogen compound is a chlorine-
or bromine-containing compound which is a weak oxidizing agent capable of oxidizing
fog centers to produce an emulsion of superior speed.
2. The process of Claim 1 in which the chlorine- or bromine-containing compound is
2-tribromomethyi- quinoline.
3. The process of Claim 1 in which the chlorine- or bromine-containing compound is
2-tribromomethylquinoxaline.
4. The process of Claim 1 in which the chlorine- or bromine-containing compound is
a,a,a',a'-tetrabromoxylene.
5. The process of Claim 1 in which the chlorine- or bromine-containing compound is
2,2,3,4 - tetrachloronaphth - 1 - one.
6. The process of Claim 1 in which the compound is added in the amount of 0.015-0.50
g per mole of silver halide in the emulsion.
7. The process of Claim 1 in which the fogging agent is cesium thiodecaborane.
8. The process of Claim 1 in which the compound is digested in the emulsion at a temperature
of 45°C to 65°C for a time of 10 to 120 minutes.
9. A process for the production of a direct positive silver halide photographic emulsion
comprising the steps of (1) preparing a silver halide precipitate in a colloid binder,
(2) fogging the resulting emulsion, (3) adding an organic halogen compound, and (4)
coating the emulsion on a support, characterized in that the organic halogen compound
is 2 - tribromomethylquinoline.
10. A process for the production of a direct positive silver halide photographic emulsion
comprising the steps of (1) preparing a silver halide precipitate in a colloid binder,
(2) fogging the resulting emulsion, (3) adding an organic halogen compound, and (4)
coating the emulsion on a support, characterized in that the organic halogen compound
is a,a,a',a'-tetrabromoxylene.
11. A process for the production of a direct positive silver halide photographic emulsion
comprising the steps of (1) preparing a silver halide precipitate in a colloid binder,
(2) fogging the resulting emulsion, (3) adding an organic halogen compound, and (4)
coating the emulsion on a support, characterized in that the organic halogen compound
is 2 - tribromomethylquinoxaline.
12. A process for the production of a direct positive silver halide photographic emulsion
comprising the steps of (1) preparing a silver halide precipitate in a colloid binder,
(2) fogging the resulting emulsion, (3) adding an organic halogen compound, and (4)
coating the emulsion on a support, characterized in that the organic halogen compound
is 2,2,3,4 - tetrachloronaphth - 1 - one.
13. A process for the production of a direct positive silver halide photographic emulsion
comprising the steps of (1) preparing a silver halide precipitate in a colloid binder,
(2) fogging the resulting emulsion, (3) adding an organic halogen compound, and (4)
coating the emulsion on a support, characterized in that the organic halogen compound
is 2 - dibromomethylquinoline.
14. A product prepared by the process of any of the foregoing claims.
1. Verfahren zur Herstellung einer direkt positiven, photographischen Silberhalogenid-Emulsion,
das aus den Stufen von (1) der Herstellung einer Silberhalogenid-Ausfällung in einem
Kolloidbindemittel, (2) des Verschleierns der resultierenden Emulsion, (3) des Zusatzes
einer organischen Halogenverbindung und (4) des Auftrags der Emulsion auf eine Unterlage
besteht, dadurch gekennzeichnet, dass man die Emulsion nach der Stufe (3) und vor
der Stufe (4) einer Reifung unterzieht, um die thermische Reaktion der organischen
Halogenverbindung mit den Schleierzentren zu fördern, und die organische Halogenverbindung
eine Chlor oder Brom enthaltende Verbindung ist, die ein schwaches Oxidationsmittel
ist, das in der Lage ist, Schleierzentren zu oxidieren, um eine Emulsion mit überlegener
Geschwindigkeit zu ergeben.
2. Verfahren nach Anspruch 1, in dem die chlor- oder bromhaltige Verbindung 2-Tribrommethylchinolin
ist.
3. Verfahren nach Anspruch 1, in dem die chlor- oder bromhaltige Verbindung 2-Tribrommethylchinoxalin
ist.
4. Verfahren nach Anspruch 1, in dem die chlor- oder bromhaltige Verbindung a,a,a',a'-Tetrabrom-
oxylen ist.
5. Verfahren nach Anspruch 1, in dem die chlor- oder bromhaltige Verbindung 2,2,3,4
- Tetrachlornaphth - 1 - on ist.
6. Verfahren nach Anspruch 1, bei dem die Verbindung in der Menge von 0,015-0,50 g/mol
Silberhalogenid in der Emulsion zugesetzt wird.
7. Verfahren nach Anspruch 1, bei dem das Verschleierungsmittel Cäsiumthiodecaboran
ist.
8. Verfahren nach Anspruch 1, bei dem die Verbindung in der Emulsion 10 bis 120 Minuten
bei einer Temperatur von 45°C bis 65°C einer Reifung unterzogen wird.
9. Verfahren zur Herstellung einer direkt positiven, photographischen Silberhalogenid-Emulsion,
das aus den Stufen von (1) der Herstellung einer Silberhalogenid - Ausfällung in einem
Kolloidbindemittel, (2) des Verschleierns der resultierenden Emulsion, (3) des Zusatzes
einer organischen Halogenverbindung und (4) des Auftrags der Emulsion auf eine Unterlage
besteht, dadurch gekennzeichnet, dass die organische Halogenverbindung 2 - Tribrommethylchinolin
ist.
10. Verfahren zur Herstellung einer direkt positiven, photographischen Silberhalogenid-Emulsion,
das aus den Stufen von (1) der Herstellung einer Silberhalogenid - Ausfällung in einem
Kolloidbindemittel, (2) des Verschleierns der resultierenden Emulsion, (3) des Zusatzes
einer organischen Halogenverbindung und (4) des Auftrags der Emulsion auf eine Unterlage
besteht, dadurch gekennzeichnet, dass die organische Halogenverbindung a,a,a',a'-Tetrabromoxylen
ist.
11. Verfahren zur Herstellung einer direkt positiven, photographischen Silberhalogenid-Emulsion,
das aus den Stufen von (1) der Herstellung einer Silberhalogenid-Ausfällung in einem
Kolloidbindemittel, (2) des Verschleierns der resultierenden Emulsion, (3) des Zusatzes
einer organischen Halogenverbindung und (4) des Auftrags der Emulsion auf eine Unterlage
besteht, dadurch gekennzeichnet, dass die organische Halogenverbindung 2 - Tribrommethylchinoxalin
ist.
12. Verfahren zur Herstellung einer direkt positiven, photographischen Silberhalogenid-Emulsion,
das aus den Stufen von (1) der Herstellung einer Silberhalogenid-Ausfällung in einem
Kolloidbindemittel, (2) des Verschleierns der resultierenden Emulsion, (3) des Zusatzes
einer organischen Halogenverbindung und (4) des Auftrags der Emulsion auf eine Unterlage
besteht, dadurch gekennzeichnet, dass die organische Halogenverbindung 2,2,3,4 - Tetrachlornaphth
- 1 - on ist.
13. Verfahren zur Herstellung einer direkt positiven, photographischen Silberhalogenid-Emulsion,
das aus den Stufen von (1) der Herstellung einer Silberhalogenid-Ausfällung in einem
Kolloidbindemittel, (2) des Verschleierns der resultierenden Emulsion, (3) des Zusatzes
einer organischen Halogenverbindung und (4) des Auftrags der Emulsion auf eine Unterlage
besteht, dadurch gekennzeichnet, dass die organische Halogenverbindung 2 - Dibrommethylchinolin
ist.
14. Produkt, hergestellt nach dem Verfahren irgendeiner der vorstehenden Ansprüche.
1. Un procédé de production d'une émulsion photographique d'halogénure d'argent positive
directe qui comprend les étapes consistant à (1) préparer un précipité d'halogénure
d'argent dans un liant colloïde,
(2) voiler l'émulsion résultante, (3) ajouter un composé organique halogéné et (4)
appliquer l'émulsion sur un support, caractérisé en ce que l'on fait digérer l'émulsion
après l'étape (3) et avant l'étape (4), de manière à promouvoir la réaction thermique
du composé organique halogéné sur les centres de voile, et en ce que le composé organique
halogéné est un composé chloré ou bromé qui est un agent oxydant faible capable d'oxyder
les centres de voile pour produire une émulsion de vitesse supérieure.
2. Le procédé de la revendication 1, dans lequel le composé chloré ou bromé est la
2-tribromométhylquinoxaline.
3. Le procédé de la revendication 1, dans lequel le composé chloré ou bromé est la
2-tribromométhylquinoxaline.
4. La procédé de la revendication 1, dans lequel le composé chloré ou bromé est le
a,a,a',a'-tétrabromoxylène.
5. Le procédé de la revendication 1, dans lequel le composé chloré ou bromé est la
2,2,3,4-tétrachloro- naphth-1-one.
6. Le procédé de la revendication 1, dans lequel le composé est ajouté à raison de
0,015-0,50 g par mole d'halogénure d'argent dans l'émulsion.
7. Le procédé de la revendication 1, dans lequel l'agent voilant est le césium thiodécaborane.
8. Le procédé de la revendication 1, dans lequel on fait digérer le composé dans l'émulsion
à une température de 45 à 65°C pendant 10 à 120 minutes.
9. Un procédé de production d'une émulsion photographique d'halogénure d'argent positive
directe, qui comprend les étapes consistant à (1) préparer un précipité d'halogénure
d'argent dans un liant colloïde, (2) voiler l'émulsion résultante, (3) ajouter un
composé organique halogéné et (4) appliquer l'émulsion sur un support, caractérisé
en ce que le composé organique halogéné est la 2-tribromométhylquinoléine.
10. Un procédé de production d'une émulsion photographique d'halogénure d'argent positive
directe, qui comprend les étapes consistant à (1) préparer un précipité d'halogénure
d'argent dans un liant colloïde, (2) voiler l'émulsion résultante, (3) ajouter un
composé organique halogéné et (4) appliquer l'émulsion sur un support, caractérisé
en ce que le composé organique halogéné est le a,a,a',a'-tétrabromoxylène.
11. Un procédé de production d'une émulsion photographique d'halogénure d'argent positive
directe, qui comprend les étapes consistant à (1) préparer un précipité d'halogénure
d'argent dans un liant colloïde, (2) voiler l'émulsion résultante, (3) ajouter un
composé organique halogéné et (4) appliquer l'émulsion sur un support, caractérisé
en ce que le composé organique halogéné est la 2-tribromométhylquinoxaline.
12. Un procédé de production d'une émulsion photographique d'halogénure d'argent positive
directe, qui comprend les étapes consistant à (1) préparer un précipité d'halogénure
d'argent dans un liant colloïde, (2) voiler l'émulsion résultante, (3) ajouter un
composé organique halogéné et (4) appliquer l'émulsion sur un support, caractérisé
en ce que le composé organique halogéné est la 2,2,3,4-tétrachloronaphth-1-one.
13. Un procédé de production d'une émulsion photographique d'halogénure d'argent positive
directe, qui comprend les étapes consistant à (1) préparer un précipité d'halogénure
d'argent dans un liant colloïde, (2) voiler l'émulsion résultante, (3) ajouter un
composé organique halogéné et (4) appliquer l'émulsion sur un support, caractérisé
en ce que le composé organique halogéné est la 2-dibromométhylquinoléine.
14. Un produit préparé par un procédé selon l'une quelconque des revendications précédentes.