DE1522497A1 - Process for the production of printing forms - Google Patents

Description

KALLE AKTIENGESELLSCHAFT 1522497 Our · sign day sheet

K 1648 FP-Dr.Wi-cr May 11, 1966

description
to register

- KALLE AKTIENGESELLSCHAFT Wiesbaden-Biebrich

for a patent axif Process for the production of printing forms

The present invention relates to the manufacture of Electrophotographic printing forms. It also relates to an electrophotographic developer. Wake up using the method of the invention of the developer is preferred to produce planographic printing forms, but letterpress forins can also be produced.

It is known to have organic photoconductive compounds in the layers of electrophotographic copying materials to use. It is also known to be electrophotographic Copy materials with organic photoconductors

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to process into printing forms «These then have one for Suitable carriers for printing purposes. In their unprocessed state, they are also used as electrophotographic printing plates designated. For example, there is known an electrophotographic printing plate in which the photoconductive layer consists of monomolecular photoconductor and high molecular weight alkali-soluble substances. This is in Usually charged, exposed and colored with Resin powder developed. The resin powder is made by baking fixed, then the layer is treated with an alkaline solution, the non-image areas be detached and a flat printing form is created. The disadvantage of this process is that the image areas are slightly smaller when treated with the alkaline solution washed away and possibly even washed away can.

Also is an electrophotographic printing plate known whose layer contains zinc oxide as a photoconductor, finely divided in a crosslinkable binder, as well as a method for processing them, in which to develop of the latent electrostatic image is a substance that catalyzes the crosslinking of the binder

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finely divided solid form is used. The image areas iverden opposite when the developer is burned in certain solvents difficult or insoluble in which the non-crosslinked non-bilateral sites, on the other hand, are easily soluble are. To the. In the manufacture of the printing form, the photoconductor layer is accordingly dissolved away at the non-image areas. Here, however, the. Already mentioned effect of flushing the image areas on, since the networking the layer VfGgen of the stored zinc oxide is not evenly bifj to the carrier durcligelit. To this disadvantage to be remedied, therefore, in a variation of the method Electrophotographic Oxymck Plates related, between the carrier and the photoconductor layer, there is also a metal-chloride or phosphate intermediate layer which enhances the adhesion contain. The washing down of the image areas is largely prevented by these habitats, however, the process still has the disadvantage of using organic solvents for removal the non-image tunnels must be used.

The present invention was therefore based on the object a ■ method to find xii.i aiii electrophotographic

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Ways to get printing forms tau meet the high demands with regard to the resolution and the print run, and their Kichtbildstellen as far as possible aqueous solution can be removed.

The invention is based on the known method sum Manufacture of printing forms from electrophotography chem Copy material having a support suitable for printing purposes and a photoconductive layer thereon by charging, imagewise exposure, developing the latent electrostatic · »glides the layer with a finely divided toner, subsequent heating and removal the photoconductor layer at the non-image areas »It is characterized by the fact that the latent electrostatic Image generated on a layer, the at least one known, polymerizable, olefinic Double bonds «keep fit or form when heated Organic photoconductor contains this «it is visible to a developer who at least partially consists of an or consists of several finely divided solid substances that are contained in the Vlrjie radical · form, then the copy material with

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the developed image on temperatures »wipe 50 and 300 C, preferably heated to temperatures between 100 and 200 C and finally in a known manner the ' organic photoconductor layer removed from the non-image areas by dissolving it away.

According to the method described above, a Flat printing form. If the carrier material is suitable, this can be converted into a letterpress form using one of the known methods, if necessary also converted into a gravure form will.

The essence of the invention can be seen in the fact that a monomeric polymerizable photoconductor imagewise is radically polymerized, the image-wise distribution of the radical donor ^ by its use

achieved as a developer substance

will.

j) ie electrophotographic used as starting material in the process Printing plate is known in principle to watch. The use of photoconductive organic Substances with an olefinic double bond In electrophoto-

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graphic layers is known to be used in Printing plates is not expressly described. However, they are generally accessible to this application, is known from German patent 1 II7 391.

In the method according to the invention, both photoconductors with vinyl as well as vinylidene groups as well as those with three or all four can be used Hydrogen of ethylene are substituted. Suitable polymerizable compounds can also unier photoconductive stilbene and styrene derivatives can be found.

Compounds bearing vinyl groups are preferably used. Vinyl carbazole, substituted vinyl carbazole, substituted vinyl oxazole, substituted vinyl triazole and Vinyl dibenzofuran. As suitable compounds that the The substituted hydroxyethyl-diphenyl-triazoles, for example, can only form vinyl groups when heated will. These split off water when heated, whereby one Vinylgruppq is formed.

As a very suitable representative of the vinylidene group Acenaphthylene are called.

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So much for the polymerizable organic photoconductors from etch AU «are sufficiently film-forming, you can do it directly placed on a suitable carrier in the process of the invention are processed. Since this, however It is usually not the case to a sufficient extent * eich has proven advantageous to use printing plates, the layer of which, according to German Patent 1,117,391, contains resins in addition to the organic photoconductor, which are soluble in aqueous alkali. Suitable resins are high molecular weight substances that make them soluble in alkali Groups wear. Such groups are, for example, acid anhydride, carboxyl, sulphonic acid, sulphonamide or Sulphonimide groups. Resins are preferred with high Acid numbers are taken into account, as these are particularly easily soluble in aqueous-alkaline solutions. Copolymers with anhydride groups can be particularly successful can be used because of the lack of free acid groups the dark conductivity of the electrophot © graphic Layer is small despite good alkali solubility. Copolymers have proven to be particularly suitable Styrene and maleic anhydride.

A preferred embodiment of the method according to

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of the invention is therefore * that one has the latent electrostatic Image is generated on a layer that contains at least one polymerizable, organic photoconductive compound with a vinyl group and an alkali-soluble binder and that after developing and heating the non-image areas of the photoconductor layer in itself in a known manner with an aqueous-alkaline liquid, optionally containing an organic solvent removed. Suitable alkaline liquids are given in German Patent 1,117,391, which has already been mentioned described.

The layer of the starting material electrophotographic Printing plate can also contain sensitizers in a known manner. These are in small Amounts, about 0.00001 to about 0.1% "based on the Photoconductor portion added to the copy layer. Suitable sensitizers, which are essentially dyes, are for example from the Belgian patent 558 O.78 "known.

The photosensitivity of the layer can be known Way by adding so-called activators

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increase. These are electron acceptors that work with the Photoconductors, which in Hegel are electron donors, Form molecular complexes. Details can be found in German patent specification 1 1 & 7 21 $ ".

As a support for the one used as the starting material electrophotographic printing plates, all materials known for this purpose can be used, such as aluminum, zinc, magnesium or copper plates, but also cellulose products, such as. Special papers, Cellulose hydrate, cellulose acetate or cellulose oxityrate films; the latter especially in partially saponified form. ± 11 plastics are also used to a limited extent, e.g. Polyamides in film form as a carrier in question.

One created in accordance with the above explanations electrophotographic printing plate wix-d for carrying out the method according to the invention in the usual manner Charged with the help of a corona. It can optionally be positive or negative charge can be sprayed on. An image-wise exposure is then applied to the charged layer creates a latent electrostatic charge image. Es l. «: T contact exposure, slide or episcopic exposure

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possible. Also rasterization with the help of a contact or Glass engraving grid can be provided. Then with a developer that consists of, or at least contains, substances that decompose into radicals when exposed to heat, the latent image made visible.

Suitable as developers are all compounds present in solid form which are used in the radical Find polymerization of olefins use. In the present case it has been shown to be particularly advantageous to use itself: Beiizoylperoxid, Dichlorbenzoylperoxxd, Sticcinylperoxid, Azoisobutyronitrile, tetraphenylhydrazine, dehydrolophxn, Diazido tubes and sodium trichloroacetate.

The development with the substances mentioned can be done in a dry way or dispersed in the form of a Liquid developer.

Another object of the invention is therefore _r a dry developer of finely divided powders for the implementation of the erfindungsgemäben'Verfahrens is characterized as ^.), It completely or partly from one or

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consists of several substances which form radicals when heated.

As a rule, only the pure radical-forming substance is used used as a developer. However, the picture should be clear can be made visible, normal resinous Tonex * can be mixed in. The proportion of radical-forming However, the substance in the dry developer should not drop below 20% by weight. It has also proven to be Proven to be expedient to pulverize the radical-forming substances down to a grain size of less than 10 u.

Mostly wix-d the developer substance with the help of a carrier brought to the layer to be developed. Mixture too with iron chips and use in the well-known magnetic brush or magnetic roller leads to favorable results.

ii.li ·; · '. advantageous because of the clean working egg and the hoi.üii resolution has sicn also with the present one Liquid development has been proven. Another The subject of the invention is therefore a liquid developer

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of a high-resistance liquid phase and a finely divided solid phase dispersed therein, which is characterized in that the solid phase consists entirely or in part of one or more substances which form radicals when heated. Here, too, preference is given to using pure radical-forming substance as the solid substance. Occasionally, however, it is advantageous if the solid phase also partly consists of a dye. The particle size should also be below 10 u . The solid substance is usually crushed in a ball mill.

Liquids that do not dissolve the solid phase are used as dispersants. Suitable are e.g. some halogenated hydrocarbons, but especially so higher, still liquid aliphatic hydrocarbons, such as one under the name Shellsol T well-known product. The sense of charge of the dispersed solid phase depends both on the properties of the radical-forming substance itself as well as on the. voted off solvents. Dispersed in Shellsol® show the radical-forming substances listed above

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Substances have the following sense of charge: Diazidostilbene and sodium trichloroacetate are negatively charged, while all other substances are positive.

However, it is possible to change or stabilize the sense of vision in a known manner by adding additives. Suitable additives are, for example, naphthenates. These are used particularly advantageously together with a low content of binders such as linseed oil. Your technical effect is from the DAS i Qk? 5 ± 6 known.

The application of the liquid developer can be done in a known manner. done by dipping or roller application. Preferred The roller application is due to the higher uniformity.

After the elimination of the latent electrostatic image with one of the above-described inventive Developer, the radical-forming substance adheres loosely to the polymerizable layer in an imagewise fashion. The polymerization is then initiated by heating. The polymerization takes place, as already mentioned, in the temperature range between 100 and IVOO C. The temperature actually selected

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expediently depends on the decomposition temperature the applied radical-forming substance. The heating is done more advantageously in an already required Temperature brought oven. Infrared emitters of sufficient intensity are also suitable. However recommends it turns into a colored developer when they are used use to increase the energy consumption of the developed image areas. The duration of the heat treatment depends of the photoconductor to be polymerized, which is responsible for the polymerization initiating radical-forming substance, the level of temperature "and the thickness of the polyraerisiorendeii Shift off. Hitunter achieves a warming, of one half a minute that the layer is polymerized through. Sometimes it takes a few minutes. as The maximum time for heating can be considered to be 5 minutes.

The image areas polymerized by the heating become insoluble to suitable solvents,. ie. in the preferred embodiment, insoluble in relation to aqueous alkaline solutions.

The solutions are eg * with a cotton ball over which

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Layer painted. The 'plates can also be placed directly in the Fl'^; ity to be immersed. Appropriately constructed devices, eg. those with liquid application rollers. The differentiation into hydrophilic and oleophilic areas desired in offset printing is observed, the polymerized organic photoconductor layer providing the oleophilic areas and the carrier surface providing the hydrophilic areas.

Subsequent to the treatment with the alkaline liquid, the printing plate is advantageously rinsed with water and if necessary by mixing over with diluted Phosphoric acid solution further increases the hydrophilicity. To Coloring with bold paint can be done in a known manner in Flat printing machines are printed with it.

However, it is also possible to remove it afterwards of the exposed carrier printing forms for letterpress and if necessary also to produce gravure printing. The detachment can be known for this purpose in single or multi-stage Etching machines happen.

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According to the method according to the invention with one of the Printing forms produced according to the invention developer have high print runs. Usually just a few Micron thick photoconductor layer is completely polymerized through to the carrier, and it is also firmly attached to it anchored. Undermining when removing the non-image areas does not occur. Since the organic If the photoconductor layers are homogeneous, grain-free layers, it is easily possible to produce the finest raster points reproduce true to the original. The method of the invention is therefore preferably also used in manufacture of printing forms from very finely screened halftone originals. That area was the electrophotographic printing plates so far largely closed.

The invention is illustrated below with the aid of a few examples explained in more detail:

Example 1:

A roughened surface of about 100 µ thick aluminum foil is mixed with a solution of 2 g of N-dimethylvinylcarbazole, 2 g of Lytron® 820 and k mg of rhodamine B in kO g

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Glycol monomethyl ether coated and dried. The coated material is positively charged to about 300 V with the aid of a corona discharge. Then it is exposed under a positive screened film original in a vacuum oven. The exposure time is two seconds when using a 200 watt light bulb at a distance of 75 cm. The charge image produced on the photosemiconductor layer is then developed in a developer bath which contains 10 g of sodium trichloroacetate in finely divided form for 100 g of Shellsol ^ T. After the superfluous dispersant adhering to the layer has evaporated, the resulting white image of sodium trichloroacetate is heated to 200 ° C. for three minutes, during which the sodium trichloroacetate decomposes. The radicals produced during the decomposition polymerize the photo-semiconductor layer made of UV-u.imethy.! Vinylcarbazole at the image areas. The layer is removed from the non-image areas by bathing it for 1 minute in a solution of 5 g of sodium metasilicate in 100 ecm of water, k0 ecm of methanol, 35 ecm of glycol and 100 ecm of glycerine and then wiping it off with a sponge. In this way a printing form is obtained with which a very large edition of several tens of thousands of prints can be achieved using the offset printing process.

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Example 2 :

Instead of the solution of N-dimethylvinylcarbazole mentioned in Example 1 use one from the corresponding. Amount of 2-vinyl-4- (O-chlor.ph.enyl) -5- (p-diethylaminophenyl) oxazole for coating an aluminum foil * The layer is charged negatively to 400 V with the help of a corona device. The exposure is carried out using a contact grid and a slide. The exposure time depends on the light source used and the magnification scale. she is usually in the order of a few seconds. The exposed plate is developed with a liquid developer, which in finely divided form 6 g of pure tetraphenylhydrazine contains in 1000 g of Shellsol ^ T. The procedure is continued as in Example 1. One obtains a screened printing form.

Example 3 ^;

With a solution of 10.5 g of 2-vinyl-4- (o-chlorophenyl) -5- (ο-diethylaminophenyl) -oxazole, 25 g Alnovol ^ 429 K, 20 g Howilith ^ CT 5 and 120 mg of Hhodamin B in 3OO g of glycol monoethyl ether an etchable zinc plate is coated and dried. The layer thickness of the dry photoconductor layer should be about 10 - 12 u. She will be with a

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Corona device negatively charged to about 400 V. The exposure can take place in the contact copying frame as in Example 1. The latent charge image produced by the exposure is developed with a dispersion of 10 g of dehydrolophin in 1000 g of Shellsol ⁰ 'T. It is then heated to 200 ° C. and the coating is removed. The zinc exposed by the stripping of the exposed areas can then be deeply etched using commercially available means. In this way a letterpress form is obtained.

Example 4 ;

A surface roughened aluminum foil is treated with a solution of 5 g of 1-hydroxyethyl-2,5-bis- (p-diethylaininophenyl) -1, 3,4-tiazole, 5 g of Lytron ¹ ^ 8SO, 10 mg of rhodamine B in 100% g Glylcolmonoätliylätlier coated. The layer is negatively charged to 400 V. It is exposed to eight 500 watt incandescent lamps on a repro camera. A halftone photograph is used as a template a dispersion of 20 g of benzoyl peroxide

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in 1000 g of Shellsol ^ T. The heating takes about 5 minutes, a slightly longer time than is usual when using vinyl compounds, since it comes from the hydroxyethyl group water has to be split off first. After the stripping of the non-image areas, one obtains a Printing form for offset printing.

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Claims (1)

KALLE AKTiENGESELLSCHAFT 152-2.4 97 _v Our sign day sheet K l648 . ', - ■ " % A FP-Dr .Wi-cr 11.5.66 8-f P ate η t ans ρ r ü c Ii e Process for the production of printing forms from electrophotographic copying material with a carrier suitable for printing purposes and a photoconductive layer with an organic photoconductor located thereon by charging, imagewise exposure, developing the latent electrophotographic image of the layer with a finely divided toner, subsequent heating and removal of the photo - "Leltersc-hicht at the non-image areas, characterized in that the latent electrostatic. image is generated on a layer which contains at least one known, polymerizable olefinic double bond containing or forming on heating organic photoconductor, this is treated with a developer , which consists at least partially avts one or more finely divided substances that form radicals in the heat, then the copy material with the developed image is heated to temperatures between 50 and 300 ° C, preferably to temperatures between 100 and 200 ° C and off finally, in a known manner, the organic photoconductor layer is removed from the non-image areas by dissolving it away. BATH ORIGINAL 909837/0555 J. KALLE SHARE IN G ESE LLSCHAFT Our sign day sheet FP-Dr.Wi-cr '11 * 5.66 2. The method aum producing printing plates, characterized in that the latent electrostatic image is generated on a layer which contains at least one polymerizable organic photoconductive compound with a vinyl group and ψ alkali-soluble binders in the method according to claim and that after developing and heating the non-image areas of the photoconductor layer are removed in a manner known per se with an aqueous-alkaline liquid, optionally containing an organic solvent. 3rd Process for the production of printing forms, characterized in that in the process according to the claims I and J the developing agents which form radicals in the heat are carried in a manner known per se as a dry powder with dex ~ the latent electrostatic image Brings layer into contact. k. Process for the production of printing forms, characterized in that in the process according to claims 1 and L .. the substances which form free radicals in the heat are used in a manner known per se in a high-resistance 909837/05 55 KALLE AKTIENGESELLSCHAFT K 1648 Unheat sign tag sheet FP-Dr .Wi-cr 11.5.66 & 3 Liquid dispersed and as a so-called liquid developer with which the latent electrostatic image brings the load-bearing layer into contact. 5. Dry developer from finely divided powder egg "for the Implementation of the method according to claims 1, 2 and Ji ι characterized in that it consists entirely or in part of a, or more substances which form radicals on heating - '. consists. . ; 6. Liquid developer composed of a high-resistance liquid phase and a finely divided solid phase dispersed therein for carrying out the method according to claims 1, 'J. and k, characterized in that the solid phase consists wholly or partly of one or more substances which form free radicals when heated. KALLE AKT1EKGESELLSCHAFT 909837/0555