US3700682A - Certain pyridinium derivatives of cycloheptyl-imidazoles - Google Patents

Abstract

The present invention encompasses certain 2-aryl or 2-pyridinium cycloheptyl-imidazoles. These compounds may be prepared by reacting 2-halogeno-tropone or 2-methoxy-tropone with the appropriately substituted amidine. They are useful as desensitizers for light sensitive silver halide photographic materials.

Description

United States Patent Soma et al.

1451 Oct. 24, 1972 CERTAIN PYRIDINIUM DERIVATIVES OF CYCLOHEP'TYL-IMIDAZOLES Filed: March 13,1967

Appl. No; 622,475

Foreign Application Priority Data March 19, 1966 Japan ..41/17040 US. Cl. ..260/295.5, 260/296, 260/309,

96/62, 96/10], 260/2955 AM Int. Cl. ..C07d 31/44, G03c 5/32 Field of Search ..260/296 B, 296 C, 295.5 B, 260/2955 C, 295 B, 295 C, 295 AM References Cited OTHER PUBLICATIONS Sunagawa et al. Chem. Abstracts (I), Vol. 64, Par. 3551-g to 3552-a, (1966, January) Nakao et al. Chem. Abstracts (ll) Vol. 63, Par. 4227, Aug. 1965 Soma et al. Chem. Abstracts (111) Vol. 63, Par.

- 13142-13143. Nov. 1965 Primary Examiner-Henry R. Jiles Assistant Examiner-Alan L. Rotman Attorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT The present invention encompasses certain 2-aryl or 2-pyridinium cycloheptyl-imidazoles. These compounds may be prepared by reacting 2-halogenotropone or 2-methoxy-tropone' with the appropriately substituted amidine. They are useful as desensitizers for light sensitive silver halide photographic materials.

1 Claim, No Drawings CERTAIN PYRIDINIUM DERIVATIVES OF CYCIJOHEYIYL-IMIDAZOLES This invention relates to a desensitizer for a light-sensitive silver halide photographic material, said desensitizer having the chemical structure represented by the below-mentioned general fonnula (I). It is the principal object of the present invention to provide a desensitizer, which does not cause any staining or coloration of photographic pictures and which has no adverse influence on the contrast of photographed images.

Heretofore, a number of compounds have been known useful as desensitizers for light-sensitive silver halide photographic materials, which compounds include, for example phenosafranine, malachite green, pinacryptol yellow, pinacryptol green, etc. These known compounds, that is the desensitizers, suffer from several drawbacks and are not satisfactory in their actual use. For instance, some of these desensitizers will stain or color the photographic picture or will impair the photographic properties of the resulting image, because their being inherently colored substances. More concretely, phenosafranine which is a substance having red color usually causes reddish coloration of the photographic materials, sometimes with decrease in contrast of the photographed images. Marachite green and pinacryptol green, both of which are green compounds, will decrease whiteness of the background of photographic pictures. Furthermore, pinacryptol green sometimes has an adverse effect against stability of a fogged emulsion. Pinacryptol yellow, which is a generally preferred known desensitizer because of its raising no problem in contrast of photographic images, will cause yellowish coloration to decrease whiteness of the surface of photographic materials. Moreover, it has a serious drawback that is unstability in a developing solution. Thus, all the known desensitizers are not satisfactory because of their undesired influence on the photographic properties of the resulting images.

In accordance with the present invention, there is provided a new desensitizer having the following chemical structure:

g i R -R2 2 wherein R, is hydrogen, lower alkyhhalogen, cyano or dialkylamino and R is aryl or pyridinium group which may be substituted. v

The compounds defined above are available at rela- 5 'tively cheap costs. Almost all of these are colorless substances, and other few are such substances as having very slight color, insufficient to cause coloration. The compounds can meet the following photographic requirements:

1. They should have a capability to decrease photocrystals;

4. They should not contaminate binders (e.g.,

gelatine).or supports; and 5. They shouldbesolubleinwa'ter. It is, of course, possible to use the compounds in a developing solution.

A compound of the above general formula (I) wherein R is substituted. or unsubstituted aryl group can be prepared according to the method described in Japanese Patent Publication No. 20706/ 1965, that is, by the reaction of 2-halogenoor 2-methoxy-tropone of the general formula (wherein X is halogen or methoxy and R; is defined as 1 above) with an amidine of the general formula 40 (wherein R is defined as above). A compound of the .be optionally substituted with alkyl, halogen, nitro, al-

koxy, carbamoyl, alkoxycarbonyl, etc. Typical compounds comprehended by the present invention are as i llqfiufl M.p. 162 C 2-phenylcycloheptimidazole.

M.p.153 c.

2-pheny14-4bromocycloheptlmidazole.

M.p. 267 C. (decomp.)

2-(m-nitrophenyl)cycloheptimidazole.

' M.p. 204 C.

2-(p-bromophenyl)eycloheptimidazole.

These compounds can. be used as desensitizers for photographic purposes in the same manner as the conventionally known desensitizers for light-sensitive silver halide photographic materials. For example, an exposed high-speed photographic film can be pretreated with an aqueous solution of a desensitizer of the present invention so that said film may be developed under relatively bright condition which enables us to conduct developing with visual inspection of the progress of development. Alternatively, the desensitizer can be added to a developing solution to be used for photographic development, whereby an exposed photographic film can be treated with said solution under relatively bright condition because of its decreased sensitivity. Incorporation of the desensitizer into a light-sensitive silver halide photographic emulsion having fogged silver halide crystals can provide us with a direct positive, light-sensitive material which directly yields a positive image through Herschel effect or solarization.

If a desensitizer of the present invention is used as a pretreating bath for imagewise exposed, light-sensitive silver halide photographic materials, it is conveniently prepared in the form of an aqueous solution at a concentration of 0.01-0.03 percent. After dipping in this solution for several minutes, the photographic material can be treated with a conventional developing solution under relatively bright safelight. If the desensitizer is used in a developing solution, it should be in amount of 0.003 to 0.02 percent. By use of a desensitizer of the invention, the developing procedures can be taken under such bright safelight which allows us to make visual inspection of the result of the developed images. Of course, there is no problem of coloration of developed images or of, any damage on the contrast of the images.

For the preparation of a direct positive lightsensitive photographic material, a desensitizer of the invention is used in the amount of 0005-1 g. per 100 g. of silver nitrate the amount of which is calculated from the silver halide content of the light-sensitive emulsion used. The appropriate amount of the desensitizer is dissolved in water or lower alcohol or the mixture of both and the resulting solution is added to the light-sensitive emulsion containing fogged silver halide crystals. Usually it is preferred to combine the desensitizer solution with the fogged emulsion just before the coating of the resulting mixture on a support, but this is not critical. The thus prepared direct-positive light-sensitive material can show well improved Herschel effect, by which an image free from any coloration and with high contrast is obtained.

The following examples described certain ways in which the principle of the invention has been applied, but are not to be construed as limiting its scope.

EXAMPLE 1 2-(m-Nitrophenyl)-cycloheptimidazole was prepared as 0.02 percent aqueous solution, into which a commercially available, high-speed panchromatic photographic film was dipped for 2 minutes, thereby to have its original sensitivity decreased to 1/100. Thus,

Alternatively, 0.1 g. of 2-(m-nitrophenyl)-cycloheptimidazole was added to a developing solution of the following formulation:

Monomethyl-p-aminophenol sulfate 2.0 g. Sodium sulfite (anhydrous) 80.0 g. l-lydroquinone 4.0 g. Borax 4.0 g.

Potassium bromide 0.5 g.

; Distilled water to make up 1000 ml.

By using the resulting mixture, a commercially available high-speed panchromatic photographic film was treated. 'The procedures could be made under relatively bright safelight condition, without causing any coloration or contamination.

. EXAMPLE 2 5 of an aqueous solution of 10 percent citric acid. The

emulsion was divided to ten portions, each of which was added with the compound indicated in Table l. The respective portions were coated on photographic papers and then dried. The thus prepared direct positive, light-sensitive photographic sheets were subjected to stepwise exposure to light through a yellow filter which can pass a light of a wave length longer than 450mg. and then treated with a D-72 type developer.

5 The sensitometric results obtained are set forth below:

the treated film could be subjected to development under relatively bright safelight. After the development, the films did not show any coloration or contamination.

Pinacryptol yellow and phenosafranine were used as the control desensitizers.

This was expressed as a specific value in compared with the reversal photographic speed of the pinacryptol yellow-loaded photographic sheet, which is rated as l00.

As apparent from the above table, the sheets in which the desensitizers of this invention were used were excellent in photographic speed andcontrast, whereas the control sheets loaded with pinacryptol yellow and phenosafranine suffered respectively from yellowish or reddish coloration.

EXAMPLE 3 One kilogram of a pure silver chloroiodide emulsion containing the equivalent to 40 g. of silver nitrate was bufiered to pH 7.5 by the addition of of 5 per cent aqueous sodium carbonate solution. Then, the emulsion was added with 10 ml. of 3 percent formalin and heated at 55 C. for 40 minutes. The thus fogged emulsion was buffered to pH 6.0 by the addition of an aqueous solution of 10 percent citric acid. The emulsion was divided to 10 portions, each of which was added with the compound indicated in Table 2. The respective portions were coated on photographic papers and then dried. The thus prepared ten direct positive, light-sensitive photographic sheets were subjected to stepwise exposure to white light and then treated with a developing solution. The sensitometric results obtained are below:

w what we claim are: H W W l. A compound of the formula;

Compds. (10) 20 mg 1120 3.74 0.0l Compds. (l l) 20 mg I050 3.62 0.02 Compds. (16) 20 mg 1090 3.69 0.01

which the desensitizers of the invention were used were more excellent in reversal minimum density and contrast, whereas the control sheets suffered from coloration of their surfaces.

wherein R is hydrogen or 6-positioned dimethylamino