GB1566802A

GB1566802A - Photosensitive imaging material

Info

Publication number: GB1566802A
Application number: GB22806/76A
Authority: GB
Original assignee: Agfa Gevaert NV; Agfa Gevaert AG
Current assignee: Agfa Gevaert NV; Agfa Gevaert AG
Priority date: 1976-06-02
Filing date: 1976-06-02
Publication date: 1980-05-08
Also published as: FR2353878A1; DE2723613C2; JPS52148304A; BE854534A; CA1104867A; JPS6024932B2; FR2353878B1; DE2723613A1

Description

(54) PHOTOSENSITIVE IMAGING MATERIAL (71) We, AGFA-GEVAERT, a Naamloze Vennootschap organised under the laws of Belgium of Septestraat 27, B 2510 Mortsel, Belgium, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to photosensitive imaging materials and to a method for imaging relying on the use of a polymer resist.

Photoresist applications are rapidly extending into many manufacturing fields with particular emphasis on microimaging and graphic arts, e.g. printing plate making.

Reprography, more particularly the production of screened negatives and positives, requires high contrast for sharp screen dot reproduction.

Miniaturization systems require high resolution and contrast so that photoresist compositions are especially useful therefor. The resolving powder of photoresists is higher than that of any silver halide system, including the Lippmann maximum resolutio emulsions [see C. R. Arnold et al, Applied Photography Focal Press London-New York (1971) p.443].

The opaqueness and contrast obtainable with silver halide film due to the nature of the finely divided silver halide and chemical liquid development is limited.

High opaqueness demands cannot be met by diazofilms producing azo dyes and diazo films producing vesicular images.

The limiting factors in the rsolution obtainable with photoresist coatings are the thickness of the resist coating, the thickness of the underlying metal coating together with the etching characteristics of the metal, which is to be removed selectively.

One of the widely used resist forming systems relies on the use of photosensitive polymers such as polyvinyl cinnamates. Photopolymers are negative-working and show good resistance to acids and alkalis. In processing the photopolymer requires the use of an organic solvent, which is a disadvantage in automatic processing with aqueous metalaching liquids that are incompatible therewith.

Another resist system is based on the use of diazo compounds. The diazo-based systems include positive- and negative-working materials. The diazo layers are processed with an aqueous solution but have a limited resistance to etch and plating baths used e.g. for the production of metal images. [see Arthur Tyrrell -- Basics of Reprography, Focal Press, London & New York (1972) p.183].

In accordance with the invention described in the published German Patent Application 2,259,759 filed December 6, 1972 by Energy Conversion a photosensitive recording material suited for the production of microimages, e.g. for microfiche cards, is described in which a separate radiation-sensitive resist-forming layer, which does not or need not have any substantial opaqueness of its own, and a separate layer of imaging material are used, the latter providing the opaqueness or other image-forming qualities.

The radiation-sensitive material in one embodiment of said invention comprises a water-soluble high molecular weight condensation product of a nitrogenous compound, which is a condensation product of a diazonium compound capable of giving off nitrogen when struck by ultraviolet radiation. The condensation product becomes waterinsoluble in the areas where it has been exposed to said radiation.

According to a preferred embodiment the imaging material consists of or comprises elementary tellurium that has been elected for its high opaqueness even in very thin layers and good adherence to many substrates. The tellurium-containing composition serving as the image-forming material is soluble in a solvent, which is a solvent different from the solvent used for the dissolution of the soluble areas of the radiation-sensitive material.

It is one of the objects of the present invention to provide easily processable imaging materials for halftone and microform production.

It is another object of the present invention to provide a method for producing highly opaque and very contrasty metal images.

In accordance with the present invention a photosensitive recording material is provided which comprises (1) a photosensitive layer containing a photosensitive nitrone of the formula:

in which: R is an aromatic hydrocarbon group or a substituted aromatic hydrocarbon group, and R1 is an aromatic or heterocyclic group or such groups which are substituted groups, in admixture with one or more polymers that are soluble in an alkaline aqueous liquid, said layer becoming insoluble in said liquid when said layer is exposed to actinic electromagnetic radiation, and (2) in contact with the photosensitive layer a subjacent supported metallic image forming layer of aluminium, zinc, tellurium or a tellurium alloy comprising at least 50 atomic percent of tellurium having a thickness in the range of 50 nm to 500 nm or a subiacent supported metallic image-forming layer of bismuth having a thickness in the range of 25 nm to 300 nm.

The nitrones can be prepared in a known manner, e.g. by reaction of an aromatic aldehyde wit han arylhydroxylamine (ref. US-Patent Specifications 2,426,894 and 3,416,922).

Exemplary of aromatic hydrocarbon groups R1 in the above formula are: phenyl, naphthyl, anthracyl, and phenanthryl and groups of higher ring systems, such as naphthacene, chrysene, pyrene, perylene, coronene or acenaphthene. Exemplary of heterocyclic groups R1 are groups derived from furan, pyrrole, thiophene, pyrrazole, imidazole, triazole, thiazole, oxazole, iso-oxazole, indole, thionaphthene, benzofuran, indazole, carbazole, dibenzofuran, pyridine, pyridazine, pyrimidine, pyrazine, quinoline, quin azoline, acridine and phenazine.

The aforementioned hydrocarbon and heterocyclic groups may contain the following substituents: a straight or branched, saturated or unsaturated, aliphatic hydrocarbon group, preferably containing no more than 8 carbon atoms in the longest chain, e.g.

a methyl, ethyl, propyl, isopropyl, butyl, 1,3 -methyl-hexyl or propenyl (1) group, a saturated or unsaturated cyclic hydrocarbon group, e.g. a cyclopentyl, cyclohexyl, dimethylcyclohexyl, cyclopentene or cyclohexadiene group; an alkoxy, hydroxyalkyl or alkoxyalkyl group, e.g. a methoxy, ethoxy, propoxy, hydroxymethyl, hydroxyethyl, hydroxyisopropyl, methoxymethyl or ethoxymethyl group; a heterocyclic group, particularly in hydrogenated form, e.g. a morpholine group, an aromatic heterocyclic group, e.g. a pyridyl group; an aromatic hydrocarbon group, e.g. an aryl, alkaryl, aralkyl, alkaralkyl, alkoxyaryl, or hydroxyalkaryl group, e.g. a phenyl, naphthyl, tolyl, xylyl, benzyl, methoxyphenyl, methoxy-anthracyl or phenylmethoxy group; a halo gentated aryl group, e.g. a chiorophenyl, bromophenyl or dichlorophenyl group; a halogen atom, e.g. chlorine or bromine, a nitro, N-hydroxyl or cyano group; or an amino, alkylamino, dialkylamino, arylamino, diarylamino or aralkylamino group, e.g.

a methylamino, propylamino, dimethylamino, diethylamino, dipropylamino methyl butyl-amino, phenylamino, naphthylamino or benzyl-ethyl-amino group.

Table 1 contains examples of a number of particularly useful nitrones with their melting point and sensitivity maximum.

TABLE 1

- Sensitivity Melting maximum point (wavelength) Compound Structural formula (0C) in nrn) Compound Structural formula ( C) in nrn)

1 -CH:N "2 109 317 0 2 X CH=; 134 349 3 HO- CH: N- 236 336 4 S CH=N- 116 353 5 02 N- -CH:- 186 364 3/ \1/ \3/ 186 364 115 334 6 H3 CO 0 By adding dyes as described, e.g., in the US-Patent Specification 3,416,922 mentioned hereinbefore an increase in photosensitivity and a broadening of the spectral photosensitivity from the UV-region to the visible light region can be obtained.

As alkali-soluble polymers can be used a copolymer of an unsaturated carboxylic acid, such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid. If the copolymer comprises an unsaturated dicarboxylic acid, the half-esters and half-amides thereof may be used too. These unsaturated carboxylic acids are coplymerised with ethylenically unsaturated compounds, which are substantially insoluble in alkaline medium and which are present in the coplymer in such a proportion that the copolyme ritself remains soluble in alkaline medium. Ethylenically unsaturated compounds that can be used for the copolymerisation are styrene and the derivatives thereof, vinyl chloride, vinylidene chloride, vinyl esters such as vinyl acetate, acrylates, methacrylates, acrylonitrile, methacrylonitrile e.g. copoly(ethylene/maleic acid) and copoly(methacrylic acid/methyl methacrylate).

Particularly suitable polymers for use in admixture with said nitrones are condensates of formaldehyde with phenol, which condensates are known as "novolaks". These polymers are highly acid resistant which is especially useful with regard to the resist formation on acid etchable metal layers.

According to Fred W. Billmeyer in the "Textbook of Polymer Chemistry" Interscience Publishers, Inc., New York (1967) p.350 novolaks are produced in acid solution by reaction of a high ratio of phenol to formaldehyde yielding a linear, soluble, fusible polymer having the structure:

where ortho and para links occur at random. Molecular weights may range as high as 1000, which corresponds to about 10 phenyl groups. These materials do not themselves react further to give crosslinked resins. Further information about the preparation of novolaks can be found in C E.llis "The Chemistry of Synthetic Resins" Volume 1 (1935) Reinhold Publishing Corp. New York p.303-309.

Good results are likewise obtained with condensates of formaldehyde with phenol or metacresol, reacted with chloroacetic acid.

Likewise suitable is a cellulose acetate phthalate having a degree of acetyl substitution (D.S. acetyl) between 1.0 and 1.7 and a degree of phthalyl substitution (D.S. phthalyl) between 0.6 and 1.2.

The proportions of alkali-soluble polymer(s) and nitrone in the photosensitive layer are preferably such that an ultraviolet exposure of said layer can effect at room temperature (20"C) a decrease in solubility of the exposed parts in an aqueous solution of 0.5 to 3% by weight of potassium hydroxide. Weight ratios of alkali-soluble polymer(s) to nitrone(s) comprised between 1:1 and 7:1 are preferred.

The photosensitive layer is applied by coating a solution of said nitrone(s) and polymer(s) to the metallic layer and evaporating the solvent by a common drying technique. The thickness of the dried photosensitive layer is preferably in the range of 0.5 to 5 pm.

According to one embodiment in the composition of the metallic layer tellurium or tellurium alloys comprising at least 50 atomic percent of tellurium are used. Typical tellurium compositions, which are very soluble in aqueous hypochlorite solutions e.g.

a composition of 81 atomic parts of tellurium, 15 atomic parts of germanium, 2 atomic parts of antimony, and 2 atomic parts of sulphur; a composition of 92.5 atomic parts of tellurium, 2.5 atomic parts of germanium, 2.5 atomic parts of silicon, and 2.5 atomic parts of arsenic; a composition of 95 atomic parts of tellurium and 5 atomic parts of silicon; a composition of 90 atomic parts of tellurium, 5 atomic parts of germanium, 3 atomic parts of silicon and 2 atomic parts of antimony; a composition of 85 atomic parts of tellurium, 10 atomic parts of germanium and 5 atomic parts of bismuth; a composition of 85 atomic parts of tellurium, 10 atomic parts of germanium, 2.5 atomic parts of indium and 2 5 atomic parts of gallium; a composition of 85 atomic parts of tellurium, 10 atomic parts of silicon, 4 atomic parts of bismuth and 1 atomic part of thallium; a composition of 80 atomic parts of telluruim, 14 atomic parts of germanium, 2 atomic parts of bismuth, 2 atomic parts of indium and 2 atomic parts of sulphur; a composition of 70 atomic parts of tellurium, 10 atomic parts of arsenic, 10 atomic parts of germanium and 10 atomic parts of antimony; a composition of 60 atomic parts of tellurium. 20 atomic Darts of germanium, 10 atomic parts of selenium and 10 atomic parts of sulphur; a composition of 60 atomic parts of tellurium, 20 atomic parts of germanium and 20 atomic parts of selenium, a composition of 60 atomic parts of tellurium, 20 atomic parts of arsenic, 10 atomic parts of germanium and 10 atomic parts of gallium; a composition of 81 atomic parts of tellurium, 15 atomic parts of germanium, 2 atomic parts of sulphur and 2 atomic parts of indium and many more, as described, e.g., in the U.S. Patent Specifications 3,271,591 and 3,530,441).

According to another and more preferred embodiment the image-forming layer consists of bismuth, Bismuth possesses the advantage of directly adhering to organic resin supports such as a polyethylene terephthalate support when deposited thereon from bismuth vapour under reduced pressure conditions.

Vapour deposition techniques are sufficiently known to those skilled in the art eg. of preparing photoconductive selenium coatings (see e.g. US-Patent Specifications 3,874,917 and 3,884,688).

Bismuth forms a black, non-light-reflecting coating showing no crazing and for a same layer thickness provides a higher spectral density than tellurium. Indeed, at a coating thickness of 200 nm tellurium offers a spectral density of about 3, whereas bismuth already at a coating thickness of 80 nm shows that spectral density. A 100 run bismuth layer has a spectral density of about 5. Further, bismuth layers whose thickness ranges from about 25 to about 50 nm corresponding with optical densities of about 0.5 to about 1.5 can be used as high energy radiation-sensitive recording medium as described, e.g., in the published German Patent Application 2,514,801 filed April 4, 1975 by Energy Conversion. Such bismuth coatings and likewise tellurium coatings can be reduced in optical density by a high energy light exposure capable of breaking up these coatings into small particles. A light energy dose of 0.5 joule per sq.cm, e.g. emitted by a xenon flash tube is, e.g., sufficient to break up these bismuth layers into small particles of coalesced bismuth. Hereby a reduction in optical density to a value of 0.2 to 0.3 is obtained. Instead of using a xenon flash tube whose light is modulated, e.g. by contact exposure, one can utilize the light energy of a powerful information-wise modulated laser beam.

Said bismuth layers may be formed in the size of microfiche or microfilm card in which the bismuth coating is divided up in image frames that may be produced therein by exposure of the overlying resist polymer layer through a line screen followed by resist development and metal etching. Such procedure and the imaging of said frames by image-wise coalescence of the bismuth may proceed, e.g., as described in Example 10.

The metallic layer of the recording materials according to the present invention is preferably applied to a polymeric film support, e.g. in the form of a sheet or belt.

Preferably a polyethylene terephthalate support, e.g. of 0.07 to 0.1 mm thickness, is used.

The present invention includes a recording method in which the above defined recording material is used to form metal images. Said method includes the steps of: (1) information-wise exposing said material to activating electromagnetic radia tion, also called actinic radiation, (2) overall contacting the photosensitive layer with an aqueous alkaline liquid to remove selectively the nonexposed or insufficiently exposed portions of the photosensitive layer, and (3) contacting the bared portions of the metallic layer with a liquid that is capable of chemically removing said portions without removing the exposed portions of the photosensitive layer.

Light sources commonly used in reproduction techniques such as mercury vapour lamps emitting ultraviolet radiation and xenon lamps may be used for exposing the photosensitive layer, the spectral sensitivity of which does not only depend on the nitrone(s) but also on the nature of (the) sensitizing dye(s) used.

The concentration of alkaline substance, e.g. potassium hydroxide, used for developing the resist layer, i.e. for selectively removing the unexposed photosensitive layer portions, may vary widely. Thus, e.g., a 0.5 to 10% by weight aqueous solution of potassium hydroxide may be used.

For the chemical etching of tellurium-containing layers aqueous hypochlorite solutions, e.g. of 0.5 to 30% of sodium hypochlorite, may be used.

For the etching of the bismuth layer preference is given to aqueous acidic iron(III) chloride solution. The concentration of iron(III) chloride is, e.g., in the range of 5 to 20% by weight. Said solution contains preferably from 0.25 to 1% by weight of citric acrid.

A likewise useful etching solution for the removal of bismuth is an aqueous solution containing 3 to 6% by weight of hydrogen peroxide and 5 to 10% by weight of sulphuric acid.

The processing of the photoexposed recording materials of the present invention is advantageously carried out in a processing apparatus, in which the material is transported automatically through processing stations in which the removal of the non-exposed portions of the photosensitive layer and the etching of the bared imaging layer portions take place in successive stations.

For example in a particularly suitable processing apparatus for use in the production of metal images e.g. bismuth-images according to the present invention, first station comprises a tray for holding an appropriate alkaline aqueous liquid, through which the photographic material is transported. After the resist development stage the surplus alkaline liquid absorbed in and adhering to the material is removed by passing the developed material through a second tray'filled with plain water whereupon the material is led through a third tray containing a suitable etch solution for the bared portions of the metallic imaging layer. Processing is completed by carrying the material through fourth tray containing plain water for rinsing the material.

Processing preferably proceeds at room temperature (about 18 to about 250C) but may proceed at higher temperatures. Care must be taken, however, not to damage the resist layer.

The alkaline developing station and etching station can be arranged separately but preferably they are grouped in a compact unit, in which the photographic material is carried automatically at a constant speed from the resist developing tray into the other trays.

The total processing in said trays normally lasts about 30 seconds at 20--300C.

A useful processing apparatus is, e.g., a common 4-tray processing station as used in the known four-bath silver halide stabilization processing (see e.g. the United Kingdom Patent Specification 1,243,180 more particularly the RAPIDOPRINT (Trade Mark) unit DD 1437).

The independence of the photosensitivity of the resist layer from the underlying highly opaque image-forming layer in the imaging materials of the present invention makes it possible to produce images with very high contrast and excellent resolution at low cost. So, mass production of microform images is made possible in a simple manner at high speed and half-tone images with high screen dot quality can be produced in a simple inexpensive equipment at low unit cost.

The present invention includes the following examples for illustrative purposes without, however, limiting it thereto. All percentages or ratios are by weight, unless otherwise indicated.

Example 1.

A photosensitive recording material suited for making an intermdeiate print in the production of a printing plate was produced as follows.

A bismuth layer of 150 nm thickness having an optical density above 4 was applied by vapour deposition under reduced pressure to a polyethylene terephthalate sheet of 0.1 mm thickness.

To this layer a coating solution was applied consisting of: 1 g of nitrone compound 1 of Table 1, 1 g of ALNOVOL PN 40 (Trade Name for a novolak having a softening point of 126"C) were dissolved in a mixture of 90 ml of acetone and 10 ml of ethylene glycol monomethyl ether).

After a drying period in the atmosphere the coating was dried at 800C in a ventilated cabinet for 15 min more. The dried photosensitive layer had a thickness of 1Lm.

The photosensitive layer of the recording material thus obtained was contactexposed for 5 min through a negative halftone image having adjacent thereto a continuous tone step wedge of constant 0.15 in a D7 Industrial Photoprinter CHEM CUT (Trade Mark) comprising six 20W lamps placed at distance of 5 cm and emitting with a maximum at 350 nm.

Processing of the exposed material was carried out in a RADIOPRINT DD 1437 4-tray processor the first tray containing a 3% aqueous solution of potassium hydroxide, the second containing water, the tnird containing an aquarius solutlbn of 12% of iron(III) chloride and 1% of citric acid, and the fourth containing water. The total processing lasted 28 s.

A screened positive image with very contrasty screen dots was obtained. In the portion of the recording material corresponding with the continuous tone wedge bismuth was retained in an area corresponding with 4 steps.

Example 2.

Example 1 was repeated with the difference, however, that the coating solution had the following composition: 1.5 g of nitrone compound 2 of the Table 1, 1.5 g of ALNOVOL PN 844 (Trade Mark for a novolak having a melting range of 85 to 95"C) 90 ml of acetone and 10 ml of ethylene glycol monomethyl ether).

The coating on the bismuth layer was effected in such a way that a dry layer of 1.5 ,um was obtained.

The exposure and processing proceeded as described in Example 1 except that the second tray contained a 3% aqueous potassium hydroxide solution instead of water.

A screened positive image was obtained. In the portion of the recording material corresponding with the continuous tone wedge bismuth was retained in an area corresponding with 3 steps.

Example 3.

The nitrone compound 3 of the Table 1 was mixed with ALNOVOL PN 430 (Trade Mark) in the ratios given in the following table. These ingredients were dissolved in a mixture of acetone/methanol 1:1 by volume and the coating effected on the bismuth layer of Example 1 in order to obtain a dry coating of 2 pm. The exposure proceeded as described in Example 1.

Table 2 gives a survey of the applied product combinations, processing, and of the photographic results obtained TABLE 2

parts of etching number of parts of nitrone treating liquid treating reproduced ALNOVOL compound developing liquid time (third time wedge PM 430 3 (first tray) s tray) s steps 1 1 5% Na,PO4.12H2O 7 12% FELL3 7 4 1% citric acid 2 1 id. 7 id. 7 4 3 1 0.8% KOH 7 id. 7 3 4 1 0.8% KOH 7 id. 7 4 5 1 1% KOH 7 id. 7 4 6 1 1% KOH 14 id. 7 4 7 1 1% KOH 14 id. 7 1 4 Example 4.

Example 1 was repeated with the difference however that the coating solution had the following composition: 2 g of ALNOVOL PN 430 (Trade Mark) 1.5 g of nitrone compound 1 of Table 1 0.5 g of nitrone compound 3 of Table 1 85 ml of acetone 10 ml of methanol 5 ml of ethylene glycol monomethyl ether.

The dried coating had a thickness of 2 ym. The exposure and processing proceeded as explained in Example 1. A screened positive image was obtained. In the portion of the recording material corresponding with the continuous tone wedge bismuth was retained in an area corresponding with 4 steps.

Example 5.

The nitrone compound 6 of the Table 1 was mixed with ALNOVOL PN 430 (Trade Mark) in the ratios given in the following table. These ingredients were dissolved in a mixture of acetone/ethvlene glycol monomethyl ether 9:1 by volume and the coating effected on the supported bismuth layer of Example 1 in order to obtain a dry coating of a thickness of 1 or 2 ssm.

The exposure proceeded as described in Example 1.

The Table 3 gives a survey of the applied product combinations, processing and of the photographic results obtained.

TABLE 3

number parts of layer or re parts of nitrone thick- develop- treating treating produced ALNOVOL compound ness ing time etching time wedge PN 430 6 (tom) liquid (s) liquid (s) steps 1 1 1.5 1 3% KOH 7 12%FeCl3 7 8-9 1% citric acid 1 1.25 1 id. 7 id. 7 8-9 1 1 1 id. 7 id. 7 8-9 1 1 2 id. 14 id. 7 8-9 2 1 2 id. 14 id. 7 56 Example 6.

Example 1 was repeated with the difference, however, that the coating solution had the following composition: 1.2 g of ALNOVOL PN 430 0.6 g of NEOCRYL EC 76 (Trade Mark for a copoly)methyl acrylate/acrylic acid) having an acid number of 187 and whose 5% solution in isopropanol has a viscosity of 8.3 cPs at 20"C), 1.8 g of nitrone compound 6 of the Table 1, 80 ml of acetone, 10 ml of ethylene glycol monomethyl ether.

The coating was effected in such a way that a dry coating of 2 jixn was obtained.

Exposure and processing proceeded as in Example 1 with the difference that the first tray contained a 2% aqueous solution of potassium hydroxide.

A screened positive image was obtained.

In the portion of the recording material corresponding with the continuous tone wedge bismuth was retained in an area corresponding with 7 steps.

Example 7.

Example 1 was repeated with the difference, however, that the coating solution had the following composition: 0.1 g of cellulose acetate phthalate (D.S. acetyl: 1.5; D.S. phthalyl: 0.75) 0.1 g of nitrone compound 1 of Table 1, 0.5 ml of acetone and 0.5 ml of ethylene glycol monomethyl ether.

The coating was effected in such a way that a dry layer of 1 ;pm was obtained.

Exposure and processing proceeded as described in Example 1 except that the first tray contained a 2% aqueous solution of potassium hydroxide.

A screened positive image was obtained. In the portion of the recording material corresponding with the continous tone wedge bismuth was retained in an area corresponding with 3 steps.

Example 8.

Example 1 was repeated with the difference however that the coating solution had the following composition: 0.5 g of CARBOSET 525 (Trade Mark for a copoly(ethyl acrylate/methyl methacrylate/methacrylic acid) (67/23/10) having a molecular weight of about 260,000 and whose 15% aqueous solution has a viscosity of 750 cPs at 250C) 0.5 g of nitrone compound 1 of Table 1, 50 ml of acetone.

The coating was effected in such a way that a dry layer of 1 ssm was obtained.

The exposure and processing proceeded as described in Example 1.

A screened positive image was obtained. In the portion of the recording material corresponding with the continuous tone wedge bismuth was retained in an area corresponding with 4 steps.

Example 9.

Example 8 was repeated with the difference, however, that the coating solution had the following composition: 0.2 g of MOWILITH-CT-5 (Trade Mark for a copoly(vinyl acetate/crotonic acid) (94.6/5.4) 0.2 g of nitrone compound 1 of Table 1, 20 ml of acetone.

A screened positive image was obtained. In the portion of the recording material corresponding with the continuous tone wedge bismuth was retained in an area corresponding with 2 steps.

Example 10.

To a bismuth layer of about 50 nm thickness having an optical density of 1.5 deposited on a polyethylene terephthalate support of 0.1 mm thickness, the photosensitive coating composition of Example 1 was applied.

The photosensitive layer was exposed through a line screen pattern, whose lines had a width of 1 mm and whose meshes sized 1.2 cm X 1.8 cm.

Through the exposure of said line screen followed by the processing of the resist layer and etching as described in Example 1 a pattern of bismuth-containing image frames forming a blank microfiche card was obtained. The blank microfiche was imaged by contact copying in conjunction with an imaged master microfiche, which was held in register with said blank microfiche card. The copying proceeded by flash exposure by means of a Xenon flash unit providing an energy flux of at least 0.5 joule per sq.cm. At the exposed portions the bismuth metal coalesced to form small particles, whereby the optical density was reduced to 0.2-0.3.

Image stabilization was unnecessary.

WHAT WE CLAIM IS: 1. A photosensitive recording material which comprises (1) a photosensitive layer containing a photosensitive nitrone of the formula:

in which: R is an aromatic hydrocarbon group or a substituted aromatic hydrocarbon group, and R' is an aromatic or heterocyclic group, or such groups which are substituted groups, in admixture with one or more polymers that are soluble in an alkaline aqueous liquid, said layer becoming insoluble in said liquid when said layer is exposed to actinic radiation, and (2) in contact with the said photosensitive layer a subjacent supported metallic image-forming layer of a metal, which is aluminium, zinc, tellurium or a tellurium alloy comprising at least 50 atdmic percent of tellurium having a thickness in the range of 50 nm to 500 nm or a subjacent supported metallic image-forming layer of bismuth having a thickness in the range of 25 nm to 300 nm.

2. A material according to claim 1, wherein the nitrone is one of the nitrones identified in the Table 1 of the specification.

3. A material according to claim 1 or 2, wherein the alkali-soluble polymer is a novolak.

4. A material according to claim 1 or 2, wherein the alkali-soluble polymer is a copolymer of an unsaturated carboxylic acid.

5. A material according to claim 1 or 2, wherein the alkali-soluble polymer is a cellulose acetate phthalate having a degree of acetyl substitution (D.S. acetyl) between 1.0 and 1.7 and a degree of phthalyl substitution (D.S. phthalyl) between 0.6 and 1.2.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The coating was effected in such a way that a dry layer of 1 ssm was obtained. The exposure and processing proceeded as described in Example 1. A screened positive image was obtained. In the portion of the recording material corresponding with the continuous tone wedge bismuth was retained in an area corresponding with 4 steps. Example 9. Example 8 was repeated with the difference, however, that the coating solution had the following composition: 0.2 g of MOWILITH-CT-5 (Trade Mark for a copoly(vinyl acetate/crotonic acid) (94.6/5.4) 0.2 g of nitrone compound 1 of Table 1, 20 ml of acetone. A screened positive image was obtained. In the portion of the recording material corresponding with the continuous tone wedge bismuth was retained in an area corresponding with 2 steps. Example 10. To a bismuth layer of about 50 nm thickness having an optical density of 1.5 deposited on a polyethylene terephthalate support of 0.1 mm thickness, the photosensitive coating composition of Example 1 was applied. The photosensitive layer was exposed through a line screen pattern, whose lines had a width of 1 mm and whose meshes sized 1.2 cm X 1.8 cm. Through the exposure of said line screen followed by the processing of the resist layer and etching as described in Example 1 a pattern of bismuth-containing image frames forming a blank microfiche card was obtained. The blank microfiche was imaged by contact copying in conjunction with an imaged master microfiche, which was held in register with said blank microfiche card. The copying proceeded by flash exposure by means of a Xenon flash unit providing an energy flux of at least 0.5 joule per sq.cm. At the exposed portions the bismuth metal coalesced to form small particles, whereby the optical density was reduced to 0.2-0.3. Image stabilization was unnecessary. WHAT WE CLAIM IS:

1. A photosensitive recording material which comprises (1) a photosensitive layer containing a photosensitive nitrone of the formula:

6. A material according to any of the preceding claims, wherein the weight ratio

of alkali-soluble polymer(s) to nitrone(s) is comprised between 1:1 and 7:1.

7. A material according to any of the preceding claims, wherein the thickness of the photosensitive layer is in the range of 0.5 to 5 ym.

8. A material according to any of the preceding claims, wherein the metallic imaging layer is present on a polymeric film support.

9. A material according to claim 8, wherein the support is a polyethylene terephthalate support.

10. A material according to claim 1 and substantially as described herein.

11. A material according to claim 1 and substantially as described in the Examples herein.

12. A recording method comprising the steps of (1) information-wise exposing the photosensitive layer of the recording material of any of the claims 1 to 11 to activating electromagentic radiation, (2) overall contacting the photosensitive layer with an aqueous alkaline liquid to remove selectively the non-exposed or insufficiently exposed portions of the photosensitive layer, and (3) contacting the bared portions of the said metallic layer with a liquid that is capable of chemically removing said portions without removing the exposed portions of the photosensitive layer.

13. A method according to claim 12, wherein the aqueous alkaline liquid is 0.5% to 10% by weight aqueous solution of potassium hydroxide.

14. A method according to claim 12 or 13, wherein the metallic layer consists of tellurium or a tellurium alloy and the bared portions are removed with an aqueous hypochlorite solution.

15. A method according to claim 12, wherein the metallic layer consists of bismuth and the bared portions are removed with an aqueous acidic iron(III) chloride solution.

16. A method according to claim 15, wherein the concentration of the iron(III) chloride in the solution is comprised between 5 and 20% by weight

17. A method according to claim 15 or 16, wherein the solution contains from 0.25 to 1% by weight of citric acid.

18. A method according to claim 12 or 13, wherein the metallic layer consists of bismuth and the bared portions are removed with an aqueous solution containing 3 to 6% by weight of hydrogen peroxide and 5 to 10% by weight of sulphuric acid.

19. A method according to any of the claims 12 to 18, wherein the metallic layer is a bismuth layer having a thickness in the range of 25 to 50 nm and the bismuth portions left after step (3) are information-wise exposed to light of a dose sufficient to break up said layer portions into small particles thereby reducing the optical density of the bismuth layer portions in the light-struck areas to a density value of 0.2 to 0.3.

20. A method according to claim 12 and substantially as described herein.