US1821281A - Manufacture of diazo-types - Google Patents

Description

Patented Sept. 1, 1931 UNIIITEDHSTATJES PATENT OFFICE K AaELvAN 15m enm'rmv AND' LOUIS VAN DER GRIN'IEN, or VENLO, nmnnnnms, as

'srenons TO means in DER enm'rnn; TRADING AS onnmrscnn rmmmx nun one GRINTEN, F VENLO, NETHERLANDS mnrao'runn or nmzo-rYrns No Drawing. Application filed June 6, 1927, Serial No. 196,993, and in the Netherlands December 11, 1926.

This invention relates to the production of diazo-types in which layers containing dlazocompounds which are stable in the dark but are decomposed by light, are exposed to light through a transparent original and are then developed.

The sensitive layer is spread on suitable carriers such as paper or the like. The papers or the. like thus obtained are suitable for lmaking reproductions of transparent images such as drawings, photographs and the like.

It'is well known that the usefulness of the process depends on the fact that in the iliumination of the sensitive layer through a .-transparent picture or the like the diazocompound is decomposed (probably with formation of a phen at the places where the light has been ab e to pass, so that formation of an azodyestuif with an azodyestufi conpling component is no longer possible, whereas at the. places at which the light cannot pass the diam-compound remains unaltered and can be coupled under suitable conditions with a coupling component to form an azoidyestufi.

In sensitive layers in which the azo component is present together with the diazo compound a simple development by alkali suiiices, for instance with gaseous ammonia :01 a similar volatile base. If the sensitive layer does not contain an azo-cornponent the colour will be obtained 'by treating with a."

mixture of alkali and an azo-coinponent;.

The image obtained is positive when a ;transparent positive has been used. The development causes also the fixation of the image because a further action of light will notalter it. p

The first technical process for dlitaining gjpositive copies was that of Green, Cross & Bevan (German Patent 56,606 of September 3rd, 1890) who used the diazo derivativeof the dyestufi prim-uline as a sensitive substance and after exposure to light through a transparent-original developed in' a bath containing an azo-dyestufi component and generally an alkali. 1

Later it wasfound by ;Andresen, photo-.

graphic correspondenz, 1895, Rufi andStein 5c ;Berichtei34, 1901, 1668, and others that not only diazo derivatives of primuline are suitable in this process, but many other diazo compounds and that alldiazo compounds are more or less sensitive to light. Rufi and Stein also used metal salts in the sensitive layer and salt in the developing bath.

Kalle, British Patent No. 210,862, discovcred that diazo anhydrides are very stablediazo compounds and suitable in the positive di'azo-type process and that these diazo compounds may be used together with azo-components in the same layer, because they are very stable against coupling. In this case development is eifected -with alkali alone, preferably with ammonia vapors. In a later patent Kalle, British Patent N 0. 234,818, describes that instead of diazo anhydrides other diazo compounds may be used with 2.20 components in the same sensitive layer, provided that they do not couple per se in an acid or a neutral condition with any az o dyestuff component either in the dark or in the light.

In another patent Kalle, Dutch Patent 14,-

150,1nentions chinone-diazides as suitable diazo compounds. All these processes are im- 751- perfect because they do not produce suflicient ly dark lines with a sufliciently clear bleached background and the background is liable to discolor in course of time.

It hasnow been found that aromatic diazo compounds containing a tertiary nitrogen atom in the para-position to the diazo-group,

such compounds being incapable of formingdiazo-anhydrides or quinonediazides in any sense and not containing other substituents which might form anhydrides with the diazogroup, such as hydroxyl-carboxyL, primary, and secondary amino or sulphonic acid groups, are also very sensitive to light and stable;'they have the advantage to give rise eel to dark coloursin the unexposed parts and to practically absolute whiteness in the exposed parts. V This complete bleaching comprises ipsof' faeto that the respective diam-compounds do not couple quickly in the medium in which they are present, because otherwise with the phenol they produce they would form an azo 'dyestuff during bleaching (which as a rule will be" an 'azo-component very. capable of para-position to the diazo group, the difficulty arises that if they are used together with an azo dyestuif component in the light sensitive layer, coupling cannot be prevented for a long time even in the usual acid medium, and when the-paper is stored the'sensitive layer will be come coloured and unfit for use after a relatively short time (a few days or even hours) 29: Though therefore the diazonium co1n-' pounds having in para-position to the diazo group-a tertiary nitrogen atom are excellent if the-azo dyestufi'component is added during development they are less fit to be used without further precaution together with diazo compounds in thelight sensitive layer.

It has been tried to reduce the, tendency to coupling of these diazo compounds by introducing in the benzene nucleus which con- 9 tains the diazo group other substituents such as halogens, alkyls, aralkyls, etc, By introducing such substituents it is possible to influence-certain properties such as the darkness of color, the rapidity of development, etc.,

. and also to reduce the tendency to' coupling to a degree but it is not possibleto reduce the tendency to coupling sufiiciently for common practice.

Diazotypecopies obtained from a sensitive layer containing diazonium compounds havingin para position to the diazo group a tertiary bound nitrogen atom, will have the same disadvantage as other diazotypes of becoming yellow or brownish during storage.

This defect is inherent toall' known diazotype processes in more or less degree. 7

According to the invention this defect has been overcome not only in the preferably used diazotype process in which diazonium salts, having in para position to the diazogroup a tertiary bound nitrogen atom, and which do not contain groups which might give rise to the forming of anhydrides, are

used but in diazotype processes generally.

The invention is based on the observation that the discoloration of the background in all kinds of diazotype processes can be prevented even for extended periods if a reducing agent is added to the sensitive layer, or during or after development of the picture.

Preferred reducing. agents are organic substances such as aldehydes, amino compounds, aliphatic amido-compounds, poly-oXy-com- 1 pounds or the like,.-and the reducing agents are preferably used together with very small quantities of the substances with catalytic action defined as anti-oxygenes by Moureu (Chemisch Zentrallblatt 1922 I 1317; Comptes Rendus 174 pages 258-26 i and following). I

If the reducing agents are added to the sensitivelayers together with the other constituents the additional advantage is obtained that the small discolouring effect due to the oxidation of the components of the layer which may occur during long storage of it in 4 the unexposed state is also prevented.

The addition of reducing agents makes it possible to maintain the required white background and thereby improve the use of the abovenientioned diazonium-compounds containing in para-position to the diazo-group a tertiary nitrogen atom as a substituent, but it does not make it possible to use always. a developing process with alkali alone, except with freshly-made sensitive layers, because this development requires a sensitive layer containing all ingredients necessary to forman azo-dyes-tuti' and the resistance to coupling of such layers is not improved sufficiently by the aforesaid reducing agent.

By the present invention, however, these difliculties are also avoided in an original manner, so that it is possible to use dia-zocompounds which show no great resistance to coupling in practical admixture with 2120- dyestutf componentsand acids which are not injuriousto paper. Thus one isless limited in the choice of the diam-compounds. One can advantageously use such diazo-compounds as, like the aforesaid d'iuzonium salts, contain a tertiary nitrogen atom as-a substituent in the para-position to the diazo-group and form with suitable azo-dyestufi' components. the desired dark tone on a completely white ground. I

v According to the invention for'the purpose in question there is used in the light sensitive layer not an azo-couplingcomponent, but a non-coupling compound which however in the development of the photoprint with an alkali is converted intoa coupling com ponent. Such compounds may be obtained for instance by the action on a coupling component of an agent which inhibits the phenolfunction. As an example of such an agent hydrorylamine may. be cited. The agent may be added to the mixture of diazo-compound and azo-couplingv component with which the sensitive layer isproduced but it may also be caused to react previously with the azo-dyestufi component so as to form a derivatlve of this-component having no tend- .ency tocouple, which. d'erivative, however,

ama

is formed (Adolf Bayer, Ber. 19, 159).

When this compound is decomposed there is formed the triketone:

which is tautomeric with phloro-glucinol.

When the triketohexamethylenetrioxime is present in the sensitive layer, the following reaction may be supposed to occur during the development of the azo-dyestufl: Triketohexamethyleuetrioxima +3Hz0zi triketohexamethylene +3NH1OH TriketohexamethylenefiPhlorogluciuol. 1

The equilibrium in thefirst reaction is practically complete on the left hand side under conditions under which the paper is stored. On treatment with an alkali the coupling of the phloro-glucinol with the diazo-compound which then occurs shifts the equilibrium of the second reaction and thereby also that of the first towards the right which soon leads to the complete consumption of the trioxime with formation of azo-dye stuff. For appreciating this equilibrium it may be remarked that 'mixtures of active coupling diazocompounds with phloro-glucinol can be stored only for a few days or even less,whereas mixtures in which'the phloroglucinol is exchanged for an equivalent quantity of triketohexamethylenetrioxime but are otherwise the same remain permanent under like conditions for months; both mixtures.

couple on treatment with, for instance, gaseous ammonia, only the coupling in the latter case proceeds somewhat more gradually. Besides triketohexamethylenetrioxime there will probably be formed in a diluted solution of phloroglucinol and hydroxylamine other non-coupling compounds (for instance a compound of the composition C ll (NHOH) 3) comymsitiona In practice there is a sufiicient quantity of water present in the paper and l in the ammonia vapour.

In the case of necessity the ammonia vapour may be prepared intentionally moist. With suficient excess of hydroxylamine, which may be added, for example, in the form of hydroxylamine-hydrochloride, the latter forms compounds not only with the phloro-glucinol but also with azo-coupling components in general (phenols), to form compounds (probably 'oximes derived from the ketoform ofthe phenol in question) which do not have a tendency to couple, although by combined action of a diazo compound and an alkali they pass into compounds which do have this tendency.

To facilitate'the formation of the hydroxylamine compound which does not have a tendency to couple and to hinder decomposition of this compound into thecoupling component and hydroxylamine during storage, it is advantageous to use an excess of hydroxylamine and to protect-the paper from damp. Because the formation of the hydroxylamine compound occurs only slowly the presence of the excess of hydroxylamine has no disadvantageous effect on the speed of development with alkali.

As a further example of a substance capable of converting azodyestufi components in a non-coupling condition semi-carbazide is mentioned.

The action of the substances such as hydroxylamine and semi-carbazide prevents the coupling in the sensitive lay-erby an action on the. azodyestuli component. Though the action of hydroxyl amine and phloro-glucinolmay be explained as indicated above it is not proved that this reaction really takes place. It may be that other products are formed.

The action on other phenolic bodies by purely aromatic constitution, but in all such l.

compounds the phenolic function is inhibited.

In all cases the conversion of the non-coupling compounds into axe-coupling components occurs in one single operation with the development of the photo print. With advantage gaseous ammonia is used but of course itis also possible to develop in an alkaline bath.

It has further been found that the print maybe developed with a pulverized alkaline substance strewn on the image. Care should be taken that sufficient moisture is present because in dry condition the development proceeds too slowly. A suitable alkaline substance for this purpose is sodium stannate.

Under certain conditions the development may be carried out in still another way:

It has been found that by using a mixture of a diazo-compound with a compound lie produced by the action of an azo-coupling component with a substancesuch as hvamine compound is decomposed by the hea ing: and the tendency of the azo-component to: couple is therefore restored. In this manner the feeble acid. or the acid decomposable by heat combined with a: strong base is expelled and with it the efi'ect of the acid residue in the diazonium compound. The medium thus becomes neutral or feebly alkaline which at raised temperature induces a rapid coupling;

In this process in which the presence of thedecomposable salt requires a high resistmice against coupling duringstorage, it is advantageous to use diazonium salts having impala-position to the diazogroup a tertiary nitrogen atom as a substitucnt and in which the benzene nucleus containing the diazo group has still one onmore other substituents.

In order to prevent the so-called bleeding of the formed azo-dyestuif it is preferable to add. salts like barium chloride. If the development is carried out in a bath, for example abath containing an axe-coupling component, the salt may lie-added to the bath. In most cases however it is preferable to bring it together with the other components in the sensitive layer.

The following examples illustrate the invention, the parts being by weight Emamp'le l.-There is made a solution of 2- parts of 1-dimethylaminobenzenet-diazonium eh-lorideby diazotizing para-aminodimethylaniline with nitrous acid in 100 parts of water. To this solution is added 0.2 part of: oxalic acid and 10 parts of barium chloride.

The solution is brushed on paper and dried.

After exposure under a transparent original the paper is developed in afeebly alkaline solution of 8-oxynaphthoic acid anili-de, to which 0.4% of' formaldehyde has been added.

There is obtained a positive brown-violet image on a white ground; which does not become yellow on keeping; Preferably, it is afterwards washed in a solution of formaldehyde of 0.4% strength.

'Eocample 2.-There is made a solution of 30 parts of 1-diisoamylamine-3:5-xylenediazonium'chlorostannate, 5 parts of phloroglncinol and 5 parts of hydroxylamine hydrochloride in 1000 parts of water.

Thesolution is applied as described in Example 1.

The picture is developed in a solution containing 0.2 per cent. of sodium hydroxide and 0.4 per: cent. of formaldehyde. There is obtainedi-a. positive which is black and does not become yellow on keeping Eaxample 3.'I=here is made a solution. of 0.2

part of phl'oroglucinol in 100 parts of water and there is added so much hydroxylaminehydrochloride thatthe reaction of phloroglucinol described in Berichte; vol. 8. page-967 and. vol. .9. page 216 has disappeared from test samples. (The reaction in question is best performed as follows :To prepare the reagent 0.2 gram of aniline-hydrochloride and 0.1 gram of sodium nitrite are together dissolved'in 100 cc. of Water. After a long time a brown precipitate is formed which is filtered: inorder to obtain a clear filtrate constituting the reagent. To make the test, 2 drops of the reagent are added to the phloroglucinol solution, previously diluted to 10 co. In presence of phloroglucinol there appears within 10 seconds a distinct yellow colour).

To this solution are then added under ordinary circumstances 1.5 parts of dimenthylmade 30 parts of l-diisoamylamine-EB: 5-xylenediazoniumchlorostannate,

5 parts of phloroglucinol,

30 parts of' oxalic acid,

20 parts of ammonium lactate,

20 parts of urotropin,

20 parts of glycerin-e aldehyde,

0.2 part of 'pyrogallol,

0.1 part of meta-phenylenediamine hydrochloride.

The solution is painted on paper and dried. The paper is only permanent for a relatively,

short time. After exposure under a drawing on transparent paper it is developed for 15 30 minutes in a chamber containing ammonia Vapour.

There is obtained a practically black picture on a white ground which does not become yellow.

Example 5.A solution is made of:

1.5 parts of 1-dimethylaminobenzene4- diazoniumchlorostannate,

0L8 part of triketohexamethylenetrioxime, 0.3 port of hydroxylamine hydrochloride,

2 parts of oxalic acid,

2 parts of ammonium lactate,

1 part of urotropin,

2 parts of glycerine aldehyde,

0.01 part of meta-phenylenediamine,

100 parts of water.

The solution-is painted on paper and dried.

After exposure under a drawing on transparent paper the picture is developed for about 15-80 minutes in a chamber containing ammonia vapour. There is obtained a black brown picture on a white ground, the latter remaining white during. storage.

Ewample 6.The procedure is' as described in Example 3. The picture obtained, however, is not developed by ammonia vapour but by friction with pulverulent sodium stannate. In this case also there is produced a black picture on a white ground that does not yel low.

Example 7.The procedure isa's described in Example 3, but a larger proportion of hydroxylamine hydrochloride is added and instead of 2 parts of oxalic acid there are 'used 3 parts of sodium acetate. The drying operation is performed particularly carefully at a low temperature. After exposure, the pic? ture is developed by heating it, for example with a'hot smoothing iron.

What we claim is V 1. The process ot rendering the background of the diazo type prints substantially stable against discoloration which comprises including therein a reducing agent capable of arresting under normal conditions the discoloration of the components forming the back-ground of said prints.

2. The process of rendering the background of the diazo type prints substantially stable against discoloration which comprises including therein a substance comprising a reducing agent, and a catalytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration-of the components forming the back-ground of said prints. 4

'3. The process of rendering the background of the diazo type prints substantially stable against. discoloration which comprises including therein a reducing aliphatic compoundcapable of arresting under normal conditions the discoloration of the components forming the back-ground of said prints. e A 4. The process of rendering the back ground of the diazo type prints substantially stable against discoloration which comprises including therein areducingamino compound capable of arresting under normal conditions the discoloration of the components forming the back-ground of said prints.

5. The process of rendering the background of the diazo type prints substantially stable against discoloration which comprises including therein an aldehyde capable of arresting under normal conditions the discoloration of the components forming the background of said prints.

6. The process of rendering the background of the diazo type prints substantially stable against discoloration which comprlses including therein a-reducing polyoxy compound capable of arresting under. normal conditions the'discoloration of the components forming the back-ground of said prints.

7 The process for making diazo type prints which comprises applying to a base a layer containing adiazo compound bleaching on exposure to light, and a reducing agent capable of arresting under normal conditions the discoloration of the components forming the back-ground of said prints, exposing such layer, and contacting the exposed layer with a developer containing an azo dyest'ufl' component.

8. The process according to claim 7 where in the reducing agent is an amino compound capable ofarresting under normal conditions the discoloration of the components forming the back-ground of said prints.

g 9. The process for making diazo type prints which comprises applying to a base a layer containing a diazo compound bleaching on exposure to light and a substance comprising a reducing agent and a catalytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the back-ground of said print, exposing such layer, and contacting the exposed layer with a developer containing an azo dyestufi' component.

10. The process for making diazo type prints which comprises applying to a base a layer containing a diazo compound bleaching on exposure to light, an azo dyestuflt' component and a, reducing agent capable of arrest ing under normal conditions the discoloration of the components forming the background of said prints, exposing such layer, and developing the exposed layer.

11. The process according to claim 10" wherein the reducing agent is an amino comtermed antioxygene of Moureu which substance is capable of arrestingunder normal conditions the discoloration of the components forming the back-ground of said prints, exposing such layer, and developing the exposed layer. a

13. The process for making diazo type prints which comprises applyingjzo' a base a layer containing a diazo compound bleaching on exposure to light, a non-coupling compound decomposable into an azo dyestufi coinponentanda reducing agent capable of arresting under normal conditions the discoloration of the components forming the back-ground of said prints, exposing such layer, and developing the exposed layer.

.14. Theprocess according to claim 13 wherein the'reducing agent is an amino compound capable of arresting under normal conditions the discoloration of the compolos I nents forming the back-ground of said prints. 15. The process for making diazo type prints which comprises applying to a base a layer containing a diazo compound bleaching on exposure to light, a non-coupling compound decomposable into an azo dyestufi' component, and asubstance comprising a reducing agent and a catalytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the back-ground of said print, exposing such layer, and developing the exposed layer.

16. The process for making diazo type prints which comprises applying to a base a layer containing a diazo compound bleaching-on exposure to light and a reducing agent capable of arresting under normal conditions the discoloration of the components forming the back-ground of said print, exposing such said prints.

layer, and contacting'the exposed layer with a developer containing an azo dyestuff component and a reducing agent capable of arresting under normal conditions the discoloratlon of the components forming the back ground of said prints.

17. The process according to claim 16 wherein the reducing agent in both instances is an aminocompound capable of arresting under normal conditions the discoloration of the components forming the back-ground of 18. The process for making diazo type prints which comprisesapplying to a base a layer containing a dia'zo compound bleaching onexposure to light and a substance comprising a reducing agent and a catalyticallyactive material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the background of said prints, exposing such layer, and contacting the exposed layer with a developer containing an azo dyestutf component, and a substance comprising a reducing agent and a catalytically active material *termed antioxygene of Moureu which substance is capable of arresting under normal -conditions the discoloration of the components forming the back-ground of 'said prints.

'19. The process for making diazo type prints which. comprises applying'to a base a layer containing a diazo compound bleaching-on-exposure to light, an azo dyestuif component, and a reducing agent capable of arresting under normal conditions the discolorationof the components forming the background of said prints, exposing such layer, and contacting the exposed layer with a developer'containing a reducing agent capable of arresting under normal conditions the discloration of the components forming the back-ground ofsaid prints.

the components forming the back-ground of veloper containing a reducing agent capable wherein the. reducing agent in both instances a compound decomposableinto an the components forming the back-ground of 20. .The process according to claim 19 wherein the reducing agent in both instances is an amino compound capable of arresting under normal conditions the discoloration of.

said prints.

21. The process for making diazo type prints which comprises applying to a base a layer containing a diazo compound bleaching on exposure to light, an azo dyestuiicomponent and a substance comprising a reducing agent and a catalytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the compo nents forming the back-ground of said prints, exposing such layer, and contacting the exposed layer with a developer containing a substance comprising a reducing agent and a catalytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the background of said prints;

22. The process for making diazo type prints which comprises applying to a base a layer containing a diazo compound bleaching on exposure to light,.a non-coupling compound decomposable into an azo dyestuit component and a reducing agent capable of arresting under normal conditions the discoloration of the components of the background of said prints, exposing such layer, and contactingthe exposed layer with a de- 10" of arresting under normal conditions the discoloration of the components forming the back-ground of said prints.

23. The process according to claim 22 is an amino compound capable of arresting under normal conditions the disgtoloration of the components of the back-ground of said prints.

24. The process for making diazo type prints which comprises applying to a base a layer containing a diazo compound bleaching on exposure to light, a non-coupling azo dyestufi component'and a substancecomprising a reducing agent and a talytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of said prints, andcontacting the-exposed layer to a developer containing a substance comprising a reducing agent and a catalytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the background of said prints.

25. The proce for makingdiazo type prints which comp ises applying to a base 130 a layer containing a diazo compound bleach-- ing on exposure to light, exposing such layer, and contacting the exposed layer with a de-. veloper containing an azo dyestufi' component and a reducing agent capable of arresting-under normal conditions the discoloration of the components forming the back ground ofsaid prints.

26. The process according to claim wherein the reducing agent is an amino compound capable of arresting under normal conditions the discoloration of the components forming the back-ground of said 27. The process for making diazo type prints which comprises applying to a base a layer conta ning a diazo compound bleaching on exposure to light, exposing such layer, and contacting the exposed layer with a developer containing an azo dyestutf component and a substance comprising a reducing agent and a catalytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the back-ground of said prints. v

28. The process for making diazo type prints which comprises applying; to a base .a layer containing a diazo compound bleachmg on exposnie to light, and an azo dyestufi com onent ex )osin such la er and contacting the exposed layer with a developer containing a reducing 'agent capable of arresting under normal conditions the discoloration of the components forming the back-ground of said prints.

29. The process according to claim 28 wherein the reducing agent is an amino compound capable of. arresting under normal conditionsthe discoloration of the components forming the back-ground of. said prints.

30. The process for making diazo type prints which comprises applying to a base a.

layer containing a diazo compound bleaching on exposure to light, and an azo dyestufi' component, exposing such layer, and contacting the exposed layer with a developer con-- taining a substance comprising a reducing agent and a catalytically active material termed antidxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the back-ground of said prints.

31. The process for making diazo type prints which comprises applying to a base a layer containing a diazo compound bleaching' on exposure to light and a non-coupling compound decomposable into an 2120 dyestuff component, exposing such layer, and contacting the exposed layer with a developer containing a reducing agent capable of arresting-under normal conditions I the discoloration of the components forming the back-ground of said prints.

32 The process according to claim 31 wherein the'reducing agent is an amino compound capable of arresting under normal conditions the discoloration of the compo nents forming the back-ground of said prints.

The process for making diazo type prints which comprises applying to a base 'a layer containing a diazo compound bleaching on exposure to light and a non-coupling compound decomposable into an azo dyestuii component, 51nd contacting the exposed layer with a developer containing a substance comprising a reducing agent and a catalytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the background of said prints.

34. The process for making diazo type prints which comprises applying to a base a 36. The process according to claim '34 wherein the salt is a salt of strong base with V a heat decomposable acid which salt upon heating yields an alkaline material.

37. The process for making diazo type. prints which comprises applying to a base a layer containing a diazo compound bleaching on exposure to light, a non-coupling compound decomposable into an azo dyestuff component, a reducing agent capable or arresting under normal conditions the discoloration of the components forming the'background of said prints, and a salt yielding upon heating an alkaline material, exposing such layer,

and developing the exposed layer by heat.

38.'The process according to claim 37,

wherein the salt is a salt of a strong base with a volatile acid which salt upon heating yields an alkaline material.

39. The process according to claim 37 wherein the salt is a salt of a strong base with a. heat decomposable acid which salt upon heatingyiclds an alkaline material.

40. As a new product, a base having a sensitive layer thereon containing a diazo compound bleaching upon exposure to light, and a reducing agent capable ofarresting under normal conditions the discoloration of the components forming the back-ground of the finished print. j p

41. The product according to claim 40 wherein the reducing agent is .an amino compound bleaching upon exposure to oxygene of Moureu which substance is capa ble of arresting under normal conditions the discoloration of the components forming the back-ground of the finished print.

43. As a new product, a base having a sensitive layer thereon containing a diazo comlight and containing in the para-position to the diazo group a tertiary nitrogen atom substituted in the benzene nucleus or not but not containing a substituent which can react with.

the diazo group, and a reducing agent capable of arresting under normal conditions :the discoloration of the components forming the back-ground of the finished print.

44. The product according to claim 43 wherein the reducing agent is an amino compound capable of arresting under normal conditions the discoloration of the components forming the back-ground of the finished print.

45. As a new product, a base having a sensitive layer thereon containing a diazo compound bleaching on-exposure to light and containing in the para-position to the diazo group a tertiary nitrogen atom substituted in the benzene nucleus or not but not containing a substituent which can react with the diazo group, and a substance comprising a reducing agent and a catalytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the background of the finished print.

46. As a new product, a base having a sensitive layer thereon containing a diazo compound, an azo dyestuff component, and a reducing agent capable of arresting under normal conditions the discoloration of the components forming the back-ground of the finished print.

L7. The product according to claim 46 wherein the reducing agent is an amino compound capable of arresting under normal conditions the discoloration of the compo nents forming the back-ground of the finished print.

48; As a new product, a base hav ng a S8IlS1- tive layer thereon containing a diazo compound, an azo dyestuif,component,.and a substance comprising a reducing agent and a catalytically active material termed antioxygene of Moureu which substance is ca- .pable .of arresting under normal conditions and a reducing agent capable of arresting under normal conditions the discoloration of the components forming the back-ground of the finished print.

50. The product according to claiin 49 wherein the reducing agent is an amino compound capable ofarresting under normal conditions the discoloration of the components forming the bacb-ground of the finished print.

51. As a new product,a base having a sensitivelayer thereon containing a diazo compound bleaching on exposure to light and containing in the'parzvposition to the di azo-group a tertiary nitrogen atom substituted in the benzene nucleus or not but not containing a substituent which can react with the diazo group, an azo dyestutl component, and a substance comprising a reducing agent and a catalytically active material termed antioxygene of Moureu which substanceis c1 pahle of arresting under normal conditions the discoloration of the components forming print.

54. tive layer thereon containing a diazo compound, a non-coupling compound decomposable into an azo dyestufi' component, a substance comprising a reducing agent and a- As a new product, a base having-a sensi- 515 catalytically active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the back-ground of the finished print.

55. As a new product, a base having ii -r sensitive layer thereon containing a diazo compound bleaching on exposure. to light and containing in the para-position toxthe diazo group a tertiary nitrogen atom substituted in the benzene nucleus or not but not containing a substituent which can rev pound bleaching on exposure to light and containing in the para-position to the diazo group a. tertiary nitrogenatom substituted in the benzene nucleus or not but not containing a' substituent which can reactwith the diazo group. a non-coupling compound decomposable into an azo dyestuil' component, and a substance comprising a reducing agent and a catalyticallv active material termed antioxygene of Moureu which substance is capable of arresting under normal conditions the discoloration of the components forming the back-ground of the finished print.

58. As a new product, a base having a sensitive layer thereon containing a diazo compound bleaching on exposure to light. and a non-coupling compound decomposable into an azo dyestufi' component.

59. The product according to claim 58 wherein the non-coupling compound is the reaction product of an azo dvestuff component and a substance inhib ting the phenol function of said are dyestufl component.

60. The product according to claim 58 wherein the non-coupling compound is the reaction product of an azo dyestuiit' compo- Dent and hydroxylamine.

61. The product according to claim 58 wherein the non-coupling compound is the reaction product of an azo dyestufi component and semicarbazide.

62. The product according to claim 58 wherein the non-coupling compound is the reaction product of phloroglucinol and hydroxvlamine.

63. The product according to claim 58v wherein the non-coupling compound is the reaction product of phlorogluc nol and semicarliazide.

64. As a new product. a base having a sensitive laver thereon containing a diazo compound hleaching on exposure to light and containing in the para-position to the diazo group a tertiarv nitrogen atom substituted in the benzene nucleus or not but not containing a substituent which can react with the diazo group, and a non-coupling compound decomposable into an azo dyestuii' component.

ponents of said layer.

65. The product according to claim 64 wherein the non-coupling compound is the reaction product of an azo dyestuff component and a substance inhibiting the phenol function of said azo dyestuif component.

66. The product according to claim'64 wherein the non-coupling compound is the reaction product of an azo dyestutf component and hydroxylamine.

67. The product according to claim 64 wherein the non-coupling compound is the reaction product of an azo dyestutf component and semicarbazide.

58. The product according to claim 64 wherein the'non-coupling compound is the reaction product of phloroglucinol and hydroxylamine.

69. The product according to claim 64 wherein the non-coupling compound is the reaction product of phloroglucinol and semicarbazide.

70. The process oi rendering a sensitive layer containing a diazo compound bleaching upon exposure to light and an azo dyestuif compbnent substantially stable against prema'ture coupling which comprises including therein a reducing agent other than an acid capable of arresting the coupling activity of the components of said layer.

.71. The process according to claim wherein the reducing agent is hydroxylout which can react with the diazo group and an azo dyestufi' component, substantially stable against premature coupling which comprises including therein a reducing agent other than an acid capable of arresting the coupling activity of the components of said layer. a

74. The process according to claim 73 wherein the reducing agent. is hydroxylamine.

75. The process according to claim 73 wherein the reducing agent is semicarbazide.

76. The process of rendering a sensitive layer containiri a diazo compound bleaching upon exposure to light and phloroglucinol substantially stable against premature coupling which comprises including therein a reducing agent other than an acidcapable of arresting the coupling activity ofthe com- 77. The process according to claim 76 wherein the reducing agent is hydroxylamine.

78. The process according to claim 76 wnerein the reducing agent is semicarbazide.

79. The process of rendering a sensitive layer comprising a diazo compound bleaching upon exposure to light containing in the para-position to the diazo group a tertiary nitrogen atom substituted in the benzene nucleus or not but not containing a substituent which can react with the diazo group, and phloroglucinol substantially stable against premature coupling which comprises including therein a reducing agent other than an acid capable of arresting the coupling activityof the components of said layer.

80. The process according to claim 79 wherein the reducing agent is hydroxylamine.

81. The""process according to claim 79 wherein the reducing agent is semicarbazide.

In testimony whereof we aifix our signatu'res.

KAREL VAN DER GRINTEN. LOUIS VAN DER GRINTEN.