US3078163A

US3078163A - Spot prevention in light-sensitive silver halide emulsion layers

Info

Publication number: US3078163A
Application number: US72300A
Authority: US
Inventors: Willems Jozef Frans; Sevens Gerard Michiel
Original assignee: Gevaert Photo Producten NV
Current assignee: Gevaert Photo Producten NV
Priority date: 1959-12-02
Filing date: 1960-11-29
Publication date: 1963-02-19
Anticipated expiration: 1980-02-19
Also published as: GB948443A; DE1124353B

Description

United States PatentOfifice 3,078,163 Patented Feb. 19, 1963 graphic layer.

SPOT PREVENIION IN LIGHT-SENSITIVE SILVER HALIDE EIViULSIQI J LAYERS "JozefFrans'Willemsand GerardMichiei Sevens, Wiiriilr- Antwerp; Bel'gium, assign'ors to' GevaertPhoto-Produc- -ten N.V., Mouser-Antwerp, Belgium, a Belgian com- P l 'i'NoiDi-awing. '"Filed Nov. 29,1960; Ser. No. 72,300 Claims rpriority, application" Belgium Dec. 2, 195% 4 Claims. (:96-67) This invention relates to a method for preventing the formation of small spots caused by the presence of heavy -metals and/ or their compounds. in iphotographic silver halide emulsions.

-Duringrcasting=and further proce'ssing of" photographic i-m-aterial, great difiiculties sometimes: arisenthe causes of which are not alwaysk-nown. r Oneof the maindifficulties is the'dustwhi'ch during the-whole cycle of the preparation can set down onto the photographic element.

Sincedrying the cast photographic layers requires quite a lot of air-and-since without special precautions this air is pollutedbydust'particlea-itis evidentithat much dust sets down onto-the still moist and stickycoated' photo- This evil canpractically completely be remedied by thoroughly filtratingthedrying air so that practically all dust'particles are removed. The drying air, however, is not the only cause of dust. Also the coating machines, the transport machines and the whole manu- =As a mat-ter of fact, even if precautions are taken in all-manufacturing steps in order to reduce dust'forma- -tion to'an absolute-minimum, this does not prevent the settling of minimal traces of dust onto the manufactured material.

The dust itself-has a very complex composition. The most occurring elements are vegetable and animal fibres .suchas paper dustand textile fibres, further soot, sand, ,insects, rustand fine metalparticles. elements do not cause a chemical reaction'on'the photographic emulsion and the particles whichnotwithstand- Some of these ing the extremely careful precautions mightset down onto the light-sensitive silverhalide-emulsion, are so sm-alland in solimited a number that they do-not-cause any visible faults in the finished photographic material.

More harm is done, however, by the chemically active substance which by its secondary reaction with the emulsion enlarges the caused. faults, not visible to the naked eye, and which according to-the nature of the dust and 'theemulsion occasions during processing the exposed material the'appearance of small light and .darlcspots. Chernically reactive dust is mainly composed of metal particles or metal compounds among others metal oxides, especially of heavy metals such as'iron, copper, tin, lead, chromium and nickel. These metal particles or metal compounds mainly originate from the construction material of the coating machinery and the working up machines.

Sometimes, however, the-used photochemicals contain traces of these metals or'of metal compounds, whilst they can also further be present in the used supports such as paper, film and glass on which the light-sensitive emulsions are coated.

' The metal particles can be affected more or less slowly in the photographic layersand the formed corrosion products:can .difiuse away from the central nucleus.

These corrosion products can exert either a sensitizing or a desensitizing action on the emulsion so that after normal bath treatment of the photographic element a black spot or a white spot respectively, is formed.

Further, most ofthese metals or their compounds can have a reducing effect and cause a spontaneous development which leads to small black spots. Other influences such as affection of the latent image and hindrance of development lead in their turn to small white spots. In all these cases, the formed small spot is always much larger than the dust particle' which is the cause of this undesirable phenomenon. This can easily be checked for instance by bleaching out--thesilver with a usual oxidation meansin the:materialshowing'ablack spot. The black spots mostly disappear but in the central part remains a very small nucleus which is only visible on enlargement.

Also fine metal particles ordust particles consisting of metal compounds which are present in a non-light-sensi tive but adjacent layer, exerts a practically same disadvantageous eifect on the superposed or subjacent light sensitive layer. The harmful "corrosion products of the metal particles or the dissolved elements of the metal compounds can indeed-reachdnto the light-sensitive layer by diitusiontand cause therein the above mentioned faults.

Wow we have found that the formation of spots in photographic images canbe avoided by adding to one or more layers which are used for the composition of the photographic material compounds according to one of the general formulae ",RyandzR eachrrepresents a member selectedfrom the R represents a member selected' fromthegroupconsist- ,ing of'a'hydrogen'atom, aphenyl group and a p-carboxy phenyl group, and "Rgrepresents. a member selected fromthe group consisting ofwa hydrogen atom and an alkyL group.

Hereinafter follow some examples. 'of suitable com- -pounds:

CHzOH-C O-GH:

Hydroxyactone .CHzOH--CO-CH2OH .Diliydroxyacetone HO CH='GOH-OHO Triosereductone Hail-+0 O.CHC O 0 02110 C O CH;

a-JAeetoxyacetyl acetic acid ethyl ester 'HO 0 0-0 OH=C OH0.0 0H

Dihydroxymaleic acid HaCOO-'-CHOH-'GH .3-113 droxy-Z-butanone (or aeetoin) H7C3'COCHOH.O3H7 5-hydroxy-4-octanone (orhutyroin) OsH -CO-OHiOH w Hydroxyacetophenone l N ll N HO HOH;, 1-phenyl-3-methyl-4,5-dihydroxypyrazole COOH l HOJN\N slats,

1-(p-carboxyphenyl)-3-methyl-4,5-dihydroxypyrazole 3 nojl N H CH3 3-methyl-4,5-dihydroxypyrazole The compounds according to the present invention can be added in different amounts to the emulsions according to the compounds chosen, the nature of the colloid binding agent for the silver halide grains and the amount and the nature of the silver halide used. Amounts of 0.5 to 2.5 g. per 10 g. of silver metal present in the emulsion as silver halide are preferably used although larger amounts may be added in case it might become necessary. They can, moreover, successfully be added to other layers than the light-sensitive layers such as for instance to a protective layer, an intermediate layer or a barytacoating.

Evidently, the method according to the present invention can be applied for the manufacture of photographic light-sensitive film as Well as of photographic paper.

The use of these compounds for counteracting the formation of spots in photographic images has the advantage of not being accompanied by any harmful secondary effect. On the contrary, some of these compounds when added to a silver chloro-bromide emulsion, increase to some extent the general light-sensitivity of this emulsion without noxious influence on the photographic properties pursued, such as for instance fog and stability.

A further advantage is that the compounds according to the present invention are well compatible with the other emulsion additives such as for instance dispersing agents, color couplers, surface-active compounds, optical bleaching agents, anti-oxidizing agents, sensitizers, antifogging agents, stabilizers, hardeners or plasticizers, etc.

The present invention is illustrated by the following examples without limiting, however, the scope thereof.

Example 1 Part of a flowable silver chloro-bromide emulsion with pH 4.5 (about 20% of silver bromide) for being applied to paper base is coated onto a strip of baryta-coated paper soiled with metal dust (test strip A); to another part of this emulsion 20 cm. of a 5% alcoholic solution of alphaacetoxy-acetyl acetic acid ester are added per kg. of emulsion and this second part of emulsion is coated onto a second strip of the same baryta-coated paper (test strip B); to a third part of this emulsion 20 cm. of a 5% alcoholic solution of triosereductone are added per kg. of emulsion whereafter also this third emulsion part is coated onto a third strip of the same baryta-coated paper (test strip C).

These three test strips are dried and exposed in such a way that after development a density of 0.6 is attained. After development, it appears that test strip A shows numerous small black spots having a density which is considerably higher than 0.6. This is not the case for the test strips B and C. Moreover, an increase of sensitivity of 20% has been observed on test strip C, without further influence on the gradation and other photographic characteristics.

Example 2 Part of a warm-tone silver chlorobromide emulsion with pH 4.7 (about 30% of silver bromide) for being applied onto paper base is coated onto a strip of barytacoated paper soiled with metal dust (test strip A); part of this material is provided with an antistress layer mainly composed of gelatin. To the usual coating composition from which this antistress layer is coated 2S cm. of a 5% alcoholic solution of 3-methyl-4,S-dihydroxypyrazole were added per litre (test strip B); another part of this paper is likewise coated with the same antistress layer not containing however 3-methyl-4,5-dihydroxypyrazole (test strip C). After exposure and development to low densit the test strip B does not show black spots, whereas the test strips A and C show many small black spots.

Example 3 A strip of a paper support with metal dust is provided with a gelatin precoat containing an antihalation sub stance (test strip A); to a second strip of the same paper support likewise soiled with metal dust a gelatin precoat is applied from a coating solution which, however, besides the same antihalation substance as in strip A, 40 cm. of a 5% alcoholic solution of 1-phenyl-3-methyl-4,5-dihydroxypyrazole were added per 1 litre of coating solution (test strip B); to a third strip of the same paper support a gelatin precoat is applied from a coating solution to which, however, besides the same antihalation substance as in strip A, 20 cm. of a 5% alcoholic solution of l-pcarboxyphenyl-3methyl-4,5 dihydroxypyrazole per litre of coating solution were added.

On the precoat of each test strip is coated the same silver-chloride emulsion with pH 5', suitable for the preparation of aluminum offset sheets such as described in the U.S. patent application Serial No. 846,256, filed October 14, 1959.

Contrary to test strip A, the test strips B and C after exposure and development show a homogeneous density without black spots.

We claim:

1. A photographic material comprising a support and at least one layer superposed thereon, one such layer being a light-sensitive silver halide emulsion layer, said material being characterized in that at least one of the layers thereof contains a compound having a formula selected from the group consisting of:

HOj no I la.

wherein carbethoxy group, a phenyl group and a furyl group; R represents a member selected from the group consisting of a hydrogen atom and an acetyl group, and R represents a member selected from the group consisting of a hydrogen atom, a phenyl group and a p-carboxy phenyl group, whereby the formation in said emulsion layer spots caused by dust such as metallic particles and the like is substantially in hibited. 2. A photographic material having a light-sensitive silver halide emulsion layer containing alpha-acetoxyacetyl acetic acid ethyl ester.

3. A photographic material having a light-sensitive silver halide emulsion layer and an antistress layer containing 3methyl-4,S-dihydroxypyrazole.

4. A photographic material having a light-sensitive silver halide emulsion layer and a gelatin precoat containing 1 (p-carboxyphenyl)-3-methyl4,5-dihydroxypyrazole.

References Cited in the file of this patent UNITED STATES PATENTS 2,346,095 Weissberger et a1 Apr. 4, 1944