EP0137217B1 - Electrophotographic recording material and process for its preparation - Google Patents

Description

The present invention relates to an electrophotographic recording material composed of an electrically conductive layer support, optionally an insulating barrier layer and a photoconductive double layer consisting of a charge carrier-generating and a charge transport layer, consisting of organic photoconductor, binder, dye and conventional additives, and a process for the production thereof.

It is known (US Pat. No. 3,121,006) to use photoconductive layers in electrophotographic recording materials which consist of a photoconductor and a material which acts as a binder. Binder layers are described which contain finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic binder. The binder is a material that is not able to transport charge carriers generated by the photoconductor particles over a substantial distance. As a result, the photoconductive pigment particles must be in practically continuous contact within the layer in order to allow the charges to be dissipated. The conductivity or the charge transport are achieved here by a high concentration of the photoconductive pigment. With such a layer structure, a pigment concentration of over 50 percent by weight is required.

It is also known (DE-OS 21 08 992, corresponding to US Pat. No. 3,904,407) to produce photoconductive layers for electrophotographic recording materials in a double-layer arrangement. The material then consists of an electrically conductive layer support, a charge generation layer and a charge transport layer. The layer generating the charge carrier can consist of a dispersed pigment. If an insulating binder is used with the dispersed pigment, a volume concentration of at least 25% pigment is required. The ratio of the layer thicknesses of the charge transport layer to the layer generating the charge carrier is 2: 1 to 200: 1.

It is also known (DE-OS 21 60 812, corresponding to US Pat. No. 4,026,704) to provide photoconductive layers which consist of top and bottom layers, both with binder and with the same organic photoconductor, with at least one additionally in the bottom layer activating sensitizer is present in an amount of 1 to 20 percent by weight based on the total photoconductor content. The cover layer consists of a binder and up to 50 percent by weight of photoconductor. The layer thicknesses are marked with 0.1 to 5 11m for the bottom layer and 5 to 20 _li m for the outer layer.

It is also known (US Pat. No. 3,533,783) to use photoconductive layers to improve the resolution of images applied by electrophotographic means, which comprise an inorganic or organic photoconductor together with an activator, such as pyrylium salts, in the lower layer and photoconductor and in the upper layer Contain binders. The thicknesses of the layers are generally given as 2.5 to 25 _µm .

A three-layer photoreceptor is described in German Offenlegungsschrift No. 31 08 618 (corresponding to US Pat. No. 4,340,655), in which a pigment concentration of 50 to 95 percent by weight in the binder used is necessary.

It is also known (DE-PS 11 17 391, corresponding to GB-PS 944 126) to use photoconductive, low-molecular weight, organic compounds for the production of printing plates by electrophotographic means and these by suitable, dissolved dyes (in accordance with DE-OS 25 26 720, US Pat. No. 4,063,948) to sensitize in the visible region of the spectrum. Instead of the low molecular weight substances, polymeric photoconductors can also be used together with an activator (DE-OS 27 26 116).

A disadvantage of the known electrophotographic recording materials with binder, organic photoconductor, dye or pigment is their relatively unsatisfactory resolution, which is particularly evident when developing a latent image charged with negative polarity with a liquid developer. Individual lines with a line width of less than 60 _l are no longer displayed at all with only reduced contrast and lines with a line width of less than 40 µm. These loss of resolution also occur with correspondingly fine vice points. Another disadvantage is the relatively high content of photoconductor. For example, in addition to the insulating binder, the photoconductive layers must contain the organic photoconductor in a total concentration of 40 to 50 percent by weight in order to achieve sufficient photosensitivity, which is noticeable in a considerable increase in the cost of the materials. In the production of printing forms by electrophotography, it is also important that the organic photoconductors are insoluble in aqueous alkaline stripper solutions. Therefore, the stripping, as is required in the application for printing plates and printed circuits, is hindered by these components. In addition, the insoluble parts are deposited in the stripping apparatus on rollers, pumps and other parts and lead to one increased maintenance. Since the transport layer with its large proportion of photoconductor is also thicker than the layer generating the charge carrier in the known double-layer arrangements, the disadvantages described also occur here. Double layers of photoconductor, for example according to DE-OS 21 08 992, applied in 4lim thickness on aluminum as a layer support, result in chargeability which are insufficient for practical use. Sufficient results can only be achieved with layer weights of more than 10 g / m ² with considerable material expenditure. Finally, it is disadvantageous that dye pigment particles from the high proportion in the charge-generating layer in contact with the metallic base are incorporated as a layer support in the pores of the surface, from which they cannot later be removed. Printing plates made with it tone during printing and are practically unusable.

It was therefore an object of the present invention to provide an electrophotographic recording material which enables high resolution, is light-sensitive with the lowest possible proportion of organic photoconductor and which is particularly suitable for use in the production of printing plates or printed circuits with low layer thicknesses is easily rechargeable and ensures a high-contrast toner image. In addition, it was an object to provide a photoconductor layer that can be easily removed from the coating, which enables the production of printing plates or printed circuits even on metallic substrates, such as copper surfaces, which could previously only be used with technical difficulties.

The solution to this problem is based on an electrophotographic recording material of the type mentioned at the outset and is characterized in that the charge carrier-producing layer consists of a highly insulating binder consisting of a compound containing high molecular weight, alkali-solubilizing groups, containing 0.5 to 20 percent by weight of dye are contained on the layer, dissolved or dispersed, that the charge transport layer consists of a highly insulating binder composed of a high-molecular compound containing alkali-solubilizing compound, in which at least one photoconductor is dissolved in amounts of 25 to 60 percent by weight, based on the layer, and the dye or dispersed in a concentration of at most 5 percent by weight, based on the layer, that a mixing zone of substances in the range from 1.5 to 2 μm, obtained by dissolving processes during production, is present in the boundary region of the two layers, and that the layer thicknesses of the charge-generating layer and charge transport layer are in a ratio of 3: 1 to 1:10, preferably in a ratio of 2: 1 to 1: 3.

It is thereby achieved that recording materials can be made available which are able to meet high demands and enable high resolution with a relatively low photoconductor concentration, based on the total layer. If the recording material according to the invention is used for printing purposes, the high proportion of binder in the charge-generating layer ensures rapid stripping. At the same time, the low proportion of photoconductors leads to better technical feasibility of the process. The use of relatively low dye concentrations in the layer generating the charge carrier also prevents the particles from being embedded in the pores of the surface of the layer support. Even with low layer weights for the photoconductive double layer, the technically required charges can be achieved with the recording material according to the invention. This is especially true when materials are used as layer supports that previously had considerable difficulties with charging, such as copper surfaces.

The schematic structure of the electrophotographic recording material according to the invention is shown in FIGS. 1 and 2. FIG. 1 shows a material which consists of an electrically conductive layer support 1, the charge generation layer 2 and the charge transport layer 3. In FIG. 2, a metallized plastic film 1, 4 is provided as a layer support on which an insulating barrier layer 5 is applied. The photoconductive double layer is located on this.

Materials with sufficient electrically conductive properties are suitable as the electrically conductive layer support 1, as have been used previously for this purpose. The layer support can be in the form of a drum, a flexible band or a plate. In a preferred embodiment, the layer support is suitable for the production of printing forms and printed circuits and consists, for example, of an aluminum, zinc, magnesium, copper, iron, nickel or a multi-metal plate. Metallized, for example metal-coated plastic films, such as aluminum-coated polyester films, or copper-clad polyimide films and plates are also suitable.

Surface-coated aluminum substrates have proven particularly useful. The surface refinement consists of mechanical or electrochemical roughening and, if appropriate, subsequent anodization and treatment with polyvinylphosphonic acid in accordance with DE-OS 16 21 478, corresponding to US Pat. No. 4,153,461 The barrier layer obtained is designated by position 5 in FIG. In general, a thermally, anodically or chemically generated metal oxide layer, for example made of aluminum oxide, can serve as the barrier layer. The barrier layer has the task of reducing or preventing the charge carrier injection from the electrically conductive layer support into the charge generation layer in the dark. On the other hand, however, it must not hinder the charge flow during the exposure process. Furthermore, the adhesion of the following layers to the layer support is favorably influenced by the barrier layer. Various natural or synthetic resin binders can be used for organic barrier layers that adhere well to a metal or aluminum surface and do not experience any detachment or detachment when the further layers are subsequently applied. The thickness of the organic barrier layer is in the range of 111 m, that of a metal oxide layer in the order of 10 to 10 ³ nanometers.

For the production of, for example, printed circuits, as are customary in electronics, the photoconductive double layer 2, 3 can also first be applied to an intermediate carrier (not shown), from which it is applied as a so-called dry resist to the layer carrier 1 or 1.4 transmitted subsequently or later. This can be done, for example, by lamination. Plastic films, such as those made of polyester, in particular of polyethylene terephthalate, have proven particularly useful as intermediate carriers.

Layer 2 contains at least one dye as the charge carrier-generating layer. The dye can be either dissolved or dispersed in the layer in the layer. The connections are known. This subheading includes, in particular, dyes from the class of the perylene-3,4,9,10-tetracarboxylic acid derivatives according to DE-PS 22 37 539, corresponding to US Pat. No. 3 871 882, of the metal-containing phthalocyanines according to, for example, DE-OS 32 45 637, the perinones according to DE-AS 22 39 923, corresponding to GB-PS 1 416 603, and / or the fused quinones according to DE-AS 22 37 678, corresponding to US-PS 4 315 981. Possible soluble dyes are: rhodamine dyes, cyanine dyes and / or triarylmethane dyes.

The preferred colorants are N, N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide (C.1. 71 130), copper-containing phthalocyanine (C.1. 74 160), Hostapermorange GR (C.1. 71 105) and / or Hostapermscharlach GO (CI 59 300) used. Soluble dyes such as rhodamine B (C.I. 45 170), astrazone orange R (C.I. 48 040) and / or brilliant green (C.I. 42 040) are preferably used.

Suitable compounds in the charge transport layer 3 which serve to transport the charge are, in particular, those which have an extensive n-electron system. These include monomeric heterocyclic compounds which are substituted by dialkyl-substituted amino groups or alkoxy groups. Heterocyclic compounds such as oxdiazole derivatives, which are mentioned in German patent 10 58 836, corresponding to US Pat. No. 3,189,447, have proven particularly useful. This subheading also includes triphenylamine derivatives, oxazole, pyrazoline, triazole and imidazole derivatives, as described, for example, in DE-PS 11 20 875.10 60 260, 10 60 714 (corresponding to US Pat. Nos. 3,257,203, 3,112,197 and 3,180 729) emerge. Hydrazone compounds such as those mentioned, for example, in DE-OS 29 19 791, corresponding to US Pat. No. 4,278,747, can also be used. 2,5-Bis- (4'-dimethylaminophenyl) -1,3,4-oxdiazole, p-methoxybenzaldehyde diphenylhydrazone and / or 1,5-diphenyl-3-p-methoxyphenylpyrazoline are preferably used.

The highly insulating binder for the charge generation layer and for the charge transport layer can be the same or different. With regard to flexibility, film properties and adhesive strength, natural and synthetic resins are suitable as such, which can be dissolved or swelled by customary solvents or solvent mixtures during the production of the layers. These include polyester resins, which are mixed polyesters of iso- and terephthalic acid with glycols. Silicone resins have also proven to be suitable. Polycarbonate resins can be used well. Binders which are soluble in aqueous or alcoholic solvent systems, optionally with the addition of acid or alkali, are particularly preferred for the production of printing forms and printed circuits. Aromatic or aliphatic, easily flammable solvents are excluded for physiological and safety reasons. Suitable resin binders are high-molecular substances that carry alkali-solubilizing groups. Examples are acid anhydride, carboxyl, carboxamide, phenol, sulfonic acid, sulfonamide or sulfonimide groups. Resin binders with high acid numbers are preferably used. Copolymers with anhydride groups can be used with good success, since the lack of free acid groups means that the dark conductivity is low, despite good alkali solubility. Copolymers of styrene and maleic anhydride, sulfonyl urethanes according to German patent application, file number P 32 10 577.0 and copolymers of acrylic or methacrylic acid have proven particularly useful.

As conventional additives, the layers contain substances that are added to the coating solution and thereby improve the surface structure and flexibility. These can be, for example, plasticizers, such as triphenyl phosphate, or leveling agents, such as silicone oils.

In the border area of the charge carriers generating layer and the charge transport layer there is a mixing zone of substances of both layers. It is obtained essentially by the fact that when the second layer is applied, layer components, in particular photoconductors, get into the layer applied first by diffusion. The mixing zone is approximately 1.5 to 2 μm, which can be determined, for example, by the fact that photoconductor components do not diffuse so deeply that so-called poisoning phenomena can be recognized by the layer support, as long as the layer thickness of the layer initially applied is chosen to be over 2 μm.

The total layer thickness of the photoconductive double layer are in the range between about 4 to 50 _li m. In the case of use for printing plates, the total layer thickness is preferably in the range from 4 to 10 μm. When used for printed circuits which are GESAM _t layer thicknesses in the range of 6 to 50 _l im.

The present invention also relates to a method for producing the electrophotographic recording material according to the invention, in which the photoconductive double layer is applied to the electrically conductive support. The process is characterized in that the coating solution or dispersion of the layer generating the charge carrier is applied and dried or dried, and then the coating solution or dispersion of the charge transport layer is covered with a layer and dried while dissolving the first layer. The drying of the double layer is preferably carried out in stages in relation to duration and temperature. The duration of the individual steps is in the range of about 10 seconds to a few minutes. The drying temperature is in the range from room temperature to 130 ° C. A method has proven particularly useful in which the applied solutions or dispersions are dried in stages in the range from room temperature to 130 ° C. in time intervals of 5 to 30 seconds.

It is hereby achieved that within the boundary region of the surfaces of the layer generating the charge carrier and the charge transport layer, a mixing zone of the substances results in a thickness of about 1.5 to 2 μm, which in particular favors the generation of charge carriers.

Solvents or solvent mixtures with boiling temperatures are used for the coating solution, which allow drying in the technically customary range and those which have good solution properties for photoconductors and binders and which are to a certain extent environmentally friendly. These include lower alcohols, lower ketones and ethers or also esters. Examples include: tetrahydrofuran, acetone, methyl glycol and butyl acetate. It has been found that fast-drying coating solutions or dispersions advantageously contain tetrahydrofuran as the solvent.

During the drying process, according to the invention, the process of dissolving the layer applied first takes place at a relatively low temperature. This is followed by drying, preferably in stages in the temperature range from 80 to 120 ° C.

The coatings are applied in a customary manner, for example by knife or spray application. The application is preferably made with a flow machine. The layers are dried, for example, in drying channels, the various drying stages being determined by the temperature of the individual areas, by the running speed of the material and by the prevailing air throughput.

The invention is illustrated by the following examples and comparative examples.

example 1

• 50 g eines Copolymerisates von Styrol und Maleinsäureanhydrid, Zersetzungspunkt 200 bis 240° C, wurden in
• 950 g Tetrahydrofuran unter Zusatz von
• 0,1 g Silikonöl, Viskosität 5 bis 20 mPa.s, gelöst. In der Lösung wurden
• 2 g N,N'-Dimethylperylen-3,4,9,10-tetracarbon- säurediimid (C.1. 71 130) durch Mahlen in einer Kugelmühle innerhalb von 2 Stunden dispergiert.

The following dispersion was applied to a support with a barrier layer, such as an electrochemically pretreated and anodized aluminum tape, which is used as a support for an offset printing plate, so that a dry layer weight of 3 g / m ² resulted.

• 50 g of a copolymer of styrene and maleic anhydride, decomposition point 200 to 240 ° C, were in
• 950 g tetrahydrofuran with the addition of
• 0.1 g silicone oil, viscosity 5 to 20 mPa.s, dissolved. In the solution
• Disperse 2 g of N, N'-dimethylperylene-3,4,9,10-tetracarbonate diimide (C.1. 71 130) by grinding in a ball mill within 2 hours.

The coating was dried.

• 50 g eines Copolymerisates aus Styrol und Maleinsäureanhydrid und
• 50 g 2,5-Bis-(4'-dimethylaminophenyl)-1,3,4- oxdiazol wurden in
• 700 g Tetrahydrofuran und
• 250 g Butylacetat unter Zusatz von
• 0,1 g Silikonöl gelöst.

Then, a layer was generated on this charge carrier
Charge transport layer applied from the following solution.

• 50 g of a copolymer of styrene and maleic anhydride and
• 50 g of 2,5-bis (4'-dimethylaminophenyl) -1,3,4-oxdiazole were in
• 700 g tetrahydrofuran and
• 250 g of butyl acetate with the addition of
• 0.1 g silicone oil dissolved.

The liquid top layer was dried for about 10 seconds at room temperature, then for 30 seconds at 60 ° C. and then for about 120 seconds at 110 ° C. Under these conditions, the layer generating the charge carrier was dissolved and a targeted mixing zone was achieved. The request of the charge transport layer was like this adjusted that the total layer weight was 6 g / m ² , which corresponds to a thickness of 6 _li m.

The coating was repeated, the total layer weight of 6 g / m ² being maintained, but the layer thickness of the charge-generating layer being varied at a constant pigment content between 0.5 and 5.5 g / m ² . This corresponds to a ratio of the layer thicknesses of the charge carrier-generating layer to the charge transport layer of 10: 1 to 1:10. Figure 3 shows the dependence of the sensitivity on the thickness of the charge-generating layer, from which the energy required for discharging to 150 V (E ₁₅₀ ) versus the layer weight of the charge-generating layer with a total layer weight of 6 g / m ^{2 is} applied.

Good results were achieved in the range from 3: 1 to 1:10.

In spite of their low content of organic photoconductor (transport compound), the layers produced in this way are distinguished by a high sensitivity when the layer is negatively charged and by a very good resolution. Information on this is contained in the attached table.

The E _1/2 values refer to exposure with halogen lamps when using heat protection filters.

The printing plate obtained after imaging, development with a commercially available liquid developer, fixation and stripping in accordance with the information in DE-AS 11 17 391 produced a print run of well over 100,000 with good tonal value reproduction; in the K field of the PMS wedge, the 20 _{l were} reproduced in the line.

Example 2 (comparative example)

• 75 g des Copolymerisats von Styrol und Maleinsäureanhydrid von Beispiel 1 und
• 25 g 2,5-Bis-(4'-dimethylaminophenyl)-1,3,4- oxdiazol in
• 900 g Tetrahydrofuran unter Zusatz von
• 0,1 g Silikonöl wurden
• 2 g N,N'-Dimethylperylen-3,4,9,10-tetracarbonsäurediimid durch Mahlen in einer Kugelmühle 2 Stunden lang dispergiert.

In a solution from

• 75 g of the copolymer of styrene and maleic anhydride from Example 1 and
• 25 g 2,5-bis (4'-dimethylaminophenyl) -1,3,4-oxdiazole in
• 900 g of tetrahydrofuran with the addition of
• 0.1 g of silicone oil
• Dispersed 2 g of N, N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide by grinding in a ball mill for 2 hours.

The dispersion was applied to a printing plate support according to Example 1 so that a layer weight of g / m ^{2 was} reached after drying. The composition of the layer corresponded to the combination of 3 g / m ^{2 of} the charge carrier-generating layer and 3 g / m ^{2 of} the charge transport layer from Example 1. The sensitivity (E _1/2 ) - ¹ is significantly reduced compared to the layer from Example 1, and the resolution of the images produced on this material is significantly worse than on the material according to example 1. in the K field of the PMS wedge was achieved not playing the 40 _li m Liniem.

Example 3

The coatings of Example 1 were repeated, except that a copper-clad polyimide film, as used for the production of flexible printed circuit boards in electronics, was used instead of the printing plate support mentioned there.

The double layers with layers of 0.5, 1.0 and 1.5 g / m ^{2 of} charge carriers could not yet be charged to over -500 V. These layers were therefore not suitable for practical use. The coatings with layers in the range of 2 g / m ² to 4.5 g / m ² , on the other hand, resulted in charges of over -500 V. After charging, exposure and development with a liquid developer, high-resolution toner images could be obtained. These foils could then be processed into high-quality flexible printed circuit boards by stripping and etching away the non-image areas.

The ratio of the layer thicknesses of the layer generating the charge carrier to the charge transport layer between 2: 1 and 1: 3 is technically particularly favorable.

Example 4 (comparative example)

The coating of Example 2 was repeated, except that a copper-clad polyimide film from Example 3 was used instead of the aluminum printing plate support.

The electrophotographic recording material thus produced could only be charged to less than -100 V and was therefore unsuitable for practical use. It is believed that when the solution of the photoconductor comes into contact with poisoning occurs on a copper surface. The problem of the lack of chargeability of thin layers (6 g / m ² ) also occurred when coating solutions with other photoconductors, such as oxazole, pyrazoline and hydrazone compounds, on copper-containing materials. A similar, if not so pronounced loss of chargeability also resulted when coating on iron- or nickel-containing materials. It has been recognized that this loss of charge can be avoided by introducing a photoconductor-free, charge carrier-generating layer in contact with corresponding metal surfaces.

At the same time, the results of Example 3 show that in the coating technique described here, when the charge-generating layer is detached, a mixing zone between the two layers of about 1.5 to 2 μm thick is formed.

Example 5

• 50 g eines Sulfonylurethans (hergestellt durch Umsetzung eines Polyvinylbutyrals mit - bezogen auf freie OH-Gruppen, äquimolarer Menge - Propenylsulfonylisocyanat, beschrieben in der deutschen Patentanmeldung, Aktenzeichen P 32 10 577.0, Beispiel 1) und
• 950 g Tetrahydrofuran unter Zusatz von
• 0,1 g Silikonöl wurden
• 2 g N,N'-Dimethylperylen-3,4,9,10-tetracarbonsäurediimid durch Mahlen in einer Kugelmühle innerhalb von 2 Stunden dispergiert.

In a solution from

• 50 g of a sulfonyl urethane (prepared by reacting a polyvinyl butyral with - based on free OH groups, equimolar amount - propenyl sulfonyl isocyanate, described in the German patent application, file number P 32 10 577.0, Example 1) and
• 950 g tetrahydrofuran with the addition of
• 0.1 g of silicone oil
• Dispersed 2 g of N, N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide by grinding in a ball mill within 2 hours.

• 50 g des beschriebenen Sulfonylurethans und
• 50 g 2,5-Bis-(4'-dimethylaminophenyl)-1,3,4- oxdiazol wurden in
• 900 g Tetrahydrofuran unter Zusatz von
• 0,1 g Silikonöl gelöst.

The solution was applied to an aluminum printing plate support. The application of the solution was regulated so that a dry layer weight of 3 g / m ² resulted. The following solution of a charge transport layer was applied to this still moist charge carrier layer (wet-on-wet coating):

• 50 g of the sulfonyl urethane described and
• 50 g of 2,5-bis (4'-dimethylaminophenyl) -1,3,4-oxdiazole were in
• 900 g of tetrahydrofuran with the addition of
• 0.1 g silicone oil dissolved.

This layer was dried for about 30 seconds at 60 ° C. and then for about 120 seconds at 100 ° C. A targeted mixing zone between the two layers was achieved under these conditions. The dry layer weight of this double layer recording material was 6 g / _m 2.

Example 6

• 100 g eines Sulfonylurethans in
• 900 g Tetrahydrofuran unter Zusatz von
• 0,1 g Silikonöl wurden
• 3 g N,N'-Dimethylperylen-3,4,9,10-tetracarbonsäurediimid sowie
• 1 g _E-Kupferphthalocyanin (Lionol Blue ERPC der Toyo Ink Manufacturing Co., Japan, dessen Röntgenbeugungsspektrum in Figur 4 wiedergegeben ist) durch Mahlen in einer Kugelmühle innerhalb von 2 Stunden dispergiert.

In a solution from

• 100 g of a sulfonyl urethane in
• 900 g of tetrahydrofuran with the addition of
• 0.1 g of silicone oil
• 3 g of N, N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide and
• 1 g of _E- copper phthalocyanine (Lionol Blue ERPC from Toyo Ink Manufacturing Co., Japan, whose X-ray diffraction spectrum is shown in FIG. 4) was dispersed by grinding in a ball mill within 2 hours.

• 50 g eines Sulfonylurethans und
• 50 g 2,5-Bis-(4'-dimethylaminophenyl)-1,3,4- oxdiazol wurden in
• 700 g Tetrahydrofuran und
• 200 g Butylacetat unter Zusatz von
• 0,1 g Silikonöl gelöst.

The dispersion was layered on a polyester film as an intermediate carrier. The coating was dried. The result was a dry layer weight of 3 g / m ² . The following solution of a charge transport layer was applied to this charge carrier layer:

• 50 g of a sulfonyl urethane and
• 50 g of 2,5-bis (4'-dimethylaminophenyl) -1,3,4-oxdiazole were in
• 700 g tetrahydrofuran and
• 200 g of butyl acetate with the addition of
• 0.1 g silicone oil dissolved.

This layer was dried for about 30 seconds at 60 ° C. and then for about 120 seconds at 100 ° C.

A targeted mixing zone between the two layers was achieved under these conditions. The dry layer weight of this double layer material on the intermediate carrier was 6 g / m2.

The double layer was then transferred to a bare aluminum foil in a laminator at 120 ° C. The electrophotographic recording material thus produced had a high charge acceptance (table) and an excellent spectral sensitivity in the range from 400 to 800 nm with positive charging.

Example 7 (comparative example)

The procedure was as in Example 6, except that the order of the coatings was reversed and carried out without dissolving and that the coating was carried out directly on an aluminum foil. The material obtained in this way therefore corresponded to the material from Example 6 in the layer structure - aluminum carrier, charge transport layer with binder / photoconductor and charge carrier-generating layer from binder / pigment.

This material had less than half the sensitivity of the material according to the invention according to Example 6. It is believed that this is due to the insufficient formation of a mixing zone between the layers. While in example 6 the easily diffusible photoconductor is already in solution and can therefore easily penetrate into the swollen or dissolved pre-layer, in this example, besides the swelling of the pre-layer, the photoconductor must also be removed with subsequent Diffusion into the layer generating charge carriers take place. This is not possible within a reasonable period of time.

Example 8

The procedure was as in Example 1, with the difference that instead of 4% N, N'-dimethylperylene-3,4,9,1 0-tetracarboxylic acid diimide 5% Hostapermorange GR (CI 71 105) was used and that the layer weight of Charge generation layer 1.5 g / m ² and that of the charge transport layer was 4.5 g / m ² .

Example 9 (comparative example)

The procedure was as in Example 8, with the difference that instead of the binder in the charge-generating layer, a mixture of 80% binder and 20% 2,5-bis (4'-dimethylaminophenyl) -1,3,4-oxdiazole has been used. This layer arrangement corresponds to the recording material described in DE-OS 21 60 812. The table shows that the addition of the photoconductor leads to a slight reduction in sensitivity and at the same time a marked reduction in the stripping speed.

Example 10

The procedure was as in Example 1, with the difference that Hostapermscharlach GO (C.I. 59 300) was used instead of N, N'-dimethy) pery) en-3,4,9,10-tetracarboxylic acid diimide. A copolymer of styrene, methacrylic acid and hexyl methacrylate, monomer ratio 10:30:60, was used as the binder.

Example 11

The procedure was as in Example 1, with the difference that instead of 2,5-bis (4'-dimethylamino-phenyl) -1,3,4-oxdiazole 1,5-diphenyl-3-p-methoxy-phenyl -pyrazoline was used analogously to DE-AS 10 60 714.

Example 12

The procedure was as in Example 1, with the difference that instead of 2,5-bis (4'-dimethylamino-phenyl) -1,3,4-oxdiazole p-methoxy-benzaldehyde-diphenylhydrazone according to DE-OS 29 19 791 was used. Charging and sensitivity of the recording materials described in Examples 8, 9, 10, 11 and 12 are included in the table.

Example 13

• 50 g eines Sulfonylurethans wurden gelöst in
• 950 g Tetrahydrofuran unter Zusatz von
• 0,1 g Silikonöl sowie
• 1 g Rhodamin B (C.I.45 170) gelöst in
• 10 g Methanol.

An electrochemically roughened and anodized aluminum tape, as used as a layer with a barrier layer for offset printing plates, was coated with the following solution:

• 50 g of a sulfonyl urethane were dissolved in
• 950 g tetrahydrofuran with the addition of
• 0.1 g silicone oil as well
• 1 g rhodamine B (CI45 170) dissolved in
• 10 g of methanol.

The coating was dried and had a dry layer weight of 3 g / m ² .

• 50 g eines Sulfonylurethans und
• 50 g 2,5-Bis-(4'-dimethylaminophenyl)-1,3,4- oxdiazol gelöst in
• 900 g Tetrahydrofuran unter Zusatz von
• 0,1 g Silikonöl sowie
• 0,1 g Rhodamin B (C.I. 45 170) gelöst in
• 1 g Methanol.

The following solution of a charge transport layer was applied to this layer.

• 50 g of a sulfonyl urethane and
• 50 g of 2,5-bis (4'-dimethylaminophenyl) -1,3,4-oxdiazole dissolved in
• 900 g of tetrahydrofuran with the addition of
• 0.1 g silicone oil as well
• 0.1 g rhodamine B (CI 45 170) dissolved in
• 1 g of methanol.

The drying was carried out as described in Example 1. The dry layer weight of this double layer was approximately 6 g / m ² . The recording material thus produced could be charged to -800 V, showed good sensitivity and, after charging, imagewise exposure, development with a liquid developer and decoating, gave rise to printing plates of high resolution.

Example 14 (comparative example)

• 50 g eines Sulfonylurethans und
• 50 g 2,5-Bis-(4'-dimethylaminophenyl)-1,3,4- oxdiazol gelöst in
• 900 g Tetrahydrofuran unter Zusatz von
• 0,1 g Silikonöl sowie
• 0,5 g Rhodamin B (C.1. 45 170), gelöst in
• 5 g Methanol,

beschichtet und getrocknet.A printing plate support as in Example 13 with a solution of

• 50 g of a sulfonyl urethane and
• 50 g of 2,5-bis (4'-dimethylaminophenyl) -1,3,4-oxdiazole dissolved in
• 900 g of tetrahydrofuran with the addition of
• 0.1 g silicone oil as well
• 0.5 g rhodamine B (C.1. 45 170), dissolved in
• 5 g of methanol,

coated and dried.

The dry layer weight was approx. 6 g / m ² .

The recording material produced in this way showed only a comparable sensitivity, despite the fact that the photoconductor content in the total layer was twice as high as in Example 13.

If the plate described here is treated with an aqueous alkaline stripper in accordance with the specifications in DE-AS 11 17 391 in a commercial stripping device, the layer can only be removed slowly due to its high proportion of insoluble photoconductor. The disk throughput is low. The Material of Example 13 according to the invention can be stripped three times as quickly due to its lower proportion of photoconductor.

Example 15 (comparative example)

Analogously to Example 13, a recording material consisting of a charge-generating layer (1.5 g / m ² ) made of 38% 2,5-bis (4'-dimethylaminophenyl) -1,3,4-oxdiazole, 57% of a copolymer was from styrene and maleic anhydride and 5% rhodamine B and a charge transport layer (10 g / m ² ) from 50% 2,5-bis (4'-dimethylaminophenyl) -1,3,4-oxdiazole and 50% of a copolymer of styrene and Maleic anhydride produced. This material largely corresponds to that described in DE-OS 21 60 812, Example 3. Under the measurement conditions used in all examples (halogen lamp with heat protection filters), this double layer had a sensitivity (E _1/2 ) - ¹ of (79 µJ / cm ² ) ^-1 .

Claims (16)

1. An electrophotographic recording material composed of an electrically conductive layer support, if appropriate an insulating barrier layer, and a photoconductive double layer comprising a layer generating charge carriers and a charge transport layer and composed of an organic photoconductor, binder, dye and conventional additives, wherein the layer generating charge carriers comprises a highly insulating binder which is comprised of a high molecular-weight compound having groups conferring solubility in alkali and which contains 0.5 to 20 percent by weight of dye, relative to the layer, in solution or dispersion, and wherein the charge transport layer comprises a highly insulating binder which is comprised of a high molecular-weight compound having groups conferring solubility in alkali and which contains quantities of 25 to 60 percent by weight, relative to the layer, of at least one photoconductor and the dissolved or dispersed dye in a concentration of at most 5 percent by weight, relative to the layer, and wherein a mixing zone of the substances, having a thickness of 1,5 to 2 µm and being obtained by incipient solution processes during manufacture, exists in the boundary zone of the two layers, and wherein the layer thicknesses of the layer generating charge carriers and of the charge transport layer are in a ratio of 3:1 to 1:10.

2. The recording material as claimed in claim 1, which has been obtained by transferring the photoconductive double layer from a temporary support to the electrically conductive support which may have been provided with a barrier layer.

3. The recording material as claimed in claim 1, wherein the dye has been selected from the group comprising perylene-3,4,9,10-tetracarboxylic acid derivatives, metal-containing phthalocyanines, perinones, fused quinones, rhodamine dyes, cyanine dyes and/or triarylmethane dyes.

4. The recording material as claimed in claim 3, wherein N,N'-dimethyl-perylene-3,4,9,10-tetracarboxylic acid diimide (C.1. 71,130), metal-containing phthalocyanines (C.1. 74,160), Hostaperm Orange GR (C.I. 71,105) and/or Hostaperm Scarlet GO (C.I. 59,300) are present as the dye.

5. The recording material as claimed in claim 3, wherein Rhodamine B (C.I. 45 170), Astrazone Orange R (C.I. 48,040) and/or Brilliant Green (C.I. 42,040) are present as the dye.

6. The recording material as claimed in claim 1, wherein the support is metallic or is a metallized plastic film.

7. The recording material as claimed in claim 6, wherein the layer support is electrochemically grained and anodically oxidized aluminum.

8. The recording material as claimed in claim 6, wherein the support is a copper-laminated polyimide film.

9. The recording material as claimed in claim 1, wherein the photoconductor has been selected from the group comprising oxadiazoles, oxazoles, pyrazolines, triazoles, imidazoles and hydrazones.

10. The recording material as claimed in claim 9, wherein the photoconductor is 2,5-bis-(4'-dimethylaminophenyl)-1,3,4-oxadiazole.

11. The recording material as claimed in claim 9, wherein the photoconductor is p-methoxybenzaldehyde diphenylhydrazone.

12. The recording material as claimed in claim 9, wherein the photoconductor is 1,5-diphenyl-3-p-methoxy-phenylpyrazoline.

13. The recording material as claimed in claim 1, wherein the layer thicknesses of the layer generating charge carriers and of the charge transport layer are in a ratio of 2:1 to 1:3.

14. The recording material as claimed in claim 1, wherein the highly insulating binder is a copolymer of styrene and maleic anhydride, a sulfonyl-urethane and/or a copolymer of acrylic acid and/or methacrylic acid.

15. A process for producing the electrophotographic recording material as claimed in claim 1, in which the photoconductive double layer is applied to the electrically conductive layer support, which comprises applying the coating solution or dispersion of the charge carrier generating layer and drying or incipiently drying it and then coating the coating solution or dispersion of the charge transport layer on top and drying it with incipient solution of the first layer.

16. The process as claimed in claim 15, wherein the drying of the applied layers is carried out in stages within the range from room temperature to 130° C for periods from 5 to 30 seconds.

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