US3519428A - Direct-positive light-sensitive photographic material - Google Patents

Description

United States Patent 3,519,428 DIRECT-POSITIVE LIGHT-SENSITIVE PHOTOGRAPHIC MATERIAL Hidehiko Ishikawa and Mikio Sato, Odawara-shi, and Masaaki Yoshioka, Tokyo, Japan, assignors to Keulfel & Esser Company, Hoboken, N.J., a corporation of New Jersey No Drawing. Filed May 19, 1966, Ser. No. 551,245 Claims priority, application Japan, May 21, 1965, 40/ 29,553 Int. Cl. G03c N06 US. C]. 9695 3 Claims ABSTRACT OF THE DISCLOSURE Direct-positive photographic material developable by application of alkaline solutions is provided by incorporating a dihydroxybenzene developer compound in the light-sensitive composition as a finely dispersed solution in a substantially water-insoluble, alkali-soluble high boiling solvent.

This invention relates to a direct positive light-sensitive photographic material which is capable of yielding a stable positive image by rapid treatment utilizing Herschel effect or solarization. More specifically, this invention relates to a direct positive light-sensitive photographic material which comprises a support and a direct positive light-sensitive silver halide emulsion layer coated thereon, said emulsion layer being provided with fogging nuclei and comprising a dispersion of a developer solution in a protective colloid such as gelatine, said developer solution being prepared by dissolving a water-insoluble, alkali-soluble developer in a high boiling solvent.

The known direct positive light-sensitive silver halide photographic materials involve those in which fogging nuclei are previously imparted to the silver halide in its emulsion and those in which an accelerator such as Pinakryptol Yellow, Pinakryptol Green, Safranine, etc.; is also added to the emulsion to have increased reversing speed. All these autopositive photographic materials when exposed to light require a series of treatments, i.e. development with a developer containing hydroquinone or the like as principal ingredient, followed by fixation, rinsing and drying. These treatments are cumbersome and time-consuming, and they do not permit rapid and eflicient reproduction. Further, the liquid developer usually suffers from variation in concentration or decrease in developing ability during its use. This, as well as insufficient water-washing, may cause difiiculties in the continuous production of stable copies.

After our extensive studies, it has now been found that if a substantially water-insoluble, alkali-soluble and high boiling solvent-soluble developer dissolved in a substantially water-insoluble, alkali-soluble or -pervious high boiling sovent is dispersed in the protected state in a direct positive light-sensitive silver halide photographic emulsion layer previously provided with fogging nuclei, the photographic emulsion layer when exposed to light can rapidly yield a stable positive image only by development with an alkaline developer and subsequent stabilization treatment. Now the present invention will be explained in full detail hereinbelow:

A developer which is suitable in the present invention ice should be insoluble or hardy soluble in water and soluble in alkali and high boiling solvents. Typical developers may be as follows:

Methyl hydroquinone dimethyl ester Phenyl hydroquinone 2-hydroxyphenyl hydroquinone Phenoxyhydroquinone 2,S-dimethoxyhydroquinone 2,5-dibutoxyhydroquinone Tetrachlorohydroquinone Sec-butyl hydroquinone 2,5-dioctyl hydroquinone 2,5-diisopropyl hydroquinone Dodecyl hydroquinone p-tert. butyl catechol A high boiling solvent which is suitable in the present invention should be insoluble or hardly soluble in water and soluble in or previous to alkali. It should be acceptable in the photographic art. Typical high boiling solvents include the following:

Tri-o-cresyl phosphate Tri-p-cresyl phosphate Tri-phenyl phosphate Di-octyl phthalate Di-n-butyl phthalate Di-propyl phthalate Di-methyl phthalate Di-ethyl phthalate m-Dimethoxybenzene N-n-butyl acetanilide N-methyl-p-methyl acetanilide 2,4-dichlorobenzophenone Ethyl N,N-diphenyl carbamate Betahenyl propionic acid In accordance with the present invention, the aboveindicated developer is well dissolved in the indicated high boiling solvent and the resulted solution is added to a protective colloid solution (e.g. aqueous gelatine solution). The mixture is treated in a colloid mill or homogenizer to obtain a dispersion which is then dispersed in a direct positive light-sensitive silver halide photographic emulsion to which fogging nuclei have been previously imparted by a common optical or chemical method. Use of a colloid mill or homogenizer is preferred to dissolve the developer in the high boiling solvent. In this case, joint use of a low boiling solvent (e.g. ethyl acetate) with the high boiling one is acceptable to facilitate dissolution of the developer. The amount of a developer used may vary depending on the types of the developer as well as of the protective colloid and high boiling solvent, but will usually be within the range of 3-200 grams per kilogram of the emulsion. In order to improve the stability of the high boiling solvent emulsion, sometimes it is recommendable to add a surface active agent (e.g. saponine, alkyl naphthalene sulfonate, etc.) to the aqueous gelatine solution.

In the present invention, the above-prepared colloidal solution which contains the high-boiling solvent solution of the developer is added to a direct positive light-sensitive silver halide photographic emulsion with fogging nuclei and the resulting dispersion is coated onto a paper, film or the like support. In this manner the developer is kept in a perfectly blocked state with a high boiling solvent, without the possibility of direct contact with silver halide in emulsion, i.e. fogging nuclei formed on the silver halide crystals. Thus, there is no possibility in undesired development of silver halide around the fogging nuclei or decomposition of the fogging nuclei in the lower pH emulsion (acidic process emulsion). In the case of the direct positive light-sensitive emulsion used in solarization, the developer which does not come into contact with silver halide crystals has no part as halogen acceptor, with the insured occurrence of desirable reversal.

In order to obtain a positive image, from a direct positive light-sensitive silver halide material of the present invention, the said material should be exposed to either white light (in the case of solarization) or yellow light (in the case of Herschel effect). After the appropriate exposure, the resulting image is developed with an alkali bath mainly comprising sodium hydroxide or sodium carbonate and then fixed with a stabilizing bath mainly comprising ammonium rhodanate or thiourea. Without water-washing, a stable positive image can rapidly be obtained. Thus no problem arises as a result of imperfect water-washing. Further, the alkali bath used in development can be used continuously for a long period, because the bath does not contain a developer. Where it is intended to use the direct positive material according to the Herschel effect, the material may be handled, without any disadvantage, under white light.

EXAMPLE 1 The following solutions are prepared separately:

Solution 1:

Gelatine20 g. Citric acid0.4 g. Water-400 cc. Solution II:

Silver nitrate-40 g. Water400 cc. Solution III:

Sodium chloride-14 g. Potassium bromide-l2 g. Water90 cc. Solution IV:

Gelatine70 g. Potassium iodide0.2 g. Water300 cc.

To the Solution I, the Solution II is added at 50 C. With stirring, the Solution III is also added. The resulting mixture is ripened at 50 C. for 40 minutes, and then the Solution IV is added thereto. After 10 minutes, the resulted emulsion is adjusted at pH 8.8 by addition of an alkali. 5 cc. of 4% formalin is added thereto to effect fog formation on silver halide crystals. After allowing to stand at 50 C. for 15 minutes, the emulsion is new tralized with an acid to have a pH value of 6.0. 3,3',9- triethyl-oxa-carbocyanine iodide and Pinakryptol Yellow in the respective amounts of 1.5 mg. and mg. per 100 cc. of the emulsion are added. The resulted emulsion can be used as a light-sensitive silver halide emulsion (Herschel effect type) containing fogged silver halide crystals.

A solution obtained by dissolving 50 g. of 4-phenylcathecol into 100 g. of tricresyl phosphate is added with stirring to 400 cc. of an aqueous 10% gelative solution containing saponine. Thereafter, the resulting mixture is passed three times through a homogenizer to effect colloidal dispersion. 500 cc. of the colloid solution thus obtained is added to 1 kg. of the fogged silver chloride light-sensitive emulsion and then the total mixture is coated on a photographic paper and then dried, thereby to obtain a direct positive light-sensitive photographic material (Herschel effect type) according to the present invention.

In order to carry out the comparative tests, another Dlllfl! Just after After 48 hours coating at 50 C. and RH Ex. 1 material 1. 60 1.55 Control 1. 10 0. 15

The above data clearly indicates that a direct positive light-sensitive photographic material of the present invention is entirely safe from decomposition of fogging nuclei.

The direct positive light-sensitive photographic material obtained in this example is exposed to yellow light through a positive original. After the exposure, the said material is dipped for 2 seconds in an alkali bath containing 20 g. of sodium sulfite and 40 g. of sodium hydroxide per one liter of Water. After development, the material is dipped for 2 seconds in a stabilizing bath containing 200 g. of ammonium thiocyanate per liter of water, thereby to effect stabilization. A stable positive image is obtained.

EXAMPLE 2 A light-sensitive silver halide emulsion containing fogged silver halide crystals is prepared in the same manner as in the first paragraph of Example 1 with exception of addition of the Pinakryptol Yellow used in Example 1. Thus, the said emulsion is of the solarization type.

Separately, a solution obtained by dissolving 80 g. of methyl hydroquinone dimethyl ester in a mixture of cc. of dibutyl phthalate and 200 cc. of methyl acetate is added to 400 cc. of an aqueous 10% gelative solution containing saponine, with stirring. After completion of the addition, the mixture is passed three times through a colloid mill, thereby to effect well emulsification. Then, the resulted emulsion is heated at 80 C. to remove the methyl acetate therefrom. This emulsion is added to the above-prepared fogged silver halide emulsion (solarization type) at the proportion of 300 cc. of the former per kilogram of the latter. The resulting emulsion is coated on a photographic paper and then dried, thereby to obtain a direct positive light-sensitive photographic material according to the present invention.

In order to carry out the comparative tests, another photographic material (control) is prepared by adding a solution consisting of 200 cc. of methanol, 30 g. hydroquinone, 1 g. of sodium pyrosulfite and a sufficient amount of water to make total 200 cc., per one kilogram of the above-indicated fogged silver halide photographic emulsion and then coating the resulted emulsion on the surface of a photographic paper.

The maximum densities of 'both of these photographic materials are measured in the same manner as in Example 1. The results are set forth below.

The direct positive light-sensitive photographic material obtained in this example is exposed to white light through a positive original and then worked up in the 5 same manner as in Example 1. A stable positive image is obtained. In the same additional test as in Example 1, concerning the stability of the fogged emulsion, no adverse eifect is found.

The above examples have been presented for the purposes of illustration and should not be taken to limit the scope of the present invention. It will 'be apparent that the described examples are capable of many variations and modifications Which are likewise to be included Within the scope of the present invention as set forth in the appended claims.

What is claimed is:

1. Direct-positive photographic material comprising a support and a light-sensitive layer thereon comprising an autopositive silver halide emulsion having fogging nuclei, said emulsion having dispersed therein a silver halide developer dissolved in a substantially water-insoluble, alkalisoluble, high-boiling solvent.

2. Direct-positive photographic material comprising a support and a light-sensitive composition thereon comprising an intimate dispersion of:

(a) silver halide having fogging nuclei; and

(11) silver halide developer dissolved in a substantially Water-insoluble, alkali-soluble, high-boiling solvent.

3. Material according to claim 2 wherein said developer is a dihydroxy benzene compound.

References Cited UNITED STATES PATENTS 2,322,027 6/1943 Jelley et al 96-74 X R 2,352,014 6/1944 Rott 9629 2,852,381 9/1958 Minsk et al 96-100 3,146,102 8/1964 Weyerts et al 9676 3,212,889 10/1965 Kennard et a1. 9695 3,260,597 7/1966 Weyerts et a1. 9676 3,287,129 11/1966 Reese et a1. 9676 3,345,170 10/1967 Evans et a1. 9695 2,856,283 9/1958 Yackel et al. 9564 3,143,414 8/1964 Yackel et a1. 9564 FOREIGN PATENTS 796,873 6/1958 Great Britain.

GEORGE F. LESMES, Primary Examiner J. P. BRAMMER, Assistant Examiner U.S. Cl. X.R. 96101, 64