US2659672A - Diazotype photoprinting materials - Google Patents

Description

' Patented Nov. 17, 195.3

- =U qm :p* srn rss PATENT OFFICE 2,659,672 nulzo'rrrn rno'roram'rmo MATERIALS Werner Paul Leuch, London, England, asslgnor to Hall Harding Limited, London, England, a corporation of Great Britain and Northern Ireland No Drawing. Application December 21, 1948, Serial N0. 66,579

Claims priority, application 'Great Britain January 9, 1948 "5 Claims. (Cl. 95-6) The present invention relates the production of light-sensitive layers by means of diazo compounds capable of producing prints in two "or more contrasting colours and in particular in "primarycolours red, yellow or blue, or in comv plementary colours such as red and green or orange and blue or yellow and violet from one D floriginal depending on the composition of the f light-sensitive layer.

, produced by this process may be drawings exe- The originals to be recuted mini: and pencil or in at least two inks or colour washes, where each ink or colour wash possesses the property of adsorbing or transmitting a quantity of light which is substantially diiferent from that absorbed orftransmitted by the other ink or colour washes on the drawing. Also the drawings can be of a kind where one ink transmits no light at all and the other a definite proportion only of the total quantity of light transmitted during a given exposure time. makes it possible to obtain two complementary This colours or two desired primary colours out of a possible of three, or three colours simultaneproduce photographic prints in two or more contrasting colours from monochromatic photographic transparencies of different degrees of density.

Other objects of the invention will be mani- .fest from the description.

It has been suggested in the past that prints in'twocolours could be obtained by means of the diazotype process from original drawings of the type described above by using a light-sensitive layer containing two diazo compounds, where one diazo would yield one colour with a certain coupling component and the other diazo a different colour, or where the light-sensitive layer, composed of the two diazo compounds, could react with two coupling components. added to it and thus could produce two different colours on development. Another method attempted for producing two colours in one print consisted in using one diazo compound which could give difierent shades of colour with one or more coupling components, according to the quantity of diazo compound left on the copy after exposure to light under a drawing or half-tone positive. All these methods have the disadvantagethat they are incapable of producing prints in primary or in complementary colours, since the denser portions of the drawing or other pattern which is to be reproduced would always contain a mixture of the two colours employed. Thus, if. for instance the light-sensitive layer were arranged in such a manner that one diazo could produce a blue dye and the other diazo a red dye, the denser portions of the drawing would be represented by a mixture of these dyes, which in this case would be violet. The less dense portions could only be either blue or red or a mix-,

ture of both with a predominance of one or the other, i.e. both colours related to violet and therefore not contrasting or complementary.

Such colours could not exhibit the good contrasts desired in a technical drawing for instance. It will be understood, that our new process produces positives from positives. The development can be carried out by ammonia gas ii the coupling component or components are already present in the sensitive layer. As an alternative to this case the development of the dyestuffs, instead of by means of ammonia gas,

can be eifected by the application of a liquid developer capable of causing the components to react with each other. In the case where no coupling component is added to the light-sensitive solution or layer prior to printing, development can be carried out by the application of a liquid in which the coupling component or components have been incorporated together with an alkaline -substance.

The principle on which the present invention operates is that two or more diazo compounds are used at least one of which (B) is incapable of forming a, dyestufi with the coupling components (C) present in the light sensitive layer (in the case of layers developed by the ammonia 5 gas method) or in the developer (in-the case of moist or semi-dry development), but is capable of coupling with its own decomposition product I (D) produced during exposure to light, and that at least one other diazo compound (A) is used which is capable of coupling with the coupling as such a manner that suflicient difference in printing out speeds results between at least two of the diazo compounds used. v

This quantity may, according to they wave length sensitivity of the respective diazo compounds, have to be varied to suit the spectral composition of ,the light used for exposure.

For use as diazo compounds (B) which are not capable under the usual conditions of development of forming a dye'stufi with the coupling component already present in the unexposed light-sensitive layer or applied subsequently with the developer, members of the class of diazo anhydrides or diazo oxides, particularly those of the naphthalene series, have been found to be specially advantageous. These generally are compounds which bleach out in a neutral or acid medium, and are incapable of forming dyestuffs with coupling components of medium coupling velocity such for example as 2.3-hydroxynaphthalene-G-sulphonic acid, or the amide of 2.4-resorcylic acid.

The other diazo compounds (A) which are ca-' pable of coupling with the coupling component (C) may be any of the diazo compounds generally used in the production of diazotype prints aetacv'a quently, and dye results on development. with such an arrangement it is therefore possible that in those portions of a drawing which transmit no light at all, only diazo component A can form a dyestufi; in this case blue with coupling component C, while diazo B, not having been affected by light, remains incapable of forming a'dye. Where both diazo compounds have been bleached out completely, a White ground is obtained; on the other hand, in the portions where there is still some diazo component A left but where diazo component B has started to decompose and form coupling component D, coupling takes place chiefly between coupling component D and diazo component A to form yet another dyestufi: in the present case this is a greenish yellow. As at the same time diazo component A also couples 'in these portions to a certain extent with coupling component C, the colour effect can vary, according to the amount of light transmitted, from a greenish blue to a yellowish green. The whole colour range possible with a given light sensitive provided they give the desired colours with the coupling component employed, and possess the required sensitiveness to light relative to the diazo compounds (B) employed with them.

The coupling components to be used according to this invention are chosen to give the desired colours with the diazo compounds used and in general are compounds of moderate coupling energy so that they do not couple with diazo compound denoted as (B) under the conditions used. Coupling components of high coupling energy such as phloroglucinol are therefore generally not suitable. A large variety of coupling components are, however, suitable, examples of such being the 6-mono-sulphonic acids of 2.3- and 3.8-dihydroxyn-aphthalenes, the amide of 2.4- resorcylic acid, resorcinolpropyl ether, m-hydroxyphenyl urea and the monoglycol ether of pyrocatechol.

The method of carrying out this process is exemplified by the following description but of course the invention is in no way limited to the colours indicated.

Two diazo compounds A and B are brought onto a suitable base such as paper, together with a coupling component C. Diazo component A is capable of forming a blue dyestufi with coupling component C under given conditions. Diazo component B however is incapable of forming a dyestuff with coupling component C under the same conditions. On the other hand diazo component B forms, during exposure to light, a coupling component D with which it is capable of forming a red dyestufi in those portions of the copy where not all the diazo component has been destroyed by the light. Where this decomposititon of B with consequent formation of coupling component D is about 50% of the total of B in the layer the red dye is most intense. It must be understood that for the purpose of this process the two diazo compounds A and B either must possess diiferent sensitiveness to the light of a given light source or must be mixed in such proportions in the sensitizing solution, that one diazo component prints out faster than the other. The proportions have to be arranged so that for instance there is still a considerable amount of diazo component B left in some of those portions where A has already been completely destroyed by the action of light. In those portions, conselayer of the described type can best be studied by exposing it under a grey wedge photometer used for sensitometry. with a definite wedge constant. We have found that a very' suitable wedge is one where the wedge constant is equal to 1.414 (V5); to this sensitometer we add, for purposes of comparison a solid black which transmits no light. When the correct exposure for a given light sensitive layer has been determined under an arc lamp, the developed print will exhibit the following colours: from white, where both the diazo compounds have been completely bleached out, via pale red to intense red (where some diazo component B is left to the maximum depth where about half the diazo component B has been converted to the coupling component D but where no diazo component A is left), to yellowish green which gradually changes, up the scale to green and bluish-green (where diazo component A exists in increasing quantity and coupling component D diminishes proportionately to the amount of light received by diazo component B) and finally to greenish-blue and pure blue respectively (i. e. from where only minute quantities of coupling component D have been formed to where no coupling component D is present). An Eder- Hecht sensitometer can be used equally well for this purpose of testing the colours. If instead of these types of wedges 'one uses a Wratten wedge utilised in three-colour half-tone printing, the colour changes on the print are more abrupt, i. e. they show up with fewer intermediate steps of shades, and practically only yield bright red, green and blue-grey, with pure blue under solid black. portions.

From the above description it can easily be visualised that a technical drawing, where certain portions are executed in black ink, or in any other ink which does not transmit light, and other portions in pencil which allows a certain amount of light to be transmitted, can be reproduced by means of the described type of lightsensitive layer in such a way that the two drawingmediums show up on the copy in two primary colours, such as blue and red and that it is possible by utilising a second pencil giving a deeper shade of grey, i. e. transmitting less light than the first pencil, to add a third colour, such as green in the present case. In the place of pencil one can use inks, either coloured or grey, with aesaeva proportions of diazo component A and diazo com- I ponent B in the layer. It instead oi two primary colours it is desired-to obtain copies in complementary colours,

ponent E. which possesses approximately the this can for instance be achieved by adding yet another coupling com-' same coupling energy as coupling component C and which produces a yellow dye with diazo component A and, of course, no colour with diazo component B. In this case the image is composed chiefly of green and'red dyes. When the original to be reproduced is a suitable photographic halftone positive, the colours obtained correspond to the various densities of the original in the same manner as on the wedge sensitometer.

A suitable light-sensitive layer of the type described contains also stabilisers which ensure good keeping qualities of the material before printing and ingredients which counteract the yellowing of the copy after it has been made. In the case of moist development of the print, the anti-yellowing agents can be incorporated in the developer, but the light-sensitive layer and developer must be compounded in such a manner 'that'no excess alkali is left on the paper after completed development, if good stability of the prints is desired.

The following examples serve to illustrate the manner in which the new light-sensitive layers may be produced, but the invention is of course in no way limited to these examples.

EXAMPLE 1 (Solution 1 ,for blue) In 150 cc. water dissolve 12 gr. tartaric acid 10 gr. thiourea 5.1 gr. zinc chloride double salt of l-N-ethyl-hydroxy-ethylamino benzene-i-diazonium chloride (Diazo compound A) 4.5 gr. 2.3 dihydroxynaphthalene 6 sulphonic acid (Coupling component C) 1o gr. zinc chloride 3 cc. diethylene glycol or glycerine (Solution 2 for red) 150 cc. water 12 gr. tartaric acid 10 gr. thiourea 6 gr. zinc chloride 3 cc. diethylene glycol 3.6 gr. sodium salt of the diazoanhydride of 2- amino-l-naphthol-B-sulphonic acid (Diazo compound B) By mixing these two solutions in equal proportions, and coating them on a suitable base such as paper in known manner, and then exposingto the light of an arc lamp the light-sensitive layer thus obtained, under a drawing such as has been described above, copies are obtained which after development by means of ammonia gas show the reproduction as follows: Dense ink lines are reproduced in blue, pencil lines in bright red in the case of lines of medium density and green in the 6 denser pencil lines or shadings. It the exposure is made under a high pressure mercury vapour tube, the red colour is replaced chiefly by yellow and orange on account of the fact that diazo compound A employed in this example is relative to diazo compound B, less sensitive to this li ht than to the light of the arc lamp. The'same applies when exposure is made in full sunligh". colours reach their full brightness only after allthe ammonia gas has left the paper. Also the prints, when freshly developed, shouldnot be exposed to strong daylight or other strongly actinic light sources until the ammonia gas has evaporated from the prints, if pure blue shades are desired. In order to obtain the best results it is essential that the apparatus used for making the copies provides good contact between the original and the light-sensitive material during printing.

If a further coupling component, such as acetoacet-o-toluidide, isadded'to Solution 1 and the quantity of 2.3 dihydroxynaphthalene 6 sulphonic acid is correspondingly diminished, green colours are obtained in place of blue beside the red. If the diazo compound in Solution 1 is replaced by an equivalent quantity of the zinc chloride double salt of 5-diethylaminotoluene-2- diazonium chloride, the blue shades obtained are more greenish. If instead of the colours 'described it is desired to obtain copies with blue colours for the dense portions of the original and the complementary orange colour for the lighter portions, one replaces the diazo anhydride used in Solution 2.by means of the diazo anhydride of 2 amino l naphthol-i-sulphonic acid. These colours can also be replaced by violet for the dense portions and yellow for the light portions by using a modified form of Solution 1 in which the 2.3-dihydroxynaphthalene-B-sulphonic acid is replaced by 2.8-dihydroxynaphthalene-6-sulphonic acid and a modified form of Solution 2 in which the diazo anhydride mentioned is replaced by the diazo anhydride of l-amino-2- naphtholl-sulphonic acid.

EXAMPLE 2 In this example the diazo compound designated as diazo compound A in Example 1 is replaced by a mixture of 3 grams of the zinc chloride double salt of 3-chloro l diethyl amino benzene-4- oliazonium choride and 4 grams of the zinc chloride double salt oi t-diethylamino-l-toluene-3- diazonium chloride. By working in the manner described in Example 1 it will be found that the light tones are reproduced in red, the medium tones chiefly in yellow and the darker tones in stance, in an original ink drawing, alterations.

may be shown in pencil and it may be desired.

in the photograph to emphasize these alterations. so that they stand out more prominently than the original drawing. By a suitable choice of component materials and of exposure, the present. process enables the dark lines of the original, drawing to be reproduced in alight colour and. the lighter lines of the drawing to be reproduced.

in a contrasting darker colour.

The-

7 EXAMPIE 3 A solution is prepared from 100 cc. of water in which are dissolved 6 gr. tartaric acid gr. thiourea 5 gr. zinc chloride 2 cc. polyglycol 3 gr. sodium salt of the diazoanhydride 01' 1- amino-2-naphthol-3.6 disulphonic acid 8 gr. zinc chloride double salt of 4-diethylaminol-diazonium chloride 1 gr. monoglycolether o1 pyrocatechol This solution when coated on paper and exposed and developed in the manner described in Example 1 gives a print in which the pencil lines of the drawing are shown in violet-blue, whereas the darker ink lines 01' the drawing are shown in bright yellow. If, however, the diazo anhydride used in this example is replaced by the diazo anhydride used in Example 1 then the pencil lines of the original drawing are reproduced in brilliant red and the ink lines of the gas method) or in the developer (in the case of moist or semi-dry development) but is capable of coupling with its own decomposition product;

and where at least one other diazo compound is used which is capable of coupling with the coupling component introduced into the light-sensitive solution or applied with the developer, and the respective quantities of the diazo compounds used in the sensitive solution are arranged in such a manner that sufilcient difference in printing speeds results between at least two of the diazo compounds used.

What I claim and desire to secure by Letters Patent is:

1. A light-sensitive layer for the production of a multi-colored' diazotype photographic print which contains a coupling component, C, and two diazo compounds at least one, B, of which is a .member of the group consisting of diazo anhydrides and diazo oxides which diazo compound is incapable of forming a dyestufi with said coupling component C but iscapable of coupling with the decomposition product, D, produced from B by the action of light and another one, A. of which is capable of coupling with said coupling component C, the relative quantities of the said diazo compounds A and B being such that there is a substantial diflerence in their printing out speeds.

2. A light-sensitive layer according to claim 1 in which the diazo compounds present in the light-sensitive layer are the zinc chloride double salt of 1-N-ethyl-hydroxy-ethylamino-benzene- 4-diazonium chloride and the sodium salt of the diazo anhydride 0: 1-amino-2-naphtho1-4-sulphonic acid and in which the coupling component is 2,8-dihydroxynaphthalene-6-sulphonic acid.

3. A light-sensitive layer according to claim 1 in which the diazo compounds present in the light-sensitive layer are the zinc chloride double salt Of 4-diethylamino-iediazonium chloride and the sodium salt or the diazo anhydride or 1- amino-2-naphthol-3.6-disulphonic acid and the coupling component is the mono-glycolether o1 pyrocatechol.

4. A light-sensitive layer for the production of a multi-colored diazotype photographic print. which contains a coupling component, C, and at least two diazo compounds one, B, of which is a member of the group consisting of diazo anhydrides and diazo oxides which diazo compound is incapable of forming a dyestufl with said coupling component C but is capable of coupling with the decomposition product, D, producedtrom B by the action 01' light. and another one, A, of which is capable of coupling with said coupling component C, the relative quantities of the said diazo compounds A and B being such that there is a substantial difference in their printing out speeds, the light-sensitive layer being further characterized in that the diazo compounds present therein are the zinc chloride double salt of 1- N ethyl hydroxy ethylamino benzene 4- diazonium chloride and the sodium salt or the diazo anhydride or 2-amino-1-naphthol-5-sulphonic acid and in that the coupling component is 2.3-dihydroxynaphthalene-s-sulphonic acid.

5. A process for the production of a multicolored diazotype print by coating at least two light-sensitive diazo compounds on a support and exposing the coated material behind a transparent design to the action of actinic light and then developing the print by coupling the diazo compounds with coupling components characterized in that the light-sensitive layer contains a coupling component, C, in that one, B, or the diazo compounds is a member of the group consisting of diazoanhydrides and diazo oxides which diazo compound is incapable of forming a dyestuif with coupling component C but is capable of coupling with the decomposition product, D, produced from said diazo compound 3 by the action of light thereon, in that a second one, A, of the diazo compounds is capable of coupling with said coupling component C, the relative quantities of A and B being such that, under the conditions of exposure to the light source employed, there is a substantial diiference in their printing out speeds, and in that after exposure to light the print is developed by treatment with an alkaline substance.

WERNER PAUL Lnucn.

References Cited in the file 01 this patent UNITED STATES PATENTS OTHER REFERENCES Spencer: Photographic Applications of Diazo Compounds," The Photographic Journal, Dec. 1928, pages 490 to 496, page 494 cited.

Claims (1)

1. A LIGHT-SENSITIVE LAYER FOR THE PRODUCTION OF A MULTI-COLORED DIAZOTYPE PHOTOGRAPHIC PRINT WHICH CONTAINS A COUPLING COMPONENT, C, AND TWO DIAZO COMPOUNDS AT LEAST ONE, B, OF WHICH IS A MEMBER OF THE GROUP CONSISTING OF DIAZO ANHYDRIDES AND DIAZO OXIDES WHICH DIAZO COMPOUND IS INCAPABLE OF FORMING A DYESTUFF WITH SAID COUPLING COMPONENT C BUT IS CAPABLE OF COUPLING WITH THE DECOMPOSITION PRODUCT, D, PRODUCED FROM B BY THE REACTION OF LIGHT AND OTHER ONE, A OF WHICH IS CAPABLE OF COUPLING WITH SAID COUPLING COMPONENT C, THE RELATIVE QUANTITIES OF THE SAID DIAZO COMPOUNDS A AND B BEING SUCH THAT THERE IS A SUBSTANTIAL DIFFERENCE IN THEIR PRINTING OUT SPEEDS.