US2378583A

US2378583A - Photographic printing material

Info

Publication number: US2378583A
Application number: US481063A
Authority: US
Inventors: Schmidt Maximilian Paul; Poser Gottlieb Von
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-12-27
Filing date: 1943-03-29
Publication date: 1945-06-19
Anticipated expiration: 1962-06-19
Also published as: FR51642E; BE441985A; FR868365A; CH232522A; DE906406C; CH230638A; BE440077A; CH217787A; DE903061C; US2322982A

Description

Patented June 19, 1945 Maximilian Paul Schmidt, Wiesbaden-Biebrich, and Gottlieb von Poser, Wlesbaden, Germany; vested in the Alien Property Custodian No Drawing. Application March 29, 1943. Serial No. 481,063. In Germany August 5, 1940 13 Claims.

The present invention relates to a process of enhancing the light-sensitiveness of photographic printing material containing diazo compounds.

It is already known that photographic printing materials can be obtained by means of light-sensitive diazo compounds. Diazo compounds which are suitable for such a process have to satisfy, as is known, a great number of requirements. Many diazo compounds are known which in various respects are well suitable for diazotype purposes, but nevertheless have not acquired any practical. importance, since their light-sensitivenessis too small.

The various colorless or only slightly colored diazo compounds particularly belong to said kind of diazo compounds. The afore-named diazo compounds are in most cases distinguished by the fact that the photographic prints prepared therewith have only a slight tendency to turn yellow. Moreover, they are particularly suitable for the production of reflex copies. They yield reflex copies very rich in contrast. Furthermore the dyestuffs forming the picture of the reflex copies strongly absorb chemically active light if suitable azo-components are .used as this is described in detail in the co-pending U. S. patent application Serial No. 27 6,420 filed May 29, 1939, now Patent No. 2,246,425. The reflex copies are therefore well suited for being reproduced on photographic printing paper, for instance diazotype paper. In spite of these favorable properties the diazo com pounds in question have acquired only very little practical importance since their light-sensitiveness is much smaller than that of the usual c01- ored amino-diazo-compounds and diazo-anhydrides. In comparison with'the latter they require an exposure to light which, for instance, is

three to ten times as long or even longer.

The termsrelatively light insensitive diazo compound" or diazo compound of small lightsensitiveness respectively in the following description and the claims mean diazo compounds the light sensitiveness of which is about at most a half of that of the 1-dlazo-4-dimethyl-aniline provided that a usual source of light, for instance the arc lamp is employed for the exposure.

In the co-pending U. S. application Serial No; 373,139 filed January 4, 1941, now Patent No. 2,322,982, there is described a process of enhancing the light-sensitiveness of photographic printing material containing relatively light-insensitive diazo compounds. In said process aromatic ketccompounds are used as sensitizers.

On further investigating the process disclosed in the afore-named application we have now found that quite generally such organic substances free from heavy metals are useful sensitizers, besides the keto-compounds named, as show a strong absorption of light within the sphere of the spectrum adjacent to the sphere of absorption of the diazo compounds towards the long waves.

. In general it is advantageous if the sensitizers absorb light'within a sphere of about 3300 to 4400 Angstrom, It is, however, not necessary that the sensitizers show a considerable absorption over the whole of said spectral region, though this is advantageous. It is suflicient if they absorb light in part of the region named. It is, however, desirable if the substances absorb light particularly in those parts of the spectral region named in which the usual sources of light, for instance the mercury vapor lamp or the arc lamp, strongly emit light.

The enhancement of the light-sensitiveness of photographic printing material containing diazo compounds attained according to the process of the present invention which enables an essential shortening of the time of exposure is due to the fact that either the sphere of absorption of the diazo compounds is enlarged by the addition of the sensitizers or that the absorption is displaced into a region which is better adapted to the emission spectrum of the sources of light actually applied. In consequence thereof the effect attained according to the present invention varies according to the source of light applied.

As sensitizers there may, for instance, be used polynuclear aromatic hydrocarbons or the derivatives thereof. These substances are preferably used in the form of water-soluble compounds, for instance as sulfonic acids or salt of sulfonic acids. They may then be added to the aqueous or aqueous-alcoholic coating solutions containing the diazo compounds. Anthracene compounds, phenanthrene compounds, pyrene compounds, perylene compounds and chrysene compoundds have, for instance, a sensitizing action if they absorb light in the manner described above.

Quinoxaline and the derivatives thereof constitute a further useful group of sensitizers. The sensitizing action of these substances is, in general, however, inferior to that of the hydrocarbons named above.

Many aliphatic keto-compounds are likewise suitable sensitizers, for instance the non-volatile derivatives of acetone, such as acetone-sulfonic acid or an acetone-sulfonic acid substituted by chlorine. Pyroracemic acid may also be used. Croconic acid is a very'suitable sensitizer. These 5 acids are likewise preferably used in the form of water-soluble salts, for instance as sodium salt or potassium salt.

Some coumarins, especially hydroxy-coumatins, may also be used as sensitizers. Furthermore, pseudoazimides are useful.

The various sensitizers named are, on exposure to light, not altered to a noticeable extent. There may, however, also be such sensitizers as, by action of light, undergo a visible alteration if the substances produced from the sensitizers on exposure to light have no detrimental action in the finished prints. The yellow, very light-sensitive diazo compounds, for instance amino-diazo-compounds which are applied, as is known, for diazotype purposes and show a relatively strong absorption within the region .of 3300 to 4400 Angstrom, may be used as sensitizers. If diazo compounds are used as sensitizers special care must be taken that the light-sensitive layers bleach out on exposure to light, i. e. that by the coupling of the decomposition product of the one diazo compound with the other diazo compound not yet decomposed a dyestufl'. is not produced during the exposure 'to light. This may be attained by a suitable selection of the sensitizer or by the addition of 'a sufilcient portion of acid to the light-sensitive layer. Besides the diazo compounds there may be used as sensitizers the reaction products of diazo compounds and sulfites,.

namely the diazo-sulfonates.

Colorless or only slightly colored substances are generally preferred as sensitizers. Dyestuiis, i. e. compounds containing auxochromes, such as hydroxyl groups or amino groups, besides the chromophores, for instance the azo group, the nitro group or the nitrose group, are often less suitable as sensitizers, this being probably due to the fact that the filtering action which superimposes the sensitizing action is sometimes very strong in the case of such dyestuffs so that on using an unsuitable source of light an enhancement of the sensibility cannot be observed as a total result. These conditions have to be taken into consideration if dyestuffs are used as sensitizers.

By means of the afore-named sensitizers the light-sensitiveness of relatively light-insensitive diazo compounds may be enhanced to a multiple so that they then satisfy the practical requirements. Colorless diazo compounds of thebenzene series which are free from amino groups may be sensitized with particularly good success, for example diazo phenols and diazo phenol ethers. Diazo phenol alkyl ethers i. e. the diazotization products of p-am'sidine, o-anisidine and similar alkyl ethers of amino-phenols are particularly well suitable for the purpose of the invention. Other suitable colorless diazo compounds are mentioned in the co-pending application 276,420. Slightly colored compounds, for

instance the tetrazotized dianisidine, may, likewise be sensitized.

The proportion of the sensitizers present in the photographic printing material may be just as large as that of the diazo compounds. eral, however, an effect may be produced by an essentially smaller quantity of the sensitizer than that named above. In many cases a few percentages calculated on the diazo-compound are sufiicient. But within certain limits there exists a proportionality between thev enhancement of sensitizers added. Additions usual in diazotypeprocesses may be given to the solutions. If colorless diazo compounds are used, it is advisable to add bleaching-out dyestufls to the solutions; the

In genprocess of exposure to light may thus be weli observed. The usual supports, such as paper and films of all kinds may be used. If films are applied, the sensitizing eflect is ingeneralmanifested particularly well.

It is also possible to use several sensitizers simultaneously. Azo components are suitably contained in the sensitized photographic printing material containing diazo compounds, so that the prints may be developed by the dry method.

The following examples serve to illustrate the invention, but they are not intended to limit it thereto:

(1) A film of regenerated cellulose is impregnated with a solution containing in 1000 cc. of water 15 grams of the double salt of zinc chloride of the diazo compound from l-amino-S-methyl- 4-methoxybenzene, 15 grams of tartaric acid, 12 grams of R-salt and 10 gramsv of potassium anthracene-2.7-disulfonate. By an exposure to light for about 1 minute under an arc lamp of 12 amperes and a development with gaseous ammonia, photographic prints of good properties may be obtained with the aid of the dried material. By the addition of the anthracene compound the exposure time is reduced to the sixth to seventh part of the time otherwise required. The sensitivity to light may be further enhanced by an addition larger than that named above of potassium anthracenedisulfonate, the gradation becoming flatter. Insteadof the anthracene compounds named there may for instance be used beta-anthracene-monosulfonic acid and the sul- Ionic acids of phenanthrene or the water-soluble salts thereof.

(2) A foil of acetyl cellulose is coated on one side with a solution containing per 500 cc. of water and 500 cc. of alcohol 110 grams of the zinc chloride double salt of the diazo compound from 2.4-dimethoxy-l-aminobenzene, 100 grams of citric acid, 60 gram of phenol and grams of the mixture of potassium perylene-3.9-disulfonate and potassium perylene-3.l0-disulfonate the light-sensitiveness and the quantity of the (cf. Zentralblatt, 1927, vol. I,'page 1833). A foil thus prepared is very well suitable for the production of reflex copies.

(3) Photographic crude paper is coated with a solution containing in 1000 cc. .of water 25 grams of the diazo compound from l-amino-4-ethoxy 3-benzene-sulfonic acid, 15 grams of tartaric acid, 20 grams of G-salt and 15 grams of potassium croconate; the paper is then dried. With the help of a paper thus coated diazotypes may be obtained.

(4) A cellulose-hydrate film is bathed in an aqueous solution containing per 1000 cc. of water 12 grams of the zinc chloride double salt of the diazo compound from 4-amino-1-phenoxybenzene, 8 grams of R salt, 15 grams of tartaric acid and 11 grams of quinoxaline; the material is then dried. Instead of the quinoxaline serving as a sensitizer there may be used the derivative of this compound, for instance the 6.7-dimethylquinoxaline, the quinoxaline-2.3-dicarboxylic acid, the 6.7-dimethyl-2.3-dimethoxy-quinoxaline or the 5.6-benzo-2.3-dimethyl-quinoxaline or the sulfonation products thereof.

(5) 15 grams of the zinc. chloride double salt of the diazo compound from 2.4-dimethoxy-1- aminobenzene, 12 grams of tartaric acid, 12 grams of R-salt and 7.5 gramsof the sulfate of the diazo compound from 4-amin'o-diphenylamine are dissolved in 1000 cc. of Water. Light-sensitive layers prepared with the help of the solution thus obtained are distinguished by an enhanced sensitivity to light in comparison with the layers obtained with the help of a similar solution which is free iromthe diazo compound of 4-amino-diphenylamine.

(6) The process is carried out as it is described in example but as a sensitizer 5 grams oi? esculetin or another similar coumarine derivative are used, for instance 5.7-dlhydroxy 4-methylcoumarine ('7) A film from regenerated cellulose is rendered sensitive to light with the help of a solution of 17 grams of the diazo compound from 2.5-dimethoxy-l-aminobenzene (zinc chloride double salt), 12 grams of resorcine, 20 grams of tartaric acid, 5 grams of boric acid and 20 grams of sodium acetone-sulfonate in 1000 cc. of water. The sodium acetone-sulfonate acting as a sensitizer may be replaced by the sodium salt of an acetone-sulfonic acid substituted by chlorine or the sodium salt of pyroracemic acid.

We claim:

1. Light-sensitive material which consists of a carrier having a layer comprising a diazo compound of the group consisting of diazo phenol, diazo phenol ether and diazo phenol alkyl ether all free from amino substituents of small lightsensitiveness and a sensitizer-consisting in an oraanic compound free from heavy metal which compound shows a strong absorption of light within the sphere of the spectrum adjacent to the sphere of absorption of the said diazo compound towards the long waves the said sensitizer being a member of the group consisting of polynuclear aromatic hydrocarbons, aliphatic keto compounds, quinoxalines, coumarines and pseudoazimides.

2. Light-sensitive material according to claim 1 wherein the said sensitizer is water-soluble.

3. Light-sensitive material according to claim 1 wherein the said sensitizer is a water-soluble sulfonated compound. a

4. Light-sensitive material which consists of a carrier having a layer comprising a diazo compound of the group consisting of diazo phenol, diazo phenol ether and diazo phenol alkyl ether all free from amino substituents of small lightof diazo phenol, diazo phenol ether and diazo phenol allq'l ether all free from amino substituents of small light-sensitiveness and a sensitizer consisting in an organic compound free from heavy metal which compound shows a strong absorption of light within the sphere of the spectrum adjacent to the sphere of absorption of said diazo compound towards the long waves the said sensitizer being a member of the group consisting of polynuclear-aromatic hydrocarbons, aliphatic keto compounds, 'quinoxalines, coumarines and pseudoazimides.

6. Light-sensitive material according to claim 5 wherein the said sensitizer is water-soluble.

7. Light-sensitive material according to claim 5 wherein the said, sensitizer is a water-soluble sulfonated compound.

8. Light-sensitive material which consists of a carrier having a layer comprising a substantially colorless diazo compound of the group consisting of diazo phenol, diazo phenol ether and diazo phenol alkyl ether all free from amino substituents of small light-sensitiveness and a sensitizer consisting in a water-soluble sulfonated aromatic hydrocarbon with three to five condensed benzene rings.

9. Light-sensitive material which consists of a carrier having a layer comprising a substantially colorless diazo phenol ether of small light-sensisensitiveness and a sensitizer consisting in a i water-soluble sulfonated aromatic hydrocarbon carrier having a layer comprising a substantially colorless diazo compound or the group consisting tiveness and a small percentage calculated on the diazo-compound, a sensitizer consisting in an organic compound free from heavy metal which compound shows-a strong absorption of light within the sphere of the spectrum adjacent to the sphere of absorption of the said diazo phenol ether towards the long waves the said sensitizer being a member of the group consisting of polynuclear aromatic hydrocarbons, aliphatic keto compounds, quinoxalines, coumarines and pseudoazimides.

10. Light-sensitive material according to claim 9 wherein the said sensitizer is water-soluble.

ll. Light-sensitive material according to claim 9 wherein the said sensitizer is a water-soluble sulfonated compound.

12. Light-sensitive material which consists of a carrier having a layer comprising a substantially colorless diazo phenol ether of small light-sensitiveness and a sensitizer consisting in a watersoluble sulfonated aromatic hydrocarbon with three to five condensed benzene rings.

13. Light-sensitive material which consists of a carrier having a layer comprising asubstantially colorless diazo phenol alkyl ether of small light-sensitiveness and as a sensitizer an alkali metal anthracene-2.7-disulfonate.

MAXIMILIAN PAUL SCHMIDT. GOTTLIEB vor: POSER.