US1769940A - Manufacture of light-sensitive films - Google Patents

Description

Patented Jul 8, 1930 UNITED STATES ULRICH DIEM-BERNET, 01 SPEIGHER, SWITZERLAND mannracrunn or uen'r-snnsrrrvn runs No'Drawing. Application-filed 1m} 17, 1927, Serial 1%. 192,168, and in Switzerland and Germany It is known to produce a light sensitive film having no sensitive co ting from cellulosesodium-xanthate (viscose) and; having the. sensitiz'er within the film'material. Such 5 known film is prepared like the sensitive salt papers by, treating finished films hitherto mainly used as a transparent packing ma- 7 terial, in one or more baths of water containing solutions of sensitiz'ers and impregnating 10 them thus with light sensitive materials. In each of these baths the film swells and extends in every direction and subsequently contracts during the drying operation, whereby .the original dimensions are only reached under the most favorable circumstances. The divergence from the original size is the greater,

the larger the number of baths through which the film has to be passed.

This is a disadvantage which renders such films unsuitable for certaln photographic pure poses and particularly for the cinematographic'art.

The present process has for its object to produce from viscose light sensitive negative and dia-positive films which have no sensitive coating but are sensitized within the body of the film and which are subjected to much less variations in tension than the impregnated film having no coating and produced by the hitherto known processes. In ,-.c ontradistinction to the known process-am. hich has been;

cording to which the film, manufactured (i. e., cast, coagulated, washed and dried) ready for sale without additions of sensitizers, is impregnated with sensitizing materials 'later on, the novel process com sists in sensitizing the film mass already during the manufacture i'. e., at least before the ultimate and complete drying of the film, 40 while the latter is still moist and therefore in its swollen condition. This is effected in that either all the sensitizing agents on at least one of the components used for sensi-v tizing purposes is incorporated in the film mass, for example after a purification bath with which the cast but not yet finished film is treated, preferably after the last purifi-.;

cation or washing bath. Preferably, simultaneously or in a subsequent step of the process, by the addition of tanning substances,

a further reducton of the susceptibility towards water and eventually of the inflammability of the film mass may be obtained.

In producing such a light sensitive film from viscose and which has no sensitive coatmg the present process In be carried into effect by imbuing the film, or example after a purifying bath with for instance a ferric salt solution (ammonium-ferric-citrate). The sensitizing of the film mass with a silver on halidmay be effected b v first adding to the film the halogen source for instance sodium-' chloride, ammonium bromide), whereupon the film charged with this component is either directly or after superficial drying impreg- 65 nated with a silver solution for instance with silver nitrate in order to cause the formation of silver halid. A tanning of the film mass may be caused either durin ijthe casting of the film ima bath containing or lnstance alum, or ammonium salts, or it is caused subsequently to the castvmg of the film by smoking the sensitized film,

for instance in formaldehyde vapours.

The light sensitive film without a coating manufactured in the above manner gives a more perfect saturation of the film mass than the hitherto know n impregnating process.

Moreover the improved process permits in a better manner than heretofore to influence so important mechanical qualities of the film such as hardness, flexibility and the like further the infiammability of the finishe product as well as to obtain the necessary esterility and'purity of the film mass'required for special photographic purposes.

It is a particular object of the present proc-3 ess to produce .a completely transparent light sensitive cellulose film having no coating which even inthe sensitized state is transparent like glass and which presents a considerable technical progress for thegsbecial purposes ,of making reflex copies. (Player type). The hitherto known processes are limited to soaked hygroscopic cellulose films in the manner of salt papers or to impregnation by means ofbaths containing silver compounds to cause the formation of silver chlorid or silver bromide within the body' of, the-film whereby a certain sensitivity but not for the purposes of the reflex copy.

The more or less pronounced dullness and cloudiness of the hitherto known films made of hygroscopic cellulose by soaking them in solutions of silver salts are due to the insuflicient penetration of the sensitizing solutions 1. A process for producing light-sensitiveinto the interior of the film and by the precipitation ofsilver salts in zones in which ,unevenly swollen layers contact, further they are due to precipitation effects between silver and chlorine of a smaller degree of dispersion as well as to such exceeding the optimum of the concentrationin silver. The manufacture of sensitized filmsv that are asclear as glass is made according to the present.

process in the following manner: After the film mass has been completely penetrated by a suitable chlorine compound, for instance 4% sodium chloride solution, the impregnation with the solution of silver salt for instance with a 10%. solution of silver nitrate, is only then caused directly, if the chlorinated film mass is still as clear as glass after drying and if it does not opalize. The impregnation with silver salts shall further only last as along as no formation of larger agglomerations occurs. If the film mass looks dull in any way after the chlorination a longer or shorter water bath has to be arrangedbefore the impregnation with the solution of silver, this bath has also to be used if a stronger solution of silver salt has to be applied.

I The manufacture of the sensitized films, which are as clear as glass, involves a great technical progress and is of the utmost importance for making reflex copies. The use of these novel copying films presents also a great advantage in producing completely transparent and at the same time true to scale copies and d'iapositive s, as such sensitive films which have nocoating and are as transparent asglass permit a simpler and quicker treatment in the developing and fixing process and thereforethey are less subject to the swelling influence of water.

I claim:

. negative andpositive films having no coating, which consists in incorporating sensitizing agents in the film mass of viscose during the manufacture of the film material.

2. A process for producing light-sensitive I negative and positive films having no coat ing, which consists in 1ncorporating'sensitizing agents in a film mass of viscose immediately after the coagulation of the film material and before final drying.

3. A process for producing light-sensitive negative and positive films having no coating, which consists in incorporating sensitizing-agents in a film mass of viscose immediately after the coagulation and the washing of the film material andbefore completion of the film by drying.

4. A process for producing light-sensitive negative and positive films having no coating, which consists in incorporating at least one component of the sensitizer in a film mass of' viscose during the manufacture of the 21m material and before final drying of the 5. A process for producing light-sensitive negative and positive films having no coating, which consists in incorporating a silver salt in a film mass of viscose during the manufacture of the film material.

6. A-process for producing light-sensitive negative andpositive films having no coating, which consists in incorporating atleast one component of the sensitizer in a film mass of viscose during the manufacture of the film material, the concentration of the sensitizer and the manner of incorporation being so chosen that the film mass remains perfectly transparent. v

' 7 A process for producing light-sensitive negative and diapositive cellulosic films from viscose, having no coating, and having the sensitizer incorporated withinthe body of the film, which consists in incorporating sensitizing agents in the film mass during the manufacture of the film while the "latter is .still in its swelled condition and before it is ultimately dried.

8. A process for producing light-sensitive negative and diapositive cellulosic films from viscose, having no coating, which consists in incorporating at least one component of the sensitizer in the film mass during the manufacture of the film while the latter is still in its swelled condition before it is ultimately. dried.

9. A'. process for producing light-sensitive negative and diapositive cellulosic films from viscose, having no coating, which consists in incorporating at least one component of the sensitizer in thefilm mass during the manu-i facture of the film, the concentration of the sensitizer and the manner of incorporation being so chosen that the film mass remainsperfectly transparent.

' 10. A process for producing light-sensitive negative and diapositive cellulosic films from viscose, havingno coating, and having thev sensitizer incorporated within the body of the film, substantially as described.

11; A process for producing viscose photographic films having no coating, which comprises introducing into the film during its manufacture and while in a swollen condition, a sensitizing agent, the film being hardened by a hardening agent.

12, A glass-clear grain-freeviscose photographic film, sensitized in its body and substantially free from subsequent alteration upon development and spots due to opalescence and uneven charging of sensitizer resulting from uneven swelling of the film.

In testimony whereof, I have signed my name to this specification. I

ULRICH DIEM-BERNET.