EP0137217A1 - Electrophotographic recording material and process for its preparation - Google Patents

Abstract

The present invention relates to an electrophotographic recording material composed of an electrically conductive layer support (1), optionally an insulating barrier layer and a photoconductive double layer consisting of charge carrier generating (2) and charge transport layer (3), consisting of organic photoconductor, binder, dye and conventional additives, the Charge carrier-generating layer (2) consists of a highly insulating binder in which 0.5 to 20 percent by weight of dye, based on the layer, is contained or dispersed, that the charge transport layer (3) consists of a highly insulating binder in which at least one photoconductor in amounts of 25 to 60 percent by weight, based on the layer, and the dye dissolved or dispersed in a concentration of at most 5 percent by weight, based on the layer, is contained, with a mixing zone of the substances obtained by app eyelet processes in the manufacture is present, and the layer thicknesses of the charge carrier generating layer (2) and charge transport layer (3) in a ratio of 3: 1 to 1:10, preferably 2: 1 to 1: 3. The recording material can be used in particular for the production of printing forms or printed circuits.

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 consisting of top and bottom layers, both with binder and with the same organic photoconductor, with at least one activating sensitizer in the bottom layer 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 given as 0.1 to 5 μm for the lower layer and 5 to 20 μm for the outer layer.

It is also known (US Pat. No. 3,533,783) to improve resolution by electrophotography _. brought images to use photoconductive layers which contain an inorganic or organic photoconductor together with an activator, such as pyrylium salts, in the lower layer and photoconductor and binder in the upper layer. 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. 4,340,658), in which a pigment concentration of 50 to 95 percent by weight is used. Binder 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 the same through suitable, dissolved dyes (according to DE-OS 25 26 720, the same US-PS 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 becomes. Individual lines with a line width of less than 60 pm are only depicted with reduced contrast and lines with a line width of less than 40 pm are no longer displayed at all. These loss of resolution also occur with correspondingly fine screen dots. 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 components in the stripping apparatus are deposited on rollers, pumps and other parts and lead to increased maintenance. _D a and in the known double-layer arrangements, the transport layer with its large proportion of photoconductor is thicker than the charge generation layer described disadvantages also occur here. Double layers of photoconductor, for example according to DE-OS 21 08 992, applied to aluminum as a layer support in a thickness of 4 μm, result in chargeability which is insufficient for practical use. Only with layer weights over 10 g / m ² are under elevation chem material-sufficient results achieved. 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 in which 0.5 to 20% by weight are used percent dye, based on the layer, dissolved or dispersed, that the charge transport layer consists of a highly insulating binder in which at least one photoconductor in amounts of 25 to 60 percent by weight, based on the layer, and the dye dissolved or dispersed in a concentration of at most 5 percent by weight, based on the layer, that there is a mixing zone of substances obtained by dissolving processes during manufacture in the border area of the two layers, and that the layer thicknesses of the charge-generating layer and charge transport layer 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. _V ER- by application of relatively low dye concentrations in the charge carrier generating layer in addition, the incorporation of the particles is avoided in the pores of the substrate surface. Even at low shifts Weights for the photoconductive double layer can be achieved with the recording material according to the invention the technically required charges. This is particularly true when materials are used as layer supports which have previously encountered considerable difficulties during 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. There are also metallized, for example metallized plastic foils, such as aluminum-coated polyester foils, or copper-clad polyimide foils and sheets.

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 in this way 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 1 μm, that of a metal oxide layer in the range 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 acts as a so-called dry resist on 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 supports.

Layer 2 contains at least one dye as the charge carrier-generating layer. The dye can be either dissolved or dispersed in the binder in the layer. The connections are known. This subheading includes, in particular, dyes from the class of perylene-3,4,9,10-tetracarboxylic acid derivatives according to DE-PS 22 37 539, corresponding to US Pat. No. 3,871,882, 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.

N, N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide (CI 71 130), copper-containing phthalocyanine (CI 74 160), Hostapermorange GR (CI 71 105) and / or Hostapermscharlach GO (CI 59 300) is used. Soluble dyes such as rhodamine B (CI 45 170), astrazon orange R (CI 48 040) and / or brilliant green (CI 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. Preferably, 2,5-bis (4 ^1- dimethylaminophenyl) -1,3,4-oxadiazole, p-methoxybenzaldehyde diphenylhydrazone and / or _1,5-D i-phenyl-3-p-methoxyphenylpyrazolin used.

The highly insulating binder for the charge generating layer and for the charge transport layer can be the same or different. As such, natural and synthetic resins are suitable with regard to flexibility, film properties and adhesive strength, which can be dissolved or swelled by common solvents or solvent mixtures during the production of the layers. These include polyester resins, which are mixed polyesters made from 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 of these 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 ver the surface structure and flexibility improve. These can be, for example, plasticizers, such as triphenyl phosphate, or leveling agents, such as silicone oils.

In the boundary region between the layer generating the charge carrier 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 thicknesses of the photoconductive double layer are in the range between approximately 5 to 25 μm. In the case of use for printing plates, the total layer thickness is preferably in the range from 4 to 10 pm. When used for printed circuits, the total layer thicknesses are in the range of 6 to 50 µm.

The present invention also relates to a method for producing the electrophotographic recording material according to the invention, in which the photoconductive is applied to the electrically conductive support Applies double layer. The process is characterized in that the first coating solution or dispersion is applied and dried or dried, and then the second coating solution or dispersion is covered and dried while the first layer is dissolved. The coating solution or dispersion of the charge-generating layer is advantageously applied and dried or dried, and then the coating solution or dispersion of the charge transport layer is covered and dried while dissolving the previous 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 gradually in the range from room temperature to 130 ° C. in time intervals of 5 to 30 seconds.

This ensures that within the boundary region of the surfaces of the charge-generating layer and the charge-transport layer, a mixing zone of the substances results in a thickness of approximately 1.5 to 2, which in particular favors the generation of charge carriers.

Solvents or solvent mixtures with boiling temperatures which are used for the coating solution enable drying in the technically customary range and those which have good dissolving properties for photoconductors and binders and which are in a way 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

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.

The coating was dried.

A charge transport layer from the following solution was then applied to this layer generating charge carriers.

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 application of the charge transport layer was adjusted so that the total layer weight was 6 g / m ² , which corresponds approximately to a thickness of 6 µm.

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. FIG. 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. The layers produced in this way stand out despite their low content of organic photoconductor (Transport connection) by a high sensitivity with negative charging of the layer and by a very good resolution. Information on this is contained in the attached table.

The E _{l / 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; the 20 pm lines were reproduced in the K field of the PMS wedge.

Example 2 (comparative example)

Die Dispersion wurde auf einen Druckplattenträger nach Beispiel 1 so aufgebracht, daß nach dem Trocknen ein Schichtgewicht von 6 g/m² erreicht wurde. Die Zusammensetzung der Schicht entsprach der Kombination von 3 g/ m² der Ladungsträger erzeugenden Schicht und 3 g/m² der Ladungstransportschicht aus Beispiel 1. Die Empfindlichkeit (E_½)^-1 ist gegenüber der Schicht aus Beispiel 1 deutlich vermindert, und die Auflösung der auf diesem Material erzeugten Bilder ist deutlich schlechter als auf dem Material nach Beispiel 1. Im K-Feld des PMS-Keils erreichte man keine Wiedergabe der 40 pm Linien.

In a solution from

The dispersion was applied to a printing plate support according to Example 1 so that a layer weight of 6 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 ( _E½ ) ^-1 is significantly reduced compared to the layer from Example 1, and the resolution the images generated on this material are significantly worse than on the material according to Example 1. In the K field of the PMS wedge, the 40 pm lines were not reproduced.

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 poisoning occurs upon contact of the photoconductor solution with a copper surface. The problem of poor chargeability of thin layers (6 g / m ²⁾ occurred hydrazone compounds to copper-containing materials, in coating solutions with other photoconductors such as oxazole, _P and yrazolin-. A similar, if not so pronounced loss of chargeability also resulted when coating on iron- or nickel-containing materials. It has been recognized that a photo-conductor-free charge carrier generating layer can be avoided ufladungsverlust in contact with corresponding surfaces of these metal _A by insertion.

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 of about 1.5 to 2 μm thick is formed between the two layers.

Example 5

In a solution from

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):

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

In a solution from

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:

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 / m ² .

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 the swollen or dissolved pre-layer, it must be in this

For example, in addition to the swelling of the preliminary layer, the photoconductor is also detached with subsequent diffusion into the layer generating the charge carrier. 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-3,4,9,10-tetracarboxylic acid diimide, 5% Hostapermorange GR (CI 71.105) was used and that the layer weight of the charge carriers generated 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 of the _E leads ntschichtungsgeschwindigkeit to a slight reduction in sensitivity with a significant reduction.

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'-dimethylperylene-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'-dimethylaminophenyl) -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'-dimethylaminophenyl) -1,3,4-oxdiazole, p-methoxy-benzaldehyde-diphenylhydrazone according to DE-OS 29 19 791 was used has been. Charging and sensitivity of the recording materials described in Examples 8, 9, 10, 11 and 12 are included in the table.

Example 13

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

The coating was dried and had a dry layer weight of 3 g / m2.

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

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, resulted in printing plates of high resolution.

Example 14 (comparative example)

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

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 slowly because of its high proportion of insoluble photoconductor remove. 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 measuring conditions used in all examples (halogen lamp with heat protection filters), this double layer had a sensitivity (E _½ ) ^-1 of (79 µJ / cm ² ) ^-1 .

Claims (19)

1. Electrophotographic recording material comprising an electrically conductive layer support, optionally an insulating barrier layer and a photoconductive double layer consisting of charge carrier-generating and charge-transport layer, consisting of organic photoconductor, binder, dye and conventional additives, characterized in that the charge-carrier generating layer consists of a highly insulating binder, in which 0.5 to 20 percent by weight of dye, based on the layer, is contained or dispersed, that the charge transport layer consists of a highly insulating binder in which at least one photoconductor in amounts of 25 to 60 percent by weight, based on the layer, and the are dye dissolved or dispersed in a concentration of at most 5 percent by weight, based on the layer containing that in the border region of the two layers has a Vermischun szone ^g of the substances, obtained by Anlöseprozesse in the preparation, v is present, and that the layer thicknesses of the charge generating layer and charge transport layer are present in a ratio of 3: 1 to 1:10. 2. Recording material according to claim 1, characterized in that the highly insulating binder is a high molecular weight, containing alkali-solubilizing substance. 3. Recording material according to claim 1 or 2, characterized in that it was obtained by transferring the photoconductive double layer from an intermediate support to the electrically conductive layer support, optionally provided with a barrier layer. 4. Recording material according to claims 1 to 3, characterized in that the mixing zone is 1.5 to 2 µm. 5. Recording material according to claim 1, characterized in that the dye from the class of perylene-3,4,9,10-tetracarboxylic acid derivatives, the metal-containing phthalocyanines, the perinones, the fused quinones, the rhodamine dyes, the cyanine dyes and / or the triarylmethane dyes is selected. 6. Recording material according to claim 5, characterized in that the dye is N, N'-dimethyl-perylene-3,4,9,10-tetracarboximide (CI 71 130), metal-containing phthalocyanine (CI 74 160), host orange GR (CI 71 105) and / or Hostapermscharlach GO (CI 59 300) are available. 7. Recording material according to claim 5, characterized in that rhodamine B (C.I. 45 170), astrazon orange R (C.I. 48 040) and / or brilliant green (C.I. 42 040) are present as the dye. 8. Recording material according to claim 1, characterized in that the layer support is metallic or is a metallized plastic film. 9. Recording material according to claim 8, characterized in that the layer support is electrochemically roughened and anodized aluminum. 10. Recording material according to claim 8, characterized in that the layer support is a copper-clad polyimide film. 11. Recording material according to claim 1, characterized in that the photoconductor is selected from the group of oxdiazoles, oxazoles, pyrazolines, triazoles, imidazoles, hydrazones. 12. Recording material according to claim 11, characterized in that the photoconductor is 2,5-bis (4'-dimethylaminophenyl) -1,3,4-oxdiazole. 13. Recording material according to claim 11, characterized in that the photoconductor is p-methoxybenzaldehyde-diphenylhydrazone. 14. Recording material according to claim 11, characterized in that the photoconductor is l, 5-diphenyl-3-p-methoxyphenyl-pyrazoline. 15. Recording material according to claim 1, characterized in that the layer thicknesses of the charge carrier generating layer and charge transport layer are present in a ratio of 2: 1 to 1: 3. 16. Recording material according to claim 2, characterized in that 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. 17. A method for producing the electrophotographic recording material according to claim 1, in which the photoconductive double layer is applied to the electrically conductive support, characterized in that the first coating solution or dispersion is applied and dried or dried and then the second coating solution or dispersion overlays and dries while dissolving the first layer. 18. The method according to claim 17, characterized in that the coating solution or dispersion of the charge-generating layer is applied and dried or dried and then the coating solution or dispersion of the charge transport layer is covered and dried while dissolving the previous layer. 19. The method according to claims 17 and 18, characterized in that one carries out the drying of the applied layers in the range from room temperature to 130 ° C and in time intervals from 5 to 30 seconds in stages.

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