JPS6344215B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a direct positive silver halide photographic emulsion, and more particularly to a direct positive silver halide photographic emulsion containing a novel spectral sensitizing dye. When a conventional silver halide photosensitive material is exposed and developed with light including light in the wavelength range to which the photosensitive material is sensitive, its blackening density increases as the exposure amount increases and reaches a maximum value; If the exposure amount is further increased, the blackening density will decrease, and a positive image will be formed. Such development is generally called solarization. In addition, even in silver halide emulsions that have been optically or chemically fogged during the manufacturing process, when the emulsion is exposed to light containing light in the wavelength range to which the emulsion is sensitive and developed, the black The concentration decreases with increasing exposure,
A positive image is obtained. As used herein, direct positive emulsion refers to an emulsion that is processed to form a positive image after normal exposure to light and normal development. Such emulsions are called prefogged direct positive emulsions. This emulsion exhibits essentially the same spectral distribution of intrinsic sensitivity as a normal negative emulsion. A direct positive emulsion utilizes photoholes among photoelectrons and photoholes generated in silver halide by light absorption of silver halide or a spectral sensitizing dye adsorbed on silver halide. Silver nuclei (Agn), which are formed as fogging nuclei in advance by photoholes (h ⁺ ) generated by exposure, are Agn+h ⁺ →Agn−1+Ag ⁺
Since the silver halide is bleached by a reaction, the silver halide whose fog nuclei have been bleached will not undergo any change in the next development step. Therefore, the blackening density of the exposed portion decreases depending on the amount of exposure. In this way, it is generally believed that a positive image can be obtained directly through the exposure and development operations. Spectral sensitization is a well-known technique for extending the sensitive wavelength range of a silver halide emulsion toward longer wavelengths or increasing the sensitivity by adding an appropriate dye during the production process of the silver halide emulsion. Many dyes are known which are advantageously used for sensitizing ordinary negative emulsions. However, the dyes used for sensitizing negative-working emulsions cannot always be used satisfactorily for directly sensitizing positive-working emulsions. Indole nucleus-containing dimethine dyes (British Patent No. 970601, U.S. Patent No. 3314796) are useful dyes for spectral sensitization of direct positive emulsions.
), pyrrole nucleus-containing dimethine dye (U.S. Patent No.
3592653, U.S. Patent No. 3598603), etc. are known. However, the biggest problem with direct positive photosensitive materials is that they do not have a sensitivity that is satisfactory for many types of photography. Therefore, increasing the sensitivity of direct positive emulsions, especially using dyes, is extremely important from a technical standpoint. An object of the present invention is to provide a direct positive silver halide photographic emulsion which provides high sensitivity. Another object of the present invention is to provide new spectral sensitizing dyes useful in direct positive photographic emulsions. As a result of various studies, we have found that dyes represented by the following general formula [] are useful as spectral sensitizing dyes for direct positive emulsions. General formula [] Here, Z and Z' represent a group of nonmetallic atoms necessary to complete the heterocyclic nucleus. n represents 0, 1 or 2. R represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group. X represents an anion. The nonmetallic atom group represented by Z and Z' in the general formula [] is preferably a 5-membered heterocyclic nucleus, which may have a substituent, a benzene ring,
A naphthalene ring or the like may be condensed. in particular,

【formula】 【formula】

【formula】

[Formula] etc. can be mentioned. Ru. Especially among these

【formula】

[Formula] is preferred. Specifically, the substituent substituted on the heterocyclic nucleus includes an alkyl group (preferably a straight chain one having 1 to 6 carbon atoms, such as a methyl group, ethyl group, propyl group, butyl group, etc.); Alkoxy group (e.g. methoxy group, ethoxy group, etc.), phenyl group,
Examples include halogen atoms (eg, chlorine atoms, bromine atoms, etc.). The alkyl group represented by R is preferably a linear one, and specific examples include methyl, ethyl, propyl, and butyl groups. As R, a hydrogen atom and a methyl group are particularly preferable. Specifically, the anions represented by X include Cl, Br, I, ClO ₄ , BF ₄ ,

Examples include [Formula]. Among them, ClO ₄ and BF ₄ are particularly preferred. From the viewpoint of stability, n is preferably 0 or 1. Preferred examples of the dye represented by the general formula [] are shown below. For the synthesis method of compounds-1 and -2, see L.
Soder and R. Wizinger's Helv.Chim.Acta 42 1733~
1737 (1959). For other compounds, the synthesis method is described by R. Wizinger and D. Du¨rr.
Helv, Chim. Acta 42 2167-2177 (1963). Next, a specific synthesis method will be explained. Synthesis Example 1 (Synthesis of -8) 3 g of dithiobenzcatechol was mixed with 10 acetyl chloride.
Dissolve in ml. While cooling and stirring, slowly add 2.5 ml of perchloric acid (70%) drop by drop. 100 ml of ether is added 15 minutes after the reaction has ended. Intermediate A was obtained by suction filtering the obtained needle-like crystals and washing with ether. On the other hand, 2-thione-benz-1,3-diol
Heat 1.84 g and 5 ml of dimethyl sulfate at 160°C for a long time. After cooling 10 ml of glacial acetic acid and 1.2 ml of perchloric acid (70%)
Intermediate B consisting of needle-shaped crystals was obtained by adding 100 ml of ether and 100 ml of ether. Next, 0.267 g of Intermediate A and 0.299 g of Intermediate B are heated in 30 ml of glacial acetic acid until boiling for 2 minutes, and after cooling, the crystals are filtered out. 1 of acetic acid and acetic anhydride:
Compound-8 was obtained by recrystallizing with 1 mixed solvent.
I got it. Synthesis Example 2 (Synthesis of -4) 0.534 g of Intermediate A obtained in Synthesis Example 1 and 0.2 g of orthoformic acid ester are heated for 2 minutes in 10 ml of acetic anhydride. After cooling, the precipitated crystals were filtered and recrystallized from acetic acid to obtain Compound-4. Synthesis Example 3 (Synthesis of -1) Add 2 g of malonic acid to 50 ml of phosphoryl trichloride POCl ₃ and stir well, and add 3 g of toluene dithiol to this.
Add. Heat while stirring until boiling. As it boils, it becomes intensely dark red in color. Boil for 5 minutes, cool, and then transfer to an ice-cooled mixed solution of 200 ml of glacial acetic acid and 50 ml of water while stirring. After the gas evolution has stopped, 10 ml of 70% HClO ₄ solution is added dropwise, stirred, and left to stand. Water was added to this solution to separate the precipitate, dried in a sulfuric acid desiccator, and recrystallized from glacial acetic acid to obtain 0.5 g of needle crystals of Compound-1. Synthesis Example 4 (Synthesis of -2) Dissolve 4 g of toluenediol in 20 ml of ice-cooled acetyl chloride. While cooling on ice and stirring, add 4 ml of 70% perchloric acid solution dropwise. Leave overnight at room temperature, protected from light. Add 20 ml of glacial acetic acid to the resulting white solid.
ml, stir, and filter. Further washing with ethyl ether yields colorless needle crystals (Intermediate A) 7.1
I got g. (Yield 99%) Intermediate A 4.6 g of Intermediate A was added to 220 ml of glacial acetic acid, and while stirring, 9.3 ml of ethyl orthoformate was added. Stir and heat this, and after it boils, immediately stop heating and leave it alone. If left to cool, the dye will precipitate. and wash with ether. The dark green powder obtained is
It is 3.7g. By recrystallizing with dichloromethane, monoclinic crystals with golden luster were obtained. As mentioned above, the dye represented by the general formula [] is excellent in sensitizing direct positive emulsions. Furthermore, when a dye represented by the general formula [] is used, a direct positive emulsion with little residual coloring can be obtained. As the silver halide emulsion used in the present invention, silver salts such as silver chloride, silver bromide, silver chlorobromide, silver iodobromide, silver chloroiodide, and silver chloroiodobromide can be used. Silver halide emulsions used in direct positive light-sensitive materials are those in which the surfaces of silver halide crystals have been covered in advance by light or chemical methods. For detailed information on how to make emulsions, please refer to “The Theory.”
of the Photographic Process, 4th Ed.”edited
by THJames 185 pages (1977), U.S. Patent No.
It is described in the specifications of No. 2717833, No. 3367778, No. 3501305, No. 3501306, and No. 3501307. The fogging process is carried out by adding a reducing agent to the emulsion under appropriate pH and pAg conditions, or by adding a reducing agent to the emulsion.
This can be carried out by heating the emulsion under pAg, uniformly exposing the emulsion to light, and the like. As the reducing agent, stannous chloride, hydrazine compounds, ethanolamine, thiourea dioxide, etc. can be used. In order to obtain a good reversal image, a normal latent image forming reaction (silver nuclei are formed by the reaction of photoelectrons and silver ions,
It is preferable to use a suitable electron trap to prevent the reaction from occurring. This purpose can be accomplished by introducing polyvalent cations into the silver halide crystal or by using an electron-capturing desensitizing dye adsorbed on the crystal surface. Depending on how they are used, emulsions are classified into the following two types (a) and (b). (For details, refer to Belgian Patent No. 695345 to
It is described in issues up to No. 695396. ) Emulsion (a): Emulsion whose surface sensitivity has been lowered by desensitizing dye Emulsion (b): Strong internal trap type emulsion Furthermore, the following two types of sensitizers are considered as sensitizers for these emulsions. For emulsion type (a) it is an electron acceptor, and for emulsion type (b) it is a halogen acceptor. Whether these sensitizers are electron acceptors or halogen acceptors can be determined by their half-wave reduction potential E1/2 ^red and half-wave oxidation potential E1/2 ^ox , which are measured using a common electrochemical method called polarography. stipulated. (Values of potential are expressed in volts with respect to the saturated acetate electrode.) E1/2 ^ox +
If E1/2 ^red > 0, it is an electron acceptor, and E1/
If 2 ^ox <0.85 and E1/2 ^red <-1.0, it is a halogen receptor. Examples of using cyanine dyes as electron acceptors are French patents 1513841, 1520817,
1520818, and an example of using a cyanine dye as a halogen receptor type sensitizer is known from French patent 1518094. Further, an example in which merocyanine dyes can be used is known from US Patent No. 24978763364026. Spectral sensitization of internally fogged emulsions is reported in Phot.Sci.Eng., Vol. 17, pp. 235-244 (1973). As electron traps capable of capturing electrons, rhodium and iridium salts can be mentioned as compounds incorporated into the silver halide crystal. Examples of compounds adsorbed onto the crystal surface include electron capture desensitizing dyes such as phenosafranin and dipyridinium salt compounds such as methylbislogen. Dipyridinium salt compounds are compounds of the following general formula [] General formula [] Here, R, R'; linear C1- _{C8 alkyl} group, benzyl group, iso- _C5H11 , aryl group X; Br _{, ClO4} , _BF4 , _{H2PO4 ,
HCO3} , _CH3COO , _SO42 ^,

[Formula], PF ₆ , SCN, and an anion selected from Cl can be used. Specific examples include the following. The grain size of silver halide in the silver halide emulsion used in the present invention is not limited within the commonly used range, but the average grain size is 0.05μ to
1.0μ is preferable, and 0.3 to 0.8μ is particularly effective. Although the silver halide grains used may be regular or irregular grains, the effects of the present invention are particularly effective with regular grains (eg, regular octahedrons, regular hexahedrons, etc.). Also, non-monodisperse emulsions may be used, but the effects of the present invention are best achieved with monodisperse emulsions (particularly those with a coefficient of variation (cv) of the size distribution of silver halide grains of 20% or less).
is more effective. The amount of the compound represented by the general formula [] used in the present invention varies depending on the amount of silver halide in the emulsion, the size of the surface area, and the purpose of use. 5×10 ^-7 to 2×10 ^-2 mol per mol of silver salt is preferred, and 5×10 ^-6 to 10 ^-3 mol is particularly effective. Methanol, ethanol,
It is conveniently used as a solution in a water-miscible solvent such as dimethyl formamide or methyl cellosolve. It is convenient to add dye to the emulsion just before coating, but it can also be added during chemical ripening or during precipitation. The soluble salts are usually removed from the emulsion after precipitation or physical ripening, and the long-known Nudel water washing method in which gelatin is gelatinized may be used as a means for this purpose. Utilizing inorganic salts such as sodium sulfate, anionic surfactants, anionic polymers (e.g. polystyrene sulfonic acid), or gelatin derivatives (e.g. aliphatic acylated gelatin, aromatic acylated gelatin, aromatic carbamoylated gelatin, etc.) A sedimentation method (flocculation) may also be used. The process of removing soluble salts may be omitted. When performing chemical sensitization, Glafkides or
Zelikman et al.'s book or H. Frieser's Die
Grundlagen der Photographischen Prozesse
mit Silberhalogeniden (Akademische
Verlagsgesellschaft, 1968) can be used. The emulsion used in the present invention mainly uses gelatin as a protective colloid, and it is particularly advantageous to use inert gelatin. In place of gelatin, photographically inert gelatin derivatives, water-soluble synthetic polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl arginate, etc. can be used. The direct positive silver halide emulsion according to the present invention further contains stabilizers for fog nuclei (for example, mercapto compounds, thione compounds, tetrazaindene compounds, etc.), omission improvers (for example, stilbene compounds,
triazine compounds, etc.), brighteners, ultraviolet absorbers, hardeners (e.g. chromium alum, 2,4-dichloro-s-triazine compounds, aziridine compounds, epoxy compounds, mucohalogen acid compounds (halogen, formyl, maleic acid compounds), coating aids (e.g. sodium polyalkylene sulfonate, saponin, anionic surfactants with a betaine structure, etc.), preservatives, plasticizers (e.g. polyalkyl acrylates, alkyl acrylates and acrylic acids) vinyl compounds such as copolymers, polyalkylene oxides, etc.),
Various additives such as color couplers can be contained. As these compounds, for example, those described in Research Disclosure Volume 176 (December 1978) can be usefully used. Emulsions according to the invention can be coated on a variety of supports to form photographic elements. The emulsion can be coated on one or both sides of the support, and the support can be transparent or opaque. Typical supports include cellulose nitrate film,
Cellulose acetate film, polyvinyl acetal film, polystyrene film, polyethylene terephthalate film and other polyester films, as well as glass, paper, metal,
Also includes trees. It is also possible to use a support made of paper laminated with plastic. The direct positive silver halide photosensitive material of the present invention can be used as a photosensitive material for copying lithographic film, a photosensitive material used for copying original drawings, and a photosensitive material for copying microphotography or X-ray photography. I can do it. Furthermore, the direct positive silver halide photographic emulsion of the present invention is useful not only when irradiated with light, but also when irradiated with electron beams, X-rays, gamma rays, and the like. After exposure, the emulsion according to the present invention is developed by conventionally known methods.
The treatment is suitably performed using a treatment bath for fixing, stabilization, etc., or a treatment bath combining these. Next, the present invention will be explained in detail with reference to Examples. Example 1 A direct positive emulsion consisting of prefogged octahedral AgBr grains (average grain size 0.6μ) was prepared as follows. That is, add 30 g of inert gelatin and 7.5 ml of 25% ammonia water to 1000 ml of water, and heat at 50°C.
Add 1N _AgNO3 aqueous solution while stirring well.
375 ml and 1N KBr aqueous solution were added over 20 minutes. During this time, the silver potential of the reaction solution was maintained at -40 mV vs SCE (saturated sweet electrode) (50°C). Then 10 ^-3 mol/
Add 100 ml of (NH ₄ ) ₂ IrCl ₆ aqueous solution and heat at 50℃.
Aged for 20 minutes. Next, while keeping the temperature and silver potential of the reaction solution at -40 mV at 50°C and stirring well, 1N of
375 ml of AgNO ₃ aqueous solution and 1N KBr aqueous solution were added over 20 minutes. Next, desalting was carried out by a flocculation method, and 90 g of gelatin was added to make the total volume 2000 ml, and the mixture was adjusted to pAg 8.0 and pH 6.5 at 50°C. In order to form fog nuclei on the surface of the emulsion grains prepared in this way, 2000 ml of the emulsion was kept at 50°C and stirred well, and 2 ml of a 10 ^-2 mol/methanol solution of SnCl ₂ 2H ₂ O was added to the 0.1 ml methanol solution. 12 _ml of a wt% aqueous solution of _HAuCl4.4H2O and a 1wt% aqueous solution of KSCN.
Added 20ml and aged for 60 minutes. Aliquot 50 ml of each of the above emulsions and add 0.1 of dye-1.
% dimethylformamide solution was added and coated onto the TAC film base. The emulsion film thickness was approximately 4 μm. The above coated emulsion was exposed to a 1 kW tungsten bulb (color temperature 2854 K) through a filter and continuous wedge for 100 seconds and treated with methol-ascorbic acid surface developer (MAA-
1) for 10 minutes at 20°C. The optical density of the developed film was measured with a Fuji self-recording densitometer, and the sensitivity value was expressed as the reciprocal of the exposure amount required to reduce the optical density by 0.2 compared to the unexposed area. The filters used in the experiment were Fuji Gelatin Filter SC52 for exposure in the absorption wavelength region of dyes, and
Fuji gelatin filter BPN42 was used for exposure in the absorption wavelength region of AgBr. The transmission spectra of these filters are shown in FIG. Table 1 shows the sensitivity values obtained in the above experiment.

[Table] As shown in Table 1, a direct reversal emulsion consisting of octahedral AgBr grains prefogged with Dye-1 was efficiently spectrally sensitized. Example 2 A direct inversion emulsion consisting of prefogged cubic AgBr grains (average grain size 0.5 μm) was prepared by the same experiment as in Example 1. However, the silver potential during the reaction was kept at +50mV vsSCE (50℃).
The amount of the aqueous solution of (NH ₄ ) ₂ IrCl ₆ added is 10 ^-3 mol/
The volume was 25ml. The sensitivity value obtained in the same experiment as in Example 1 was
Shown in the table.

[Table] As shown in Table 2, the direct reversal emulsion consisting of cubic AgBr grains prefogged with Dye-1 was efficiently spectrally sensitized. Example 3 Cube whose interior is pre-covered by:
A direct inversion emulsion consisting of AgBr grains (average grain size 0.5μ) was prepared. That is, add 30 g of inert gelatin and 7.5 ml of 25% ammonia water to 1000 ml of water, keep at 50°C and stir well, and add 1N of water.
375 ml of AgNO ₃ aqueous solution and 1N KBr aqueous solution were added over 20 minutes. During this time, the silver potential of the reaction solution was +50mV.
vs SCE (50°C). Then 10 ^-3 mol/
Add 30 _ml of methanol solution of _SnCl2.2H2O ;
Aged at 50°C for 30 minutes. Next, while keeping the temperature and potential of the reaction solution at 50°C and +50 mV, and stirring well,
375 ml of 1N _AgNO3 aqueous solution and 20 ml of 1N KBr aqueous solution
Added within minutes. Next, desalination was performed by a flocculation method, and 90 g of inert gelatin was added to bring the total volume to 2000 ml, and the mixture was adjusted to pAg 8.3 and pH 6.5 at 50°C. Take 50 ml of each of the above emulsions and extract the following compounds.
0.5 ml of a 0.11% methanol solution was added. compound a Then add a known amount of a 0.1% solution of dye-1 or -2 in dimethyl formamide and TAC
Coated on a film base. The coated emulsion was exposed in the same manner as in Example 1. The exposed film is
It was developed for 5 minutes at 20°C using the developer shown below. The optical density and sensitivity of the developed film were measured in Example 1.
It was done in the same way. Developer formulation Metol (monomethyl-p-aminophenol sulfate) 2.4g Hydroquinone 9.6g Anhydrous sodium sulfite 108.0g Anhydrous sodium carbonate 63.0g Potassium bromide 6.0g Potassium iodide 0.5g Add water to make 1 In the above experiment The sensitivity values obtained are shown in Table 3.

[Table] As shown in Table 3, dyes -1 and -2 were formed into 0.5μ cubes with pre-fogged interiors.
A direct inversion emulsion consisting of AgBr particles was efficiently spectrally sensitized. Example 4 Since the absorption wavelength, light absorption strength, adsorption strength, etc. of dyes differ depending on the target dye, a comparison of the spectral sensitization abilities of different dyes can be made using spectral sensitization as described below. A comparison was made using the relative quantum yield φr. The relative quantum yield (φr) is expressed by the following formula (1). φr (λ) = 400 x E ₄₀₀ x A ₄₀₀ / λ x E λ x A λ... (1) where λ: Maximum absorption wavelength of the spectral sensitizing dye (nm) A ₄₀₀ : Maximum absorption wavelength of the sample for light with a wavelength of 400 nm Absorption rate Aλ: Absorption rate of the sample for light with a wavelength of λnm E ₄₀₀ : Amount of light required to obtain an optical density value of "Dmax - 0.2" when performing sensitometry with light with a wavelength of 400nm Eλ: Wavelength of 400nm The amount of light required to obtain an optical density value of "Dmax - 0.2" when performing sensitometry with the light of
It was determined by equation (2) from the amount of transmitted light lt and the amount of reflected light Ir. A=1-lt/lo-lr/lo...(2) For details on how to measure φr, see W.West & B.H.
Carroll, “The Theory of the Photographic
"Process 4th Ed." Edited by TH James, Macmillan
Publishing Co., Inc., 1977, Chapter 10 (P255~
256). Therefore, a comparison of the spectral sensitization ability using φr was carried out between Dye-1 of the present invention and the following dyes using an emulsion similar to that shown in Example 1. Table 4 shows the measured values of φr.

[Table] As seen in Table 4, the dye-1 of the present invention
The relative quantum yield of spectral sensitization is higher than that of other similar structural dyes, and it is found that it is an excellent sensitizing dye for direct positive emulsions.

[Brief explanation of the drawing]

Figure 1 shows two types of filters used in Example 1.
The transmission spectra of BPN42 and SC52 are shown. The horizontal axis shows wavelength (μm), and the vertical axis shows transmittance (%).

Claims (1)

[Scope of Claims] 1. A silver halide photographic emulsion for direct positive use, characterized by containing a methine dye represented by the following general formula []. General formula [] Here, Z and Z' represent a group of nonmetallic atoms necessary to complete the heterocyclic nucleus, and n is 0, 1, or 2.
represents. R represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group. X represents an anion.