US2893866A - Photosensitive material and a process of making same - Google Patents

Description

United States Patent PHOTOSENSITIVE MATERIAL AND A PROCESS OF MAKING SAME Theodor Haefeii, Ennethurgen, Switzerland, assignor to Cinetechnik A.G., Zurich, Switzerland No Drawing. Application March 15, 1955 Serial No. 494,547

Claims priority, application Germany March 15, 1954 5 Claims. (Cl. 96-75) This invention relates to photosensitive material and more particularly to light sensitive photographic material containing diazo and tetrazo compounds of the diphenylamine group as light sensitive compound, and to a process of making same.

Diazo compounds of bases of the diphenylamine series stabilized by means of aluminium or magnesium salts, and their coupling or, developing with 2,3-hydroxy naphthoic acid arylides and other coupling components of the naphthol AS group are known. It is furthermore known that said diazo and tetrazo salts of bases of the diphenylamine series are unstable in aqueous solution, for instance, in the dyeing bath, and on carriers. Such compositions, in the undeveloped state, can be stored, at the most, for 2-3 days only.

It is one object of the present invention to provide a photographic light sensitive material comprising diazo and tetrazo salts of the diphenylamine series which compounds are stable for a considerable period of time and, therefore, are useful in the manufacture of photographic and movie fihns, of photographic papers and other photographic materials.

Another object of the present invention is to provide a process of making such light sensitive photographic material and of substantially increasing the sensitivity to light of such material.

Other objects of the present invention and advantageous features thereof will become apparent as the description proceeds.

According to the present invention, it was found that treatment of a cellulose hydrate layer with aqueous solutions of diazo and tetrazo salts derived from diphenylamine bases yields a light sensitive material which is stable and can be stored for an almost unlimited period of time. By subjecting such a photosensitive layer to a ripening process for 2-3 months at a temperature of 18-22 C. preferably 20 C. while excluding light and air, the sensitivity of said material which initially has a sensitivity of about 11 pictures per second can be increased to such an extent that it is possible to use said material, for instance, in a film printing machine with a speed of 30-40 pictures per second.

Said ripening process furthermore imparts to the light sensitive layer more uniform gradation than is exhibited by such layer directly after applying said diazo and tetrazo salts to the cellulose hydrate layer. Such a more uniform gradation, of course, is of great advantage in the production of satisfactory photographic pictures. The optimum gradation being obtained after a ripening period of about 14 days. The higher the initial gradation the lesser its reduction on ripening. When starting with initial gradations of 1.5, 2 and 3 these are reduced to 0.8, 1.6 and 2.4 respectively.

The sensitivity to light of said diazo and tetrazo salts can be further improved by using said salts in their 2,893,866 Patented July 7, 1959 purest form, i.e., without any addition of filler salts as they were present in the diazo compounds heretofore known in the dyestulf industry.

Gradation of the finished color picture can readily be affected and adjusted and can be considerably varied from soft to hard, i.e., from semitone for lavender prints to high contrasts for outline drawings. According to the present invention, gradation depends to a considerable extent upon the size of the dyestuif molecules. Thereby the molecular size is to be understood as particle size. Optimum gradation is achieved with compounds of the smallest molecular size. This is probably due to the fact that larger particles tend to form colloidal particles in solution.

Due to the fact that the salts used in accordance with the present invention are salts e.g. chlorides or sulphates of diazonium compounds, which in an aqueous medium form true molecular solutions, which obey to the laws of electrolytic dissociation, the development of the particle size is in close relationship to azeocomponents used in the coupling reaction (e.g. derivatives of beta-hydroxynaphthoic acid) which in turn form colloidal solutions in aqueous media. The effect of these naphthols of the AS series on the molecular size of the dye to be formed by coupling varies Within wide limits, so that the ability of gradation of the light sensitive material may be Widely varied by choosing the appropriate coupling component and by control of the pH-value during the coupling-reaction which is penformed in aqueous solution. Thereby the optimal gradation (for movie and photographic films) is obtained with compounds (coupling-compo nents) which due to their chemical configuration form smallest dye particles. The pH-value of the coupling component (azo component in aqueous solution) is between about 12 and 13.5, the temperature of the solution between 18 C. and 22 C.

The diazo and tetrazo compounds of the diphenylamine series are charged in aqueous solution with such a strongly positively polar-charge that the strongly negatively polar cellulose hydrate surface as it is obtained, for instance, on superficially saponifying acetyl cellulose by means of alkali hydroxide, binds so many dyestuff molecules that satisfactory depth of color is combined with sufiicient gradation and is achieved even on sensitizing said cellulose hydrate foil only on one side.

It is very surprising that diazo and tetrazo salts of the I diphenylamine series can be employed for making photographic light sensitive materials, since it was known that said salts are unstable in aqueous solution. Their combination with a cellulose hydrate carrier is surprisingly stable. A further increase in stability is achieved by adding acetic acid to the dye bath. The pH-value of the layer should, however, not exceed 7. Any other suitable aliphatic carboxylic acid like citric acid or tartaric acid may also be used.

The diazo and tetrazo salts of the diphenylamine series are suitable not only for producing so-called black-andwhite pictures but also for producing colored pictures.

The following examples serve to illustrate the present invention without, however, limiting the same thereto.

Example 1 An acetyl cellulose film is superficially saponified by a treatment with 5% sodium hydroxide solution at a temperature of 65 C. during 12-18 minutes and is thereby partly reconverted into cellulose hydrate on its surface. Said alkaline bath contains 60 ml. of a suitable leveling agent per liter, preferably an addition product of ethylene oxide to alkyl phenols having 12-14 carbon atoms 2;sas,see s as their alkyl chain. Such addition compounds correspond, in general, to the formula wherein Ris an alkyl radical having from 12-14 C-atoms and. nan integer from 3-19,.preferably 11-13. Thepreferred thickness of the hydrolised layer being about 0.01 mm., but may vary between 0006-0012.

An. aqueous solution of the. tetrazo. compound of p aminodiphenylamino-p azo-4-amino 5-ethoxy-2-toluene instabilizedform, said. solution containing 100' goof said dyestufi per literwbath, is appliedtosaidsuperficiallysaponified acetyl celluloseby means of rubber rollers. The dye bathtcontains. preferably 10 cc. of acetic acid per liter in order to stabilize the resulting light sensitive blank film material for anunlimitedperiod oftime when keeping-said. material under exclusion fromlight-and air, for instance, in tin cans. Before storing thesensitized film isedried at 30-45 C. preferably 40 C. in an air-stream under exclusion of ultra-violet radiation.

Developing. the exposed film by means of the anilide of -2.3-hydroxy naphthoic acid yields a black-and-white photographic picture.

Example 2 Example 3 An. aqueous solution of the stabilized diazo compound of 4t-amino diphenylaminesulfateon chloride which contains 20 cc. of acetic acid and 100 g. of said diazo compound perlitenis applied to superficiallysaponified cellulose acetate foil, asdescribedin Example. 1.

Exposure to light of said photographic material, and development with a di-acetoac etic adid-o-tolidide yields a photographic picturein yellow-and-white.

Example 4 An aqueous solution of the stabliized diazo compound of 4-amino 3-methoxy diphenylamine which contains 12 cc. of acetic, acid and 100 g. of said diazo compound per liter, is appliedtto a superficially saponifiedcellulose acee tate'foil, as described in Example 1.

Exposure to light of said photosensitive material and development with 2,5 dimethoxy 4 chloro anilide of 2.3-hydroxy naphthoic acid yieldsa photographic picture inred-and-white.

Example 5 A cellulose hydrate-film prepared asin- Example 1 is treated with a solution containing 100 gms. of the diazo compound of 4-amino-4rethoxydiphenylamine in one liter-of water containing 16 ml acetic acid. After exposure under a pattern and development with 2.3-hydroxyanthracene carboxylie acid-ortho-toluidide a green picture is obtained.

1 Example 6 A11- acetyl cellulose film treated according to one of the foregoing Examples 1-5 with a diazo compound after exposure is treated at a temperature of '20 C. with an aqueous solution of the coupling component 2.3-hydroxy-.

naphthoic. acid-ortho-toluidider The pictures. obtained are. sharnand clear becausethe size of the naphthol molecules corresponds to that of the diazo component.-

When working at higher temperatures the naphthol molecule becomes larger and therefore, the particle size of the dye becomes also larger.

Example 7 An acetyl cellulose filmpretreated according to one of the foregoing Examples 1-5 with a diazo compound, after exposure is treated-with an aqueous solution of the coupling component 2,-3-hydroxynaphthoic acid-orthoanisidide at any desired temperature. The particle size of the dye will in any casebe larger than in Example 6, the chemical structure of this coupling component being such that it can-be adapted to the molecule of the-diazonium salt neither by choice of the temperature nor by controlling the pH value.

Example 8 The acetyl cellulosefilm pretreated with a diazo-compound asdescribed in any of the Examples, 1-5, after, exposure is treated with an aqueous solution of'the coupling component 2-acetosacetlyaminor6-ethoxybenzothiazoleat any-desired temperature. I In: any case, dueto the molecular structure of the azo component, the. particle size of thev dyeformed will be larger than; inExample 8. Even. the control of the .pH-value will notadapt-the molecule ofthis component .to the molecule of thediazonium compound.

In place of the above mentioned diazo andtetrazocompounds, there canbe used other diazo and tetrazo compounds of basesof the diphenylamine series, which are known in the art.

The most preferred diazo compounds to be used in the process of this invention are 4-aminodiphenylamine and its substitution products having at least one lower alkyl or lower alkoxy group in one of the phenyl rings of said amino diphenylamine amino compound. The tretrazo compounds used in this inventionare derived from-p,p'-diphenylamine and its subst'itution'productsas. indicated. above; Especially suitable compounds are apparently compounds obtained. byncoupling diazotized 4:amino..dia phenylamine with iaromatic amino compounds, such as, 7 lower; allroxy substituted. tolidine compoundsand the like Stabilization of said compounds is effected, for instance, by the addition of alurniniumsulphate-or-magnesiumsul p phate. Stabilization mayalso be effected by removing the oxidation-products from .the diazo compounds and, precipitating the latter-with neutral salts which do. not. undergo hydrolytic cleavage at room temperature ,inthe p s qe f a dhav n a-s l pH- u ,.,l lre bor acid. Anad dition of materials which, like urea bindthe free nitrous acid is favourable.

Satsistactory results are obtained when using about 10%- solutions of said dyestuifcomponents. It is, of course, also possible to employ solutions of alower concentration. The-concentration should, however, not. exceed about 10%= and should not be substantially lower than-6%.:

After. applying the solutionof said diazo and tetrazo. compounds-s to the .cellulose hydrate .base, the material is subjected to a dryipggprocess at-a temperature between. 9-1451 nipreferah y 40f C.

As,statedabove thqnew photosensitive material haste sensitivity which permits exposures of of a second and even less, i.e. of a second.

In place of superficially saponified acetyl cellulose, there may be used other types of regenerated cellulose or cellulose hydrate for micro films, whereas a cellulose hydrate derived from acetyl cellulose has proved to be the preferred starting material for movie films. Superficial saponification of said cellulose acetate material may be carried out with sodium or potassium hydroxide solutions of a concentration between about 2% and about 5%. The temperature is preferably between about 62 C. and 68 C. In place of the leveling agent added to the alkali hydroxide solution of Example 1, there may be used other leveling and emulsifying agents such as wetting agents known in the art, for example Turkey red oil, alcohols, etc.

In place of acetic acid, there may be added other organic acids to the aqueous solution of diazo and tetrazo salts of bases of the diphenylamine series such as the aliphatic carboxylic acids having 1-4 carbon atoms, provided that the pH does not exceed 7. Apparently it is of advantage to said solution to impart a pH of between about 5 and about 7.

Ripening of the new photosensitive material and increase of its sensitivity to light is elfected by simply storing the said material while excluding excess of air and light at a preferred temperature of 20 C. maximum light sensitivity and gradation being achieved within 3-4 months and 2 Weeks respectively.

Of course, many changes and variations may be made in the preparation of the cellulose hydrate layer, the preparation of the diazo and tetrazo compounds employed, the method of applying said diazo and tetrazo compounds to said cellulose hydrate layers, the ways and means of increasing the sensitivity to light and the stability as well as the gradation properties of the new photosensitive material, and the like may be made by those skilled in the art in accordance with the principles set forth herein and in the claims annexed hereto.

The term cellulose hydrate as used herein and the claims annexed hereto indicates any regenerated cellulose which is obtained by alkaline saponification of cellulose esters. The preparation of the carrier used in this invention is more fully disclosed in my copending application Ser.No. 408,037.

I claim:

1. A process of making light sensitive cinematographic and photographic material, said process comprising in combination, the steps of embedding the light sensitive substance consisting of a chloride of nitroso-free diazo compound of 4-methoxy-4-amino-diphenylamine having the formula in a superfically saponified cellulose hydrate layer, said layer having been saponified by caustic sodawith an equalizing agent having the formula wherein R is an alkyl radical having from 12-14 C-atoms and 11 an integer from 3-19, and ripening the embedded diazo compound by storage during a period of one to three months, whereby film of constant low contrast characteristics is produced.

2. The process in accordance with claim 1, comprising the initial step of adding to the diazo compound prior to its application to the cellulose hydrate layer from 10 to 25 cm. CH COOH per liter of solution.

3. The process in accordance with claim 1, wherein the cellulose hydrate layer is formed by superficially saponifying an acetyl cellulose foil with a 5 to 10% NaOH solution containing an equalizing agent having the formula at a temperature of 62 C. to 68 C., wherein R is an alkyl radical having from 12-14 carbon atoms and n is an integer from 3-19, the chloride of nitroso-free diazo compound of 4-methoxy-4-aminodiphenylamine being strongly positively charged.

4. The product of claim 1.

5. The process in accordance with claim 1, comprising charging the diazo compound with a strongly positive polar charge to provide a strongly negatively polar cellulose hydrate surface, whereby the ripening is facilitated.

References Cited in the file of this patent UNITED STATES PATENTS 2,789,904 Benbrook et al. Apr. 23, 1957 FOREIGN PATENTS 337,868 Great Britain Nov. 13, 1930

Claims (1)

1. A PROCESS OF MAKING LIGHT SENSITIVE CINEMATORGRAPHIC AND PHOTOGRAPHIC MATERIAL, SAID PROCESS COMPRISING IN COMBINATION, THE STEPS OF EMBEDDING THE LIGHT SENSITIVE SUBSTANCE CONSISTING OF A CHLORIDE OF NITROSO-FREE DIAZO COMPOUND OF 4''-METHOXY-4-AMINO-DIPHENYLAMINE HAVING THE FORMULA