GB2032125A - A Method of Providing Contrast Reduction in Image Reproduction with a Diazotype Material and Diazotype Materials Adapted for the Application of said Method - Google Patents

Abstract

Contrast is reduced in diazotype materials by image-wise exposing the material in conjunction with a photosensitive non-diazo print out material. A print-out mask which absorbs the radiation to which the diazo compound is sensitive is formed during exposure. The diazotype material comprises a layer containing at least one diazo compound and in said layer or another layer adjacent thereto or in close proximity therewith at least one photosensitive non-diazo compound by means of which by exposure to actinic radiation at least one substance can be formed that absorbs actinic radiation to which the diazo compound is sensitive. The print-out and diazotype materials may be separable. An arrangement is also disclosed in which the print-out material is in the original to which diazotype material is exposed.

Description

SPECIFICATION A Method of Providing Contrast Reduction in Image Reproduction with a Diazotype Material and Diazotype Materials Adapted for the Application of Said Method The present invention relates to a method of providing contrast reduction in image reproduction with a diazotype material and diazotype materials adapted for the application of said method.

It is generally known that diazotype materials of common composition have a steep gradation and are unsuited for use in the broad field of continuous tone reproduction of which the duplicating of X-ray photographs is an example.

The use of diazotype material is excluded for the reproduction of continuous tones mainly because of the high contrast in the low densities and low contrast in the higher densities [ see J.

Kosar in Light-Sensitive Systems-John Wiley 8 Sons, Inc., New York (1965) p. 304].

Many attempts have been made to remedy for the lack of correct continuous tone rendition with diazotype materials. A survey of design of continuous tone diazotype imaging films has been given by Gilbert Zweig in Phot. Sci. Eng., Vol. 21, No. 8 Nov./Dec. 1977, p. 343-347. From the discussion in that article appears that there are no ideal solutions and that the price that must be paid to achieve extended tonal quality is a reduced photographic speed. This is due to the fact that in order to provide a better continuous tone rendition either mixtures of diazo compounds with rather widely varying photosensitivity and/or yellow or ultraviolet filter layers are introduced.

In the systems operating with combinations of diazo compounds of different photosensitivity, differences in coupling speed and deviation in colour tone of the print from the toe to the shoulder portion of the sensitometric curve are practically unavoidable. These effects are undesirable and render impossible the production of prints with neutral black colour throughout all the portions of the print. The presence of a yellow dye or ultraviolet light absorbing compound in overall equal concentration in the diazotype layer reduces speed in an overall way and depresses contrast not only in the highlight region but also considerably in the shadow region of the image where contrast is initially low already.

Another proposed approach to the problem is in the use of a diazo compound whose photolytic products absorb ultra-violet (U.V.) radiation.

Normally used diazo compounds, however, are changed into a species that absorbs actinic light very poorly (see U.K. Patent Specification 871,216, page 3, lines 40 - 46), so that the latter approach seems rather hypothetical.

The method of the present invention for providing contrast reduction in image reproduction by imagewise exposure to actinic radiation of a diazotype photographic material containing at least one photosensitive diazo compound, is characterized in that during said exposure in conjunction with said material a printout mask is formed by means of a photosensitive non-diazo compound, which print-out mask absorbs actinic radiation to which said diazo compound is sensitive.

By actinic radiation is understood ultra-violet radiation and even visible light as far as it can bring about the decomposition of the diazo compound(s) in the diazotype material.

The present invention includes such a method wherein the print-out mask is formed either in an element integral with, or separate from the diazotype photographic material.

The ingredients for forming the print-out image when not chemically interfering on coating and storage may be used in the diazotype material in the layer containing the diazo compound(s) but will normally be applied in a layer apart therefrom.

The present invention therefore provides according to one embodiment a specially adapted diazotype material suited for use in said method, wherein said material includes in a permanently united combination, i.e. in integral association, a layer containing at least one diazo compound and adjacent or in close proximity to said layer an other layer containing at least one photosensitive non-diazo compound by means of which by exposure of the layers to actinic radiation at least one substance can be formed that absorbs actinic radiation to which the diazo compound is sensitive.

The present invention provides according to a second embodiment a combination of photosensitive materials wherein said combination comprises: (1) a diazotype material, which contains a diazo compound, and in contact with said material, (2) at least one print-out material that is separable from the diazotype material and wherein, by means of a photosensitive non-diazo compound upon exposure to actinic radiation at least one substance can be formed that absorbs actinic radiation to which the diazo compound is sensitive.

Good results are obtained with a print-out material capable of producing a print-out image having a maximum gradient of the sensitometric curve, i.e. density versus relative log exposure curve, lower than 0.6, preferably of about 0.4.

The present method using a print-out recording system in combination with the diazotype material does not lower speed in an overall equal way as is the case by using a U.V. or yellow filter layer and does not depress too much the contrast in the shadow region of the images i.e. the region receiving the lower radiation doses. By proper selection of the sensitometric properties of the print-out composition images can be obtained with the diazotype material which images have improved linearity in the sensitometric curve.

In the production of the layer or material having print-out properties for lowering, according to the present invention, the gradation characteristics of a diazotype material any non j#,i#/o#/#l#;t3o#~oo#~mi#tl//on#nna#x#l# diazo substance or mixture of non-diazo substances for print-out image production may be used with the proviso that they (it) allow(s) the production of (a) substance(s) absorbing actinic radiation during the photolysis of the diazo compound(s) of the diazotype material involved.

Among the printout systems that are useful for application according to the present invention photochromic systems can be mentioned. Many inorganic and organic compounds show a change in electromagnetic radiation absorption when exposed to actinic radiation. So, it is possible to select such photochromic compound wherein shorter wavelength U.V. absorption brings about a shift of radiation absorption to longer wavelengths whereto an elected diazo compound is more sensitive.

Many of the photochromic systems are reversible so that after playing its role of photomask forming compound in the present invention the photochromic compound, which may be originally colourless, can be reverted to that state and in that way does no longer interfere with the dye image obtained from the diazo compound(s). Examples of such photochromic compounds are given by E. Brinckman, G.

Delzenne, A. Poot and J. Willems in Unçonventional Imaging Processes The Focal Press--London and New York (1978) p. 98-100 and in the United States Patent Specification 3,442,648.

Other print-out systems suitable for use according to the present invention are based on the photolysis of free or complexed photosensitive organic polyhalogen compounds that are capable of producing an acid and are used in chemically reactive contact with a dye precursor compound(s), e.g. leuco bases that undergo a colour change by reaction with an acid.

Examples of such acid-sensitive systems are also exemplified in the above book of E. Brinckman et al, pages 83~93.

In these processes preference is given to the spiropyran print-out system that ope#rates with a photosensitive organic polyhalogen compound e.g. carbon tetrabromide and a spiropyran type dye precursor that by reaction with photochemically formed hydrogen halide is transformed into a pyrylium dye salt.

Spiropyran compounds, photosensitive organic polyhalogen compounds and chemical and spectral sensitizing agents for that print-out system are described etg. in the United States Patent Specifications 3,810,762-3,810,763- 3,813,245 and 3,980,480. Other suitable pyrylium dye precursors are ketostyryl compounds as described, e.g., in the United States Patent Specification 3,817,752.

A print-out system for the production of yellow-orange images based on the use of carbon tetrabromide and indole is described by R. H.

Sprague and M. Roscow in Phot. Sci. Eng., Vol. 8, No. 2, March-April 1964, p. 93. The dye precursors forming a yellow dvestuff are preferred or t e purpose o e pre dye precursor is, e.g., 1', 3',3' -trimethyl spiro [ 2H - 1 - benzopyran - 2,2' - indolinei.

Another print-out system suitable for use according to the present invention is based on a photoredox reaction. Herein e.g. the photosensitive non-diazo compound is a photooxidant being capable of forming on exposure free radicals that are able to oxidize leuco derivatives of dyes. A photo-oxidant that is particularly useful for that purpose is, e.g. an hexaarylbiimidazole as is described, e.g., in the United States Patent Specifications 3,585,038 and 3,734,733. In the former document many colour-forming oxidizable compounds are mentioned such as (1) p-arylene dii-tertiary amines, (2) p-phenylenediamines, (3) 0,0'-disubstituted diphenols wherein the substituents are halogen, lower alkyl or lower alkoxy, and the paraposition to the hydroxyl is unsubstituted, and (4) organic sulfhydryl compounds.Among these oxidizable compounds the O,0'-disubstituted diphenols that yield yellow compounds are preferred, e.g. 4,4'-dihydroxy 3,3',5,5'-tetramethyldiphenyl.

The amounts and proportions of the substances forming a print-out image are chosen in view of the desired gradation correction.

The presence of a print-out image having a colour different from the colour formed with the diazo compound(s) is not necessarily disturbing in image detail recognition. As described in the United States Patent Specification 3,721,823 good image-detail-reproduction in X-ray photographs can be obtained by producing colour images of opposite gradation and contrasting colours. An example of such combination of contrasting colours is the combination of black image parts on a yellow background.

If, however, completely colourless or white image background areas are required the printout image is formed in a material separately from the diazo type material, or use is made of a diazotype material integral with a print-out composition or layer that yields an image only absorbing U.V. radiation or a visible image that can be reverted to the colourless state.

According to one embodiment an only UVabsorbing substance can be photochemically produced, e.g. by photochemically decomposing biimidazolyl compounds. The spectral absorption of these compounds and of products formed therewith is described by K. Maeda and T.

Hayashi in Bull Chem. Soc. Japan 43 (1970) 429~37.

According to still another embodiment pyrylium or thiapyrylium leuco dyes that after their transformation in dye salt form can be bleached again to non-UV-absorbing leuco compounds by reaction with an alkaline substance, e.g. the alkali used in the coupling reaction of the diazo compound with a coupling agent are used.Said leuco dyes correspond to the following general formula:

wherein: (1) T' represents a member which is either an alkyl radical having from 1 to about 15 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, amyl, isoamyl, hexyl, octyl, nonyl, decyl, dodecyl pentadecyl and the like, an alkoxy radical having from 1 to about 8 carbon atoms like methoxy, ethoxy, propoxy, butoxy, amyloxy, hexoxy, octoxy, etc,, or an aryl radical of the benzene series such as phenyl, naphthyl, etc., with phenyl being preferred and including substituted aryl radicals such as alkylphenyl radicals like 4-ethylpheny, 4- propylphenyl, etc., alkoxyphenyl radicals like 4 ethoxypheny, 4-methoxyphenyl, 2-hexoxyphenyl, 3,4-di methoxyphenyl, 2-hydroxyethoxyphenyl and the like as well as additional substituted aryl radicals like 4-hydroxyphenyl, 3,4-dichlorophenyl, 3,4-dibromophenyl, 4-chlorophenyl, or 2,4dichlorophenyl.

(2) T2 represents a member which is either a hydrogen atom, an alkyl radical having from 1 to about 15 carbon atoms such as those described hereinabove in conjunction with the T1 substituent, an alkoxy radical having from 1 to about 8 carbon atoms as those described in relationship to T1 or an aryl radical also as those described above with reference to T', phenyl being preferred, and (3) D represents either an oxygen atom or a sulfur atom.

These leuco dyes are transformed by reaction with a photographically formed acid into the corresponding UV-absorbing pyrylium and thiapyrylium dye salts. Such dye salts are described in the United States Patent Specification 3,679,415 and correspond to the following general formula:

wherein T1, T2 and D have the same meaning as above and X- is an anion.

The latter specification relates to diazotype elements having an extended exposure latitude obtained with a specific overall UV-absorbing layer.

The term "diazo compound" in the present invention relates to diazonium salts.

Useful diazonium salts and coupling agents therefor include benzene diazonium salts described in the above United States Patent Specifications 3,676,138 and 3,679,415.

In the production of the diazotype print one can use the two component process in which the diazo compound and a coupler therefor are applied simultaneously with a stabilising acid to a carrier medium or one can use the one component process where the diazo compound is applied alone optionally in the presence of an acid. In the first case ammonia fumes are normally used to lower the pH of the recording layer, whilst in the second case usually a thin film of liquid containing the coupler together with buffering salts in aqueous alkaline medium is applied.

For case of coating and stability of the coated layer, both the print-out composition and the diazotype composition are generally incorporated in a resinous matrix such as those described hereinbelow, conventionally each in an amount of from about 20 to about 50 parts by weight per 100 parts of matrix vehicle.

In addition to the dye-forming components, the diazo-type composition can contain and usually does contain other additives such as stabilizers and the like to advantageously modify its photographic and chemical properties. A preferred class of additives includes acid stabilizers with the proviso that they do not interact with the print-out composition. The acid operates to prevent premature coupling of the diazonium salt and coupler compound. Acid stabilizers include organic acids such as 5sulfosalicyclic acid and the like as well as numerous other organic and inorganic acids. The amount of acid stabilizer normally varies from about 1 part to about 6, and preferably from about 2 to about 5 parts by weight per 100 parts of polymeric matrix.Additionally, metal salts such as zinc chloride can also be present as a development accelerator or dye brightener, generally in an amount of from about 0.5 to about 1.5 parts by weight per 100 parts of matrix vehicle.

Another, and especially desirable, class of additives for diazotype compositions comprises hindered phenols containing in the 2-position either an alkyl or a cycloalkyl radical and in the 4position an alkyl radical, an alkoxy radical, a hydroxyl radical or a thioether radical, which with the hindered phenolic moiety completes a hindered bisthiophenol and more generally a symmetrical bisthiophenol. These hindered phenols restrain fading of the developed azo dye image. Such hindered phenols are described in detail in the U.S. Patent No. 3,951,381.

The diazotype compositions are preferably carried in a film-forming hydrophobic polymeric matrix or binder when preparing photographic elements, both for ease of coating and physical stability of the resultant light-sensitive layers.

Advantageous matrix vehicles include a wide variety of polymeric substances such as, for example, cellulosic ethers such as ethylceullose, butylcellulose as well as cellulose esters such as cellulose acetate, cellulose triacetate, cellulose propionate, cellulose acetate propionate, cellulose butyrate and cellulose acetate butyrate; vinyl polymers such as poly(vinyl acetate) poly(vinylidene chloride) poly(vinyl butyral), copolymers of vinyl chloride and vinyl acetate, polystyrenes, poly(methylmethacrylate), copolymers of alkyl acrylates and acrylic acid, etc.; polyesters such as the esterification product of pcyclohexanedicarboxylic acid and 2,2,4,4 tetramethylcyclobutane-1 3-diol, as well as additional polymers such as polyphenylene oxides, terpolymers of ethylene glycol, isophthalic acid and terephthalic acid and terpolymers of pcyclohexane dicarboxylic acid, isophthalic acid and cyclohexylenebismethanol. Depending on the type of non-diazo print-out composition, a hydrophilic or hydrophobic binder can be used as matrix for the said composition.

In the preparation of the adapted diazotype photographic elements of the present invention, a support material such as described hereinbelow is coated with the print-out light-sensitive layer(s) superposed onto the diazotype layer(s) such that they can be exposed simultaneously by light rays.

Advantageous support materials include conventional photographic film base materials, for example, cellulose esters such as cellulose acetate, cellulose triacetate, cellulose acetate butyrate, etc., poly-a-olefins such as polyethylene and polypropylene, polyesters such as poly(ethylene terephthalate), polystyrenes, polycarbonates, as well as metals such as zinc and aluminium and paper including polyethylene and polypropylene coated papers. Other support materials that are suitable for use herein are known in the art. It is advantagsous that the support be transparent or substantially so if the image is to be viewed or copied via transmitted light.

Coating is typically by solvent coating means since it offers the potential for rapid, convenient, continuous operation and alternative coating techniques such as immersion, flow coating, whirl coating, brushing, doctor blade coating, hopper coating and the like can be used if desired.

Coating is generally effected by first dissolving the photographic image-forming composition in a suitable solvent along with a matrix polymer if described. The coating solutions conventionally contain from about 2 to about 20 weight percent solids and preferably from about 4 to about 10 percent solids. In these solutions when a matrix polymer is utilized, the photographic imageforming components are typically included in an amount of from about 20 to about 5Q parts by weight per 100 parts of polymeric binder. Wider variations are possible where desired, but the above-mentioned ratios are typical for most conventional preparations.After coating by such means as whirl coating, brushing, doctor blade coating, hopper coating or the like, typically at a wet thickness of from about 25 microns to about 125 microns, the coated material is dried to prepare a composite photographic element of this invention.

Exposure is advantageously to a source of light radiation which is rich in ultraviolet and actinic rays such as a mercury arc lamp.

After exposure, which can be, for example, through a continuous tone photographic transparency, the element is suitably treated or contacted with an alkaline medium such as one including aqueous ammonia vapor or anhydrous ammonia gas to produce a coloured, azo dye image in unexposed areas and thereby forming a positive copy corresponding to the original.

During image development the alkaline medium optionally bleaches the print-out image to a colourless form. Such can be obtained by producing the print-out image with pyrylium dye salts.

Although the present invention is primarily directed to conventional diazotype photographic materials containing only one diazotype layer the use of diazotype materials containing a plurality of diazotype layers, e.g. of different photosensitivity, is not excluded. Examples of such materials that contain a plurality of diazotype layers, but in combination with a UV-absorbing layer, are described in the United States Patent Specifications 3,661,591 and 3,679,415.

The present invention is illustrated by the following examples without, however, limiting it thereto.

The ratios and percentages are by weight unless otherwise indicated.

Example 1 Preparation of the Print-out Material Onto an unsubbed polyethylene terephthalate film having a thickness of 0.075 mm the following composition was coated at a wet coverage of 125 g persq. m: copoly(N-vinylcarbazole-methyl acrylate-hydroxyethyl acrylate) (60/35/5) 3 9 iodoform 1 g 1 ',3',3'-trimethyl-spiro [ 2H-1 benzopyran-2,2'-indoline ] 0.4 g 1,2,2-trichloroethylene 100 g The coating was dried at 400 C.

Procedure A) Onto a commercial diazotype duplicating film Bexford P-13178 (trade name of Bexford Ltd., Brantsham Manningtree, Essex, England) the above print-out material was placed with the print-out layer into contact with the diazotype layer. The obtained sandwich was exposed through a continuous tone wedge (constant 0.15) placed into contact with the support of the printout material. The exposure proceeded for 30 s with a UV-emitting high-pressure mercury vapour tube of 3000 W placed at a distance of 60 cm.

The diazotype material was developed with wet ammonia vapour.

B) The procedure under A) was repeated with the difference, however, that the print-out material was left out of the arrangement in the exposure.

Sensitometric Evaluation The density measurements of the prints obtained in the procedures A) and B) were effected with a Macbeth Densitometer Model TD102 using a green filter.

The obtained results are presented as density (D) versus relative log exposure (rel. log E) graphs in Fig. 1, wherein graphs 1 and 2 relate to the results obtained in procedure A) and B) respectively.

Hereby the lowering of gradation resulting from the image-wise exposure of the diazotype material through the print-out material is clearly demonstrated.

Example 2 Preparation of the Print-out Material The following solutions A and B were homogenized in a high-speed mixer at 500C.

Solution A 4,4'-dihydroxy-3,3',5,5' tetramethyl diphenyl 1.08 g 2,2'-bis(o-chlorophenyl) 4,41,5,5'-tetraphenyl- biimidazole 3 9 chloroform 30 ml ethyl acetate 13.5 ml Solution B gelatin 10 9 Iaurylbenzenesulphonic acid sodium salt 0.28 g water (400C) up to 200 9 After the homogenizing a part of the solvents was evaporated with a rotatory-vacuum evaporator keeping the mixture at a water bath of 50 C. Concentrating was effected up to a residue of 1 75 g, which was then diluted with water up to 200 g.

The obtained mixture was coated onto a subbed polyethylene terephthalate support of 0.1 mm thickness at a wet coverage of 126 g per sq.

m. The layer was gelled at 200C for 1 min and dried at 40-450C for 3 min.

Procedure The procedures A) and B) of Example 1 were repeated but now as diazotype material XIDEX DEM (trade name of Xidex, Portreeves House,1~ 2, East Bay, Colchester Essex, England) combined with the above print-out material was used.

Evaluation The density measurements obtained after the procedures A) and B) are graphically represented in Fig. 2. Herein the graphs 3 and 4 relates to the sensitometric curves obtained with the procedures A) and B) respectively.

Here too the lowering of gradation by the use of the print-out material is clearly demonstrated.

In Fig. 3 the sensitometric curve representing density (D) versus relative log E of the photomask formed in the print-out material is given.

Example 3 In order to demonstrate the difference in effect on the diazotype print when a continuous equal density filter instead of an image-wise formed photomask of opposite gradation is used, the following procedure was followed: the print-out material of Example 2 was overall exposed under the exposure conditions of Example 1, which are the same as those of Example 2. Hereby a yellow filter layer having an overall density equal to 0.84 measured through blue filter was obtained.

This filter layer was placed on top of the diazotype material of Example 2 and an imagewise contact-exposure was effected through the continuous edge as in Example 1 The sensitometric curve of the obtained diazotype print is represented in Fig. 4. From the graph can be learned that in the toe portion there is no gradation lowering at all and that in the shoulder portion the gradation is lower considerably, which points to under-exposure.

The methods and materials of the present invention can be advantageously used for the reproduction of X-ray photographs obtained with silver halide emulsion film. Since silver is one of the metals for which an increasing production shortage exists and which has to be recovered as much as possible, non-silver diazotype materials will present a solution to that problem. Because of the inherent low photosensitivity and/or low image amplification of said non-silver materials these materials will not find use in direct recording where high sensitivity such as in X-ray fluorescent screen recording with silver halide radiographic materials is required. In the production of prints, however, from already obtained silver images these materials have valuable properties such as e.g. their high resolving power by virtue of a grain-free structure.

In the accompanying schematic drawing (Fig.

5) a radiographic system is illustrated wherein a silver halide film material only serves for making the original continuous tone prints and a gradation-corrected diazo system of the present invention serves for the reproduction of these originals wherefrom the silver is recovered later on.

In said Fig. 5 daylight-shielded photographic silver halide film material 1 is fed from a supply reel 2 into the X-ray exposure station 3. Herein the silver halide material 1 is image-wise exposed through an object 4 in contact with an X-ray intensifying screen 5 that fluoresces when struck by the X-rays of the X-ray source 6. After exposure, which may proceed in rapidly following frames as in cineradiography, the exposed part of the continuous roll of film 1 is accumulated in a film accumulator 7 waiting therein for its processing in the developer station 8. Herein the film 1 remains for the time required fordevelopment optionally also fixing, rinsing and drying.

Thereupon the film 1 arrives in the printing station 9, wherein a continuous tone copy of each developed film frame is made with the light source 10 projecting actinic radiation through each film frame onto the gradation-corrected diazo film 11 of the present invention.

The diazo film 11 containing a non-separable print-out top layer (not shown in the drawing) for forming a print-out image absorbing U.V.

radiation or yellow light is fed from a feed roller 12 into the printing station 9 in which contact exposure of the diazo film 11 with the developed silver halide film 1 takes place. After development in the developing station 13 and diazo film 11 is cut to the required size in the cutting station 14 from which it reaches a film receptor 15. The silver halide film material 1 is wound on a take-up core 16 and is then sent to a unit (not shown) wherein the silver is recovered.

According to a modified embodiment the photographic silver halide film can contain a coating of a suitable print-out composition e.g.

below the silver halide emulsion layer and the diazo film does not contain a print-out layer.

Claims (11)

Claims

1. A method of providing contrast reduction in image reproduction by image-wise exposure to actinic radiation of a diazotype photographic material containing at least one photosensitive diazo compound, characterized in that during said exposure in conjunction with said material a printout,.mask is formed by means of a photosensitive non-diazo compound, which print-out mask absorbs actinic radiation to which said diazo compound is sensitive.

2. Method according to claim 1, characterized in that said diazotype photographic material comprises in permanently united combination a layer containing at least one diazo compound and adjacent or in close proximity to said layer a layer containing said non-diazo compound or said diazotype material contains the diazo compound and non-diazo compound in the same layer.

3. Method according to claim 1, characterized in that the photographic material containing said diazo compound is image-wise exposed in contact with a separate print-out material containing said non-diazo compound, which printout material is separated from said photographic material after the exposure.

4. Method according to any of claims 1 to 3, characterized in that said photosensitive nondiazo compound is a photochromic compound.

5. Method according to any of claims 1 to 3, characterized in that the photosensitive non-diazo compound is a photosensitive organic polyhalogen compound that produces by said exposure an acid and in that a leuco base is used, in chemically reactive contact with the polyhalogen compound, so as to produce during exposure by reaction with said acid a substance absorbing said actinic radiation.

6. Method according to any of claims 1 to 3, characterized in that, the photosensitive nondiazo compound is a photooxidant forming on exposure to actinic radiation free radicals that oxidize during exposure a leuco derivative of a dye forming hereby a substance absorbing said actinic radiation.

7. A diazotype material comprising a layer containing at least one diazo compound characterized in that the said material comprises in the said layer or in another layer adjacent or in close proximity to said layer and in permanently united combination therewith at least one photosensitive non-diazo compound by means of which by exposure to actinic radiation at least one substance can be formed that absorbs actinic radiation to which the diazo compound is sensitive.

8. A diazotype material according to claim 7, characterized in that said photosensitive nondiazo compound is a photochromic compound.

9. A diazotype material according to claim 7, chracterized in that said photosensitive non-diazo compound is a photosensitive organic polyhalogen compound capable of producing an acid and said material contains in chemically reactive relationship with the polyhalogen compound a leuco base that produces by reaction with said acid a substance absorbing actinic radiation to which the diazo compound is sensitive.

10. A diazotype material according to claim 7, characterized in that said photosensitive nondiazo compound is a photo-oxidant being capable of forming on exposure to actinic radiation free radicals that are able in said material to oxidize a leuco derivative of a dye forming hereby a substance absorbing actinic radiation to which the diazo compound is sensitive.

11. A combination of photosensitive materials wherein said combination comprises: (1) a diazotype material, which contains a diazo compound, and in contact with said material, (2) at least one print-out material that is separable from the diazotype material and wherein, by means of a photosensitive non-diazo compound upon exposure to actinic radiation at least one substance can be formed that absorbs actinic radiation to which the diazo compound is sensitive.