US3300304A

US3300304A - Electrophotographic material and process

Info

Publication number: US3300304A
Application number: US146398A
Authority: US
Inventors: Kosche Horst
Original assignee: Renker Belipa Fa GmbH
Current assignee: Renker Belipa Fa GmbH; RENKER-BELIPA G M B H Firma
Priority date: 1960-10-03
Filing date: 1961-10-02
Publication date: 1967-01-24
Anticipated expiration: 1984-01-24
Also published as: DE1216690B; GB1008632A

Description

United States Patent Claims. 0!. 96-1.5)

Electrophotography is a method of reproduction, under which electrical charges and their changes influence the production of images. The electrophotographic material used for this purpose usually consists of a conductive or non-conductive support, on which is brought a photooonductive layer which is over a conductive middle layer. The photoconductive layer is put into a state of hgh photosensibility by charging itwith an electrostatic charge, for the purpose of performing a reproduction. As soon as such electrophotographic material is photoexposed under a pattern in a process of contact, a process of projection or an epidiascopic process, a latent electrostatic image of charge is obtained corresponding to the pattern. T h s charge image can be rendered visible by manifold processes of developing, which are based on the fact, that electrically charged preferably coloured materials are attracted by the charge remaining on the electrophotographic material and are afterwards cause-d firmly to adhere by fixation. By use of suitable pulverized or liquid developers consisting of a mixture or a dispersion of at least two components of different dielectric constants, it is possible to produce positive as well as negative reproductions of an original.

The electrophotographic layer, when eleotrostatically charged and acting together with a support layer effecting the discharges determined the photosensibility of the electrophotographic layer, and hitherto generally consisted of a combination of a photoconductor and a binder of insulating qualities with a specific electrical resistance of about 10 to l0 S2/cm.

In the production of electrophotographic layers it was assumed that this kind of layer is rendered active only, if consisting of a photoconductor and binders of insulating qualities, the purpose of the latter being to prevent discharge in the unexposed areas.

As a rule the photo conductor is used in the binder in shape of a solid solution or in a fine dispersion, resulting in a practically grainless reproduction of the electrophotographic image.

Contrary to this the procedure, according to the invention, is based upon the idea of producing photoconductors possessing per se binding qualities and of applying them in the manufacture of electrophotographic layers.

Compounds specified as photoconductors with proper binding qualities comprise, in one molecule, groups of the following kinds:

1) Groups determining electrophotographc efiiciency, i.e. so called photoconduction of the respective compound; t

(2) Groups, capable of reacting to such compounds showing sufficient adhering qualities with regard to the support of the photo conducting layer which may consist of a metal plate, an aluminium plate or the like.

The aforementioned groupings according to Nos. 1 and and 2 must be present in the same molecule designated above as photoconductors with proper binding qualities.

For the production of a photoconductor with proper binding qualities it is thus required to bring to reaction a photo conducting compound, possessing the qualities mentioned above under Nos. 1 and 2, with an organic compound, guaranteeing after reaction the necessary sufir- "ice cient power of adherence to the support of the conducting layer.

These photoconductors with proper binding'qualities are capable of forming per se, without addition of other binders, an electrophotographic layer of a condition ranging from hard to flexible with good adhering qualities and with excellent electrophotographic efficiency. Such kind of photoconductors with proper binding qualities are produced, as already indicated, by the reaction of a photoconductive compound with organic compounds forming after this reaction enlarged molecules of resinous products having excellent adhesive qualities to metals, papers or artificial resins, eventually being simultaneously capable of forming films.

According to the invention, such photoconductors with proper binding qualities before the forming of the electrophotographic layer are supplied in form of resinous compounds, eventually separated from by-products and afterwards Worked from their solution, dispersion or smelting toward producing an electrophotographic layer. It has especially been found that epoxy compounds and organic isocyanate compounds reacting with electrophoto graphically active compounds possessing the qualities aforementioned under 1 and 2, under molecule enlargement and by forming products of fair adhesive qualities, eventually by forming resinous products, in the reaction produce such photoconductors with proper binding qualities. Surprisingly, in the course of these changes, the organic eleotrophotographically active materials (photoconductors) do not lose their electrophotographic efficiency.

It is known, that by the reaction of compounds hearing epoxyor isocyanate groups with components containing hydroxyor amino-groupings artificial res ns of fair adhesive qualities powers may be obtained. It was in no way, however, to be supposed'that photoconductive compounds when bearing groups capable of reacting with compounds containing epoxyor isocyanate groupings, would not losetheir electrophotographic efiiciencies, when reacting with epoxyand/or isocyanate compounds,

It has to be considered in connection herewith that by the reaction mentioned new'groupings partly strongly and differently polarized are created, the infiuencesof which, with regard to the efii-ciency of the photoconductor, were neither known nor presumable and that furthermore there should originate from them sufiiciently adhesive materials constituting the electrophotographic layer. Furthermore, during the reaction mentioned a considerable enlargement of the molecules takes place, because the isocyanate or epoxy compounds engaged in the reaction possess per se a higher density and a complicated structure. I

According to the invention for, the production of proper adhesive photoconductor-s of preferably organic compounds with a structure eleotrophotographically active is used a base compound, containing, besides, groups capable of reacting with isocyanate of epoxy groups under enlargement of the molecules. Compounds of .the kind mentioned are'brough't to reaction with epoxy compounds or isocyanates Groups of these compounds capable of reacting in the sense of the invention are e.g. H,

, NH NHR, -NH',' COOH,, 'CONH CONHR,' SO H, SO NH SO NHR, OH, SH capable of reactions wherewith R may designate an possibly substituted isocyclic or heterocyclic ring system.

For the production of photoconductors with appropriate binding qualities, the photoconductors, e.g. of the classes of compounds given in the following, can be caused to react with epoxy resins or isocyanates, if they contain the aforesaid groups capable of reaction with epoxides or organic isocyanates, possibly besides other substitutents not capable of reaction.

photo As suitable classes of compounds there are given by way of example:

1,3,4-oxdiazol compounds according to the German Patent 1,058,836, multinuclear cyclic hydrocarbons according to German Patent 1,060,259 1,3,4-triazol compounds according to German Patent 1,060,260, azomethines according to German Patent 1,060,712, 4,5-diphenyl-imidazolone or 4,5-diphenyl-imide-azole-thio-(2)- compounds according to German Patent 1,060,713, pyrazoline compounds according to German Patent 1,060,714, acyl-hydrazones according to German Patent 1,101,145, anthracene compounds according to German Patent 1,102,556, compounds according to German Patent 1,105,- 713, aryl-furanes, aryl-thiophenes and aryl-pyrroles according to German Patent 1,105,714, 1,2,4-triazine com-- pounds according to German patent application published under number 1,099,846, l,2,5,6-tetra-azo-cyclo-octateracene-(2,4,6,8)compounds according to German Patent 1,110,007, keto-aniles, thiazole compounds; aromatic or heterocyclic ketones or thioketones, organic metal complex compounds, acridine dyestuffs according to the dates and definitions given by Schultz, Farbstofitabellen, vol. 1, 7th edition (1931), pages 383-390, chinoline dyestuffs according to dates and definitions given by Schultz, Farbstofftabellen, vol. 1, 7th edition (1931) pages 391-398, azine dyestuffs according to dates and definitions given by Schultz, Farbstofftabellen, vol. 1, 7th edition (1931), pages 407-429, oxazine compounds and dyestuffs according to Schultz, Farbsto-lftabellen, vol. 1, 7th edition (1931), pages 430-447, flavone compounds such as morine, quercitrine, etc. These dyestuffs shall not contain any -SO groups not capable of reaction and shall not be present inform of salts.

As reaction compounds containing epoxy or isocyanate groups for the production of properly adhesive photoconductors, compounds of these classes already known or newly to be created may be chosen, if they contain one epoxy and/or isocyanate group at least per molecule and if their structure is of such a kind, that they render adhesive qualities or are able to form films after reaction with the system communicating electrophotographic efficiency. For the supply of bidimensional condensated photoconductors, electrophotographically active substances with two groups capable of reaction may be taken as a base on one hand, brought to reaction with compounds having at most two epoxy or isocyanate groups. Proper-1y, adhesive photoconductors of resinous structure on the other hand may be obtained by bringing to reaction electrophotographically active materials, showing at least one groupment capable of reaction with an epoxy or isocyanate compound, having at least two'of these groups per molecule.

It is furthermore possible to change the photoconductors according to the invention to such an extent as to adapt them to spec-ial requirements, be it by introduction of most different chemical compounds, having one or several epoxy and/ or one or several isocyanate groups and which, besides, are of different chemical structures be it by further partial reaction not only with photoconductors but also with other materials not electrophotographically efficient and effecting, e.g. a cross-linking, the materials according to the invention with regard to their qualities of electrophotographic efficiency, of solubility, adhesion as well as in their mechanical dates, e.g. resilience, eveness and resistance of surface, resistance against other materials etc.

As reaction components containing isocyanate groups those are of value having one or several isocyanate groups e.g. attached to the aromatic ring system, or furthermore those to be brought to partial reaction with aliphatic and/or aromatic monoor poly-amines and/or monoor poly-alcohols and/or monoor poly-carbonic acids. Prototypes of these compounds are toluylene-2,4-(2,6)- di-isocyanate, tri-phenyl-methane-4,4, 4"-tri-isocyanate, naphtalene-1,5-di-isocyanate, di-merized isocyanates, f.i. formed from 2 mols of toluylene-2,4-di-isocyanate or products resulting from the partial reaction of 1 mol of 3-tri-hydroxy-methylene propane with 3 mols of toluylene 2,4-di-isocyanate. Another choice with regard to the structure of the isocyanates and their further change to components of reaction containing free isocyanate groups is given by G. Schulz, Die Kunststoffe, Munich, Carl Hanser, Verlag, 1959, pages 243-251.

As reaction components containing epoxy groups, several classes are known. The reaction per se of photoconductors fit for this purpose with simple epoxides, as ethylene or propylene oxide, results in wax-like compounds, when polycondensation occurs. For special uses, however, those are of value, deriving from the type of phenyl-glycide-ether, ethyl-glycide-ether, and di-glycideether of the 5,fi-bis(4-oxy-phenyl)propane with epichlorohydrin, while their epoxy groups are conserved, eventually also their higher molecular products of reaction, containing several of the groups set into brackets in the following formula:

R meaning an aliphatic radical and H. Epoxides, however, also of longer chains, linear or branched aliphatic structure containing one or several epoxy groups are of value, whereby reaction production from 2,3-epoxy-propanol-(1)-allyl-ether may be supplied with further reticular qualities in the electrophotographic layer, according to the type of drying oils, eventually by a siccative process. Suited are, furthermore, epoxy esters of aliphatic or aromatic monoor poly-carbonic acids of the general structures. i

wherewith R can mean an aliphatic or aromatic group.

A choice with the execption of the epoxy esters is given by G. Schulz, Die Kunststolfe, 1959, pages 240-243.

As already outlined, for the purpose of adaption of properly adhesive photoconductors with regard to their possibility of use isocyanate or epoxy groups, not having reacted during the reaction with the groups supplying electro-photographic qualities, can be brought to reaction for the purpose of further reaction with materials, reacting with epoxy or isocyanate groups. Such reaction components are e. g. alcohols, preferably of longer chained structures or of those containing several hydroxyle groups, but also unsaturated alcohols, wherewith the latter are inclined toward reticular structure, eventually if submitted to a siccative process.

But also monoor poly-amines, as e.g. amines or acidamides, obtained from C2'C20-fat-aCidS are useful. Suited are also such kinds of organic compounds, containing one or several free carboxyl groups as e.g. phthalic acid, terephthalic acid, tri-mesine acid, adipine-, suberic-, azeleinor sebacine-acid, unsaturated di-carbonic acids as malein-, fumaric acid, citric acid, fat acids, oxyor ketofat acids or polyunsaturated acids, as linseed oil-, fishor train oil-acids, permitting a subsequent hardening accordreaction, as e.g. proteins or their products of decomposition, as amino acids, cellulose, cellulose-ether or -ester, acetals or esters of the polyvinyl alcohol with hydroxyl groups capable of reaction and the like.

Furthermore, the additional components of reaction can be formed in such a way that they possess substituents reacting with different speed with epoxy or isocyanate groups. Suited are e.g. for a partial reaction such-compounds bearing a hydroxyl-, sulfhydryL, carboxyl or acidamide-group and additionally an aminoor iminogroup. In such a way longer chained aliphatic w-amino alcohols as well as amino-phenolsor -naphthols, react at low temperatures of reaction already practically completely with their aminoor imino-group together with epoxides or'isocyanates forming properly adhesive photoconductors dissolving in solvents.

This photoconductor after production of theelectrophotographic layer by way of heightened temperature of reaction or by catalysts, per example by burning .in at 130-.160 C. can be brought to reaction e.g. with the hydroxyl group." As a product of reaction, an electrophotographic layer is. obtained, no more'solub'le or under difficulties only, under'a three dimensional reticulation of the oxy or isocyanate groups, still present in the molecule, but not having been caused to react.

A further possibility of variation consists in that the groupings rendering electrophotographic activity possesses two or more groups per molecule reacting with different speed of reaction with isocyanates or epoxides, and that it reacts with one of it, that is, with an epoxy, and with the other one which is different from the first component of reaction containing epoxy or/and isocyanate groups.

The electrophotographic layers, produced according to the procedures of the invention obtained under application of properly adhesive photoconductors, evidently contrast with usual present practice according to which photoelectric layers must consist of a solid solution or dispersion of a photoconductor in a binder possessing insulating qualities.

The proper adhesive photoconductors formed, accord ing to the invention, have the advantage compared with the solid solutions of photoconductors in a binder of insulating qualities, that the materials according to the invention do not tend towards cristallization, that in organic solvents photoconductors difficult to dissolve are rendered easier soluble that'no cristallization or separation of the photoconductor can take place, when the limits of compatibility are passed can ensue from the electrophotographic layer and that the difficulties regarding their permitting to be combined with binders of insulating qualities, also with regard to the choice of the solvents applicable will not arise, furthermore, that the rate of the groupments causing the photographic effect to those causing adhesion is constant and also remains constant during the process, while the solvent is evaporated. A further advantage of the procedure according to the invention is to be seen in that that the electrophotographically active groups possess a spacious defined arrangement in the photographic layer, that they are present in a molecular distribution and that they do not tend toward the formation of agglomerations of the photoconductor as it is the case with binders of insulating qualities. The materials according to the invention therefore also render more homogeneous and uniform electrophotographic layers.

For the production of properly adhesive photoconductors, according to the invention, electrophotographically active materials are brought to reaction with isocyanate and/or epoxides groups containing compounds,

eventually under simultaneous or subsequent addition of further materials capable of reaction with epoxides and/ or isocyanates which are not photoconductors, preferably in solvents eventually under raising of temperature and/or under presence of catalysts.

' The forms of this procedure by which the produced properly adhesive photo conductor during the reaction in precipitated from the solvent, while the original products remain soluble are especially valuable for the separation of the same.

The photoconductors properly adhesive can serve per se, that is, without the addition of binders for the production of the electrophotographic layer. For the shifting of the spectral sensitivity of the layer produced usual sensitizing dyes can be added to the same.

The electrophotographic material, also called electrophotographic plate, without limiting its application to plate shaped products, usually comprises of a support material either conducting electronics and ions or electrically 3 non conducting. For electrically conducting material, f.i.

are considered metals in form of plate shaped objects, as also surfaces rendered rough by a galvanic or mechanical procedure eloxated, phosphorized, electrically conducting papers, fleeces, tissues or foils.

' Especially valuable are such flat surfaced objects, as papers, fleeces or foils, rendered conducting by being coated with a thin metallic layer in the vacuum. If a non conducting support is used it is advisable, in order to increase the capacity of conduction between the electrophotographic layer and the support to use an auxiliary interspace layer which increases and holds constant the electrical capacity of conduction.

It is furthermore necessary if support materials of absorptive capacities are applied to provide these with a covering auxiliary layer, favoring the formation of the electrophotographic layer in uniform condition and equal thickness. For the production of such auxiliary layers increasing the conductive capacities or serving as a cover there may be used, for example, organic colloids, as gum arabic polyvinyl alcohol, partial acetals of the vinyl alco hol, gelatine, agar-agar, carragheen, polyuronic acids or their salts, water soluble cellulose-ether and -esters, as methyl cellulose or alkali salts of the cellulose glycol acid, as well as of the polyacrylates or methacrylates, acrylacid-amides, starch, starch-ether, starches discomposed as dextrines or roasted starches, per se or in combination with mediums holding them in a humid state, as for example glycerine sorbite, polyglycolene, polyglycol ethers as well as with salts as f.i. zinc chloride, calcium chloride, ammonium chloride, ammonium nitrate, etc., as well as also in connection with polyalcohols, boric acid etc. For special methods of application it is necessary in order to increase the stability of the capacity of charge of the electrophotographic plate to arrange an electrical interspace barrier layer between the electrophotographic layer and the support, permitting the flow of discharge in one direction only. Suitable for this purpose are especially oxides of copper, cadmium, as well as of aluminum.

The properly adhesive photo conductor rendering the electrophotographic layer is spread upon this support material prepared in such a manner.

The electrophotographic layer can be produced by dissolving the properly adhering photoconductor e.g. in a solvent or bringing it to a fine dispersion in a solvent or in water and to spread this preparation by way of spreading means, e.g. centrifugation, wash-up rolls, or scraping means, as with rakes or air brushes, with pressure rolls, transfer or distributing rolls, by dipping or electrostatic spraying. For special forms of application it can however, be suitable superficially to embed the properly adhesive photoconductor in a melted condition in a support material in a very thin layer. Furthermore, the properly adhesive photoconductors can be spread in a melted condition onto the support material, wherewith one can make use of the liquid state of the photo-guiding mal terial eventually caused by higher temperatures or high pressure in extruders or press means, preferably in such ones permitting a calibration for obtainng uniform thickness of the layer.

The production of image .by way of the electrophotographic material using properly adhesive photoconductors according to the invention can ensue in the known manner just the same as with other electrophotographic materials. For this purpose the electrophotographic material is for instance charged with a coronar discharge of 3-8 kv. negatively or positively or an electrical potential is communicated to it by contact or frictional electricity. Afterwards the electrophotographic material is photo-exposed. At the spots influenced by the light, the electrical potential is diminished or eliminated. The remaining residue charges, arranged in the shape of the pictures to be reproduced are rendered visible by way of known developing systems, such as toners of artificial materials, dyestuffs and/or soots, as well as glass pearls or metal powder. Likewise the rendering visible of the latent electrophotographic image is effectuated with liquid developers wherewith the liquid phase of the developer must have a smaller electrical capacity of conduction and a dielectric constant different from the one of the matter dispersed in it and used for the creation of the image and for the rendering adhesive, which are preferably dyed.

The image rendered visible by this developing is fixed according to known procedures as for instance, by smelting it or by the effect of the toner causing the solvents to swell.

The electrophotographic material developed but not yet fixed is furthermore suitable for the production of transfer copies, by way of transferring the toner of the developed electrophotographic image by electrostatic means onto other support materials, as for instance, ordinary paper, foils or metal plates.

The electrophotographic material, according to the invention, permits a repeated reproduction of the image on the same plate, by bringing onto the same plate after the fixation of an electrophotographic picture previously created further images and onto the image already cre ated, wherewith these images can be created in several and different colours. The material, according to the invention, is furthermore suitable for continued creation of images, especially if the image created is rendered Onto other materials by way of a transfer procedure. With this form of application an interim cleaning is necessary of the electrophotographic material of adhering toner residues, as well as eventually the complete discharge before the new creation of image. It is herewith possible, to produce a greater number of different reproductions with one and the same electrophotographic plate, Wherewith the continued procedure of transfer can be rendered consecutive and automatic. It is further-more possible, to remove the developed electrophotographical image by wiping it off and without a renewed charging and photo exposure, by effect of the developer system alone, to have the image newly reappear. Herewith the contrast increases, as the surface-bound residue charges, serving the image compilation, were removed. This method permits corrections to be made also with regard to the quantities of the toner to be applied. Preferably a dimly lighted room is used for the Work.

A further form of application of the electrophotographic layer supplied according to the invention under application of properly adhesive photoconductors consists in the production of printing plates, especially for the offset printing process.

Herewith a conducting support material, consisting of metal plates or metal foils also such ones having been roughed up by mechanical or galvanic means to a surface condition of finest grain structure, or of conducting paers, foils or fleeces eventually after covering it with a colloidal layer having it coated with the electrophotographical layer. If using metal foils with grain structure or of aluminum plates with a porous hydrophilic surface produced by oxidizing or phosphatizing the production of pressure plates succeeds also without the intermittance of a printing dye repellent hydrophilic colloidal layer. None conducting support materials can, however, also be used, if the colloidal layer is rendered electrically conducting. For the production of the colloidal layer gelatine, polyvinyl alcohol, alginates, salts of the acryl or methacryl acids, acryl-acid amides, cellulose-ether or -esters swelling in water, zinc salts of the resinous acids or polyurone acids etc. are usable. For this form of application the properly adhesive photoconductor is created in a form still dissolvable in solvents and a threedimensional reticulation is avoided.

The printing plates produced according to the procedure of the invention are electrostatically charged in known ways and photo-exposed under a pattern or in the procedure of projection. By developing with a toner, capable of absorbing fat printing dyes and being insoluble in solvents, permitting to dissolve the electrophotographic layer, the electrophotographic image is created. The same is fixed by solvents causing the toner to swell or by heating up to about C. Afterwards by overwiping or by bathing in a mixture of solvents the electrophotographic layer is dissolved while the image created by the toner remains. The colloidal layer situated beneath the electrophotographic layer of the hydrophilic support adequate for printing purposes is laid bare. With the application of aluminum or zinc plates the printing plate is rendered ready for use by wiping over it with a 30% phosphoric acid and afterwards by rendering it humid, eventually under addition of moistening means, the printing dye suitable for offset printing processes is brought onto it. Printing plates of this kind permit high numbered edition under exact printing procedures.

The following represent special realized forms of the invention without limiting the object of the invention to them:

EXAMPLE 1 The example relates to the production of a photoconductor properly adhesive, the electrophotographically active grouping of which is derived from the class of the thiazoles, the free amino group of which is brought to reaction with a modified isocyanate containing three free isocyanate groups per molecule.

50 g. of 2 (4 aminophenyl) 6 methylbenzthiazole,

fusing point=l92 C., are dissolved under reflux boiling in 750 cm. of water free cyclohexanone, the solution is filtered hot.

87.5 g. of the modified tri-isocyanate (commercial product produced by Farbenfabriken Bayer AG. and sold under the trademark Desm odur L), 75 weightapercent in ethylacetate are added to it and brought to reaction for 30 minutes after removal of the ethyl acetate under reflux boiling at a temperature of C. The solution is left standing overnight, While the reaction product is flocked out. The precipitation is filtered, boiled up with 500 cm. of acetone, whereby small parts of 2-(4'-aminophenyl)-6-methylbenzthiazole having not reacted, are dissolved. Separated from the insoluble product of reaction by filtration in a hot state, washed several times with cold acetone on the suction filter and dried by 100 C., a product of addition is obtained softening between 220-225 C. and afterwards congealing to a hyaline state. This product of reaction dissolves in cyclohexanone, dimethylformamide, methylcyclohexanone, for-mamide, tetrahydrofurane and hardly dissolves in hot fbenzole. The compound practically colorless is already usable in this form as a properly adhesive photoconductor.

9 For the. production of the electrophotographic layer 100 g. of the before mentioned properly adhesive photoconductor is dissolved in 500g. of cyclohexanone and 200 g. of methyl-ethyl-ketone and a layer is spread onto a surface cleansed aluminum plate by way of a centrifuge, that a thickness of layer is obtained of 0.005 mm. in dry state. After expulsion of the solvent by heating the plate up to 120-130 C. in an air current, followed by a cooling down to room temperature the 'electrophoto-graphic plate is ready for use. It consists of an even surface of high gloss, together with a considerable hardness of surface.

Electrophotographic plates spotted by fat or toners can easily be cleansed by washing with water and washers, without losing their efiiciency'. For this purpose the electrophotographic plate is rubbed with a moist cotton pad, rinsed with distilled water and-dried in a warm air current. The plate can immediately be used again.

The electrophotographic plate thus produced is charged for a short time under an arrangement of spray electrodes with 6-7 kv., photo-exposed under a pattern with a cold light UV valve for 3-16 seconds and afterwards powdered with a mixture, consisting of the toner and small glass pearls, the toner consisting of piccolastic resin, soot and black dyestuffs. On a support of metallic g-loss an image rich in contrasts is produced possessing a large spectral dispersion, which can be firmly fixed by heating up to 120 C. and by the reaction of the vapors of the solvents attacking the developing powder. The electrophotographic-plate has a high sensibility already'in the long wave ultraviolet spectral region. In the light of an electric bulb, 'as well as in. diffuse day light, its sensitivity is so small that the production of the picture can be carried through in a moderately blacked out room by full electric bulb light.

EXAMPLE 2 The example relates to the production of a properly adhesive photoconductor, the electrophotographically active groupings derived from the class of the thiazoles and which possesses a free amino group for the further reac tion with isocyanates. This electrophotographically active group is brought to reaction in such a way with a modified isocyanate with three free isocyanate groups per molecule, that small parts of free isocyanate groups are sustained for the realization of reticulating reactions.

40 g. of 2-(4-aminophenyl)-6-methylbenzthiazole, fusing point=192 C., are dissolved under reflux boiling in 750 cm. of water free cyclohexanone; the solution is filtered in a hot state;

90 g. of the modified tri-isocyanate (commercial product produced by Farbenfabriken Bayer A.G. and sold under the trademark Desmodur L), 75 weight-percent in ethylacetate are added and brought to reaction after removal of the ethyl-acetate for 30 minutes under reflux boiling at a temperature of 155 C. The solution is then cooled down to room temperature and is left to itself overnight, while the photoconductor flocks out. It is separated by filtration. In

500 cm. of acetone afterwards suspended and suctionfiltered, the filter residue is washed several times with cold acetone.

80 g.'of the reaction product still somewhat moistby acetone are dissolved in 250 cm. of cyclohexanone and 20 cm. of ethyl-glycol added to it and left to react during 20 minutes at a temperature of 125 C. The properly adhesive photoconductor is dissolvable in cyclohexanone. The reaction product obtained is thinned down with 100 cm. of fmethylethylketone and heated up to 60 C.,

usedfor the covering layer of a cleansed aluminum plate inacentrifuge.v The plate covered with said layer is dried in a warm air current and afterwards burnt in a drying chamber or by way of an ultrared radiator for 30 minutes at a temperature of 130140 C. Its thickness of layer is 0.006 mm. An electrophotographic layer is obtained especially resisting against scratches and practically insoluble in solvents, which layer is used for the production of images according to Example 1. It is of the same water and washer resistance qualities as the electrophotographical plate mentioned in Example 1.

Transfer The electrophotographic plate is negatively charged with 7 kv. photo-exposed for 10 seconds under a pattern to cold light UV-valves and developed with the commercial product sold under the trademark Graph-o-Fax- Toner. charged with 1 kv. A sheet of common writing paper is laid upon the powder image not yet fixed and brought together'with the plate into the electric field of a tension of 7 kv., in such a way, that the negative arrangement of electrodes is situated behind the back cover of the paper. By transfer on the writing paper there is obtained from the reverse side powder image an original of high contrast and clearly readable. The image transferred is fixed by heating up to 110 C.

EXAMPLE 3 This example relates to the production of a properly adhesive photoconductor, the electrophotographically active groups which derive from the class of thiazoles and which possess an amino group capable of further reaction with isocyanates.

In the first stage of reaction it proceeds that a considerable surplus part of free isocyanate groups is sustained after the reaction with the thiazole compound, which may then be brought to reaction with a fat alcohol in order to increase resilience.

455 g. of 2-(4-aminophenyl)-6-methylbenzthiazole, fasing paint 192 C., are dissolved in 400 cm. of cyclohexanone at 60 C. and added to it are 175 g. of the modified tri-isocyanate (commercial product produced by Farbenfabriken Bayer A.G. and sold under the trademark Desmodur L) and after the removal of the ethylacetate at C. heated up during 7 minutes until the cyclohexanone begins to boil. To this solution are added in one gulp 40 g. of an n-C -fat alcohol (commercial product sold under the trademark Lorol C during 15 minutes a heating up to 150 C. ensues and then cooling down is permitted. The reacting solution remains clear after having cooled to room temperature. It is of a high viscosity and may be thinned down with acetone or chloroform without a precipitation ensuing.

For separation the properly adhesive photoconductor is precipitated from the reacting solution by pouring it into 2 litres of benzene (boiling range -140 C.), the properly adhesive photoconductor being obtained after several decantations-and comminutions in benzine and after drying at 100 C. in a vacuum drying chamber as a whitegrey powder.

For the production of the electrophotographic layer. 50 g. of the properly adhesive photoconductor produced as described above is dispersed in cm. cyclohexanone and dissolved by heating up to 100 C. The solution is then cooled and 200 cm. of acetone are added to it. The solution formed remains durable at room temperature. There is no C -fat alcohol odor.

A cleansed aluminum plate is so covered with a layer in the centrifuge, that a thickness of layer of 0.004 mm. in dry state is obtained. After spreading of this preparation it is dried in a warm air current and afterwards heated up for the expulsion of cyclohexanone residues to The electrophotographic plate is now positively 100 C. in the air current. The surface of the electrophotographic layer is adhesive and elastic at this temperature. If cooling down to room temperature is effectuated an electrophotographic layer of high gloss, suflicient hardness and great resilience is forming.

It is dissolvable in a mixture of 2 parts of ethanol and 1 part of acetone and can be used for the production of printing plates. This electrophotographical plate may also be cleansed with water and washers from adhesive toner materials and fat traces, as e.g. finger prints, with out causing loss of the electrophotographic efficiency after drying.

EXAMPLE 4 g. of (4-hydroxybenzylidene)-4'-N-di-ethylaminoaniline in 250 g. of cyclohexanone. Small parts not dissolved are removed by filtration and in the solution are added under stirring 44 g. of the modified tri-isocyanate (commercial-product produced and sold by Farbenindustrie Bayer AG. under the trademark Desmodur L), 75 weight-percent in ethyl acetate and after expulsion of the ethyl acetate brought to reaction for 40 minutes at 120 C.

The reaction product, spread onto a glass plate, congeals to a yellow colored resinous product with good adhesability on the support layer.

100 cm. of the reaction solution obtained, durable in cool state, are thinned down with 300 cm. of methyl-ethyl-ketone; this solution being then by way of a centrifuge spread in such a manner on an aluminum plate of high gloss, which has been carefully cleansed, that a thickness of layer of about 0.006 mm.

is uniformly forming.

This electrophotographic layer is of gold yellow colour and is highly photo-sensible as well in strong bulb light as in the ultraviolet spectral region.

Charged according to Examples 1-3 and photo-exposed during 1-3 seconds to cold light UV-valves, an electrophotographic image rich in contrasts is obtained after developing with the toner sold under the trademark Grapho-Fax, well known as a commercial product, in combination with glass pearls. This image is fixed by help of warmth. This electrophotographic plate is furthermore adequate for the image transfer according to Example 2.

EXAMPLE 5 On a transparent paper of 60 g./m. weight, a preparation adequate for the production of a conductive interspace layer consisting of g. of polyvinyl alcohol, of medium molecular weight 10 g. of polyethylene-glycol-ether,

10 g. of sodium chloride, and 930 cm. of Water is spread with a wash up roll and scraped by way of an air rake, so that a layer of a thickness uniform of 8 g./m. in dry state is formed.

The auxiliary layer being dried down to a humidity rate of 1218% in a warm air current after the spreading,

is coated on a centrifuge, with a scrape solution, used for the production of the electrophotographic layer according to Example 3, in such a way that an electrophotographic layer of a thickness of 0.006 mm. is obtained. After drying of the electrophotographic layer subsequent climate conditioning at a relative 65% air humidity at 20 C. the electrophotographic material is ready for use.

The transparent and practically colorless material is rendered photo-sensitive by help of a 8 kv. arrangement of spray electrodes, consisting of tungsten wires commonly used in the electric bulb manufacturing the material being charged with an intermediate space of 15 mm. and a distance of 15-20 mm. from the positive electrode formed as a support layer, in such a way that the electrophotographic layer is laid by the negative electrodes.

Photo-exposed under a pattern to UV-cold light valves during 20 seconds and afterwards developed by a developing system, consisting of the commercial toner sold under the trademark Graph-o-Fax, a commercial product, and glass pearls as well visible reproduction is obtained suitable on account of its transparence as an intermediate original after its being fixed by trichloroethylene vapours.

Unfixed the developed electrophotographic material is usable for the transfer of images.

EXAMPLE 6 The example refers to the reaction of a photoconductor of the thiazole class with an epoxy compound of the di-2,3-epoxy-propane-ether group of the bis-fifi-( l hy droxyphenyl propane. i

The mixture of reaction is condensated for 60 minutes at 154 C. and afterwards cooled down to 40 C.

To this product of reaction are added: 450 g. of methylethyl-ketone; this preparation is used for the production of the electrophotographic layer.

This coating of an aluminum plate of high gloss and ofa thickness of O.1O.3 mm. is effectuated, by spreading the solution committing the electrophotographic layer with a centrifuge in such a way on to the surface, that a layer of a thickness of about 0.006 mm. in dry state is obtained The electrophotographic layer is slightly surface dried in a warm air current and submitted to an aftertreatment during 30 minutes at C. for the expulsion of solvent residues. After cooling the electrophotographic layer congeals and is ready for use. It renders a well readable reproduction of a pattern of high contrasts after being charged up to 6 kv., photo-exposed to UV-cold valves for 15 seconds and developed according to Examples 1 to 5; the image can afterwards he fixed by heating up to 110 C.

EXAMPLE 7 This example describes the use of a support material of insulating qualities, on which it is possible, to create an electrophotographic image by help of organic properly adhesive photoconductors although no discharge of electronics essential can take place on account of the insulating qualities of the support.

For this purpose a plate of window glass of the thickness of about 2 mm. is coated by help of a centrifuge with a properly adhesive photoconductor described under Example 4, in such a Way that the thickness of the electrophotographic layer is about 0.03 mm. The electrophotographic layer is superificially dried on the centrifuge with an ultra red radiator and afterwards burnt in for 10minutes at about C. The electrophotographic'layer 13 thus formed has excellent adhesive powers to glass and besides a great hardness and a considerable resistance against grinding wear. This electrophotographical layer is dissolved by higher ketones, cyclohexanone and dimethylformamide. i

This electrophotographic plate produced by making a glass plate serves as support and is charged up under an arrangement of spray electrodes of 7 kv. for 10 seconds, in such a way that the tungsten wires serving as negative electrodes are confronted to the electrophotographic layer with a distance of 13 mm., while the glass support is laid upon the positive electrode. The electrophotographic plate charged and thus made photo sensitive is photo exposed for seconds under a pattern to UV-cold light valves and after developed with a developing system, consisting of glass pearls and the direct toner sold under the trademark Graph-o-Fax. An electrophotographic image of high contrasts is produced on a transparent support which image after being fixed by heating up to 120 C. or by solvent vapours can firmly be fixed onto the electrophotographic layer. This electrophotographic plate is suited for repeated production of electrophotographical images and can be used for the production of further copies by help of other methods of reproduction.

The following Examples 8, 9, 10 and 11 describe properly adhering photoconductors, the electrophotographically active groupings of which originate form the photoconductive ket-to-aniles, which groupings bear the substituents, capable of reacting with epoxide or isocyanate groupings.

EXAMPLE 8 N(4-ethyl-(B-oxyethyl)-aminophenyl-rnethylene) 3'- nitro-aniline of subsequent formula was produced by reaction of benzoyl-3-nitro-aniline with N-ethyl- (B-acet-oxyethyl -aniline with phosphoroxy-chloride at 120 C. and subsequent saponification of the acetyl group.

The isocyanate component, containing about two free isocyanate groups per molecule which component communicates adhesion and is used for the production of proper-adhesive photoconductors, is produced in the following way:

32 g. of 2-ethyl-2-butyl-propandiol-l,3 (corresponding to 2 mols) are dissolved in 100 g. of cyclohexanone and then dissolved in 70 g. of tol-uylene-2,4-diisocyanate (it is also possible to use 70 g. of toluylene-2,6-diisocyanate or 70 g. of a mixture of both of the compounds) 200 g. of cyclohexanone are added.

50 g. of modified isocyanates, described above are dissolved in g. of cyclohexanone. Added are methylene)-3-nitro-aniline, dissolved in '200 g. of cyclohexanone, and the mixture is brought to Herewith an aluminium plate submitted to a galvanic pre-treatment is coated in such a way, that a thickness of layer of 0.0060.02 mm. in dry state is formed. After drying at C. in an air current an electrophotographic layer well adhesin-g to metals and scratch-resistant results, fit for being used according to the preceding examples after negative or positive charging for the reproduction of images and eventually for their transfer.

EXAMPLE 9 30 g. of 4-di-methyl-amino phenyl-phenylmethylene)-3'- oxy-aniline of the subsequent formula CH OH are dissolved in warm condition in 100 g. of cyclohexanone. To this solution are added 27.7 g. of the modified isocyanate with three isocyanate groups per molecule (commercial product produce-d and sold by Fa-rbensindustrie Bayer A.G. under the trademark Desmodur L) 75 weight percent in ethyl acetate, thinned down with 50 g. of cyclohexanone, and after expulsion of the ethylacetate condensated for 1 hour at 148 C.

The reaction product by this reaction has suffereda considerable increase of viscosity no longer permits three dimensional reticulation with diisopropylene-triarnine.,

The solution is of green color.

15 g. of above condensated solution are thinned down with 25 g. of :methyl-ethyl-ketone,

15 g. of cyclohexanone, and

15 g. of buty-l-acetate and for the coating of a copper foil cleansed at its surface, of a thickness of 0.01 cm. by washing up and scraping with a rake from roll to roll coated and afterwards burnt in for a short time with ultrared radiators at 150 C. and then cooled.

The electrophotographic layer originating from the proper adhesive protoconductor, has a thickness of about 0.004 m m.; it is of high photosensibility already in the long wave UV-region and produces images rich in contrasts fit for transfer of images, f.i. onto writing paper. The electrophotographic layer moderately dissolves in ethanole, wherewith the toner image burnt in, the latter containing polystyrol or other artificial resins undissolvable in alcohols, firmly adhering remains on the surface, while the said layer is at once dissolvable by ketones and esters. It is therefore especially adapted for the production of printing plates. The electrophotographic layer firmly adheres to metals and has a good resilience at high scratch-resistance. t

The electrophotographic material described above is excellently suited for the image transfer. For this purpose it is treated with a tribo-electric powder, consisting of a toner and glass pearls or iron powder, and the ensuing electrophotographic image is not fixed. Afterwards the electrophotographic plate is caused closely to contact a transfer sheet consisting of paper, of paper soaked in artificial resins, or artificial materials, and thus introduced into a sufiiciently strong electric field, the electrode of which charged up differently to the toner charge is arranged toward the reverse of the transfer sheet. The electrophotograpric image transferred is then fixed by heating up or by solvent vapours, eventually under simultaneous heating.

A special sample concerns the production of an offset printing plate, for which a toner suited for printing purposes is transferred from the electrophotographic layer onto a commonly used printing plate, as used for fiat printing submitted to a special treatment for offset printing on which plate it is firmly fixed. This printing plate is suited for the production of flatprinting.

EXAMPLE 10 170 g. N-(4-di-methyl-amino-phenyl)-phenyl-methylene 2'-methyl-4-nitro-5-butyl-.amino-aniline of subsequent formula, fusing point f=l03 C.

Dried at 130 C. a hard but resilient electrophotographic layer adhering well to the support material is produced, rendered photosensitive after a negative or positive charging under an arrangement of spray electrodes of 5-8 kv. or by friction electricity, the region of photosensibility ranging from that of a mercury high pressure lamp to electric bulb light, reproductions rich in contrasts being obtained after development.

EXAMPLE II 65 g. of N-(3-oxy-napthyl)-4-di-methyl-aminophenylmethyl-aniline of the following formula:

CH3 CH3 produced by reaction of naphthol AS with dimethylaniline and phosphoroxy-chloride are dissolved in 250 cm. of cyclohexanone, a solution being added of 87.5 g. of the modified isocyanate with 3 free isocyanate groups per molecule (commercial product produced and sold by Farbenindustrie Bayer A.G. under the trademark Desmodur L), 75 Weight-percent of ethyl-acetate, dissolved in 16 200 cm. of cyclohexanone, and condensated for 2 hours under reflux boiling. Subsequently 16 g. of a C -fat alcohol are added and reacted under a further 30 minutes of reflux boiling. The photo conductor properly adhesive of resinous qualities can be separated by precipitation with benzine.

Examples 12, 13, 14 describe the reactions of photoconductors of the classes of the eventually substituted aromatic or heterocyclic-ketones or thio-ketones, both of the ring systems of which are connected by CO or (IJS groups, containing further subst-ituents in the ring system or in the lateral chains, reacting with isocyanates and/or expoxides forming proper adhering photoconductors.

EXAMPLE 12 31 g. of 2-(4-di-ethyl-amin0-2-oxy-benzoyl)-benzo-acid and 0.3 g. of rhodamine B are dissolved in cm. of cyclohexanone. To the cooled solution are added 47 g. of the reaction product, containing'three free isocyanate groups per molecule produced from 1 mol of l-tri-methylol-propane and 3 mol of toluylene-2,4- di-isocyanate and/or toluylene (e.g. a commercial product produced and sold by Fanbenindustrie Bayer A.G. under the trademark Desmodur L) 75 weightpercent in ethyl-acetate, dissolved in 100 cm. of cyclohexanone.

This mixture is condensated for 20 minutes at 151 C. under reflux boiling, a perceivable increase of viscosity ensuing. The product of reaction is only limitedly compatible with acetone. If mixed with acetone at a rate of 10:1 the proper adhesive photoconductor is precipitated. The reaction can be directed in such a way that a cross-linking does not yet take place.

25 g. of the reaction solvent are added to 25 cm. of methyl-ethyl-ketone and 35 cm. of dioxane and after filtration they serve for the production of the electrophotographic layer, an aluminum foil having a chemical-galvanic gloss coat to it, being coated withit by help of a centrifuge, so that a layer thickness of 0.006 mm. in dry state is formed.

The plate coated is superficially dried on the centrifuge, by way of an ultra red radiator, and then burnt in for 5 minutes at C. An electrophotographic layer glossy and mechanically firm adhering on the support as well as of a high grinding resistance is obtained. This electrophotographi-c plate is charged electrostatically at -7 kv. for 3 seconds and photo-exposed under a pattern for three seconds to UV-fluorescence valves and afterwards developed with glass pearls and a direct toner. An elec trophotographic image of high contrasts is obtained.

Another method of the reproduction of image consists in that the above described electrophotographic plate is photoexposed in charged condition in a magnifying means, outfitted with a 150 watt-cinema-projection lamp with an opening rate of 1:5.6 at a distance of 30 cm. between objective and plate through a micro film. After development an electrophotographic image rich in contrasts is here also obtained.

EXAMPLE 13 g. of 4-N-ethyl-(;8-oxy-ethyl)-amino-benzophenone 200 g. of the modified isocyanate (commercial product produced and sold by Farbenindustrie Bayer AG. under the trademark Desmodur L), 75 weight-percent in ethyl-acetate, and at 100 C. condensated for so long a time (usually minutes), that the solution is still compatible with methyl-ethyl-ketone and that no gelatination takes place.

100 cm. of the reacting solution are thinned down with 200 cm. of methyl-ethyl-ketone, and this solution is spread in uniform thickness of layer of about 0.008 mm. onto an aluminum foil of high gloss.

The electrophotographic layer formed is dried at 120 C. in an air current and then burnt in at 140 C. for a short time. The electrophotographic material formed after being charged with 7 kv. and being photo-exposed under a pattern to a mercury high pressure lamp or an impulse discharge valve after development produces reproductions rich in contrasts.

EXAMPLE 14 For the production of the electrophotographic material there is used as a support material a glass fibre fleece impregnated with artificial resins having an. even surface, on which latter it was exposed to aluminum vapors. Onto this material there is spread in the centrifuge a solution consisting of 50 cm. of the above-mentioned product of reaction thinned down with 100 cm. of methyl-ethyl-ketone and 0.5 g. of brilliant green (according to Schultz, Farbstoiftabellen, 1931, No. 760), the spread solution being superficially dried by ultra red radiators and being burnt in at 120 C.

A firmly adhesive electrophotogr-aphic layer of high grinding resistance results this layer according to the abovementioned examples being suited for the production of electrophotographic reproductions. The electrophotographic material has a serviceable photo-sensibility at electric bulb light.

EXAMPLE 15 50 g. of 4-di-methyl-amino-phenyl-3'-oxy-naphthyl-2'- ketone of subsequent formula:

are dissolved in 200 cm. of cyclohexanone. Added hereto are 104 g. of the isocyanate component described in Example 8, 52 weight-percent in cyclohexanone, and condensation is effectuated at 135 C. for minutes.

50 cm. of the reaction product are thinned down with 50 cm. of methyl-ethyl-ketone and 50 cm! of ethyl-amyl-ketone and afterwards filtrated.

This solution is spread by help of a scrape machine outfitted with dosage rollers onto a cellulose paper exposed to aluminum vapors of 80 g./m. weight, dried in a warm air current and then post-heated at 120 C. for a short time.

On account of the green color the proper adhesive photoconductor is photo-sensitive. Negatively charged for 5 seconds with 7 kv. under a corona discharge with UV-cold light-valves and photo-exposed under a positive 18 pattern, after development with glass powder and a direct toner an image rich in contrasts is produced, fixed by heating or by solvent vapors.

Another method of development generally applicable is the use of so-called liquid developers consisting of a dispersion of dye particles under addition of soluble or dispersed artificial resins. In analogy herewith is the application of developers of powder condition with electrophotographical layers derived from properly adhesive photoconduotors.

This development can be carried through if the liquid phase of the developer is thus formed that the electrophotographic layer is not dissolved. Preferably such electrophotographic layers are used, submitted to a postcondensa'tion after production.

The following Examples '16, 17 describe properly adhesive photoconductors the electrophotographic classification of which is derived .from the class of acridine-dyestuifs, according to Schultz, Farbstofitabellen, vol. 1, Leipzig, 1931, pages 383390, as well as Ullmanns Encyklop'aldie der Techn. Chemie, vol. 3, Munich-Berlin, 1953,.

pages 7l-72, which possess swbstituents, capable of reacting with epoxides or isocyanates and which have been caused to react with epoxideor isocyanate-containing compounds communicating an adhesive eifect. Preferably salt-free acridine stuffs are used for the production of properly adhesive photoconductors.

EXAMPLE 16 g. of the modified tri-isocyanate (commercial product produced and sold by Farbenindustrie Bayer A.G. under the trademark Desmodur L) are dissloved in 200 cm. of methyl-ethyl-ketone. Added to it is a solution consisting of 50' g. of 2,7-di-amin-o-3,6-dimethyl-9-methyl-acridine (name of dye Euchrysine 2 GNX), according to Formelbild 5 (structure) in Ullrnanns Encyklopadie der technischen Chemie, vol. 3, 1953, page 71, dissolved under reflux boiling in 200 cm. of acetone and 300 cm. of methyl-ethyl-ketone, and condensated by further reflux :boiling for 10 minutes. Afterwards are added 14 g. of n-butanol and a further reaction is carried on for another 10 minutes as described above. The reacting solution containing the proper adhesive photoconductor is thinned down with 200 cm. of inethyl-glycol-a cetate and afterwards used for the coating layer of metal foil supplied with a galvanic oxide gloss, lined on paper.

The electrophotographic layer is dried at C. in a warm air current and afterwards submitted to a finish drying by a short time beating up with ultrared radiators. This electrophotographic material is highly photo-sensitive in the spectral region ranging from violet to blue, as produced by luminous matter-fluorescence lamps, used for photographic tracing purposes. Further, it shows a high degree of photo-sensibility in the spectral region of impulse discharge valves as used for photographic purposes.

EXAMPLE 17 90 g. of the modified tri-isocyan-ate (commercial product produced and sold by F-arbenindustrie Bayer AG. under the trademark Desmodur L), 75 weight-percent in ethylene acetate, are added to 50 cm. of cyclohexanone and brought to reaction for '10 minutes at C.

24 g. of di-Z-ethyl-hexyl-amine having also been added.

71 g. of 3-a-mino-6-di-methyl-amino-9-(4'-di-methylamino-phenyl)-acridin-e (Farbstotftabellen, vol. 1, 1931, No. 911), a free base, are dissolved in a hot state in 700 cm. of cyclohexanone, filtered in hot condition and used for the reaction together with the abovementioned reacting solution for 20 minutes at about 150 C. This properly adhesive photoconductor is excellently suited, on account of its increased solubility in ethanole or other commonly used solvents, for the production of an electrophotographic layer on such support materials, change-able after production of the electrophotographic image and subsequent fixation of the toner by heating, into printing forms, preferably for offset printing process. For this purpose the preparation rendering the photosensitive layer is either spread onto a paper pattern, submitted to a preceding treatment according to U.S. patent specifications Nos. 2,534,650, 2,681,617 or 2,559,610 or metal patterns are used for supports suitable for printing purposes, said patterns preferably of aluminum, being roughened to most fine grain condition either by galvanic or other means, their drying being effectuated at increased temperature in an air current. After production of the electrophotographic image under application of a toner suitable for printing purposes, the plate fixed by heat is slightly wiped over with an alcohol moistened cotton pad not dissolving the electrophotographic layer made to serve for the reproduction of the image. By a quick wiping over with phosphoric acid the printing plate is rendered ready for use. From a positive pattern a positive printing mould is obtained permitting a high numbered printing edition according to the offset process.

The following Examples 18 and 19 refer to properly adhering photoconductors, the electrophotographically active groupings of which derive from the compounds described by German Patent 1,060,713, and which bear additional substituents capable of reaction with isocyanates and/ or epoxides and which afterwards are brought to reaction with compounds containing isocyanate or epoxide groups communicating adhesive qualities to the properly adhesive phot-oconductor.

EXAMPLE l8 For the reaction is used a compound not described in German Patent 1,060,713, this compound being 1,3- di-m-oxyphenyl-4,S-di-phenyl-imide azole thione (2), fusing point=274 C., of following structure:

@ N N'- c C; o

100 g. of the above compound are dissolved in a warm state in 300 cm. of cyclohexanone, a solution being added to it consisting of 110 g. of an isocyanate component more fully described in Example 8, this compound having approximately 2 isocyanate groups per molecule, dissolved in 200 cm. of cyclohexanone, this mixture reacting under reflux boiling at about 150 C. for 30 minutes.

This solution is then cooled down and left to itself overnight, small parts of the imide-azole-thione-compound not having reacted crystallizing out and being filtered off.

100 cm. of the above-mentioned reaction products are added to 75 cm. of methyl-ethyl-ketone and to 75 cm. of dioxane. This solution is used for the production of the electrophotographical layer by spreading it onto a paper the surface of which having been prepared against the intrusion of organic solvents and afterwards drying this layer.

The eleotrophotographical material thus formed is negatively charged by help of a coronar discharge of about 6 kv. and under a positive pattern photo-exposed to a mercury high pressure lamp, and afterwards powdering it with a developing powder in the known way. A positive image of the pattern is obtained which is fixed by heating. The toner used for the developing, with a particle size ranging from 15 to about 50a is mixed with a support material causing the toner to be charged up tribo-electrically, antipolar to the charge used for the reproduction of the image on the paper. Usual toners consist of an artificial resin component capable of firmly holding the charge, as, for instance, tolylstyrol, maleinate resins, cumarone resins, phenol resins, products of resinous qualities from colophonium and others, soots or dyestuffs and eventually with an addition of organic black dyestuffs, as known to be used for additions to carbonic papers.

EXAMPLE 19 81 g. of 1-m-oxyphenyl-3,4,5-tri-phenyl imide azolone (2), fusing point=190 C., of the fol-lowing structure:

-Q @xyQ After separation and expulsion of the ether a soft resin of high viscosity remains. The reaction product is adequate for the formation of resilient electrophotographic layers firmly adhering to the support, the aforesaid product undergoing a considerable increase of its hardness and grinding resistance when burnt in at 130 C.

A solution is added con- 30 cm. of the resinous proper adhesive photoconductor are dissolved in 100 cm. of cyclohexanone and added to it are 100 cm. of methyl-ethyl-ketone.

This solution is used for the coating of an aluminum plate. Under application of measures known for the production of an electrophotographic image, as hereintofore described, reproductions rich in contrasts are obtained.

EXAMPLE 20 The example outlines the use of compounds according to the general formula of German Patent 1,060,714 as the essential ones, containing the component communicating electrophotographic efliciency if containing groupments capable of reaction with epoxides and/or isocyanates and causes them to react toward the production of properly adhesive photoconductors with isocyanate or epoxide groups containing compounds.

20 g. of 1,3-di-phenyl-S-p-oxyphenyl-pyrazoline according to Formula 17 in German Patent 1,060,714, fusing point=145 C., are dissolved in warm status in 60 cm. of cyclohexanone, a solution being added to it consisting of 58 g. of the modified tri-isocyanate (commercial product produced and sold by Farbenindustrie Bayer AG. under the trademark Desmodur L), weight percent in ethyl-acetate and g. of cyclohexanone. After expulsion of the ethylacetate reaction ensues at C. for 10 minutes after which are added 20 g. of a commonly used C -fat alcohol, and reaction is carried on for a further period of 20 minutes at 115-l20 C. In order to separate the properly adhe- :siv'e photoconductor the above reaction product is poured into 600 cm. benzine, B.P. 110140 C., While stirring the same, the properly adhesive photoconductor being precipitated. After washing with benzine the same is dried at 80 C. in an air current.

g. of the dried photoconductor properly adhesive are dissolved in warm status in 30 =cm. of cyclohexanone and after cooling down 15 cm.

of methyl-ethyl-ketone are added.

For the production of the electrophotographic layer this solution is spread by centrifuge onto an aluminum plate of high gloss and then dried in an air current at 120 C. An electrophotographic layer of high gloss, firmly adhesive to metals, results having a high degree of photo-sensitivity when photo-exposed with UV-fluorescence lamps.

According to the above examples negatively charged with 7 kv. and photo-exposed under a positive pattern with the application of a direct tonerand glass pearls, an electrophotographic contrast image of a high capacity of photo-dissolution results which can be fixed by heating and/or the effect of exposure to solvent vapors. This electrophotographic material is excellently suited for the transfer of the unfixed electrophotographic image in an electrophotographic field onto other materials of plane surface, such as paper, artificial resin foils or paper-printing patterns commonly used in commerce for the offset process.

EXAMPLE 21 24 g. of hexane-1,6-diole and 70 g. of a technical mixture of 65 weight percent of toluylene-2,4-di-isocyanate and 35 weight percent of toluylene-2,6-di-isocyanate in 250 crn. of cyclohexanone and, caused to react for 4 hours at 145 C.

After distilling off of the cyclohexanone in a vacuum a transparent hard resin is obtained, soluble in cyclohexanone, di-methyl-formamide, higher ketones and partly in di-oxane, softening at about 140 C. and melting at 210 C. It is suited per se for forming an electrophotographic layer.

For its production 5 g. of the above described reaction product are dissolved in 50 cm. of cyclohexanone.

30 cm. of methyl-ethyl-ketone and 20 cm. of acetone are added.

After the cooling down to This solution is spread by way of a centrifuge onto an aluminum plate chemically or galvanically rendered glossy and if need be oxidized, it is then dried at 120 C., a layer thickness of about 0003-0008 mm. being formed. The electrophotographic plate is now ready for use and shows vivid metal gloss being practically colorless. It is most photo-sensitive in the longer wave-UV- region.

Charged up with 7 kv. under a pattern or by being photo-exposed to long wave UV-light in a photographical process, then developed with a direct toner and glass pearls, an electrophotographic contrast image of strong holding capacity for electrostatic charges results which is caused to adhere by way of usual fixing procedures such as heating or exposing to solvent vapors.

This electrophotographic material is suited for the production of sign boards, patterns and records in the metal industry, for the recording of packings, the production of printed current circuits, as well as for the transfer of the image not yet fixed in an electric field onto other materials of plane surfaces.

The following Examples 22, 23 describe the production of properly adhesive photoconductors the electrophotographically active groupings of which are derived from the class of substituted styryl-phenyl-ketones and which bear additional substituents capable of reacting with epoxides and/or isocyanates and have these react for the production of properly adhesive, preferably resinous, photoconductors with compounds containing epoxide or isocyanate groups said compounds communicating adhesive qualities.

EXAMPLE 22 g. of 4-di-methyl-amino-4-oxy-styryl-phenyl-ketone,

fusing point=205 C., according to the following for- H 0 i colors deep yellow, are dissolved in 300 cm. of cyclohexanone.

88 g. of the modified tri-isocyanate (commercial product produced and sold by Farbenindustrie Bayer AG. under the trademark Desmodur L), 75 weight-percent in ethyl-acetate are added and reaction takes place at 150 C. for 20 minutes.

cm. of the reacting solution are added to 50 cm. of methyl-ethyl-ketone and 50 cm. of ethyl-amyl-ketone and after having been spread onto an aluminum foil drying takes place at C. in an air current.

Charged up according to the above examples, photoexposed to a mercury high pressure lamp and sufficiently developed, a contrast image, also fit for transfers, results.

EXAMPLE 23 25 g. of 4-di-methyl-arnino-3-amino-styryl-phenyl-ketone of the following structure and of yellow color:

are brought into a solution of 50 g. of an epoxide resin of the type of di-phenylpropane reacted with epichlorhydrin, partly under enlargement of molecules condensed per se (commercial product sold under the trademark Epikote 1001, Shell), brought into 250 cm. of ethyl-amyl-ketone and dissolved under heating and stirring. Held at about 100 C. for 20 minutes under reflux boiling the solution undergoes a perceivable increase of viscosity.

100 cm. of the reaction product are thinned down with 50 cm. of methyl-isobutyl-ketone and 50 cm. of methyl-ethyl-ketone and for producing a non-adhesive surface added to 5 g. of the modified tri-isocyanate (commercial product produced and sold by Farbenindustrie Bayer A. G. under the trademark Desmodur L), 75 weight-percent in ethyl-acetate, and

0.5 g. of Victoria blue base, according to Schultz, Farbstoiftabellen, 1931, vol. 1, No. 822, and at once used for the production of the electrophotographic layer. For a support material a copper foil is used having an even front side but a sponge conditioned back, and is connected on its back with a resilient artificial resin of high melting point or with caoutchouc. Onto the front side of this material the dissolved properly adhesive photo-conductor is spread and dried at 100 C. in an air current until the expulsion of the solvent has been achieved and dries it and the front side is heated for a short period at 120 C. by radiation heat.

The electrophotographic material is, as described in the above examples, suited for the production of electrophotographic reproductions.

What I claim is:

1. In a photographic reproduction process which comprises exposing an electrostatically charged, supported photoconductive layer to light under a master to discharge the layer at the exposed portions and developing the resulting image with an electroscopic material, the improvement which comprises employing as the photoconductive layer a reaction product of (A) an organic photoconductive compound containing groups that carry active hydrogens reactive with isocyanates and (B) an organic compound containing at least two reactive isocyanate groups.

2. The process of claim 1, wherein the organic compound (B) contains the isocyanate groups attached to an aromatic ring system.

3. The process of claim 1, wherein the organic compound (B) is reacted with a polyhydric alcohol prior to the reaction with the photoconductive compound (A).

4. The process of claim 1, wherein the organic compound (B) is reacted with the photoconductive compound (A) and after this reaction further reacted with another compound containing groups that react with isocyanates, said other compounds being selected from the group consisting of organic compounds containing free hydroxyl groups, monoand polyamines, and organic compounds containing free carboxyl groups.

5. The process of claim 1, wherein to said reaction product are added sensitivity dyes to shift the region of spectral sensitizing.

6. The process of claim 1 wherein compound (A) is 2-(4-amino phenyl)-6-methyl benzthiazole, and compound (B) is a tri-isocyanate.

7. The process of claim 1 wherein compound (A) is (4-hydroxy benzylidine)-4'-N-di-ethyl amino-aniline, and compound (B) is a tri-isocyanate.

8. The process of claim 1 wherein the photoconductive compound (A) is N 4 ethyl (/3 hydroxyethyl)-amino phenyl-methylene-3-nitro-aniline, and compound (B) is the reaction product of 2-ethyl-2-butyl-propane diol-1,3 and toluylene-2,4 (respectively 2,6) diisocyanate.

9. The process of claim 1 wherein the photoconductive compound (A) is 4-di-methyl-amino-phenyl-phenyl methylene (3'-hydroXy-aniline) and (B) is a tri-isocyanate.

10. The process of claim 1 wherein the photoconductive compound (A) is N-(4-di-methyl-amino-phenyl)- phenyl methylene 2' methyl 4-nitro-5-butyl-aminoaniline, and (B) is a tri-isocyanate.

11. The process of claim 1 wherein the photoconductive compound (A) is N (3 hydroxy napthyl) 4' dimethyl-amino-phenyl-methylene-aniline, and (B) is a triisocyanate.

12. The process of claim 1 wherein the photoconductive compound (A) is 2-(4-di-ethyl-amino-2-hydroxy-benzoyl)-benzoic acid, and (B) is a reaction product containing three free isocyanate groups per molecule and produced from one mol of 1-tri-methylol-propane and 3 mols of toluylene-2,4-di-isocyanate.

13. The process of claim 1 wherein the photoconductive compound (A) is 4-amino-4'-di-methyl-amino-benzophenone, and (B) is a tri-isocyanate.

14. The process of claim 1 wherein the photoconductive compound (A) is 4-dimethyl-amino-phenyl-3'-hydroxy-napthyl-2-ketone, and (B) is the reaction product of 2-ethyl-2-butyl-propane diol-1,3 and toluy1ene-2,4-(respectively 2,6) (ii-isocyanate.

15. The process of claim 1 wherein the photoconductive compound (A) is 2,7-di-amino-3,6-di-methyl-9-methyl-acridine, and (B) is a tri-isocyanate.

16. The process of claim 1 wherein the photoconductive compound (A) is 3-amino-6-dimethyl-amino-9-(4-dimethyl-amino-phenyl)-acridine, and (B) is a tri-isocyanate.

17. The process of claim 1 wherein the photoconductive compound (A) is 1,3-di-m-hydroxy-phenyl 4,5-diphenyl-imide-azole-thion-(2), and (B) is a reaction product containing about 2 isocyanate groups per molecule, being produced from 2-ethyl-2-butyl-propane dio1-1,3 and toluylene-2,4-(respectively 2,6) (ii-isocyanate.

18. The process of claim 1 wherein the photoconductive compound (A) is l-m-hydroxy phenyl-3,4,5-triphenyl-imide-azolone-(2), and (B) is a tri-isocyanate.

19. The process of claim 1 wherein the photoconductive compound (A) is 1,3-diphenyl-S-p-hydroxy-phenylpyrazoline and (B) is a tri-isocyanate.

20. The process of claim 1 wherein the photoconductive compound (A) is 4-dimethyl-amino-4-hydroxy-styryl-phenyl-ketone, and (B) is a tri-isocyanate.

References Cited by the Examiner UNITED STATES PATENTS 2,697,028 12/1954 Baker et al. 96-1 2,811,510 10/1957 Leubner et al. 96-1 2,980,535 4/1961 Schroeter 96-1 3,025,160 3/1962 Bunge et al. 96-1 3,037,861 6/1962 Hoegl et a1 96-1 3,041,165 6/1962 Sus et al. 96-1 FOREIGN PATENTS 562,336 5/1958 Belgium.

NORMAN G. TORCHIN, Primary Examiner.

PHILIP E. MANGAN, Examiner.