DE69814573T2 - Residue-free recording element without material removal for the production of planographic printing plates - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a residue-free thermosensitive Non-ablatable imaging element. The present invention concerns in particular a residue-free heat sensitive non-ablatable Imaging element for producing a lithographic printing plate, the no dissolving Processing requires.

GENERAL STATE OF THE ART

Lithographic printing is the process in which the printing of specially manufactured surfaces of which certain areas attract lithographic paint and other areas after wetting with water will repel the paint. The ink-attracting areas form the printing image areas, the ink repellent Areas the background areas.

In the field of photolithography a photographic material in the photo-exposed areas (negative working) or in the non-exposed areas (positive working) on one hydrophilic background imagewise oily or made bold colors attractive.

More common in manufacturing lithographic printing plates, also as surface lithographic plates or planographic printing plates, becomes a support that has an affinity for water has or such affinity obtained through chemical processing with a thin layer coated with a radiation sensitive composition. As layers with a radiation-sensitive composition are photosensitive polymer layers, the diazo compounds, dichromate-sensitized hydrophilic colloids and a variety of synthetic ones Contain photopolymers. In particular, diazo-sensitized layer dressings widely used.

While the imagewise exposure the exposed areas of the photosensitive layer insoluble and the unexposed areas remain soluble. The printing plate will subsequently with a suitable liquid designed to contain that contained in the unexposed areas Remove diazonium salt or diazo resin.

Printing plates are also known which have a light-sensitive layer, which with imagewise exposure soluble in the exposed areas is made. While Subsequent development then becomes the exposed areas away. A typical example of such a photosensitive Layer is a layer based on quinonediazide.

The photographic described above Materials used to make the printing plates, are usually exposed through in a contact copier a photographic film made using a lithographic printing process contains the image to be reproduced. Such a procedure is cumbersome and labor-intensive, on the other hand, however, the printing plates thus obtained wait with one excellent lithographic quality.

Tests have been made been on the use of a photographic film as described above To be able to do without procedures and in particular a printing plate directly based on that too embodying reproductive image To generate computer data. The sensitivity of the above-mentioned photosensitive However, layers are not sufficient for direct laser exposure. Accordingly, it has been proposed to use a photosensitive layer Coating silver halide layer. The silver halide can then directly under computer control by means of exposed by a laser. Then the silver halide layer develops and a silver image is developed on the light-sensitive layer receive. This silver picture then serves as a mask during a all-over Exposure of the photosensitive layer. After full exposure the silver image is removed and the light-sensitive layer is developed. Such a method is described for example in JP-A 60-61 752, however, has the disadvantage of being a complex development and related developing liquids needed become.

GB 1 492 070 describes a process in which a metal layer or a layer containing gas black is applied to a photosensitive layer. This layer of metal is then ablated by means of a laser, whereby on the photosensitive Layer an image mask is obtained. The photosensitive layer is then through the image mask through a full-surface ultraviolet exposure subjected. After removing the image mask, the photosensitive Developed layer and received a printing plate. This method but still has the disadvantage that the image mask on cumbersome Paths removed before developing the photosensitive layer must become.

On the other hand, there are also methods in which imaging elements are used to produce printing plates, which are more sensitive to heat than to radiation. The radiation-sensitive imaging elements used to produce a printing plate as described above have the particular disadvantage that they must be protected from light. Furthermore, the Emp sensitivity in terms of shelf life problematic and they have a lower point sharpness. There is a clear trend on the market towards heat-sensitive printing plate precursors.

In EP-A 444 786, JP-63-208036 and JP-63-274592 are for the near infrared region sensitized photopolymer etching reserve layers disclosed. So far, none of them have proven to be commercially viable and all require wet development for washing out the unexposed areas. In EP-A 514 145 described a laser addressed plate, in which the by the Laser exposure generated heat the particles in the plate coating melt and coalesce lets and doing a change of their solubility properties causes. Here, too, wet development is required.

A somewhat different approach is being used in U.S. Patent No. 3,787,210, U.S. Patent No. 3,962,513, EP-A 001 068 and JP-04-140191 disclosed. The one generated by laser exposure of a donor sheet Heat will used a physical transmission a resinous material from the donor to one in intimate contact with to effect the receiving element held by the donor. Indicates the surface of the Receiving elements have suitable hydrophilic properties, so can the receiving element can then be used as a printing plate. With this The process has the advantage that no wet development is required. However, is to achieve realistic writing times YAG high power lasers (or similar Laser type), which requires a limitation in the usability of this Procedure entails.

On the other hand are from the current State of the art also known polymer layers, their surface properties change in response to exposure. WO-92/09934 Imaging elements disclosed which are hydrophilic when irradiated expecting layers, and in WO-92/02855 coatings described, which become sticky when irradiated. Included in both cases the layers an acid sensitive Polymer and a photochemical source of strong acid. In both cases is the preferred acid sensitive Polymer derived from a cyclic acetal ester of acrylic or methacrylic acid, such as tetrahydropyranyl (meth) acrylate.

In WO-92/02855 the acid sensitive Polymer with a low Tg polymer added to a layer to make, which is initially non-sticky, but when irradiated due to the chemical conversion of the acid sensitive polymer Undergoes phase separation and becomes sticky. It is true that here possibility mentioned by laser exposure, However, details are not given and there is no sensitivity across from Infrared radiation mentioned only opposite Ultraviolet radiation and visible light. The same materials but in an article entitled "Advances in Phototackification", presented in "Paper 1912-36" on the occasion of the "1993 I5 & T / SPIE Conference, Symposium on Electronic Science and Technology " This article further discloses that the photo acid generator is an infrared dye (especially a squarylium dye with thiopyrylium end groups) replaced and the exposure made with a diode laser device can be. This dye has no acid-generating properties known. This technology is discussed in U.S. Patent No. 5,286,604.

This is possible from WO-92/09934 Mixing of an acid sensitive Polymer known with one or more photo acid generators. To the imagewise exposure with ultraviolet radiation or visible light, the exposed Areas preferably wetted with water and the layers can be developed without wet development can be used as lithographic printing plates. Laser addressing is not mentioned.

In EP-A 652 483 a lithographic Printing plate disclosed that does not require resolving processing. The lithographic printing plate contains a substrate with an encapsulated one heat sensitive layer, the under the influence of heat becomes relatively hydrophilic. This system is a positive one Preserved printing plate. An analog system, but a negative one Pressure plate results, but is not known.

In DD 217 914 the manufacture a lithographic printing plate by laser irradiation of a light-insensitive hydrophilic material applied to an anodized aluminum support discloses, the material containing dyes or other ingredients can and the aluminum oxide layer with a at the wavelength of Lasers absorbent dye is colored.

DD 213 530 describes a procedure for the production of printing plates for flexographic and planographic printing Laser irradiation of layers using spectral sensitizers a spectrum that changes when irradiated included, disclosed.

A method is disclosed in US-P 4,034,183 disclosed for the production of a planographic printing form, one with a hydrophilic, consisting of a light-insensitive compound Layer of coated carrier exposed imagewise , the improvement being that the imagewise exposure of the layer with laser radiation with such intensity and over such a period is made that the exposed areas are made hydrophobic and oleophilic, whereby the printing plate obtained without further processing for printing can be used in a planographic printing press.

GB-A 2 203 438 describes a radiation-sensitive and heat sensitive Polymer with conjugated polyenes and sulfonic acid groups and an absorbency for given Bands of at least 0.6 are disclosed.

A method is disclosed in U.S. Patent No. 4,081,572 for the production of a printing or copying template, wherein (a) a self-supporting template substrate and (b) a specific hydrophilic Polymer are provided, (c) the substrate with the polymer is coated and (d) the polymer in image formation in a targeted manner Way by warming is made hydrophobic.

In JP 60 132 760 discloses the surface of a plate material that contains an oleophilic polymer that is rendered hydrophilic to form a non-image area, which is then irradiated with a laser to selectively remove a hydrophilic functional group and thus the desired printing plate receive.

TASKS OF PRESENT INVENTION

Object of the present invention is to manufacture a non-ablatable imaging element negative working, lithographic, no resolving processing to provide the required pressure plate.

Another task of the present The invention is a non-ablatable imaging element for the production of a lithographic, no resolving processing required printing plate with good color attraction the exposed Areas and without foaming in the unexposed areas provide.

BRIEF PRESENTATION THE PRESENT INVENTION

The above tasks are solved by a heat-sensitive non-ablatable as defined in claim 1 Imaging element for producing a lithographic printing plate, preferred embodiments in the subclaims To be defined.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The imaging element according to the invention contains one carrier and as a top layer, an image-forming layer that is thermally switchable binder and optionally a light to heat converting Connection contains. A thermally switchable binder is a polymer or copolymer, under the influence of heat a polarity change from hydrophilic to hydrophobic or vice versa. In the the present invention, a switchable binder is used, that before the warming is hydrophilic and by heating is made hydrophobic. This difference in surface polarity is enough to a conventional one To produce offset printing plate. In the thermal according to the invention switchable binders are polymers or copolymers with monomer units, the two pendant carboxylic acid groups or their salts or half esters formed therefrom, hereinafter as "dicarboxylic acid monomers" designated, included. A sodium, potassium, Serve ammonium or tetraalkylammonium ion. Also in question there are traces of alkali such as traces of triethylamine and pyridine. This Hydrophilic functions react under the influence of heat other functional groups and thus form a hydrophobic structure.

A suitable switchable binder for use in the imaging element of the invention is a maleic acid containing binder that is hydrophilic and under the action of warmth a more hydrophobic, maleic anhydride containing binder results. Other suitable switchable binders are binders, the fumaric acid, itaconic, 3- or 4-vinylphthalic acid, Cis-1,2,3,6-tetrahydrophthalic or contain cis-5-norbenendo-2,3-dicarboxylic acid. These acids can to be mixed into a single copolymer. Not just the diacids, but are also the monoalkyl esters and the salts formed therefrom suitable. examples for such half esters are monobutyl maleate copolymers, monoisopropyl maleate copolymers, Maleic acid-2-butoxyethylestercopolymere, Maleinsäureisobutylestercopolymere and isooctyl ester copolymers. These half esters can also in combination with another dicarboxylic acid monomer be used in a copolymer.

Not just through copolymerization from Z. B. Maleic acid copolymers obtained, but also polymer derivatives by Grafting of e.g. B. Maleic acid on unsaturated Polyolefins obtained are very suitable switchable polymers.

The switchable binder according to the invention can be a copolymer that continues to have other monomer units such as a Acrylate, a methacrylate, a vinyl halide, a vinyl ester, a vinyl ether such as n-butyl, isobutyl and 2-chloroethyl vinyl ether and contains olefins such as propylene, isobutylene and 1-octadecene. Especially a compound from the group consisting of one is preferred Methyl vinyl ether copolymer, an ethene copolymer and a styrene copolymer. The binder is very particularly preferably a maleic acid and Copolymer containing vinyl methyl ether.

The ratio of the dicarboxylic acid monomer to the comonomer can be between 100: 0 and 20: 80 va ri or suffices for the particular structure or state (ie anhydride or another structure) to influence the overall solubility of the top layer. Usually the ratio is around 50:50 due to the tendency to alternate copolymerization. The weight average molecular weight is generally between 5,000 and 70,000, preferably between 10,000 and 40,000 g / mol.

Although not preferred, the imaging layer contain more than a switchable polymer. The imaging layer can also be another binder included to the hydrophilic or hydrophobic properties of the Improve layer.

Come as a hydrophilic binder hydrophilic (co) polymers such as homopolymers and copolymers of acrylamide, methylolacrylamide, methylolmethacrylamide, acrylic acid, methacrylic acid, hydroxyethyl acrylate, Hydroxyethyl methacrylate or maleic anhydride-vinyl methyl ether copolymers in question. The hydrophilicity of the (co) polymer or (co) polymer mixture used is preferably higher or equal to the hydrophilicity of at least 60% by weight, preferably to at least 80% by weight hydrolyzed polyvinyl acetate. A favorite The hydrophilic binder is polyvinyl alcohol.

Come as a hydrophobic binder a water insoluble Polymer like a cellulose ester, a copolymer of vinylidene chloride and acrylonitrile, poly (meth) acrylates and polyvinyl chloride in question. Preferred hydrophobic binders are hydrophobic binders such as those in conventional binders used with positive or negative working PS plates, z. B. novolak, polyvinylphenols, carboxyl-substituted polymers etc. Typical examples of these polymers are in DE-A 4 007 428, DE-A 4 027 301 and DE-A 4 445 820.

The image-forming layer or a layer just below this layer preferably contains a compound which can convert light into heat. Infrared absorbing components are preferably used as suitable light to heat converting compounds, although the absorption wavelength is not of great importance as long as the absorption of the compound used falls within the wavelength range of the light source used for imagewise exposure. Particularly useful compounds are, for example, dyes and, in particular, infrared-absorbing dyes and pigments and, in particular, infrared-absorbing pigments. Examples of infrared-absorbing dyes are described in EP-A 97 203 131.4. Examples of infrared absorbing pigments are carbon black, metal carbides, metal borides, metal nitrides, metal carbonitrides, oxides with a bronze structure and oxides with a structure related to the bronze family, but without the A component, e.g. B. WO _2.9 . Conductive polymeric dispersions can also be used, such as conductive polymeric dispersions based on polypyrrole or polyaniline. The light converting compound is preferably embedded in the cover layer, but can also be embedded in an underlying layer.

It is clear that the light in warmth converting connection necessarily into the imaging element according to the invention is to be embedded if the imaging of the imaging element is done by exposure.

The connection to convert light into heat is preferably in an amount between 1 and 25% by weight, based on the total weight of the imaging layer, especially preferably in an amount between 2 and 20 wt .-%, based on the Total weight of the imaging layer, in the imaging element contain. The connection that light can convert into heat is very particularly preferably in such an amount in the imaging Contain element that im Wavelength range an optical density of at least between 800 nm and 1,100 nm 0.35 is obtained.

Furthermore, this is IR sensitive Layer preferably one opposite visible light and UV light desensitized layer. This preferably across from Visible light or UV light desensitized layer does not contain radiation-sensitive ingredients such as diazo compounds, photo acids, photo initiators, quinonediazides, Sensitizers, etc., in the wavelength range between 250 nm and absorb 650 nm. Calling this way can be against daylight insensitive printing plate can be obtained.

The image-forming layer is preferably applied in a ratio between 0.1 and 10 g / m ² , particularly preferably in a ratio between 0.5 and 5 g / m ² .

The carrier can be both hydrophobic and be hydrophilic and be both a rigid support and a flexible support.

In the imaging element of the present Invention can be the carrier be an anodized aluminum beam. A particularly preferred carrier is an electrochemically grained and anodized aluminum support.

According to another embodiment of the invention is the carrier a flexible beam like a paper support or a plastic film. As a flexible support according to this embodiment is particularly preferred a plastic film, for. B. a subbed Polyethylene terephthalate film, a cellulose acetate film, a polystyrene film, a polycarbonate film, etc. The plastic film carrier can opaque or translucent his.

A polyester film carrier coated with an adhesion-improving layer is particularly preferred. Adhesion-improving layers which are particularly suitable for the use according to the invention contain a hydrophilic binder and colloidal silica, as described in EP-A 619 524, EP-A 620 502 and EP-A 619 525. The amount of silica in the adhesion-promoting layer is preferably between 200 mg / m ² and 750 mg / m ² . Furthermore, the ratio of silica to hydrophilic binder is preferably above 1 and the specific surface area of the colloidal silica is preferably at least 300 m ² / g, particularly preferably at least 500 m ² / g.

Can between the carrier and the top layer the imaging element other layers such as adhesive layers and Contain antihalation layers,

Regardless of whether the imaging element a dye according to the invention contains or not, the imaging member may be between the support and the top layer optionally contain a reflective layer. The reflective layer can be any layer that the infrared radiation reflects, however, is preferably one Aluminum layer with high optical density, e.g. B. a layer made of vacuum evaporated aluminum.

The imaging element can after any known technique by applying the various Layers are made. Alternatively, the imaging element using one or more located in close proximity to the press coating equipment on the press on which the carrier is already appropriate.

The imaging according to the invention can be done with a Thermal head can be made. Imaging scanning exposure is preferred using a laser, preferably one in the infrared or near infrared, d. H. in the wavelength range between 700 and 1,500 nm, emitting laser. Are very particularly preferred near infrared emitting laser diodes. The exposure of the Imaging element can be used with lasers with both short and long Pixel dwell times are made, lasers are preferred with a pixel dwell time between 0.005 μs and 20 μs.

After exposure is the imaging element ready to use and can be used as a lithographic printing plate become,

In a further embodiment according to the invention can the exposure of the imaging element with the already in the image forming element is clamped in the printing press. A computer or other source of information leads to this Printhead or a laser a line of graphic and text information.

The printing plate according to the invention can also in the form of a seamless sleeve can be used as a printing plate in a printing cycle. This cylindrical Printing plate, the diameter of which corresponds to the diameter of the printing drum is the same, is pushed onto the printing drum instead of the conventional one Ways than in conventional Made printing plate arranged on the printing press become. More details about Sleeve printing plates can be found in "Grafisch Nieuws", publisher Keesing, 15, 1995, Pages 4 to 6.

The present invention will now illustrated by the following examples, but without them to restrict. All parts and percentages mean parts by weight unless otherwise noted.

EXAMPLE 1

0.35 g of GANTREZ AN 139 BF (a copolymer of vinyl methyl ether, maleic acid and maleic anhydride available from GAF, USA) and 0.0365 g of the IR-absorbing dye IR-1 are mixed in 4.5 g of a solvent mixture consisting of 44% THF, 34% methoxypropanol and 22% methyl ethyl ketone, dissolved. This solution is applied in a wet layer thickness of 16 μm to an aluminum substrate, a dry layer having a thickness of 1.15 g / m ^{2 being} obtained after drying.

For the exposure of this imaging element is used (distributed by CREO, Canada) Creo 3244 trendsetter at 2400 dpi, a drum speed of 40 TpM and a laser power operated by 11 watts.

After exposure of the imaging element a printing plate is obtained which is used for printing on a GTO 52 printing press (Trade name of Heidelberg, Germany) is used, whereby as printing ink K + E 197 (trade name of Kast and Ehinger) and as a fountain solution, the 5% G648 (trade name of Agfa-Gevaert, Belgium) and 10% isopropyl alcohol contains to be used. Good deductions will be obtained. H. Deductions with good Color attraction in the exposed areas and without foaming in the unexposed areas.

EXAMPLE 2

0.35 g of GANTREZ AN 139 BF (a copolymer of vinyl methyl ether, maleic acid and maleic anhydride available from GAF, USA) and 0.0365 g of the IR-absorbing dye IR-1 are mixed in 4.5 g of a solvent mixture consisting of 44% THF, 34% methoxypropanol and 22% methyl ethyl ketone, dissolved. This solution is applied in a wet layer thickness of 16 μm to a subbed polyethylene terephthalate substrate, a dry layer having a thickness of 1.15 g / m ^{2 being} obtained after drying.

For the exposure of this imaging element is used (distributed by CREO, Canada) Creo 3244 trendsetter at 2400 dpi, a drum speed of 40 TpM and a laser power operated by 11 watts.

After exposure of the imaging element a printing plate is obtained which is suitable for printing on a GTO 52 printing press (trade name von Heidelberg, Germany) is used, with K + E 197 (trade name of Kast and Ehinger) and as fountain solution a solution, the 5% G648 (trade name of Agfa-Gevaert, Belgium) and 10% isopropyl alcohol contains to be used. Good deductions will be obtained. H. Deductions with good Color attraction in the exposed areas and without foaming in the unexposed areas.

Claims (8)

A heat-sensitive, non-ablatable imaging element for the production of a lithographic printing plate which does not require any resolving processing, the imaging element on a carrier as a cover layer containing an imaging layer with a thermally switchable hydrophilic binder, the thermally switchable binder being made more hydrophobic under the action of heat and is a (co) polymer which contains monomer units from the group consisting of maleic acid, fumaric acid, itaconic acid, 3- or 4-vinylphthalic acid, cis-1,2,3,6-tetrahydrophthalic acid, cis-5-norbeno-2,3- Dicar contains acid and its half-esters formed therefrom. An imaging element according to claim 1, characterized in that this thermally switchable hydrophilic binder is a copolymer that furthermore monomer units from the group consisting of vinyl methyl ether, Contains ethene and styrene. An imaging member according to claim 1 or 2, which further a light in warmth converting link contains. An imaging element according to claim 3, characterized in that the Light in warmth converting compound is an infrared absorbing dye. An imaging element according to claim 3, characterized in that the Light in warmth converting compound is an infrared absorbing pigment. An imaging element according to claim 3, characterized in that the Light in warmth converting compound in an amount between 1 and 25% by weight, based on the total weight of the imaging layer, in the imaging element is included. An imaging element according to claim 3, characterized in that the Light in warmth converting compound in such an amount in the imaging Element is included in the Wavelength range an optical density of at least between 800 nm and 1,100 nm 0.35 is obtained. A method of making a lithographic printing plate by imaging an imaging element according to any one of claims 1 to 7th