US 3770448 A
Photographic images are obtained by a dry process by imagewise exposing and then heating a light-sensitive material containing a substantially non-lightsensitive silver salt, a compound of the pyrazolin-5-on series capable of reducing the silver salt at a temperature of between 60 DEG and 160 DEG C in the presence of photolytically formed heavy metal nuclei and a light-sensitive silver or other heavy metal compound capable of forming such nuclei upon exposure to light.
Description (OCR text may contain errors)
United States Patent I 11 1 Poot et al. I Nov. 6, 1973 54] LIGHTSENSITIVE PHOTOGRAPHIC 3,149,990 9/1964 c6165 96/ll4.l MATERIAL 3,457,075 11/1969 Morgan 96/1141 3,531,286 9/1970 Renfrew 96/1 14.1
Inventors: Albert Lucien Poot; Frans Clement Heugebaert, both of Kontich; Eric Maria Brinckman, Mortsel, all of Belgium; Anita Von Kiinig, Leverkusen; l-lelmut Kampfer, Cologne, both of Germany Assignee: Afga-Gevaert Aktiengesellschaft,
Leverkusen, Germany Filed: Apr. 26, 1971 Appl. No.: 137,604
Foreign Application Priority Data Apr. 29, 1970 Germany P 20 20 939.6
US. Cl. 96/1l4.l, 96/66 R, 96/66 T lnt. Cl G03c 1/02, G030 5/30 Field of Search 96/1 14.1, 66 HD,
96/66 T, 48 HD References Cited UNITED STATES PATENTS 7/1969 Sorenson 96/1l4.l
OTHER PUBLICATIONS Handbook of Photography, ed. by Henney et al., I939, ed. pp. 329-333.
Primary Examiner-Norman G. Torchin Assistant ExaminerM. F. Kelley Att0meyConnolly and Hutz 57 ABSTRACT 8 Claims, No Drawings This invention relates to a single-layer or multi-layer lightsensitive recording material containing an oxidising agent, a reducing agent and a lightsensitive compound whose photolytic products initiate a redox reaction between the oxidising agent and reducing agent on subsequent heating.
In conventional photographic recording processes, photographic materials containing lightsensitive silver halide/gelatin emulsion layers are exposed to light and subsequently treated with a developer solution, and the resulting developed image is finally fixed in a fixing bath.
This conventional recording process has previously been modified in several different ways in order to avoid the use of aqueous treatment baths. The object of all such efforts has been to modify the known process in such a way that a recording of adequate quality is obtained in a dry process, optionally employing heat, with as few process steps as possible.'
According to a known process there is used a photographic material which contains an oxidising agent, a reducing agent and a relatively small quantity of a lightsensitive substance whose photolytic products found at the light-struck areas initiate a redox reaction. Organic silver salts are used as the oxidising agents and aminophenols, hydroxylamines, pyrazolidones or phenols as the reducing agent. Phenylene diamine or etherified naphthols, for example 4-methoxy-1-naphthol, have also been used for this purpose. Suitable lightsensitive,
compounds include heavy metal salts which, on exposure, form nuclei of the free metal. More particularly, the lightsensitive compounds are light-sensitive silver salts, for example silver halides, which on exposure undergo photolysis to form silver. The redox reaction is initiated by these photolytic heavy metal nuclei.
As a result of these conventional processes, it is possible to produce photographic images of satisfactory quality under dry conditions. One serious disadvantage of the materials used in this process, however, is their relatively poor shelf life, which is attributable in particular to the sensitivity of the reducing agents to oxidation by atmospheric oxygen. In order to provide a shelf .45
life that is satisfactory for practical requirements, it is thus necessary to take additional measures to protect the reducing agents against the effect of atmospheric oxygen. In most instances, this is done by adding antioxidants. It is among the objects of this invention to provide photographic processes and materials therefor, by which it-is possible to obtain high-quality photographic images under dry conditions.
A photographic recording material for, the production of dry copies has now been found which contains a silver salt that is substantially non-sensitive to light as oxidising agent, a reducing agent and a lightsensitive heavy metal compound which on exposure photolytically forms metal nuclei through which a redox reaction is initiated under the effect of heat, the reducing agent used being a compound of the pyrazolin-S-one series which is able to reduce the non-lightsensitive silver salt at a temperature of from 60 to 160 C. in the presence of photolytically formedheavy-metal nuclei.
Particularly suitable reducing agents include pyrazolin-5-one compounds ofthe kind which contain at least one hydrogen atom or a 4-aminophenylamino group in the 4-position of the pyrazoline ring. It is preferred to use pyrazoline derivatives of the following formula B4 TIT-31 in which R represents (1) hydrogen, (2) a saturated or olefinically unsaturated aliphatic group having up to 18 C- atoms, preferably up to five C-atoms, which can optionally be substituted, for example by phenyl, as in the ably up to five C-atoms, by halogen such as fluorine,
chlorine or bromine, by nitro, by amino, by substituted amino groups, for example alkylated or acylated, especially acyl groups derived from aliphatic carboxylic acids, or by phenoxyor alkoxycarbonyl groups, (4) a heterocyclic group, for example a ring of the furan or pyridine series, or a condensed heterocyclic ring obtained therefrom by anellation of an aromatic ring system, or (5) a cycloalkyl group, such as cyclohexyl or cyclopentyl;
R represents (1 hydrogen, (2) a saturated or olefinically unsaturated aliphatic group having up to 18 carbon atoms, in which case the aliphatic group can contain further substituents, for example phenyl, as in the case of a benzyl or phenylethyl group, halogen such as fluorine, alkoxycarbonyl, hydroxyl or alkoxy, (3) aryl, especially a group of the phenyl series in which case the aryl ring can be substituted, for example by alkyl or alkoxy with preferably up-to five C-atoms', by halogen such as chlorine or bromine, by hydroxyl, by nitro or by acyl, (4) a heterocyclic group, especially a ring of the pyridine, furan or thiophene, series, (5) a cycloalkyl group, such as cyclohexyl or cyclopentyl, (6) an alkoxycarbonyl group with up to l8 C-atoms preferably up to five C-atoms 7) a hydroxyl group which can be etherified, especially with aliphatic radicals with up to 18 C- atoms, (8) an amino group which can be substituted, for example by alkyl-or acyl groups, especially those derived from aliphatic c'arboxylic acids with up to 18. C-atoms or with benzoyl, (9) a carbamic acidester group, especially with aliphatic ester groups with up to 18 carbon atoms or (10) a carbamoyl group. R represents (1) hydrogen, (2) a saturated or olefin ically unsaturated aliphatic group having up to 18 C- atoms, preferably with up to five C-atoms, which can be substituted, for example by phenyl as in the case of benzyl or phenylethyl groups, with halogen such as chlorine or bromine, by nitrile, by alkoxy, by amino groups which in turn can be substituted, for example by alkyl, phenyl, substituted phenyl for example dialkylaminophenyl or sulfophenyl, by carbamoyl, alkoxycarbonyl, piperidyl or the like, (3) aryl, especially a group of the phenyl series which can in turn be substituted,
for example by alkyl or alkoxy with preferably up to five C-atoms, (4) amino, which can be substituted for example by acyl, especially those of aliphatic carboxylic acids with up to 18 C-atoms or benzoyl, (5) alkoxy with preferably up to five C-atoms like the aforementioned aliphatic group, and which can contain further substituents, (6) halogen, for example, chlorine or bromine, (7) cycloalkyl such as cyclopentyl, or (8) carbamoyl, and when R represents hydrogen R can also represent an alkylene chain between two pyrazolone rings of the above formula; and
CII3 Num bnr 1 R2 R3 R 4 3 (kHz-F CH; CHzn-C'H3 N l L N (Jo-H5 C 0H5 The pyrazolin-5-one derivatives used in accordance with the present invention can be obtained by known methods. Suitable methods are described, for example, in the monograph by RH. Wiley and P. Wiley Pyrazolones, pyrazolidones and Derivatives 1964) (Interscience Publishers, New York) and in German Pat. specification No. 1,155,675.
As already mentioned, suitable oxidising agents for the image-producing redox system include silver salts of organic acids which show little or no lightsensitivity under the conditions of the process. Reference is made for example to silver sacchan'de, silver 5- chlorosalicylaldoxime, silver 5-nitrosalicylaldoxime or preferably a silver salt of a long-chain fatty acid with up to about 30 C-atoms, for example silver stearate, silver palmitate or silver behenate, or the silver salts of aliphatic carboxylic acidscontaining a-thioether group described in US. Pat. No. 3,330,663.
The non-lightsensitive silver salt used as oxidising agent and the pyrazolin-5-one used as reducing agent are generally employed in a molar ratio of from 1:1, to
Inorganic or organic salts of silver, mercury or gold are examples of suitable lightsensitive heavy metal salts which on exposure form metal nuclei able to initiate the image-producing redox reaction. Heavy metals of Sub-Group lb of the Periodic System of elements, especially silver salts, are preferred. Of these silver salts, silver halides'are especially suitable.
The light sensitive heavy metal salt most suitable for the particular redox system employed can be found by a few laborating tests. For example, an aqueous suspension of the metal salt can be mixed with the components of the redox system, in which case no changes should occur in darkness. If this mixture is exposed to UV-radiation, it should become colored relatively quickly. If this is observed, the. heavy metal salt is suitable for use with the'redox system. The lightsensitive heavy metal salt is preferably used in relatively small quantities of from about 0.05 to 0.2 percent by weight, based on the weight of the oxidising agent. This proportion of photosensitive salt is sufficient for mostsystems. In exceptional instances, this percentage can of course be increased or reduced.
The lightsensitive heavy metal salt, for example the silver halide, should be present in such small quantities that the photolytically formed heavy metal nuclei can initiate the redox reaction, although the concentration of the silver halide should be so low that the metal nuclei formed cause little or no discoloration of the photographic material.
The silver halide can be added to the casting solution for the layer containing the components for the redox reaction or alternatively can be prepared in situ in the casting solution, i.e., by precipitating the silver halide in the mixture. In this case, the silver ions for the precipitated silver halide can be provided substantially by the nonlight-sensitive silver salt.
Just like the silver halide, the non-lightsensitive silver salts present as oxidising agents can be prepared in known manner by precipitating silver salt solutions, for
example silver nitrate, with the alkali metal salts of the organic acids. The free acid can of course also be present during precipitation. In order, however, to produce layers as transparent as possible, it is of advantage for the excess of free acid to be extremely limited,"or e'ven for stoichiometric quantities of the organic acid and of the silver salt to be used. Q
The silver halides can be produced from the nonlight-sensitive silver salts in various different ways. For example, the surface of the non-lightsensitive silver salts can be treated with vapours of hydrohalic acids, for example hydrochloric acid, hydrobromic acid or hydriodic acid. The quantity of silver halide formed at the surface can be kept within the required limits by adjusting the concentration of-the hydrogen halide in the vapour phase, and the treatment time. i
The non-lightsensitive silver salts of the organic acids can, of course, also be treated with a solution containing halogen ions, such as chloride ions, bromide ions or iodide ions. The halogen ions can be provided by the hydrohalic acids themselves or by their salts, especially their ammonium 'or alkali metal salts.
The non-lightsensitive silver salts are reacted with the compounds yielding halogen ions preferably in the form of their suspensions in a volatile non-aqueous liquid. It is also possible, however, to react the dry salts with hydrohalic acid vapours for example.
In addition to hydrohalic acids and their salts, for example the already mentioned alkali metal salts and ammonium salts, alkaline earth metal salts or other metal salts, for example zinc salts and mercury salts, it is also possible to use ionisable organic halogen compounds, for example triphenylinethyl chloride, triphenylmethyl bromide, 2-bromo-2-methylpropane, Z-bromobutyric acid, 2-bromoethanol or benzophenone dichloride.
Formation of the lightsensitive silver halides from the non-lightsensitive silver salts of the organic acids is preferredfor the production of the materials according to the present invention. This enhances the ability of the silverhalides to form, on photolysis, silver nuclei which are particularly active in initiating the redox reaction.
Although separate preparation of the silver halides and subsequent mixing with the non-lightsensitive silver salts also leads to useful materials, the photolytic heavy metal nuclei formed from mixtures of this kind are generally not so effective.
To prepare the material according to the present invention, the components of the redox system and'the I lightsensitive heavy metal are used together with a suitable binder. Preferred binders include organic polymers, such as copolymers of vinyl chloride and vinyl acetate or of butadiene and styrene, polyethylene, polyamides, polyisobutylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl pyrrolidone, polystyrene, chlorinated rubber, polyvinyl butyral, polymers or acrylic acid or methacrylic acid esters or copolymers of derivatives of acrylic acid and methacrylic acid, and cellulose derivatives such as nitrocellulose, cellulose acetate, cellulose propionates or mixtures thereof such as cellulose acetobutyrates.
Although the lightsensitive layer can be a selfsupporting layer, it is preferably applied to a suitable layer support. The layer support must be stable at the processing temperature of from 60 to 200 C. Examples of suitable supports include sheets or films of paper, cellulose acetate, polyethylene terephthalate, textile fabrics, metal foils or glass. 1n the case of paper supports, they can comprise the usual auxiliary layers such as baryta layers, polyethylene layers, etc.
The concentration of the reducing agent and of the oxidising agent in the layer can be varied within wide limits.
In general, weight ratios between the components of the redox system and the binder of from 4:1 4to about 1:1 have provded to be adequate.
The thickness of the lightsensitive layer can also be adapted to suit the requirements of the particular reproduction process. In general, layer thicknesses of from S to 100 microns are sufficient for normal requirements. The layer supports preferably have the usual thickness of from about 0.1 to 0.8 mm.
The lightsensitive layers can also be optically sensitised by the addition of dyes. Preferred sensitisers include those compounds of the kind that are also normally used for optically sensitising conventional silver halide emulsion layers, i.e., cyanine dyes, merocyanines, oxonoles or thiocyanines of various kinds, for example those described in the book by EM. Hamer entitled The Cyanine Dyes and Related Compounds, 1964.
The usual white pigments, for example silicon dioxide, and toners such as for example phthalazone, phthalazone derivatives, or phthalimide, can be added to the photosensitive layers.
The photographic materials according to the invention can be processed in known manner. Image-wise exposure is carried out with the light sources commonly used in the photographic art, for example. mercury lamps, quartz-iodine lamps or ordinary incandescent lamps. The type of light source used will depend upon the spectral sensitivity of the heavy metal salt used. When silver halides are used, as is preferably the case, ordinary incandescent lamps are sufficient. The exposure time amounts to a few seconds.
The exposed material is then uniformly heated at a temperature of from about 60 to 160 C. The time and the temperature required for heat treatment will be governed by the type of redox system used. Times of from 3 to 80 seconds are generally sufficient. As a rule, a dark brown to black image is obtained and can be immediately used.
In the procedure described above, negative copies of the original are, of course, obtained. Positive copies can be obtained by a transfer process. In this case, pyrazolin-S-one compounds which can be transferred under the influence of heat are used in the lightsensitive layer. After the lightsensitive material has been exposed to form an image, it is heated in contact with an image receiving layer. The image-receiving layer contains reagents which undergo a color-producing reaction with the pyrazolin-S-one derivative transferred from the unexposed areas. For example, the same nonlightsensitive silver salts of organic acids which are normally present in the lightsensitive layer can be used for this purpose.
EXAMPLE 1 Lightsensitive material: An equimolar mixture of silver behenate and behenic acid is prepared by precipitating silver nitrate with a solution of sodium behenate and behenic acid in alcohol and water. The precipitate is carefully washed and dried.
The suspension for the preparation of the layer is prepared by treating'the mixture indicated below for 12 hours in a ball mill:
240 ml of methanol v 125 ml of a 10 percent by weight solution of polyvinyl-n-butyral in methanol 20 ml of a 10 percent by weight solution of poly-N- vinyl-pyrrolidone in methanol 30 g of the equimolar mixture of silver behenate and behenic acid 10 ml of a 1 percent by weight solution of ammonium bromide in methanol 1.2 g of phthalazone 15 g of compound 10.
The above mixture is applied to a paper support in a concentration of 100 g/m and dried at room temperature.
The lightsensitive layer is exposed through a transparent original. A 750 watt UV-lamp is used as the light source. The exposure time is 2 seconds, the distance from the light source 5 cm. This is followed by heating for 5 seconds at a temperature of C.
A black-brown negative image of the original is obtained. Similar results are obtained by using compounds 12, 33 or 34, for example, instead of compound 10.
EXAMPLE 2 Lightsensitive material: Sub-casting suspension: 1.8 g of the equimolar mixture of silver behenate and behenic acid 3 g of cellulose acetate 3 g of phthalazone 4.5 ml of calcium bromide solution (1 g dissolved inml of methanol) 5.7 ml of mercuric acetate solution (1 g 1 ml of glacial acetic acid dissolved in 100 ml of methanol) 3 ml of 1-methyl-3-allyl-5-[2-(3-ethylben'zoxazo1yliden-( 2 )-ethylidene]-2-thiohydantoin solution (0.01 g dissolved in 100 ml of chloroform) 0.15 g of silicon dioxide 55 g of acetone 1 g of 88:12 vinyl chloride/vinyl acetate copolymer dissolved in 20 g of butyl acetate Top-casting: 10 g of polyvinylbutyral 1.5 g of phthalazone 5 g of compound 44 100 ml of methanol The sub-casting suspension is ground in a ball mill for about 16 hours, applied to baryta paper and dried. The application is such that the applied layer contains from 0.3 to 0.4 g/m of silver in the form of the silver salt. The top casting is then applied to the dried sub-casting. The reducing agent is applied in a quantity of from 0.5 to 1.5 g/m.
Instead of compound 44 the following reducing agents can also be added to the top layer:
6 g of compound 5 6 g of compound 6 4 g of compound 8 5 g of compound 10 5 g of compound 13 g of compound 14 5 g of compound 23 5 g of compound 29 6 g of compound 31 4 g of compound 35 5 g of compound 36 4 g of compound 37 5 g of compound 40 5 g of compound 57 5 g of compound 60 Instead of being added to the top layer like compound 44, the reducing agents can be added to the sublayer suspension and ground with this suspension in a ball mill for about 30 minutes, for example:
6 g of compound 5 4 g of compound 27 4 g of compound 50 Processing:
The lightsensitive material is exposed for 3 to 30 seconds with tungsten lamps, depending upon their intensity and upon the required gradation, and developed by heating. The developing time ranges from 3 to 80 seconds depending upon the temperature, which can be in the range from 60 to 160 C. and the apparatus used. Suitable developing apparatus include heatable presses, drying cylinders, rollers, the apparatus described in Belgian Pat. No. 628,174 and in French Pat. Nos. 1,512,332; 1,416,752 or 1,419,101, and conventional commercial apparatus. In order to protect the layer and to produce a high-gloss image, the layer side of the material can be developed under heat in contact with a polyester film.
Brown, brown-black to neutral-black images on a white to yellow background are obtained upon heating depending upon the reducing substance used and the processing conditions.
1. A photographic composition containing in layer form a substantially non-lightsensitive silver salt as an oxidizing agent and a reducing agent in a combination substantially latent under ambient conditions and a light-sensitive heavy metal compound which photolytically forms metal nuclei that upon heating of the composition initiate into reaction the oxidizing agent and the reducing agent to produce a visible change wherein the improvement comprises the reducing agent is a pyrazolin-S-one of the following formula:
in which R represents hydrogen, a saturated or olefinically unsaturated aliphatic group having up to 18 carbons, aryl, a heterocyclic group or cycloalkyl;
R represents hydrogenQa saturated or olefinically unsaturated aliphatic group having up to 18 carbons, aryl, a heterocyclic group, an amino group, cycloalkyl, alkoxycarbonyl having up to 18 C- atoms, hydroxyl, a carbamic acid ester group or a carbamoyl group;
R represents hydrogen, a saturated or olefinically unsaturated aliphatic group having up to 18 carbons, aryl, alkoxy, halogen, cycloalkyl, or carbamoyl;
R represents hydrogen or a 4-aminophenylamino group; and R and R together can represent the ring members required to complete a fiveor sixmembered ring.
2. The composition of claim 1, wherein the photosensitive heavy metal salt is a silver halide.
3. The composition of claim 1, wherein the heavy metal salt is present in a quantity of from 0.05 to 0.2 percent by weight, based on the weight of the nonlightsensitive silver salt.
4. The composition of claim 1, wherein the non-lightsensitive silver salt is a silver salt of along-chain fatty acid. a I
5. The composition of claim 1, wherein the non-lightsensitive silver salt is silver behenate.
6. The composition of claim 1, wherein the non-lightsensitive silver salt is a silver salt of an aliphatic carboxylic acid substituted by a thioether group.
7. The composition of claim 1 in which the silver halide compound is a silver salt formed in situ.
8. The composition of claim 1 in which the silver halide compound is a silver salt formed on the surface of the non-lightsensitive silver compound.