US2476240A - Manufacture of photographic film base - Google Patents

Description

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Patented July 12, 1949 MANUACTURE 0F PHGTOGRAPHIC FILM BASE Keith Fainulener, Binghamton, N. Y., assigner to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware Application September 17, 1943, Serial No. 502,757

(Cl. 11th-34) il llaiins. 1

This invention relates to a method of manufacturing sheets or foils and is particularly concerned with the production of photographic films.

in the manufacture of photographic films, the film has a tendency to generate static electricity, during the manufacture of the film base and the subsequent coating and handling operations to which the film is subjected during the course of manufacture. ilille discharge of these static charges after a photosensitive layer or coating has been applied to the film base will cause typical static markings on the photographic emulsion, and these become visible upon development. Many treatments have heretofore been suggested for preventing or minimizing such static markings. Many of these known anti-static treating processes consist of applying to the film a special layer containing an agent which will impart anti-static properties to the nlm. However, it is frequently diicult to so arrange the various coating steps that this anti-static layer will be applied before any of the photosensitive emulsion layers are applied to the film. It also frequently happens that such anti-static layers cannot be conveniently applied to the film prior to a photosensitive emulsion due to difficulties in attaining proper adhesion between the anti-static layer and the photographic emulsion. Unless such an anti-static layer is applied to the film before any photosensitive layer is applied, static electricity may accumulate on the film and be discharged therefrom during the handling of the film and thus cause static markings in the photosensitive layer or layers.

It has heretofore been suggested that photographic lms whose base is a cellulose ester such as cellulose acetate or nitrate may have antistatic properties imparted thereto by saponifying one or both sides of the foil of cellulose ester by treatment with a strong alkali metal hydroxide for a substantial period of time until the surface of cellulose ester is saponifled. While such treatment renders the foil or nlm of cellulose esters anti-static it is objectionable since it is difficult to obtain good adhesion between such saponiiled surfaces of the cellulose ester and the usual gelatin emulsions which are applied thereto. llt should also be noted that this type of treatment is necessarily limited to lnis having as abase some cellulose derivative.

It is therefore an object of the present invention to provide a method of treating foils or lms destined for use as photographic films which Will impart anti-static properties to the film during its course of manufacture and before any photosensitive layer is applied thereto. A further object is to provide such a method which is compatible with the conventional steps employed in manufacturing photographic lms and which does not necessitate any substantial modification of either the manufacturing procedure or the finished film. Other and further objects vill be apparent as the description progres-ses.

have discovered that if a gelatin dispersion in organic solvents of the type commonly employed as a subbing layer on photographic films is iirst applied to the usual cellulose acetate or cellulose nitrate fllm base and this subbing layer is than Washed with a weak Solution of alkali metal hydroxide in a suitable solvent such as methanol, static electricity will not be generated on the g lotographic film during its manufacture or handling in the course of manufacture` have also discovered that the washing of the gelatin subbing layer with weak alkali is not detrimental to the adhesion of the other layers commonly applied to the photographic film such as the photosensitive emulsion layer, anti-halation layers, nlter layers and the like.

.in order to more fully describe my invention, there is attached hereto and made a part of the specification a sheet of drawings in which Fig. I is a diagrammatic representation of a photographic lm manufactured in accordance with the present invention, While Fig. II is a diagrammatic representation of apparatus suitable for applying an alkaline Wash to the film.

Referring to the drawings, i designates the nlm base which may be a foil or film of a suitable cellulose ester such as cellulose acetate or cellulose nitrate. This film base l is coated on both with gelatin subbing layers 2 and 2' which .re applied in the usual manner. After the gelsubbing layer has been applied and dried is washed with a solution of from 0.05 to 0.5 .'llrali metal hydroxide dissolved in a suitable solvent, preferably an organic solvent such as methanol and is then dried. The alkaline wash may be applied to the nlm in any manner customarily employed to apply layers of materials or ls-'ashes to photographic films, such as with the use of rollers, brushes, dipping the film in a bath of a suitable wash or floating it on the sur-- face of the wash. For the sake of completeness of description there is shown diagrammatically a preferred manner of applying the wash to the nlm. As there illustrated the web of nlm base l having the layers of gelatin sobbing solution 2 and 2" on each .side thereof and traveling in the direction shown by the arrow is led over roller A so that the gelatin subbing layer 2 barely touches the surface of a bath B of alkali dissolved in a suitable solvent which is contained in tank C s that a bead of the alkali wash is struck across the face of the film base and the gelatin subbing layer 2 is wetted by the alkali wash. The alkali wash thus applied to the gelatin subbing layer is then permitted to dry thereon. While in the method of applying the alkali wash to the gelatin subbing layer described above, the film is in contact with the wash only momentarily and may require about two minutes to dry, it appears that a somewhat longer time of Contact and a shorter or longer drying time would exert no detrimental effect. It should be understood that other methods may be employed for applying the alkali wash to the film; thus the film may be immersed in the dilute alkali bath or rollers andv brushes and the like may be employed in known manner for applying the wash. Potassium hydroxide appears to be the most effective alkali, although all the alkali metal hydroxides, lithium, sodium, potassium, rubidium and cesium hydroxide are operative. These are preferably applied in solution in an organic solvent, such as methanol, ethanol, the like or mixtures of the same with each other or other organic solvents such as acetone, since the most effective protection is obtained when they are so applied. However, if desired they may be applied in solution in an inorganic solvent such as water, but due to the tendency of water to leave marks on the film, I prefer to avoid its use. I preferably include in the alkali wash a spreading agent such as butyl Cellosolve in order to promote contact between the alkali wash and the gelatin layer. I may also use the alkali metal carbonatos and phosphates, or if desired I may employ ammonia vapor or ammonium hydroxide. However, since the alkali metal carbonates and phosphates are only slightly soluble in most organic solvents their use in the preferred method of practicing this inventionvis prevented.

rIhere are then applied to the lm in the usual manner the photosensitive emulsion layers 3 and 3 and thereafter clear` gelatin anti-abrasion layers l and il may be applied in the usual manner.

It should be understood the film illustrated in the drawing is illustrative only of a form 0f lin produced in accordance with the present invention and many modifications may be made therein. Thus it is possible to obtain suitable antistaticproperties of lm during the course of its manufacture by applying the alkali Wash to only one of the gelatin subbing layers 2 and 2. It should also be understood that while the type of film illustrated in the drawings is a diagrammatic illustration of a typical X-ray film, the present invention is applicable to films which are coated with a photosensitive emulsion on only one side. It should further be understood that several photosensitive emulsion layers may be applied to one side of the film as is customary in the so-called monopack or integral tripack color films. In such case suitable anti-static properties are imparted to lm by applying an alkali wash to the gelatin subbing layer nearest the lm base. It is not necessary to wash with alkali all the gelatin layers commonly applied to the film, although such washing generally exerts no detrimental effect. It should also be understood that the gelatin subbing layers may contain dyes to impart a particular color thereto, for instance, as is customary in the manufacture of X-ray lm, or dye may be incorporated in the gelatin subbng layer in order to have this layer serve the function of a filter layer or in certain cases as an anti-halation layer. However, since most dyes employed for this latter purpose are destroyed by alkalies, it is generally preferable to avoid applying an alkali wash to gelatin layers containing such dyes. Various other modications may be apparent to those skilled in the art.

The following specific example serves to illustrate the present invention. A cellulose acetate nlm base was coated on both sides with a gelatin subbing solution having the following general formula:

After this subbing solution was dried a wash consisting of 0.2% potassium hydroxide dissolved in methanol was applied and the washed film was then dried. A conventional photosensitive gelatino silver halide emulsion 3 was then applied to the subbing layer 2 and subsequently a photosensitive emulsion layer 3 was applied to ie subbing layer 2. Conventional clear gelatin anti-abrasion layers t and 4 were then applied to photosensitive layers 3 and 3 respectively in the known manner and the finished film was then dried. It was found that the film manufactured in this manner exhibited no static markings on development. Whereas a film manufactured on the same apparatus and under the same conditions, except that the alkali wash of the gelatin layer was omitted, contained numerous static markings.

While the present invention has been described as applied to the manufacture of photographic nlms having a cellulose ester base, it should be understood that it is applicable generally to photographic films whose base is an electriable highly polymeric colloid, such as foils of ethyl cellulose and other cellulose ethers, polyvinyl chloride, synthetic and natural resins, casein derivatives and the like, which have been sugm gested as suitable for use as photographic films.

Where in the appended claims the term alkali metal hydroxide is employed, it should be understood that I intend to include as an equivalent thereof an ammonium hydroxide. The term alkali as employed in the claims refers to the alkali metal hydroxides and ammonium, and also the recognized equivalents are the same, such as the alkali metal carbonatos and phosphates. I do not intend, however, to include the alkaline earth metal hydroxides, carbonatos, phosphates and the like in the term alkali I claim:

1. In the manufacture of photographic films wherein a light sensitive emulsion is coated on a base comprising a foil of an electriable organic film-forming material, the method of minimizing static markings on said light sensitive emulsion due to the accumulation `thereon of static electricity and the discharge thereof, which comprises, applying to said foil, a gelatin subbing layer, wetting for about two minutes the thus applied gelatin layer with a dilute solution containing 0.05 to .5% of an alkali, and applying to said foil a layer of a light sensitive emulsion.

2. In the manufacture of photographic films wherein a light sensitive emulsion is coated on a base comprising a foil 0f an electriable organic film-forming material, the method of minimizing static markings on said light sensitive emulsion due to the accumulation thereon of static elec tricity and the discharge thereof, which comprises applying to said foil, a gelatin sulobing layer, wetting for about -tWo minutes the thus applied gelatin layer with a dilute solution containing 0.05 to .5% of an alkali metal hydroxide, and applying to said foil a layer of a light sensitive emulsion.

3. The method dened in claim 2 in which the alkali metal hydroxide is potassium hydroxide.

4. The method dened in claim 2 in which the alkali metal hydroxide is sodium hydroxide.

5. The method defined in claim 2 in which the gelatin dispersion is washed with a dilute solution of an alkali metal hydroxide dissolved in an organic solvent therefor.

6. The method dened in claim 2 in which the gelatin dispersion is washed with a dilute solution of potassium hydroxide dissolved in methanol.

7. The method dened in claim 2 in which the gelatin dispersion is washed with a dilute solution of sodium hydroxide dissolved in methanol.

8. The method dened in claim 2 in which the gelatin dispersion is washed with a dilute solution of an alkali metal hydroxide in an organic solvent therefor containing a minor amount of a spreading agent.

9. In the manufacture of photographic lms wherein a light sensitive emulsion is coated on a base comprising a foil of a cellulose derivative,

the method of minimizing static markings on said light sensitive emulsion due to the accumulation thereon of static electricity and the discharge thereof, which comprises applying to said foil a gelatin subbing layer, wetting for about two minutes the thus applied gelatin layer with a dilute solution of an alkali metal hydroxide containing from 0.05% to 0.5% alkali and applying to said foil a layer of a light sensitive emulsion.

10. The method defined in claim 9 wherein the cellulose derivative is a cellulose ester.

11. The method as dened in claim 9 wherein the cellulose derivative is a cellulose ester and the dilute solution of an alkali metal hydroxide is a 0.05% to 0.5% solution of an alkali metal hydroxide in a lower aliphatic alcohol,

KEITH FAMULENER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 723,054 Smalley Mar. 17, 1903 1,680,635 Renwick Aug. 14, 1928 1,683,315 Stincheld Sept. 4, 1928 1,801,375 Stock Apr, 21, 1931 1,954,512 Allison Apr. 10, 1934 2,054,284 Forstmann Sept. 15, 1936 2,110,496 Babcock Mar. 8, 1938 2,117,814 Nadeau May 17, 1938

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