US1936525A - Process of manufacturing photosensitive bodies - Google Patents

Description

Patented Nov. 21, 1933 e e PROCESS OF MANUFACTURING PHOTOSEN- SITIVE BODIES Carl Roehrich, Berlin, Germany, assignor to the firm Silfree Aktienge'sellschaft (Silfree Limited) ,Vaduz, Lichtenstein No Drawing. Application January 9, 1929, Serial 'No. 331,384, and in Germany January 21,

7 Claims. (Cl. 957) The present invention concerns an improved centage of salts in the solution, used for the immethod of manufacturing sensitive plates, films pregnation, the more sediment accrues. and the like. The appearance of these sediments decreases It has been hitherto known to manufacture considerably the usefulness of the plates or s'sensitive plates, films and the like, by'coating films. Firstly, the colloid-layer being non-uni- 60 a support, consisting of glass, celluloid or any iorrnly sensitized, the light must act more Weakly other transparent material or of thin metal foils, on the Weaker sensitized parts of the layer than with a layer of colloids, such as gelatin, glues or on the stronger sensitized ones, causing irreguthe like, which is sensitized by impregnation with larities and shadows on the subsequently pro- 10 suitable chemicals. duced picture. 5

Various means and numerous methods of im- A further source of faults lies in the alterations pregnating the plates and films are known. effected on the entering light by means of the Silver-salts are very frequently used as sensitizmore or less crystallized sediments, inasmuch as ing chemicals, the films, prepared with said salts, this light is reflected, broken and diffracted by on being exposed to the light, turning more or each single crystal face. It is therefore impossi- 70 less dark at all parts which have been exposed ble for the entering light to penetrate such films to the light, uninterrupted, whereby the quality of the picture Other wellknown sensitizers cause the gelatin obtained is further impaired. to harden by the action of the light at those Furthermore these sediments are nearly alparts of the film, which had been exposed to the Ways coloured, in most cases yellow, thereby act- 75 light, whilst the parts protected against the light g as Coloured filters for the incident ht. are left soluble and absorbent. The present in- This impa the action of the ght, as coloured vention relates especially to plates, films and fi ter a knOWn tOebSOrb Parts Of e light, the like, sensitized in this way, which therefore can not act on the deeper lay- After the exposure, the film hasto be subjected ers of the eolloid- The Sediments u cause so to a further treatment for the purpose of rendere150 Considerable losses of light y- The ing the picture visible. This can be reached, present invention has for its pu p s to avoid for example,.by the action of certain dyes or the d a es entioned above.

other sensitizers, which are absorbed by the non- Q Object of the inVentiOI} is to p p Sellhardened parts of gelatin, whilst the hardened SltlVe plates, films and the llke, the surfaces of 85 parts are left free, which are free from sediments.

As sensitizers of this second type, chromic'acid Another f a of t nv nt i to menusalts are generally used. The chromic acid salts factule Sensltlve e i SenS 1t1Zed h meansef are often applied to the plates or films together Chrome Salts, the sensltlzels helhg uniformly (1 S- with other metal salts in aqueous solution or in tllbuted throughout the collold layer. 9o alcoholic solution diluted with water, the im- A further feafture 15 1 rrovldesuch SenSltlZed pregnation being frequently Carried out by im; layers, into which the ineident light may freely mersing the material to be sensitized in a bath m1nt'en:upted y dlffractmg f of the said solutions. ter absorption is 001m t stlu z ifi presen; m E pleted the films are subjected to a subsequent O p 2 t e dr ing process and are then ready for use. Sur ace 0 W t 15 tree 00 t q t y c thereby avoiding losses of energy of the incident On removmg the j salqsensltlzlgg light, effected by absorption in the coloured sedibath, traces of the sensitizing solution remain menm 45 on the surface of the film, besides those parts From the foregoing can be seen that the of the solution absorbed by the colloid layer. tures produced o such films r plates, free Thelough investigations have Shown that these from sediments, will be clearer, sharper and free remaining traces are not uniformly distributed fro Shadows, veils and other irregularities, and over the sur ace of the film, but that they form that these good results moreover can be attained 50 globules. Thus the surface looks like a fatty by using for the exposure less light energy or urface, on which water has been applied. which is a very considerable advantage in prac- During the drying process, the liquid Solvent tical worka shorter duration of exposure than is evaporated from the globules and sediments hith t V are formed on the surface of the film. It was first attempted to achieve this end by 55 It was further found, that the higher the pertreating the films and the like with water, after impregnation with the sensibilizing solution, where it was found that no or only the very slightest decrease of sediment was effected by this treatment. Satisfactory results were, however, not reached by this method.

Further experiments showed that the treatment of the sensitive material with diluted alcohols gives very satisfactory results. For this purpose the sensitive films or plates, after inrpregnation with the sensitizing solution as above mentioned, are subjected to the action of an alcohol. This treatment may be performed in any suitable way, for example by running the sensitive material under treatment through weak alcoholic solution or by applying said solution to the sensitive surface of the material in any wellknown way.

When thus treated, the globules on the surface of the film disappear, the remaining traces of liquid are uniformly distributed over the whole surface, and no sediments appear, when the film is dried.

This result may be considered as effected by loosening the surface tension by the alcohol, thereby balancing the forces acting from the surface of the film on the liquid.

A solution containing a 10% alcohol solution has been found sufficient for most purposes. Ethyl alcohol for example may be used, other alcohols however giving good results too. Precaution must be taken with regard to the duration of this treatment, as the aqueous solution naturally lixiviates the sensitized layer, and therefore may reduce the sensitiveness should the treatment be continued too long. It will suflice in most cases to submit the film to the alcohol for about 12' seconds. As a rule the duration of this treatment is only a fraction of the previous time of impregnation, and may range for example between 10 and 20, seconds.

The after-treatment described may be performed immediately after the sensibilization is concluded or before the sensitizing solution has perfectly dried.

In the following a preferred form of this treatment is described as an example, without however limiting the invention to theparticular details of the method, as given below.

A transparent film of celluloid is coated with a layer of gelatin, and is then, for the purpose,

of sensitizing, immersed in a bath containing:

Bichromate of ammonia gr.

Sulfate of copper l. 5 gr; Ammonia 200 ccm. Alcohol 150 com. Water 1000 com.

After remaining in this bath for about 3 minutes, the film is removed and immediately transferred to a second bath containing 10% ethyl alcohol in Water. After about 12 seconds, the film is removed and subsequently dried. The drying is preferably carried out in one of the wellknown drying devices with warm air, a temperature of g about 23-24 C. being suitable- For large scale manufacture the above proposed after-treatment may be combined with the usual continuous process of manufacturing films. This may be done for instance by guiding the film uninterruptedly and continuously through the second bath, after having been sensitized-in the first bath, and by then drying the film uninterruptedly and continuously.

From this method a film results, the surface of which is free from sediments, and wherein the -sensitizers are uniformly distributed; During the exposure the light can enter freely into the colloid layer and can act freely on the uniformly distributed sensitive material. For the exposure less light-energy or a shorter duration of exposure is needed, than with the films used hitherto, containing sediments.

Without further analysis, the foregoing will so fully reveal the gist of this invention that others can, by applying current knowledge, readily adapt it for various utilizations by retaining one or more of the features that, from the standpoint of the prior art, fairly constitute essential characteristics of either the generic or specific aspects of this invention and, therefore, such adaptations should be, and are intended to be, comprehended within the meaning and range of equivalency of the following claims.

I claim:

1. The process of manufacturing photo-sensitive bodies having a colloid layer, which comprises photo-sensitizing said layer with an agent adapted to harden the layer by reaction with light, and treating said bodies with a dilute aqueous solution of an alcohol to free the photo-sensitive surface of non-uniformly distributed sediments, the treatment being continued for only a short time so as to leave the sensitivity of the,

said bodies substantially unimpaired.

2. The process of manufacturing photo-sensitive bodies having a colloid layer which comprisesphoto-sensitizing said layer with an agent adapted to harden the layer by reaction with light; and treating said bodies with a dilute aqueous solution of an alcohol immediately after the sensitizing is completed to free the photosensitive surface of non-uniformly distributed sediments, the treatment being continued for only a short time so as to leave the sensitivity of the said bodies substantially unimpaired.

3. The process of manufacturing photo-sensitive bodies having a colloid layer whichcomprises photo-sensitizing said layer with an agent adaptedto harden'the layerby reaction with light; and treating said bodies with a dilute aqueous solutionof an alcohol containing about 10% alcohol to free the photo-sensitive surface of non-uniformly distributed sediments, the treatment being continued for only a short time so as to leave the sensitivity of the said bodies substantially unimpaired.

4. The process of manufacturing photo-sensitive bodies having a colloid layer which comprises photo sensitizing said layer with an agent adapted to harden the layer by reaction with light; and treating said bodies with a dilute aqueous alcoholic solution which containsabout 10% of ethyl alcohol to free the photo-sensitive surface of non-uniformly distributed sediments, the treatment being continued for only a short time so as 'to leave the sensitivity of the said bodies substantially unimpaired.

5. The process of manufacturing photo-sensitive bodies having a colloid layer which comprises photo-sensitizing said layer with an agent adapted to harden the layer by reaction with light; and treating said bodies for about 10 to-20 seconds with a dilute aqueous solution of an alcohol to free the photo-sensitive surface of non-uniformly distributed sediments, and leav ing the sensitivity of said bodies substantially unimpaired.

6. The process of manufacturing photo-sensichromates and alcohol in aqueous solution; subsequently treating said bodies with a dilute aqueous solution of an alcohol to free the photo-sensitive surface of non-uniformly distributed sediments, the treatment being continued for only a short time so as to leave the sensitivity of the said bodies substantially unimpaired.

CARL ROEHRICH.