JPS6054664B2 - Silver halide emulsion for direct positive photography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to direct positive photographic silver halide emulsions containing fogged type silver halide grains, and more particularly to silver halide emulsions containing fogged silver halide grains formed in an environment with high silver ion concentration. This invention relates to a fogged direct positive photographic silver halide emulsion.

Silver halide emulsions for fog-imparting direct positive photography still do not have sufficiently high photographic sensitivity, and in particular, in the field of printing photosensitive materials, direct positive halftone images are produced by exposing the film in close contact with a contact screen. It cannot be said that it is practically sufficient for the purpose of forming.

In addition to photographic sensitivity, forming a high-quality halftone image requires high contrast and low minimum density (hereinafter referred to as Dm, n). Moreover, unlike the formation of negative images, the direct formation of positive images has the disadvantage that a phenomenon called fateful secondary reversal is likely to occur, and this point must also be paid close attention to. The object of the present invention is to provide a silver halide emulsion for direct positive photography which overcomes the above-mentioned drawbacks.

The first objective is to provide a direct positive photographic silver halide emulsion with higher resolution. Another objective is to obtain a direct positive image with high contrast and low Dmln. Yet another objective is to prevent secondary inversion and always obtain a stable direct positive image. Another object of the present invention is to provide a silver halide emulsion for direct positive photography which provides positive images with improved halftone dot quality.

The silver halide emulsion for direct positive photography of the present invention (hereinafter referred to as direct positive emulsion) is a solarization type direct positive emulsion that is previously fogged and obtains a positive image by destroying the fog by exposure to light.

Conventionally, this type of direct positive emulsion has sensitivity and contrast characteristics that are determined by the method of imparting fog to the silver halide formed in large amounts, or by selecting or adding a compound called an organic demulcent that effectively destroys fog. Improvements have been made. This is because the reversal process of this type of direct positive emulsion is thought to be mainly a surface phenomenon of silver nitride. The present invention is characterized by a method for forming the interior of silver halide grains, particularly the center portion.

Silver halide grains are obtained by adding and mixing aqueous solutions of a water-soluble silver salt such as silver nitrate and an aqueous alkali halide solution to an aqueous solution of gelatin or the like which serves as a hydrophobic protective colloid of silver halide.

The silver halide according to the present invention is prepared under a strip diameter in which the i ion concentration and the hydrogen ion concentration of this mixed solution have specific values. One feature of the present invention is that the silver ion concentration and hydrogen ion concentration are kept high until the addition of at least one of the two particles of the total silver amount is completed. Most conventional silver halide grain formations have been carried out at silver ion concentrations below 10@-6 mol/'. This is also related to the fact that the solubility product of silver halide takes a value almost similar to this. The method according to the present invention forms silver halide grains while maintaining a higher silver ion concentration than conventional methods. The concentration is preferably approximately 10-5 to 10-1 mol/e, which is a higher concentration than the conventional one. If the density is low, a sufficiently high sensitivity cannot be obtained, and if the density is too high, the image Dmi
n becomes high or a quadratic inversion occurs. Overall, approximately 10-4 to 10-2 mol/e is more preferred. The time when the silver ion concentration should be kept high is until at least one part of the total amount of silver is added. If this value is small, the effect of the present invention cannot be achieved. Total silver amount 2
After addition of 1/0, the silver ion concentration was reduced to 10-6 mol/e.
You can lower it below. Also, at the end of addition, 10
-6 mol/e or less is desirable. It is generally known that silver halide grains can be formed in any of basic, neutral and acidic conditions.

The method according to the present invention is carried out at a slightly low pH value even in an acidic range while maintaining a high silver ion concentration. When the intensity becomes high, undesirable phenomena such as a decrease in sensitivity and an increase in Dmin of the image occur, and the effects of the present invention cannot be obtained. The lower the pH value, the more effective it is, but there are problems such as a decrease in the protective ability due to hydrolysis of the protective colloid, etc., or corrosion of the mixing tank due to the acid used to lower the pH, so it is almost P.
Up to Hl is practical. This pH value can be adjusted as long as the silver ion concentration is kept high during the process of silver halide grain formation, and even if the silver ion concentration is lowered and then raised to about 8, the effect of the present invention will not be affected. However, the pH is 7.5.
It is preferable not to exceed , from the viewpoint of obtaining a lower Dmin. The silver ion concentration of the mixed solution required for the present invention can be easily obtained by controlling the concentration and addition amount of water-soluble silver salt and water-soluble alkali halide, and the hydrogen ion concentration can be easily obtained by controlling the concentration and addition amount of water-soluble silver salt and water-soluble alkali halide. It can be obtained using a suitable acid such as sulfuric acid.

It is desirable that the prepared silver halide undergoes a desalting step in which salts and acids, which are reaction by-products, are removed by washing with water.

The direct positive emulsion containing silver halide thus prepared has the advantage that variations in photographic performance depending on the manufacturing rod are extremely small, making it possible to supply a stable product. Effective protective colloids used in the present invention include gelatin and modified gelatin, which are commonly used in photography.

The silver halide used in the present invention includes silver bromide, silver chloride, silver chlorobromide, silver iodobromide, and silver chlorobromoiodide, but the silver iodide content may be 10 mol percent or less. is necessary.

If silver iodide exceeds 10 mol percent, sensitivity decreases. The most preferred silver halide composition is silver iodobromide containing 10 mole percent or less of silver iodide. Furthermore, the silver halide grains used in the present invention preferably have an average grain diameter of about 0.05 to about 2 microns, but for printing to form halftone images, silver halide grains of about 0.1 to about 1 micron are suitable. Particularly preferred.

In addition, the particle size frequency distribution is good whether it is wide or narrow.
Narrower is preferable. Further, the shape or structure of the silver halide grains may be regular or irregular, but regular grains are particularly preferred. The direct positive emulsion of the present invention preferably contains a combination of an internal electron acceptor (ie, a noble metal atom contained within the silver halide grains) and an organic desensitizer that adsorbs to the silver halide surface. In the prior art, it has been assumed that the internal electron acceptor and the organic desensitizer achieve the same purpose as a fog nuclear destruction accelerator, and that it is sufficient to contain either one of them. However, in the direct positive emulsion of the present invention, the organic desensitizer used in the absence of an internal electron acceptor may cause undesirable secondary inversion depending on its type and amount; When used, not only higher sensitivity can be obtained, but also it is excellently effective in preventing secondary reversal. In order to incorporate internal electron acceptors into silver halide grains, water-soluble noble metal compounds such as chlorides of octavalent metals such as iridium and rhodium are added at a rate of about 10-8 to 10-5 mol per 1 mol of silver halide. It may be added as an aqueous solution when preparing silveride particles. Representative examples of the organic desensitizer used in the present invention include the compounds shown below.

Organic desensitizers such as dimethine cyanine dyes containing 2-(nitrosubstituted phenyl)indole nuclei, bis-(1-alkyl-2-phenylindole-3) trimethine cyanine dyes, cyanine dyes containing aromatic substituted indole nuclei, imidazoquinoxaline dyes. , asymmetric cyanine dyes containing a carbazole nucleus, trimethine cyanine dyes containing a 2-aromatically substituted indole nucleus, 2,3,3-trialkyl? - cyanine dyes containing a nitroindole nucleus, cyanine dyes containing a complex fused pyrimidinedione nucleus, quaternization with a 2-isoxazoline-5-one nucleus, a 2-pyrazoline-5-one nucleus or a complex fused pyrimidinedione nucleus; Merocyanine dye, cyanine dye containing a 2-allylimino (or alkylimino)-4-allyl (or alkyl)-3-thiazoline nucleus, merocyanine quaternary having a 3-arylamino or 3-lower fatty acid amide substituted 2-pyrazolin-5-one class ammonium salt dyes, pyrylium, thiapyrylium, selenapyrylium salt dyes, cyanine dyes with a nitro-substituted 2-arylindole nucleus, bipyridinium salt dyes, cyanine dyes containing a pyrrole nucleus bonded at the 2-1 carbon atom, 1,2 -diaryltrimethine indole dyes, cyanine dyes containing 4-pyrazole nuclei, polymethine dyes containing imidazole nuclei,
Dimethylene cyanine dyes containing a 2-phenyl-substituted indole nucleus, trimethine cyanine dyes containing two indole nuclei, cyanine dyes containing a 1-cyanoalkyl-arylindole nucleus, and desensitizing dyes in which the two nuclei are nitro groups. cyanine and merocyanine dyes having groups, cyanine dyes containing a 1-alkyl-2-phenyl substituted indole nucleus, cyanine dyes containing a 1-alkoxy-2-arylindole nucleus, cyanine dyes having an imidazo[4,51b]quinoxaline nucleus, Dyes containing a cyclohebutanetriene ring, dimethine cyanine dyes containing an indole nucleus, cyanine dyes containing a pyrazolo[1,51a]benzimidazole nucleus, cyanine dyes containing a pyrazolo[5,1-b]quinazolone nucleus, pyrrolo[ 2,3-b] dimethine cyanine dye containing a pyridine nucleus, cyanine dye containing a pyrrole nucleus,
Dyes containing a pyrrolo[2,1-b]thiazole nucleus, cyanine dyes containing an indole or indolenine nucleus containing a benzoyl or phenylsulfonyl substituent, and the like. These organic desensitizers are dissolved in a suitable solvent in silver halide after desalting, and added in an amount of 10-4 to 10-4 per mole of silver halide.
2 moles are added. The direct positive emulsion of the present invention is fogged. After water-soluble salts have been removed, it may be carried out using conventionally known techniques. Fog may be imparted using a reducing agent alone or in combination with a reducing agent and all compounds. For example, a method of imparting fog using a combination of a reducing agent and all compounds described in US Pat. No. 3,501,307 is effective. Representative of such useful reducing agents include, for example, formalin, hydrazine, polyamines (e.g., triethylenetetramine, tetraethylenepentamine, etc.), thiourea dioxide, tetra(hydroxymethyl)phosphonium chloride, boron compounds ( Examples include amine borane, sodium borohydride, etc.), stannous chloride, and the like. Representative examples of all compounds include chloroauric acid, potassium chloroaurate, potassium auricyanide, gold sulfide, gold selenide, and the like. By further adding thiosulfate, thiocyanate, cyanide, etc., images with higher contrast can be obtained. The degree of fog in the direct positive emulsions of the present invention can be varied over a wide range.

The degree of fogging is determined by the silver halide composition and grain size of the silver halide emulsion used, the type and concentration of the fogging agent used, and the PH of the emulsion at the time of imparting fog. It is related to pAg, temperature, time, etc. The direct positive photographic silver halide emulsion used in the present invention is a solarization accelerator such as soluble halogen salts such as potassium iodide and potassium bromide described in Japanese Patent Publication No. 47-2427, and soluble halogen salts such as potassium bromide described in Japanese Patent Publication No. 47-4282. selenium compounds such as those described in JP-A No. 50-8902; It is possible to sensitize with 1a photoactive compounds and the like.

The direct positive photographic silver halide emulsions of the present invention contain solarization promoters such as soluble halogen salts such as potassium iodide and potassium bromide, selenium compounds, halogen-free photoactive compounds, and optical sensitizers such as dimethine trimethine cyanine dyes. Halogen-substituted hydroxyphthalein dyes, phenazine dyes, benzothiazole, cyanine dyes containing benzoselenazole nuclei, cyanine dyes containing naphthoxazole nuclei, triphenylmethane dyes, cyanine dyes containing indolenine nuclei, 2-pyridine-rota cyanine dye containing a nin nucleus, cyanine dye containing a thiazole nucleus, asymmetric cyanine, quinoline, meso-substituted cyanine dye, cyanine dye containing a rhodanine nucleus, cyanine dye containing a benzimidazole nucleus, polymethine dye having three nuclei, merocyanine dye The sensitization is further sensitized by a material selected from the following.

Other photographic additives can also be added to the direct positive silver halide emulsion of the present invention.

That is, or triazoles, asaine tenes,
Organic and inorganic stabilizers such as quaternary benzothiazolium compounds, mercapto compounds, or water-soluble inorganic salts of cadmium, cobalt, nickel, manganese, thallium, gold, zinc, etc., formalin, glyoxal, mucolic acid, etc. Hardening agents such as aldehydes, s-triazines, epoxies, aziridines, and vinylsulfonic acid are used.
Examples of coating aids include saponin, sodium polyalkylene sulfonate, and polyethylene glycol. lauryl or oleyl monoether, amylated alkyl taurine, and as a sensitizer, for example, polyalkylene oxide and its derivatives are preferably used. Furthermore, it is also possible, for example, to contain color couplers. the. In addition, a whitening agent, an ultraviolet absorber, a preservative, a matting agent, an antistatic agent, etc. can also be contained as necessary. The direct positive emulsion of the present invention may contain, as protective colloids, natural substances such as gelatin and gelatin derivatives, as well as hydrophilic polymers such as polyvinyl alcohol, polyvinyl acrylate, and polyvinylpyrrolidone.

The direct positive emulsion thus obtained can be applied to any suitable photographic support such as glass, film such as cellulose acetate, polyester, polystyrene, etc., paper,
It is coated on a support such as baryta coated paper, polyolefin coated paper, such as polyethylene or polypropylene coated paper. For example, polyolefin-coated paper can be treated with electron impact to improve the adhesion of the emulsion. The direct positive emulsion of the present invention can be applied to various uses.

For example, various photographic materials for printing such as halftone positives, duplicating, reproduction, offset masters, special photographic materials such as X-rays, flash photography, and electron beams, and general copying and microcopying. It is used in a variety of direct positive silver halide photographic light-sensitive materials, such as those for color, direct positive color, diffusion transfer, color diffusion transfer, and one-bath development/fixing. These photosensitive materials can be processed with various developers depending on the purpose.

For example, it can be processed with a general black-and-white developer (for example, a phenidone-hydroquinone developer, a methol-hydroquinone developer, a hydroquinone developer, or a tanning developer), a color developer (for example, a phenylenediamine developer), and the like. After development, normal fixing processing can be performed.
The present invention will be specifically illustrated below with reference to Examples.

Example 1 A direct positive emulsion that caused fog in silver halide grains formed in an environment with a high silver ion concentration caused fog in silver halide grains formed in an environment with a low silver ion concentration. Photographic sensitivity is increased compared to direct positive emulsions.

This example shows this fact. [Emulsion A] Add a silver ion concentration of 10-3M to a gelatin aqueous solution at 70°C.
0.011e, an aqueous solution of silver nitrate and an aqueous solution of potassium bromide and potassium iodide are simultaneously and gradually mixed in 6 parts.

The pH during the precipitation step was maintained at approximately 2 with sulfuric acid. After mixing 4
% potassium hydroxide, water-soluble salts were removed by conventional flocculation methods, and gelatin was added to finish. Silver iodobromide grains containing 2.5 mole percent silver iodide with an average grain size of 0.20 microns were obtained. [Emulsion B] Add a silver ion concentration of 10-2M to an aqueous gelatin solution at 70°C.
The aqueous solution of silver nitrate and the aqueous solutions of potassium bromide and potassium iodide are simultaneously and gradually mixed in all six quantities while maintaining the temperature at 0.011e.

After mixing, the silver ion concentration was reduced to 10 with an aqueous solution of potassium bromide.
It was lowered to -9M011e. The pH during the precipitation step was maintained at approximately 2 with sulfuric acid. After the mixing was completed, the mixture was neutralized with 4% potassium hydroxide, water-soluble salts were removed by a conventional flocculation method, and gelatin was added to finish the mixture. Silver iodobromide grains containing 2.5 mole percent silver iodide with an average grain size of 0.20 microns were obtained.
[Emulsion C] Same as Emulsion B, except that the silver ion concentration at the time of mixing was changed to 1.
The only difference is that it is kept at 0-5M011e.

After mixing, the silver ion concentration was reduced to 10 with an aqueous solution of potassium bromide.
It is the same to lower it to -9M011e. The average particle size is 0.18μ. Emulsion A. ．． B and C at PH=8
．． The PAg was adjusted to 8.0, 60 m9 of formalin was added per mole of silver halide, and the mixture was aged for 3 times at 65°C.
Next, 3.0 m9 of chloroauric acid was added per mole of silver halide, and the mixture was aged at 65° C. until the respective maximum performance was obtained, causing fog.

An organic desensitizer (1,1'',3,3-tetramethyl-5-methylsulfonyl-5''-nitro2'-p-
Nitrophenylindo-3-indolocarbocyanine methylenesulfonate) was added, and coating aids and hardeners were added to adjust the pH to 6.5 and PAg to 8.5, and each emulsion was placed on a polyester film base. A sample was obtained by applying 3.0 y of silver per square meter and drying. Each sample thus obtained was exposed using an optical wedge for sensitometry, and developed with the following developer at 20° C. for 3 minutes. [Developer composition] Sodium bisulfite and formaldehyde adduct
60y sodium carbonate (
monohydrate) 85f hydroquinone
18y potassium bromide
Add 2f water to make 1e.

The photographic performance of each processed sample was measured and the results are shown in Table 1.

Note that the positive sensitivity was determined from the reciprocal of the exposure amount required to destroy fog up to a density of 02 in white exposure for practical purposes.

The sensitivity is expressed as a relative sensitivity, with the sensitivity of the sample of emulsion A being 100. As is clear from the above results, high sensitivity and high contrast can be obtained by using silver halide grains formed in an environment with high silver ion concentration.

Similar results were obtained by repeating the above method using reducing agents such as hydrazine, triethylenetetramine, tetraethylenepentamine, thiourea dioxide, tetra(hydroxymethyl)phosphonium chloride, amineborane, and sodium borohydride. It will be done.

Example 2 A direct positive photographic silver halide emulsion in which fog was produced in silver halide grains formed in an environment with a high silver ion concentration until the addition of at least 112 parts of the total silver amount was completed.
The photographic sensitivity is increased compared to a direct positive photographic silver halide emulsion which is formed in an environment where the silver ion concentration is high by less than 112% of the total silver amount and which causes fog in the silver halide grains.

This example demonstrates this fact. [Emulsion D] Add a silver ion concentration of 10-2M0 to an aqueous gelatin solution at 70°C.
While maintaining the temperature at 11e, an aqueous solution of silver nitrate and an aqueous solution of potassium bromide and potassium iodide are simultaneously and gradually mixed in an amount of 1125 over 2 minutes and 24 seconds.

Therefore, the silver ion concentration was adjusted to 10-9 with an aqueous solution of potassium bromide.
The silver ion concentration was reduced to M011e, and the rest was mixed for 57 minutes and 3 forgings while maintaining the silver ion concentration. The PHL silver halide composition during the precipitation step and the subsequent operations were the same as for Emulsion A. The average particle size is 0.20μ. [Emulsion E] Same as Emulsion D, except that the silver ion concentration was 10-2M.
The only difference is that the total addition amount is simultaneously and gradually mixed for 6 minutes at 0.011e, and then the silver ion concentration is brought to 10@-9M011e with an aqueous solution of potassium bromide, and the remainder is mixed for 54 minutes.

The average particle size is 0.20μ. [Emulsion F] Same as Emulsion D, except that the silver ion concentration was 10-2M.
At step 011e, 1 powder of the total addition amount is mixed simultaneously and gradually in 3 powders, and the remaining 11 powders are further mixed in 1 powder.

Therefore, the silver ion concentration was reduced to 10-9 with an aqueous solution of potassium bromide.
The only difference is that M011e is used and the rest is mixed in one batch. The average particle size is 0.25μ. [Emulsion G] Same as Emulsion D, except that the total addition amount of 1-ha is mixed in 3 powders, and then the rest is mixed in 3 powders, and the silver ion concentration at the time of mixing is changed from the beginning of mixing. 10-2M011e, and gradually lower it as the mixture is mixed, and when the total amount of addition is about 6 pupil, it is changed to 10-6M011e, and when the mixing is finished, it is 1
The only difference is that it is set to 0-9M011e.

The average particle size is 0.25μ. [Emulsion B] As mentioned above, the silver ion concentration was maintained at 10-2M011f during mixing, and was set to 10-9M01' after mixing.

Emulsion D. ．． E. ．． F. As in Example 1, G and B are fogged, an organic desensitizer and the like are added, coated and dried to obtain a sample. These samples were exposed and developed as in Example 1,
The photographic performance was measured and the results are shown in Table 1-2. As is clear from the above results, high sensitivity and high contrast can be obtained by using silver halide grains formed in an environment with high silver ion concentration until at least one to two parts of the total silver amount has been added. It turns out that it can be done.

Example 3 Emulsions AlBlC and G with PH=8.8 and PAg=8.0
80 m9 of formalin per mole of silver halide was added, and fogging was carried out at 60C until the maximum performance was obtained. Organic desensitizers were added as in Example 1, and the sample was coated and dried. I got it.

These samples were exposed and developed as in Example 1, and the photographic performance was measured. The results are shown in Table 3. As is clear from the above results, when using silver halide grains formed in an environment with high silver ion concentration, high density and high contrast can be obtained even when only a reducing agent is used as a fogging agent. I understand.

Similar results can be obtained by repeating the above method using other reducing agents as described in Example 1. Example 4 During the precipitation step, silver halide grains formed at a pH of 4 or less give higher positive sensitivity than silver chloride grains formed at a pH greater than 4.

This example shows this fact. [Emulsion H] Same as Emulsion B, except that it was silver iodobromide grains containing 5 mol percent of silver iodide.

The average particle size is 0.20μ. [Emulsion 1] Same as Emulsion H, except that the pH during the precipitation step was 6.5.
The difference is that

The average particle size is 0.22μ. Example 1 Emulsions H and I
A sample is obtained by applying fog, adding an organic desensitizer, etc., and coating and drying. These samples were exposed and developed as in Example 1, and the photographic performance was measured. The results are shown in Table 4. As is clear from the above results, it was found that higher sensitivity can be obtained when the pH during the precipitation step is lower.

Example 5 When silver halide grains formed in an environment with high silver ion concentration are doped with an internal electron acceptor and an organic desensitizer is used in combination, a higher positive potential is obtained than when only an organic desensitizer is used as the electron accepting compound. Sensitivity can be obtained.

This example shows this fact.

[Emulsion G]

This is already described in Example 2.

[Emulsion J]

Same as Emulsion G, except that 5 x 10-7 mol of iridium dipotassium hexachloride per mol of silver halide is added to the aqueous gelatin solution immediately before starting the mixing of the silver nitrate solution and the alkali halide solution. .

The average particle size is 0.25μ. Example 1 Emulsions G and J
The organic desensitizer (1,3,3-trimethyl-[,2''-diphenyl-3-indropyrrolo[2,3-b]pyridocarbocyanine perchlorate)
etc., apply and dry to obtain a sample. These samples were exposed and developed as in Example 1, and the photographic performance was measured. The results are shown in Table 5.
It was shown to. As is clear from the above results, it was found that when an organic desensitizer and an internal electron acceptor were used in combination, higher positive sensitivity was obtained than when using only an organic desensitizer, and secondary inversion was suppressed. .

Similar results were obtained when the above method was repeated using rhodium chloride.

Example 6 [Emulsion K] An aqueous solution of silver nitrate and an aqueous solution of sodium chloride and potassium bromide are mixed in an aqueous solution of (6) containing gelatin for 20 minutes while maintaining the silver ion concentration at 10?9M011'. .

The pH during the precipitation step was maintained at approximately 2 with sulfuric acid. After mixing 4
% potassium hydroxide, water-soluble salts were removed by conventional flocculation methods, and gelatin was added to finish. Silver chlorobromide grains containing 20 mole percent silver bromide were obtained with an average grain size of 0.20 microns. [Emulsion L] Same as Emulsion K, except that the silver ion concentration during mixing was increased to 1.
The only difference is that the silver ion concentration is maintained at 0-4M011' and after the mixing is completed, the silver ion concentration is reduced to 10-9M011e with an aqueous solution of sodium chloride.

The average particle size is 0.19p. Example 1 Emulsions K and L
Apply fog, add an organic detoxifying agent, etc., and apply.
Dry and obtain a sample. These samples were exposed and developed as in Example 1, and the photographic performance was measured. The results are shown in Table 6. As is clear from the above results, in the case of silver chlorobromide particles,
It can be seen that high sensitivity and high contrast can be obtained by using silver halide grains formed in an environment with high silver ion concentration.

Claims (1)

[Claims] 1. Until the aqueous solution of water-soluble silver salt and water-soluble alkali halide is added to the protective colloid solution at least one-twentieth of the total amount of silver to form silver halide, the silver ion concentration of the mixed solution is 10^-^ A silver halide emulsion for direct positive photography imparted with fog, characterized in that it is prepared by adding and mixing 1 to 10^-^6 mol/l so as to keep the pH at 4 or less.