WO1991004153A1

WO1991004153A1 - Electro-photographically produced offset printing plate with hydrophilic tonered areas and oleophilic untonered areas

Info

Publication number: WO1991004153A1
Application number: PCT/EP1990/001540
Authority: WO
Inventors: Klaus-Peter Jaeckel; Reinhold J. Leyrer; Volker Muench; Peter Strohriegl; Dietrich Haarer
Original assignee: Basf Aktiengesellschaft
Priority date: 1989-09-13
Filing date: 1990-09-12
Publication date: 1991-04-04
Also published as: DE59010226D1; EP0491761B1; JPH05502111A; FI920474A0; DE3930584A1; EP0491761A1; DK0491761T3

Abstract

The novel electro-photographically produced offset printing plate comprises an electrically conductive dimensionally stable substrate (A), at least one photoconductive layer (B) and a printing surface (C) composed of hydrophilic, water-bearing, unprinted tonered areas (c1) and oleophilic, colour-bearing printing untonered areas (c2). The novel offset printing plate can be made by the prior art manner making use of hydrophilic toner or toner which can be easily hydrophilised chemically by conversion with suitable reagents, thermo-chemically by heating and/or photo or radio-chemically by irradiation with electromagnetic or particle radiation.

Description

Offset printing plate produced by electrophotography with hydrophilic areas emphasized and oleophilic areas not emphasized

description

The invention relates to a new offset printing plate produced by electrophotography, which has an electrically conductive dimensionally stable support and a photoconductive layer.

The invention also relates to a new electrophotographic process for the production of offset printing plates.

Offset printing plates and methods for their production by electrophotographic means are known, for example, from EP-A-0 131 215, EP-B-0 031 481, EP-A-0 150 419, EP-A-0 162 216, EP-A-0 156 308, EP-A-0 131 292, EP-A-0 152 889 or EP-A-0 198488.

An electrophotographic is usually used for the production of the offset printing plates in the known electrophotographic way

Recording element used, which has an electrically conductive carrier and at least one photoconductive layer, the photoconductive layer containing at least one binder, at least one charge carrier-producing compound (sensitizer), at least one charge carrier transporting compound (photoconductor) and optionally additives. As is known, this electrophotographic recording element is charged electrically positively or electrically negatively, for example by means of a high-voltage corona discharge. The electrically charged photoconductive layer is then exposed imagewise with actinic light, with ultraviolet, visible or infrared light being used, depending on the sensitizer used. As a result of the exposure, the photoconductive layer becomes electrically conductive in its exposed areas, so that the previously generated electrostatic charge can flow off in these areas via the electrically conductive support. This creates a latent electrostatic image on the recording element, which can be developed into a visible image with the aid of suitable liquid or solid toners. This technique of image-based information recording is also generally referred to as xerography, the physical process on which the recording method is based also known as the "Carlson process". As is known, the toner image is then fixed on the photoconductive layer by heating for the production of the offset printing plate. The unexposed and therefore toner-free areas of the photoconductive layer are then washed away or decoated with the aid of suitable developer solvents. Here, the exposed areas of the photoconductive layer are protected from decoating by the toner fixed thereon. The offset printing plate produced in this known manner generally takes on oily printing inks on its hydrophobic toner image areas and water on its hydrophilic areas exposed by decoating, so that it is suitable for offset-typical printing processes.

The basic disadvantage of this known method for producing an offset printing plate by electrophotographic means is that the stressed electrophotographic recording element after

Fixing the toner image must be decoated with developer solvents so that the offset-typical differentiation of the printing plate surface into oleophilic or hydrophobic ink-carrying printing areas and hydrophilic water-carrying non-printing areas occurs. The greatest care must be taken in this de-coating step, because otherwise the printing areas will be damaged, which naturally results in a deterioration in the imaging quality. In addition, only carriers which are both electrically conductive and have a hydrophilic surface can be used in this method, which severely limits the selection options.

Methods for producing an offset printing plate by electrophotographic means, in which the stripping step is omitted, can be found in EP-A-0 289 056, EP-A-0 326 132 or EP-A-0 326 169.

In the process known from EP-A-0 289 056, an electro-photographic recording element is used, the photoconductive layer of which is covered with a special cover layer. This cover layer is inherently hydrophobic or oleophilic, but it can be hydrophilized by treatment with suitable chemical reagents, which is referred to in EP-A-0 289 056 as "oil-desensitization treatment". In this case, chemically bound non-polar functional groups present in the top layer are hydrolyzed or saponified, so that chemically bound polar functional groups are formed which impart hydrophilic water-carrying properties to the surface of the top layer. During the production of the offset printing plate, the concreted areas of the surface of the cover layer are protected from the hydrophilization by the hydrophobic or oleophilic toner fixed thereon, so that ultimately one The result is an offset printing plate, the printing surface of which is composed of hydrophilic, water-bearing, non-printing, unstressed areas and oleophilic, ink-bearing, printing, stressed areas.

In the process known from EP-A-0 326 132, the photo-conductive layer of the electrophotographic recording element contains a partially cross-linked binder with chemically bound non-polar functional groups which can be converted into carboxylic acid groups by the "oil desensitization treatment". The chemical reagents suitable for this are described in detail in EP-A-0 326 132.

In the process known from EP-A-0 326 169, the photoconductive layer of the electrophotographic recording element contains, in addition to the binder with non-polar functional groups which can be converted into carboxylic acid groups, a polymer which is heated by heating or by exposure to electromagnetic radiation can be crosslinked chemically, as well as a crosslinking aid. Otherwise, this method does not differ from the method known from EP-A-0 289 056 or EP-A-0 326 132.

The disadvantage of the process known from EP-A-0 289 056 is that the photoconductive layer must always be covered by a cover layer of a special material composition, which, however, adversely affects the adhesion of the toner particles to the surface of the imagewise exposed electrophotographic recording element during concreteing ¬ tert. As for the methods of EP-A-0 326 132 and EP-A-0 326 169, these are limited to the use of electrophotographic recording elements with zinc oxide-containing photoconductive layers. In addition, with all of these processes, desensitization to oil (oil-desensitization treatment) must always be carried out, which may also damage the printing areas of the offset printing plate.

The object of the present invention is to find a new offset printing plate produced by electrophotographic means and a new electrophotographic manufacturing process which no longer have the disadvantages of the known electrophotographic offset printing plates and the known electrophotographic processes for their production. The new offset printing plate produced by electrophotography should above all be stable in terms of print run and should have an excellent differentiation in its surface into printing and non-printing areas, so that excellent printed products in particularly high circulation can be produced. In contrast, the new electrophotographic manufacturing process should deliver the new offset printing plate in a simple and reproducible manner.

The object of the present invention was surprisingly achieved by the new offset printing plate produced by electrophotography, the printing surface of which is composed of hydrophilic water-bearing, non-printing, concrete areas and oleophilic, color-bearing, printing, unconcreting areas. The use of toners which either are already hydrophilic in themselves or which can be hydrogenated during or after the production of the new offset printing plate has contributed to this surprising solution.

The object of the present invention is accordingly the new offset printing plate produced by electrophotography

A) an electrically conductive dimensionally stable support,

B) at least one photoconductive layer and

C) a printing surface made of

Ci) hydrophilic water-bearing non-printing areas with concrete areas and from c ₂ ) oleophilic color-bearing printing areas with no concrete areas

is composed.

Another object of the present invention is the new method for producing an offset printing plate by electrophotography

i) imagewise exposure of an electrically negatively or electrically positively charged electrophotographic recording element, which has an electrically conductive support (A) and at least one photoconductive layer (B), to actinic light, as a result of which a latent on the surface (C) of the electrophotographic recording element electrostatic charge image is generated

ii) developing the electrostatic latent image by means of a toner, resulting in a toned image, iii) fixing the stressed image on the surface (C), resulting in the offset printing plate, and optionally

iv) post-treatment of the offset printing plate,

the new process being characterized in that either a hydrophilic toner or a toner is used which is hydrophilized on the surface (C) in process step iii) and / or in the aftertreatment step iv).

For the sake of brevity, the new offset printing plate produced by electrophotographic means is referred to below as "offset printing plate according to the invention". Accordingly, the new process for producing an offset printing plate by electrophotography is referred to as the "process according to the invention".

The essential feature according to the invention or the essential component according to the invention of the offset printing plate according to the invention is its printing surface (C), which is composed of hydrophilic water-bearing non-printing areas (ci) and oleophilic ink-bearing printing areas (c ₂ ). Accordingly, the non-printing areas (c) are formed by toner particles which have been applied to the surface of an electrophotographic recording element in a manner known per se. In contrast, the printing areas (c ₂ ) are formed by that part of the surface of an electrophotographic recording element which was not covered by toner particles in the production of the offset printing plate according to the invention.

The surface of the electrophotographic recording element can in turn be the hydrophobic or oleophilic surface of the photoconductive layer (B) or the surface of a 0.1 to 5 μm thick, electrically insulating layer applied to the photoconductive layer (B) act oleophilic layer (D). Furthermore, the surface can be matted by roughening or by incorporating oleophilic polymeric particles such as polymethyl methacrylate, polystyrene or cross-linked phenolic resins.

The oleophilic properties of the surface are determined by the material composition of the photoconductive layer (B) or the layer (D). Accordingly, any photoconductive layers (B) or layers (D) having an oleophilic ^¬ upper surface due to their material composition, suitable as a component of the offset printing plate according to the invention. However, photoconductive layers (B) with a hydrophilic surface can also be considered as part of the offset printing plate according to the invention. However, the relevant offset printing plate according to the invention then necessarily contains a layer (D) with an oleophilic surface.

Regardless of which surface (C) it is, it is not attacked by the offset-typical printing inks. The surface (C) has preferably been partially or completely crosslinked thermally by heating, by reacting with suitable chemical reagents and / or by irradiation with electromagnetic radiation or particle radiation.

The photopolymerizable layers (B) with an oleophilic surface are preferably used as part of the offset printing plate according to the invention.

Examples of suitable photoconductive layers (B) which can be considered as part of the offset printing plate according to the invention are the customary and known inorganic photoconductive layers (B) made of selenium or doped silicon and the organic photoconductive layers (B) which contain at least one binder (bi) , contain at least one charge carrier producing compound or a sensitizer (b ₂ ), at least one charge carrier transporting, organic or inorganic compound or a photoconductor (b3) and optionally additives (b ^).

Examples of suitable binders (bi) are cellulose ethers, polycarbonates, polyester resins, polystyrene, polyvinyl chlorides, polymethacrylates and styrene / acrylonitrile copolymers, of which the crosslinked are used with particular preference.

Examples of suitable sensitizers (b ₂ ) are known from the prior art mentioned at the outset.

Examples of suitable photoconductors (b3) are zinc oxide or the customary and known low molecular weight oxazole derivatives (DE-B-11 20 875), oxdiazole derivatives (DE-B-10 58 836), triazole derivatives (DE-B-10 60 260), azomethines (US-A-3 041 165), pyrazoline derivatives (DE-B-10 60 714), imidazole derivatives (DE-B-11 06 559), arylamines (DE-B-27 12 557), 1,3-dithiol derivatives (DE -B-33 38 204), benzotriazole derivatives (EP-A-0 131 292), triazolylpyridine derivatives (EP-A-0 150 419), pyrazolotriazole derivatives (EP-A-0 156 308), triphenyltriazole derivatives (EP-A-0 162 216) or hydrazone derivatives (EP-A-0 001 599, DE-A-29 19 791 corresponding to US-A-4 367 273 and US-A-4 278747, GB-A-2 088074 and DE-A-31 40 571) or the likewise customary and known olig eren or polymeric polyvinyl carbazoles or arylamine polymers (EP-A-0 052 961) and (meth) acrylate polymers and Organopolysiloxanes with pendant carbazolyl groups.

If polymeric photoconductor used (b _ß), then to the concomitant use of binders (bi) can be omitted.

Examples of suitable additives (b) are the customary and known leveling agents, wetting agents, fillers and reinforcing fillers and crosslinking aids such as organic peroxides, organic silanes or epoxy resins.

In the offset printing plate according to the invention, the photoconductive layer (B) is generally 0.5 to 40, preferably 0.8 to 25, advantageously 1 to 20 and in particular 1.5 to 15 μm thick.

The production of the photoconductive layer (B) of the offset printing plate according to the invention has no special features in terms of method, but is instead produced in a conventional manner known from the prior art, its constituents being used in customary and known amounts. For this purpose, reference is made, for example, to the patents mentioned at the beginning.

Examples of suitable layers (D) are layers of crosslinked or uncrosslinked organic polymers such as cellulose ethers, polyester resins, polyvinyl chlorides, polycarbonates, polyolefins, styrene / acrylonitrile copolymers and photopolymerized mixtures, which, in a customary and known manner, involve exposing layers from the above in a conventional manner mentioned polymers, photopolymerizable monomers and photo polymerization initiators are available with actinic light. In addition, the layers (D) may also contain the additives (b) mentioned above.

The production of the layers (D) does not methodically Besonder¬ units on, but is usually carried out by casting v ^~ ι - ung and drying the wet film thus obtained, after which the egg so .- ,. ιe layer (D) in a customary and known way, for example ÜJ ^, -: T Photo¬ polymerization, can be crosslinked.

The offset printing plate according to the invention contains a dimensionally stable, electrically conductive carrier. For this come the usual and known aluminum, zinc, magnesium, copper, steel or multi-metal plates, Polymer films with a metallized surface, such as aluminum-vapor-coated polyethylene terephthalate films or electrically conductive special papers. The production of the electrically conductive, dimensionally stable supports (A) also has no special features in terms of method, but instead takes place according to the customary and known methods of producing metal plates, metallized polymer films and electrically conductive special papers.

In the offset printing plate according to the invention, the electrically conductive dimensionally stable support (A), the photoconductive layer (B) and, if appropriate, the layer (D) are arranged one above the other in the order given and bonded to one another in a firmly bonded manner. This arrangement is usually referred to as an electrophotographic recording element. The production of the electrophotographic recording element also has no special features in terms of method, but rather takes place in a customary and known manner according to the methods known from the prior art.

It is advantageous for the offset printing plate according to the invention if the concreted image areas (cj) are glued or fused to the printing surface (C) and / or chemically bonded, because this results in a particularly abrasion-resistant offset printing plate according to the invention. The chemical linkage of the stressed image areas (ci) in the surface (C) may have been accomplished chemically by reaction with suitable reagents, thermochemically by heating and / or by irradiation with electromagnetic radiation or particle radiation.

In addition, it is advantageous for the offset printing plate according to the invention if the toner particles in the concreted areas (cj) are glued or fused together and / or chemically bonded to one another. The chemical linkage of the toner particles to one another can be accomplished chemically by reacting the toner particles with suitable reagents, thermochemically by heating and / or by irradiation with electromagnetic radiation or particle radiation.

Furthermore, it is advantageous for the offset printing plate according to the invention if the toner particles in the stressed areas (ci) contain chemically bound non-polar functional groups which are chemically photochemically or by reacting with suitable reagents, thermochemically by heating and / or by irradiation with electromagnetic radiation Allow radio-chemical decomposition to form chemically bound polar functional groups. It is of particular advantage for the offset printing plate according to the invention if the toner particles in the concreted areas (cj) contain chemically bound polar functional groups which are converted from the chemically bound nonpolar functional groups originally present in the concreted areas (ci) by reaction with suitable reagents have been generated chemically, by heating thermochemically and / or by irradiation with electromagnetic radiation or particle radiation photo- or radiochemically.

According to the invention, all chemically bonded nonpolar functional groups are suitable, which can be converted into chemically bonded polar functional groups chemically by reaction with suitable reagents, thermochemically by heating or by irradiation with electromagnetic radiation or particle radiation. Accordingly, all those non-polar functional groups which have the above-mentioned property profile are suitable for the intended use according to the invention. These non-polar functional groups can be bound in the concreted areas (ci) to the pigments for coloring, the surface-active substances for stabilization and / or to the substances for charge control of the toner particles originally used for the production of the concreted areas (cj).

Examples g <- suitable chemically bound non-polar functional groups sir. from EP-A-0 019 770 (DE-A-29 22 748), EP-A-0 289 056, DE-A-37 21 741, EP-A-0 326 132, EP-A -0 134 574, EP-A-0 101 587 or EP-A-0 326 169 or from the article by Ito et al., "A Sensitive Deep UV Resist System", in SPE Regional Technical Conference, Ellenville, New York, November 1982 or US-A-4,491,628.

Examples of particularly suitable chemically bound nonpolar functional groups are carbon, sulfonic or phosphonic anhydride groups; the anhydrides of acidic sulfate or phosphate ester groups; Carbon, sulfonic, phosphonic, sulfuric or phosphoric acid ester groups; Silyl ether and silyl ester groups; Aryl, alkyl and arylalkyloxycarbonyl groups; N-cyclohexyl carbodiimide groups; o-nitrobenzyl acrylate groups; tert-butoxy carbonyl groups; o-quinonediazide groups; Epoxy groups; cyclic acetal groups or other groups with at least two sterically close hydroxyl groups which are connected to a single, at least double functional protective group; and ethylenically unsaturated photopolymerizable and / or radiochemically crosslinkable groups. Chemically bonded polar functional groups which are suitable for the use according to the invention are, in particular, polar functional groups which are attached to the pigments for coloring, the surface-active substances for stabilization and / or the substances for charge control for the Production of the toned areas (ci) originally used toner particles are bound and which impart hydrophilic properties to the toned areas (cj). Accordingly, all those polar functional groups which have this property profile are suitable for the use according to the invention.

Examples of highly suitable chemically bound polar functional groups to be used according to the invention are carbon, sulfone and phosphonic acid groups, acidic sulfur and phosphoric acid ester groups, amino and hydroxyl groups and also polyalkylene oxide, in particular polyethylene oxide groups, of which the hydroxyl groups and the polyethylene oxide groups are of particular advantage and are therefore used with particular preference according to the invention.

For the offset printing plate according to the invention, it is also of very particular advantage if the areas (ci) which have been stressed have large amounts, i.e. 10 to 90% by weight, based on the concreted areas (cj), of hydrophilic inorganic oxides and / or chalcogenides. Pyrogenic silica and aluminum oxide are of particular advantage here. According to the invention, they are therefore used with very particular preference.

A further particular advantage results for the offset printing plate according to the invention if at least the oleophilic, color-guiding, unstressed areas (c ₂ ) of their printing surface (C) are matted.

The printing surface (C) of the offset printing plate according to the invention which is essential for the invention can be produced in any manner. However, it is particularly advantageous to produce the printing surface (C) by the process according to the invention.

The method according to the invention is based on the electrophotographic recording element described in detail above, which contains at least one electrically conductive dimensionally stable support (A), at least one photoconductive layer (B) and optionally the layer (D). This electrophotographic recording element is charged in a customary and known manner after its production by means of a high-voltage corona discharge and is either electrically negative or electrically positive then exposed imagewise with a reprographic camera or a computer-controlled laser, which is known to produce a latent electrostatic charge image.

This latent electrostatic charge image is then known to be toned with the aid of a liquid or solid toner, resulting in a toned image.

According to the invention, a toner is used here, the toner particles of which impart hydrophilic water-bearing properties to the areas (ci) of the offset printing plate according to the invention after their production. Thus, either hydrophilic toners or toners are used for the method according to the invention, which are hydrophilized when the toners are fixed or when the resulting offset printing plate according to the invention is aftertreated, i.e. they are given hydrophilic water-carrying properties. This ensures that the concreted areas (ci) of the printing surface (C) obtained in this way do not use offset printing inks but water when using the offset printing plate according to the invention and accordingly do not print.

Those toners are preferred for the process according to the invention which are only hydrophilized during the implementation of the process according to the invention.

In the method according to the invention, after the latent electrostatic charge image has been concreted, the resulting concreted image is fixed on the surface of the electrophotographic recording element.

This step can be followed by a suitable post-treatment step.

The toners preferably used in the process according to the invention, which are hydrophilized in the fixing and / or in the aftertreatment step, contain the chemically bound nonpolar functional groups described in detail above, from which chemical reaction by reaction with suitable reagents, thermochemical heating and / or by irradiation with electromagnetic radiation or particle radiation photochemically or radiochemically the polar functional groups essential for the function of the offset printing plate according to the invention can be produced. The content of these chemically bound and polar functional groups in the toners preferably to be used according to the invention is in principle adjusted so that in the course of the Method according to the invention give the hydrophilic water-carrying properties of the concrete areas (ci). The suitable content of chemically bonded nonpolar functional groups in the toners to be preferably used according to the invention can easily be determined by a person skilled in the art on the basis of preliminary tests or simple considerations, for example by using the ones from EP-A-225 547 or DE-A-38 21 199 known solid toners or the liquid toners known from US Pat. No. 4,661,431 in a manner known per se using pigments for coloring, surface-active substances for stabilization and substances for charge control which contain the non-polar functional groups described in detail, manufactures. For example, he can use EP-A-0 326 132, EP-A-0 326 169, EP-A-0 289 056, DE-A-37 21 741, US-A-4 491 628 , EP-A-0 101 587, EP-A-0 134 574 and EP-A-0 019 770 use known high and low molecular weight substances for the production of the toner particles in question, these substances having the function of the surface-active substances for stabilization and / or the substances for charge control can take over. The person skilled in the art can then easily recognize the suitable content of nonpolar functional groups by the fact that the toners resulting from the preliminary tests still have the properties which are essential for their function as toners, at the same time by reaction with suitable reagents chemically, by heating thermochemically or by Irradiation with electromagnetic radiation or particle radiation can be photo- or radiochemically hydrophilized. Therefore, taking these two boundary conditions into account, the person skilled in the art can either obtain the toners particularly preferably used for the process according to the invention by varying the customary and known toners or can select them from the customary and known toners.

In the method according to the invention, in particular those toners of the type described above are used which contain large amounts, i.e. 10 to 90% by weight, based on the toner, of finely divided hydrophilic inorganic oxides and / or chalcogenides, in particular pyrogenic silica and / or aluminum oxide.

In the method according to the invention, the particularly preferably used toner particles are glued or fused to the surface of the electrophotographic recording element and / or to one another when fixed, or chemically by reaction with suitable reagents, thermochemically by heating and / or by irradiation with electromagnetic radiation or particle radiation photo- or radiochemically linked. This can also take place during the post-treatment step or be completed. According to the invention, when carrying out these two process steps, the chemically bound nonpolar functional groups described in detail above are converted into the chemically bound polar functional groups essential for the function of the offset printing plate according to the invention, in particular into the carbon, sulfonic or phosphonic acid groups. converted into the acidic sulfur or phosphoric acid ester groups, into the amino and hydroxyl groups or into the polyalkylene oxide groups.

The person skilled in the art can very easily select the methods of gluing or fusing or chemically linking the toner particles to the surface of the electrophotographic recording element and / or to one another on the basis of the chemically bound nonpolar functional groups present in the toner particles. For example, it becomes

the carbon, sulfonic and phosphonic acid anhydride groups, the anhydrides of acidic sulfate or phosphate ester groups, the carbon, sulfonic, phosphonic, sulfur or phosphoric acid ester groups, the silyl ether and silyl ester groups, the aryl, alkyl and arylalkyloxycarbonyl amino groups, the N-cyclohexyl-carbodiimide groups, the epoxy groups, the cyclic acetal groups or the other groups with at least two sterically close hydroxyl groups, which are linked to a single, at least double-functional protective group by reaction with suitable reagents chemically,

the epoxy groups thermally by heating,

the o-nitrobenzyl acrylate groups, the tert-butoxy carbonyl groups, the o-quinonediazide groups or the ethylenically unsaturated groups by irradiation with electromagnetic radiation or photochemically

the ethylenically unsaturated groups by radiochemical irradiation with particle radiation

implement. For this purpose he can also add suitable crosslinking aids such as photopolymerization initiators, initiators of thermal radical polymerization, organic silanes or epoxy resins to the toner particles.

For the method according to the invention, it is of particular advantage if the toner particles are simultaneously hydrophilized in the gluing or fusing carried out in the above manner and / or in the chemical linkage. It is also of particular advantage for the method according to the invention if the surface of the electrophotographic recording element is matted by mechanical or electrical roughening by means of a high-voltage discharge corona and / or by the incorporation of finely divided organic fillers.

For the concreting of the electrophotographic recording element used in the method according to the invention, the customary and known methods and apparatus for concreting with solid or liquid toners can be used, e.g. the device Elfasolautomat® EA 692 from Hoechst, the device OPC® 200 from Polychrome or preferably the Performer® from Chemco Engineering.

Methods and apparatuses which are known per se can likewise be used in the method according to the invention for heating the electrophotographic recording element which is emphasized in the procedure according to the invention. Examples include heating in drying cabinets or irradiation with infrared lamps.

The usual and known methods and apparatuses can also be used for irradiating the stressed electrophotographic recording element with electromagnetic radiation or with particle radiation. The apparatuses with sources for X-rays, UV radiation, visible light or electron radiation, as are usually used in the field of reprography or X-ray or electron beam lithography, may be mentioned as examples.

Likewise, the suitable reagents used in the process according to the invention are customary and known. Their selection depends primarily on the chemically bound non-polar functional groups present in the toner particles on the one hand and on the other hand on the chemically bound polar functional groups to be produced therefrom. Furthermore, these suitable reagents can either be a constituent of the toner particles or they can only be used as gases, as solids, during the fixing and / or during the fixing of the toner particles on the surface of the electrophotographic recording element and / or during the aftertreatment of the offset printing plate according to the invention or added in the form of solutions. Their addition in the form of aqueous or organic solutions is preferred.

The suitable chemical reagents are therefore acidic or basic, oxidizing or reducing, co complexing or not complexing, organic, inorganic or organometallic Substances, their mixtures or their aqueous or organic solutions, of which the solutions are preferably used.

Examples of highly suitable chemical reagents are alkane carboxylic acids and mineral acids and their salts, alkali and alkaline earth metal hydroxides and alcoholates, organic amines, ammonia, compounds with two or more chelating functional groups such as nitrilotriacetic acid and their salts, epoxides, organic silanes, boranes and radical-providing compounds ¬ such as initiators of thermal radical polymerization and photopolymerization.

Further examples of well-suited chemical reagents can be found in EP-A-0 136 132.

The treatment of the concreted electrophotographic recording element and / or the offset printing plate according to the invention with these solutions is carried out in a customary and known manner, for example by immersing the relevant electrophotographic recording elements and / or the offset printing plates according to the invention in these solutions or by spraying the electrophotographic recording elements and / or of the offset printing plates according to the invention with these solutions.

If the process according to the invention is carried out using these solutions, the offset printing plate according to the invention obtained in this way is processed in a customary and known manner, e.g. in a convection oven, dried.

Preferably, the method according to the invention is carried out using the methods and apparatus for irradiation with electromagnetic radiation, i.e. carried out photochemically, and also using the corresponding toner particles described above, which contain the corresponding photosensitive, chemically bound, nonpolar functional groups. You can do without any treatment with stripping solutions or with chemical reagents.

The offset printing plate according to the invention has special technical advantages in its manufacture and use. It is no longer necessary to produce a stripping step in which it is known that the printing areas of the offset printing plate in question can be damaged or even detached. In addition, the offset printing plate according to the invention can in practice be easily adapted to predetermined printing conditions. In addition, the offset printing plate according to the invention in contrast to the conventional in simple way of producing printed products which are "negative" in relation to the image to be reproduced. This is due to the fact that, in the conventional offset printing plates produced by electrophotography, the concreted areas ultimately form the oleophilic ink-guiding printing areas, whereas this is not the case with the offset printing plate according to the invention. This results in possible applications which have hitherto not been possible with known offset printing plates produced by electrophotographic means.

The method according to the invention also has particular unexpected technical advantages. It is extremely variable and adaptable both with regard to the electrophotographic recording elements which can be processed by the method according to the invention and with regard to its design options. The method according to the invention therefore makes it possible to produce offset printing plates according to the invention, which in practice are outstandingly adapted to the respective application.

The offset printing plate according to the invention, but in particular the one produced by the method according to the invention, also reproduces those image elements which are otherwise difficult to reliably reproduce in the best quality. When printing on an offset printing unit with offset printing inks of the "oil-in-water" type, the printing areas (c ₂ ) of their printing surface (C) accept the oily colors outstandingly, whereas their non-printing areas (cj) are outstandingly water-conducting . This results in excellent contrast and extremely precise printing, which leads to excellent printed products overall. Since the offset printing plate has an advantageously long service life under the printing conditions, a high circulation is also achieved.

Examples

For the following examples, three electrophotographic recording elements were produced according to the following general procedure:

I. Manufacture of electrophotographic recording elements; general test instructions:

I.l The production of poly (6-N-carbazolylhexyl methacrylate)

200 ml of a solution of 9-borabicyclo [3.3.1.] Nonane (9-BBN) in tetrahydrofuran (0.5 mol / l) were placed in a heated 500 ml three-necked flask. After a solution of 100 mmol of N-5-hexenylcarbazole in 100 ml of dry tetrahydrofuran was added dropwise, the resulting reaction mixture was stirred at room temperature for 3 hours. Then one after the other

60 ml of ethanol, 20 ml of 6 normal sodium hydroxide solution and 40 ml of hydrogen peroxide (30%) are added to the reaction mixture. After refluxing for one hour, 200 ml of water were added to work up the reaction mixture, and the tetrahydrofuran was then stripped off. The resulting N- (6-hydroxyhexyl) carbazole was extracted with ether and the ether solution was dried and evaporated. Thereafter, the resulting crude product was recrystallized from hexane / acetone (9: 1). This in

Pure N- (6-hydroxyhexyl) carbazole obtained in 61% yield was in the form of white crystals.

A solution of 30 mmol of methacrylic acid chloride in 10 ml of dichloromethane was added dropwise to a solution of 25 mmol of N- (6-hydroxyhexyl) carbazole and 30 mmol of triethylamine in 100 ml of dry dichloroethane. The reaction mixture was then stirred at room temperature for 3 hours and then washed with 2 normal sodium hydroxide solution and water for working up. The 6- (N-carbazolyl) hexyl methacrylate formed was isolated after concentrating the reaction mixture by column chromatography on silica gel (eluent: dichloromethane). The 6- (N-carbazolyl) hexyl methacrylate thus obtained in a yield of 70% was in the form of a colorless oil and showed the following characteristics:

IR (film): 1715 cm " ¹ (ester), 1635 cm ^{" 1} (C = C)

1625, 1595, 750, 720 cm ^-1 (carbazole)

1H-NMR (CDC1 ₃ ): δ = 1.3-1.9 (m), 4.02 (t), 4.23 (t), 5.46 (m), 6.00 (m),

7.1-7.2 (m), 7.3-7.5 (), 8.0-8.1 (m) intensity ratio: 11: 2: 2: 1: 1: 2: 4: 2 17.6 mmol of 6- (N-carbazolyl) hexyl methacrylate and 0.18 mmol of azobisisobutyronitrile were dissolved in 50 ml of dry toluene. The solution was degassed and then heated to 60 ° C for 48 hours with stirring. After cooling, the polymer obtained was precipitated from the solution by adding methanol and reprecipitated twice from chloroform / methanol for further purification. In this way, pol (6-N-carbazolylhexyl methacrylate) was obtained in a yield of 88%. The polymer was characterized by IR spectroscopy and GPC. The characteristics are given below.

IR (film): 1720 cπT ¹ (ester), 1625, 1595, 750, 720 cm ^"1 (carbazole)

Gel permeation chromatography, GPC: The molecular weight determined by means of GPC (polystyrene standard) was 66,000 (M _w : 84,000, M _n : 28,000,

So much poly (6-N-carbazolyl methacrylate) was prepared in this way that the amount was sufficient for the production of the electrophotographic recording elements.

1.2 Production of the electrophotographic recording elements

Three 14% solutions in tetrahydrofuran were prepared from the polymethacrylate containing pendant carbazolyl groups prepared in accordance with number 1.1. After filtration, these solutions were poured onto three selenium-vaporized carrier foils and the tetrahydrofuran was evaporated. The resulting three photoconductor layers had a thickness of 10 μm after drying. The selenium-vaporized carrier film was an approximately 100 μ thick polyethylene terephthalate film which was vapor-coated with a thin aluminum layer. The selenium layer evaporated on the aluminum had a thickness of approx. 1 μm.

The result was three identical electrophotographic recording elements in which the photoconductor layers composed of the polymethacrylate containing pendant carbazolyl groups adhered firmly to the self-vaporized carrier films and did not break or peel off when the recording elements were bent. The electrophotographic recording elements had the following application properties, measured in a customary and known manner by the Carlson process:

• maximum potential acceptance E _max : 229 kV / m • Dark drop within 20 seconds after electrostatic charging: 8%

• Photo waste caused by the 5-second full exposure 5 with visible light: 80%

example 1

The production of an offset printing plate according to the invention by the method according to the invention using a liquid toner which can be photochemically hydrophilized; Test specification:

1.1 The production of the liquid toner which contains chemically bound non-polar functional groups which, when exposed to UV light, provide 15 chemically bound polar functional groups; Test instructions:

At first it was out

20 1400 g of gasoline (isopar H from Exxon),

283 g of a customary and known rosin (rosin), 557 g of the diazo resin of the formula

which had been prepared by partial esterification of a p-cresol novolak with 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride 5 and had a 1,2-naphthoquinonediazide content of 65% by weight (RP2 from PCAS ), 168 g of an ethylene-vinyl acetate copolymer (AC 400 from the company

Allied Corp.), 168 g of an ethylene-acrylic acid copolymer (AC 540 from Allied), 0 200 g of an aluminum oxide pigment with an average particle size of <1 μm, and 83 g of a phthalocyanine pigment, a mixture was prepared by stirring for 10 minutes in an impeller stirrer at a speed of 8000 revolutions per minute (rpm) at a temperature of 70 to 80 ° C.

This mixture was made in the impeller stirrer with a speed of 8000 rpm at 70 to 80 ° C. for 10 minutes with 2000 g of a latex

1000 g of a gasoline (Isopar H from Exxon),

50 g of a stabilizer (polymer based on the polymer, 40% by weight of o-nitrobenzyl acrylate, 56% by weight of lauryl methacrylate and 3% by weight of glycidyl methacrylate which had been esterified with 1% by weight of methacrylic acid) and 950 g latex particles (particles of 0.4 to 1 μm in size made from a polymer, based on the polymer, 45% by weight of o-nitrobenzyl acrylate, 52% by weight of methyl methacrylate and 3% by weight of methacrylic acid)

and 670 g of a stabilizer solution

Isopar H and the above stabilizer

The resulting mixture was mixed with 3700 g of Isopar H and then stirred for 30 minutes in an impeller stirrer at 1500 rpm at a temperature of 50 to 55 ° C. According to this there were 9061 g of a so-called predispersion which is used to produce the actual toner dispersion, i.e. of the liquid toner.

For this purpose

920 g of the predispersion,

56 g carnauba wax,

60 g of the Neocryl EX 550 polymer dispersion from Polyvinyl Chemical Industries, Division of Beatrice, and

822 g Isopar H

mixed in a ball mill at a speed of 300 rpm at room temperature. After mixing, a further 1000 g of Isopar H were added.

The liquid toner thus obtained was heated at 60 ° C for a further 30 minutes, after which it was ready for use. 1.2 The implementation of the method according to the invention; Test instructions

One of the three electrophotographic recording elements was charged in the usual and known manner with a DC corona from a distance of 1 cm within 20 seconds and then exposed imagewise in a reprographic camera with visible light. The resulting charge pattern was electrophoresed in a conventional manner in the Performer® liquid toner device from Chemco Engineering.

The toned electrophotographic recording element was dried and then briefly heated to 130 ° C., so that the toner particles melted or stuck together and to the surface of the electrophotographic recording element.

The concreted electrophotographic recording element was then irradiated with UV light over the entire area in a tube flat exposure unit (emission maximum in the wavelength range from λ = 350 to 420 n) for 2 minutes. Here, both the o-nitrobenzyl acrylate groups and the 1,2-naphthoquinonediazide groups were cleaved in the areas of the electrophotographic recording element with the formation of chemically bonded carboxylic acid groups (polar functional groups), as a result of which the areas which were emphasized were rendered hydrophilic and the offset printing plate according to the invention resulted.

The offset printing plate according to the invention was clamped onto a printing cylinder and used in an offset printing unit using customary and known offset printing inks of the "oil-in-water" type for the production of printed products.

Here, the oleophilic or hydrophobic ink-bearing, unstressed areas (c ₂ ) of the printing surface (C) of the offset printing plate according to the invention accepted the oil colors excellently, whereas the hydrophilic, water-bearing non-printing areas (ci) remained completely color-free. This resulted in very high quality printed products, which reproduced the motif of the original used for image-wise exposure even in the finest picture elements. In game 2

The production of an offset printing plate according to the invention by the method according to the invention using a liquid toner, 5 which can be photochemically hydrophilized; Test specification:

Example 1 was repeated, except that a polymer consisting of, based on the polymer, 50% by weight of o-nitrobenzyl acrylate, 45% by weight of methyl methacrylate and 5% by weight of methacrylic acid was used instead of the diazo resin according to Example 1 to produce the liquid toner .

The resulting offset printing plate according to the invention had the same outstanding application properties as that of Example 1.

15 Example 3

The production of an offset printing plate according to the invention by the method according to the invention using a solid two-component toner which can be photochemically hydrophilized; Trial 0 regulation:

3.1 The production of the solid toner, which contains chemically bound non-polar functional groups which, when exposed to UV light, provide chemically bound polar functional groups; Test 25 regulation:

In a mixer, 80 parts by weight of a polymer, based on the polymer, 50% by weight of o-nitrobenzyl acrylate, 30% by weight of styrene and 20% by weight of butyl ethacrylate, 15 parts by weight of finely ground AI2O3 (average 30 particle size <1 μm), 4 parts by weight of carbon black and 1 part by weight of stearylpyrrolidino [1,2-α-benzimidazolium] bromide (cf. DE-A-38 21 199) mixed intensively, kneaded at 120 ° C. , extruded and pre-ground.

By grinding in a fluidized bed counter jet mill with classifying wheel and 35 subsequent classifying, toner particles between 5 and 25 μm were produced with an average particle size of 15 μm.

To produce the so-called developer, 1 part by weight of the toner particles were precisely weighed out with 99 parts by weight of an iron powder with particle sizes between 40 75 and 175 μm, an average particle size of 120 μm and spherical shape and on a roller stand for 10 minutes activated. 3.2 The implementation of the method according to the invention; Test specification:

The third electrophotographic recording element was, as described in Example 1, section 1.2, charged and exposed imagewise. The resulting electrostatic charge image was emphasized in the commercially available dry toner device "Elfasolautomat® EA 692" from Hoechst using the activated developer manufactured in accordance with number 3.1. Thereafter, the concreted electrophotographic recording element, as described in Example 1, Section 1.2, was further processed to the offset printing plate according to the invention. This had the same outstanding performance properties as the offset printing plates according to the invention of Examples 1 and 2.

Claims

1. Offset printing plate produced by electrophotographic means with

A) an electrically conductive dimensionally stable support,

B) at least one photoconductive layer and

C) a printing surface made of

Ci) hydrophilic water-bearing non-printing concrete

Areas and from c ₂ ) oleophilic color-bearing areas without concrete

is composed.

2. The offset printing plate according to claim 1, characterized in that the photoconductive layer (B) is covered by a 0.1 to 5 microns thick, electrically insulating, oleophilic layer (D), the unstressed surface areas of the oleophilic color-guiding printing unstressed areas (c ₂ ) form the printing surface (C).

3. The offset printing plate according to claim 1 or 2, characterized in that the concrete areas (ci) with the surface (C) glued or fused and / or chemically connected.

4. The offset printing plate according to claim 3, characterized in that the chemical linkage of the stressed areas (ci) with the surface (C) by reaction with suitable reagents chemically, by heating thermochemically and / or by exposure to electromagnetic radiation or particle radiation photo - Or has been radio-chemically accomplished.

5. The offset printing plate according to one of claims 1 to 4, characterized in that the toner particles in the concreted areas (ex) are glued or fused together and / or chemically bonded to one another.

6. The offset printing plate according to claim 5, characterized in that the chemical linkage of the toner particles to one another by reaction with suitable reagents chemically, by heating thermo¬ chemically and / or by irradiation with electromagnetic radiation or particle radiation has been accomplished photo- or radiochemically.

7. The offset printing plate according to one of claims 1 to 6, characterized in that the stressed image areas (ci) contain chemically bound non-polar functional groups, which chemically by reaction with suitable reagents, by heating thermo¬ chemically and / or by irradiation with electromagnetic Have radiation or particle radiation converted photochemically or radiochemically into chemically bound polar functional groups.

8. The offset printing plate according to one of claims 1 to 7, characterized in that the stressed image areas (ci) contain chemically bound polar functional groups which chemically bonded nonpolar functional groups by reaction with suitable reagents chemically, by heating thermochemically and / or by Irradiation with electromagnetic radiation or particle radiation have been generated photo- or radiochemically.

9. The offset printing plate according to one of claims 1 to 8, characterized in that at least the non-stressed areas (c ₂ )

Surface (C) are matted.

10. Process for making an offset printing plate

i) imagewise exposure of an electrically negatively or electrically positively charged electrophotographic recording element which has an electrically conductive dimensionally stable support (A) and at least one photoconductive layer (B) to actinic light, as a result of which on the surface (C) of the electrophotographic Recording element generates a latent electrostatic charge image,

ii) developing the latent electrostatic charge image using a toner, resulting in a toned image on the surface (C), iii) fixing the stressed image, whereby the offset printing plate is obtained, and optionally

iv) post-treatment of the offset printing plate,

characterized in that a hydrophilic toner or a toner is used which is hydrophilized on the surface (C) during process step iii) and / or during the after-treatment step iv).

11. The method according to claim 10, characterized in that for the purpose of fixing in process step iii) the concrete image is heated, reacted with suitable chemical reagents and / or irradiated with electromagnetic radiation or with particle radiation.

12. The method according to claim 11, characterized in that during the aftertreatment iv) the offset printing plate is heated, reacted with suitable reagents and / or irradiated with electromagnetic radiation or with particle radiation.

13. The method according to any one of claims 10 to 12, characterized gekenn¬ characterized in that the photoconductive layer (B) is covered by a 0.1 to 5 microns thick, electrically insulating, oleophilic layer (D), the unstressed surface areas after Process step iii) or the aftertreatment step iv) form the oleophilic ink-carrying printing areas (c ₂ ) of the surface (C).

14. The method according to any one of claims 10 to 13, characterized in that in the process step iii) and / or in the aftertreatment step iv) the toner particles are reacted chemically by reaction with suitable reagents, thermochemically by heating and / or by irradiation with electromagnetic radiation or with particle radiation photo- or radiochemically hydrophilized.

15. The method according to any one of claims 10 to 14, characterized gekenn¬ characterized in that in process step iii) or in the aftertreatment step iv) the toner particles are glued or fused together and / or by reaction with suitable reagents chemically, by heating thermochemically and / or photo- or radiochemically combined with one another by irradiation with electromagnetic radiation or with particle radiation.

16. The method according to any one of claims 10 to 15, characterized gekenn¬ characterized in that solid or liquid toners are used, the toner particles of which contain chemically bound polar functional groups.

5

17. The method according to any one of claims 10 to 15, characterized gekenn¬ characterized in that solid or liquid toners are used with toner particles which contain chemically bound non-polar groups which in process step iii) and / or in the after-treatment step iv)

10 by reaction with suitable reagents chemically, by heating thermochemically and / or by irradiation with electromagnetic radiation or with particle radiation photo- or radiochemically chemically bound polar functional groups.

15 18. The method according to claim 17, characterized in that the chemically bound non-polar groups are carbon, sulfonic and phosphonic anhydride groups; around anhydride groups of acidic sulfate or phosphate esters; around carbon, sulfone, phosphonic, sulfur and phosphoric acid ester groups; around silyl ether and silyl ester groups; by 0 aryl, alkyl or arylalkyloxycarbonylamino groups; around N-cyclohexylcarbodiimide groups; around o-nitrobenzyl acrylate groups; o-quinonediazide groups; Epoxy groups; cyclic acetal groups or other groups with at least two sterically closely spaced hydroxyl groups which are connected to a single, at least twice functional protective group; and are ethylenically unsaturated groups.

19. The method according to any one of claims 16 to 18, characterized gekenn¬ characterized in that it is the chemically bound polar functional groups 0 to carbon, sulfonic and phosphonic acid groups; acidic sulfuric acid and phosphoric acid ester groups; around amino and hydroxyl groups; and is alkylene oxide groups.

20. The method according to any one of claims 10 to 19, characterized in that it is in the appropriate chemical reagents to aqueous or organic solutions of acidic or basic, oxidizing or reducing, complexing or non-complexing, organic, inorganic and organometallic substances or the pure substances concerned themselves or their mixtures.

21. The method according to claim 20, characterized in that the substances are alkane carboxylic and mineral acids and their salts; alkali and alkaline earth hydroxides and alcoholates; organic amines and ammonia; to chelate compounds with two or more

5 the functional groups; are epoxides and radical-donating substances.

22. The method according to claim 20 or 21, characterized in that the substances in question are contained in the toner particles.

10

23. The method according to any one of claims 10 to 22, characterized gekenn¬ characterized in that the toner particles contain large amounts of finely divided hydrophilic inorganic oxides and / or chalcogenides.

15 24. The method according to claim 23, characterized in that the

Toner particles contain fumed silica and / or alumina.

25. The method according to any one of claims 10 to 24, characterized gekenn¬ characterized in that the surface (C) at least in their unstressed

20 areas (c ₂ ) is matted.

26. Offset printing plate according to one of claims 1 to 9, characterized gekenn¬ characterized in that it has been produced according to the method according to any one of claims 10 to 25.

25

30

35

40