DE2252397A1 - PROCESS FOR MANUFACTURING A PRINT FORM AND A SUITABLE EMULSION - Google Patents

Description

"Process for the production of a printing form and an emulsion suitable for this"

The invention relates to the production of printing forms or printing templates and in particular a process for the production of a printing form, according to which a normally oleophilic / hydrophobic Material is optionally electrostatically charged and then brought into contact with a medium. This medium is attracted and only converts the surfaces which are oleophilic State are to be transferred. The larger background areas are usually made hydrophobic in order to repel paint

- 2 patent attorneys Dipl.-Ing. Martin Licht, Dipl.-Wirtsch.-Ing. Axel Hansmann, Dipl.-Phys. Sebastian Herrmann

8 MÖNCHEN 2, TH E RES I E N STRASS E 33 · Telephone: 281202 · Telegram address: Lipatli / Munich Bayer. Vereinsbank Munich, branch. Oskar-von-Miller-Ring, account no. 882495 Postal check account: Munich No. 1633 97

Oppenau office: PATENT ADVOCATE DR. REINHOLD SCHMIDT

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and to form a print image on an unchanged background area.

One known method uses electrostatic techniques to produce printing forms. The normally oleophilic / hydrophobic, However, starting material or working material which can be converted into a hydrophilic / oleophobic state is charged on a surface and then optionally discharged, whereby the charge only remains in the desired pressure areas or pressure areas. That The material is then brought into contact with a toner, which is itself oleophilic / hydrophobic and which is not in hydrophilic / oleophobic State is transferred. The toner is then melted by means of heat and / or pressure. Afterward the working material is immersed in a conversion solution which turns the non-toner non-image area into a hydrophilic / oleophobic State while the toner and the material underneath it, protected by the toner, is oleophilic / remain hydrophobic. The printing form is now suitable for printing, using a printing ink in a conventional manner served on a fat or oil basis.

Although this method is suitable for producing a good printing form is, it still requires three separate process steps to produce the printing form after the image was created by electrostatic charging, i.e. after the image has been created in an electrostatic way on the source or working material, this must be provided with toner, after which you melt the toner and then the background area

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converts. These three procedural steps are time consuming and require the use of considerable equipment and dedicated, Controls.

According to the invention, a method for producing a Created printing form in which the oleophilic / hydrophobic material optionally charged according to the shape of the desired image, after which the material is emulsionized electrically conductive droplets of a conversion means in contact which is in a non-conducting, non-transforming medium. This will create the areas you want optionally through electrical interaction of the charged surfaces with the particles of the conversion agent converted.

The present invention relates to a simplified method for Production of a printing form using an electrostatic method. According to the invention, a material is used which is oleophilic / hydrophobic in nature, but can be converted into the hydrophilic / oleophobic state. The material must be suitable for charging on one side and for optional discharge in order to achieve a desired pattern of electrically charged and to be able to produce uncharged surfaces. Zinc oxide is the most suitable and most common material that meets these requirements corresponds and consequently forms the preferred base material. Of course, other suitable materials can also be used can be applied.

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According to the invention, the zinc oxide is provided on a substrate or carrier, which is either the shape of a drum, a sheet or strip of material. The zinc oxide is exposed in a conventional manner by first the entire surface is electrostatically charged, after which one exposes the surfaces that cannot be converted as desired to a light source so that the light hits the one it hits Surface discharges. In this way, a certain image or surface distribution is obtained that is electrically charged and not charged Area share e.

The zinc oxide is then mixed with an emulsion of a conversion solution coated in a non-converting, non-conductive liquid with a low dielectric constant is emulsified and dispersed. With an emulsion of this form, the fine droplets of the conversion or conversion solution are bound by the electrical charge to those surfaces which carry an electrical charge. When the conversion solution contacts these surfaces, the material goes from the more oleophilic / hydrophobic state Property in the state of hydrophilic / oleophobic Property transferred or converted. However, the fine droplets are not electrically from the non-image areas, i.e. attracted by the uncharged surfaces, as there is no corresponding charge on these surfaces. It therefore exists very little contact between the fine droplets and the non-image areas. Accordingly, non-image areas are not converted while the charged surfaces are subject to this transformation.

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After converting the charged surfaces, the material is removed from the conversion or conversion solution and is ready to print. If conventional oil-based or fat-based paints are used, the unconverted paints will not be converted Areas used for printing while the converted areas are not used for printing. If, however, conventional exposure methods are used, then it is the background areas which remain oleophilic / hydrophobic, so that the background areas are used for printing with conventional printing processes and conventional grease or oil-based inks, while the image areas are not used for printing. There are some Process for producing a print-free background and a print image. Such a method makes use of an oil supply instead of water to apply the oil to the traditional material using a water-based paint. the The result is that the image areas are suitable for printing, but that the oil in the background areas prevents this color pick up and apply the pressure. These oils should be non-destructive to the material used and one for safety reasons have a sufficiently high ramming point. There are various hydrocarbons and mineral oils that can be identified as prove satisfactory.

Another method is the so-called "reversing" method, after which the optionally charged photoconductive material is converted will. In this process, a conversion medium is used, which electrically flows through the charged bottles is repelled, used within the emulsion. In this case, the conversion medium touches the uncharged surfaces

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and converts them, while the charged surfaces use the conversion or the conversion medium and remain without conversion <.

According to a further process, a reversed image "negative" is first created created, after which one uses this negative as an imaging element to optionally load the zinc oxide. That on Zinc oxide depicted in this way forms the charged background and a non-charged image area, so the background is transformed while the image areas are not converted to use the image areas for printing and the background areas not to be used for printing.

There are various combinations of liquid emulsions, which are optionally suitable, the charged areas according to the invention to convert. The requirements dictate that a conversion solution be able to convert from an electrical To be attracted to charge while the liquid in which it is absorbed is essentially non-conductive and has a low dielectric constant owns. For best results, the electrical resistance of the non-conductive medium should be

10 ohms - cm or greater, while the dielectric constant should be less than 3.4.

There are various media that meet these conditions. Either an aqueous one is preferred as the conversion solution Ferrocyanide solution or an aqueous phosphate solution is used, while a hydrocarbon is used as the insulating liquid will. The following composition is used for a conversion solution of the ferrocyanide form:

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Parts by weight. Components

75 water

8 monoammonium phosphate

1.5 potassium ferrocyanide

15 glycerin

The following composition is used for a typical phosphate conversion solution used:

Parts by weight of ingredients

75 water

10 monoammonium phosphate

1 phosphoric acid

15 glycerin

Many liquid hydrocarbons are suitable for the insulating liquid. For example, Isopar H from Humble Oil and Refinging Company or Sovasol 35 from Mobil Oil Company be used satisfactorily as an insulating liquid, within which the conversion solution can be emulsified.

The size of the droplets in the conversion solution is preferred of the emulsion between 0.5 and 500 microns (0.0005-0.5 mm), ideally around 10 microns. Such an emulsion can be more satisfactory Way produced and maintained using ultrasonic vibration or vibrations. When a ferrocyanide conversion solution or a phosphate conversion solution in either Isopar H or Sovasol 35 is sufficient

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a power generation of 400 watts at 20 kilohertz to create and maintain the emulsion. If you wish, you can not conductive surfactant such as Span 85 from Atlas Powder Company added in the amount of about 1 part per 1000 parts of emulsion to help stabilize the dispersion, although agents of this type are not required.

The exact proportions or proportions of the conversion solution and * the insulating liquid can be changed within wide limits. The only essential requirement is that the droplets be sufficiently fine and sufficiently dispersed that they are attracted to the charged areas of the zinc oxide while not being present in sufficient quantity to substantially convert any of the uncharged areas. For this reason, the electrical resistance of the resulting emulsion should be approximately 10 ohm-cm or greater. In the case of ferrocyanide conversion solution or phosphate conversion solution within either Isopar H or Savasol 35, it has proven to be expedient to achieve satisfactory results by adding 1 to 10 parts by volume of conversion solution to 100 parts by volume of insulating liquid. However, this approach is presented for illustrative purposes only and not in a limiting sense.

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Claims (3)

PATENT CLAIM E: ι 1 .j A method for producing a printing form, characterized in that a surface material is prepared which is normally oleophü / hydrophobic, but can be converted into the hydrophilic / oleophobic state and is suitable for optionally receiving and holding a charge that the surface the sheet material is selectively charged to produce a first electrically charged surface image and a second substantially free of electric charge existing surface image that an emulsion of a first liquid is prepared within a second liquid, the first liquid being electrically attracted by the surface charge and is capable of converting the oleophilic / hydrophobic material to the hydrophilic / oleophobic state, while the second liquid does not substantially convert the material and is incapable of removing the charge from the charge surface, and that the optionally charged material is immersed in the emulsion for a sufficiently long time , around to convert the charged areas so that the charged areas adopt a hydrophilic / oleophobic state, while the non-charged areas have an oleophilic / hydrophobic state. 2. The method according to claim 1, characterized in that the converted areas the areas intended for printing water-based inks with oil can be used for printing purposes. 309818/1065 2257/197 3. The method according to claim 1, characterized in that the unconverted areas are the areas used for printing, making grease-based paint with water for the purpose of Pressure can be used. 4. The method according to claim 1, characterized in that the first liquid is an aqueous solution of a conversion agent. 5. The method according to claim 4, characterized in that the Conversion agent is selected from the group of aqueous ferrocyanides and aqueous phosphates. 6. The method according to claim 5, characterized in that the first liquid in a proportion of 1-10 parts per 100 parts of the second liquid is used. 7. The method according to claim 1, characterized in that the second liquid consists of a hydrocarbon. 8. The method according to claim 1, characterized in that the 13 electrical resistance of the second liquid 10 ohms - cm or is more, and that the dielectric constant is less than 3.4. 9. The method according to claim 8, characterized in that the electrical resistance of the emulsion is 10 ohm-cm or more. 309818/1065 ? 2 5? 3 9 10. The method according to claim 1, characterized in that the first liquid has a droplet size of 0.5 - 500 microns. 11. Emulsion, characterized by a first liquidity, which is dissolved in a second liquid, the first liquid Is electrically attractable and suitable, a material more oleophilic / hydrophobic Property to be converted into a material hydrophilic / oleophobic property, and that the second liquid The given work material does not substantially convert and is unsuitable for an electrical charge from the surface of the material to dissipate. 12. A method for producing a printing form, characterized in that a sheet material is prepared which is normally oleophilic / hydrophobic, but can be converted into the hydrophilic / oleophobic state and is suitable for optionally receiving and holding a charge that the surface the sheet material is selectively charged to produce a first electrically charged surface image and a second surface image which is substantially free of electrical charge, that an emulsion of a first liquid is prepared within a second liquid, that the first liquid is electrically repelled by the surface charge and is suitable to convert the material oleophilic / hydrophobic property into a material hydrophilic / oleophobic property, that the second liquid is essentially not suitable to convert the material and to dissipate the charge on the surface of the material, and that the optionally charged material sufficiently la ng is immersed in the emulsion to convert the uncharged surfaces, where- 3 0 9 8 18/1085 hydrophilic / oleophobic character due to the uncharged surfaces gain while the charged surfaces are oleophilic / hydrophobic Have character. 309818/1065